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CAMDEN POWER STATION 6,6kV SWITCHGEAR
6,6kV SWITCHGEAR REQUIREMENTS FOR THE
WORKS SUPPLIED BY THE CONTRACTOR
Title:
Camden AHP Medium Voltage Switchgear
Requirements
Document Identifier:
Camden Power Station
383-CAHP-AAAC-D00132-1
HBS / Functional
Location):
*BCA, *BCG
Area of Applicability:
Electrical Plant
Functional Area:
Operating, Common plant,
Electrical reticulation
Revision:
0
Total Pages:
47
Next Review Date:
TBA
Disclosure Classification:
Controlled disclosure
Compiled by
Supported by
Functional
Responsibility
Authorized by
J. A. Moolman
MP Ngubo
P Rakeketsi
T Railo
Snr Consultant
Elec Lead Engineer
EPI - Discipline
Elec CoE
Power Stations
GTE- Electrical Design
Application CoE
Manager
Manager
GTE- Electrical Design
Application CoE
GTE- Electrical Design
Application CoE
Date:
Date:
Date:
Date:
REQUIREMENTS FOR THE WORKS SUPPLIED BY THE CONTRACTOR
Page 1
CAMDEN POWER STATION 6,6kV SWITCHGEAR
CAMDEN POWER STATION
6,6kV SWITCHGEAR
REQUIREMENTS FOR THE WORKS SUPPLIED BY THE CONTRACTOR
Index
Table of Contents
1
General .............................................................................................................. 5
1.1
SCOPE
5
1.2
EQUIPMENT TO BE SUPPLIED AND INSTALLED
5
1.3
APPLICABILITY
6
REFERENCES
6
1.4
2
3
4
Normal and Special Service Conditions .......................................................... 6
Definitions and Abbreviations .......................................................................... 6
Ratings and Operating Conditions .................................................................. 7
4.1
PANEL RATINGS
7
4.2
RATINGS - SWITCHING DEVICES
7
4.3
RATED VOLTAGE
7
4.3.1
4.3.2
4.3.3
4.3.4
System normal power supply conditions ................................................ 7
Circuit Breaker Auxiliary Coils ................................................................ 8
Harmonic Voltage Distortion .................................................................. 8
System abnormal power supply conditions ............................................ 8
4.4
RATED INSULATION LEVEL
9
4.5
RATED FREQUENCY LEVEL
9
4.6
RATED NORMAL CURRENT AND TEMPERATURE RISE
9
4.7
RATED SHORT-TIME WITHSTAND CURRENT
10
4.8
RATED PEAK WITHSTAND CURRENT
10
4.9
RATED DURATION OF SHORT CIRCUIT
10
4.10
RATED SUPPLY VOLTAGE OF CLOSING AND OPENING DEVICES AND OF
AUXILIARY AND CONTROL CIRCUITS
10
4.11
RATED SUPPLY FREQUENCY OF CLOSING AND OPENING DEVICES AND OF
AUXILIARY CIRCUIT
10
5
Design and Construction ................................................................................ 10
5.1
SWITCHGEAR AND CONTROLGEAR
5.1.1
5.1.2
11
General ................................................................................................ 11
Operating Service Requirements ......................................................... 11
REQUIREMENTS FOR THE WORKS SUPPLIED BY THE CONTRACTOR
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
5.1.3
5.1.4
5.1.5
5.1.6
5.1.7
5.2
Internal Arc Classification .................................................................... 12
Segregation of Compartments ............................................................. 13
Power Cable Entry and termination ..................................................... 19
Earthing ............................................................................................... 21
SPECIAL CONSIDERATION FOR INTERNAL ARC PROOF DESIGN 21
PROTECTION
5.2.1
5.3
22
General ................................................................................................ 22
INTELLIGENT ELECTRONIC DEVICES
5.3.1
5.3.2
5.3.3
5.3.4
5.3.5
5.3.6
5.3.7
5.4
ARC DETECTION SYSTEM
5.4.1
5.4.2
5.4.3
5.4.4
5.5
PROTECTION SCHEMES
ARC PROTECTION SCHEME
CIRCUIT BREAKERS
33
General ................................................................................................ 33
Inter-changeability ............................................................................... 33
Circuit-breaker truck connections ........................................................ 33
Shutters ............................................................................................... 34
Mechanisms ........................................................................................ 34
Tripping Devices .................................................................................. 35
Indicating Devices................................................................................ 35
Auxiliary Contacts ................................................................................ 35
Control Connector................................................................................ 36
Insulation Level .................................................................................... 36
EARTHING DEVICES
5.8.1
5.8.2
30
General ................................................................................................ 30
Current Detection Methods .................................................................. 30
Circuit Breaker Failure Protection ........................................................ 31
Busbar Chamber Protection................................................................. 31
Protection of Circuit Breaker Compartment ......................................... 31
Protection of Cable Termination Compartments .................................. 31
Buszone Protection Scheme ................................................................ 32
DC Fail Function .................................................................................. 32
5.7.1
5.7.2
5.7.3
5.7.4
5.7.5
5.7.6
5.7.7
5.7.8
5.7.9
5.7.10
5.8
27
Motor Protection Scheme (Motors ≥ 1 MW) ......................................... 27
MV Interconnector Protection Scheme ................................................ 28
Transformer Feeder Protection Scheme (Transformer < 10 MVA) ...... 29
MV Incomer Protection ........................................................................ 29
5.6.1
5.6.2
5.6.3
5.6.4
5.6.5
5.6.6
5.6.7
5.6.8
5.7
26
Protection Relays................................................................................. 26
Light Sensors....................................................................................... 26
Monitoring ............................................................................................ 26
Auxiliary Relays ................................................................................... 26
5.5.1
5.5.2
5.5.3
5.5.4
5.6
22
Design and Construction...................................................................... 22
Functions ............................................................................................. 23
Software .............................................................................................. 24
Analogue Voltage and Current Inputs .................................................. 24
Output Contacts ................................................................................... 24
Testing of Devices ............................................................................... 25
Buszone Protection Relay .................................................................... 25
36
General ................................................................................................ 36
Busbar Earthing Devices ..................................................................... 37
REQUIREMENTS FOR THE WORKS SUPPLIED BY THE CONTRACTOR
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
5.8.3
5.9
Cable Earthing Device ......................................................................... 37
ACCESSORIES
5.9.1
5.9.2
5.9.3
5.9.4
5.9.5
5.10
38
Current Transformers .......................................................................... 38
Voltage Transformer ............................................................................ 38
Indicating and Measurement Instruments ............................................ 39
Selector Switches ................................................................................ 39
Cable Live Indicators ........................................................................... 40
TERMINALS
5.10.1
5.10.2
5.10.3
5.10.4
40
Material and Construction .................................................................... 40
Mounting .............................................................................................. 40
Types ................................................................................................... 40
Wiring and Cable Lugs ........................................................................ 40
5.11
LABELS
41
5.12
NAMEPLATES
41
5.13
SWITCHGEAR INTERLOCKING SYSTEMS
42
TESTING AND DOCUMENTATION OF TEST REPORTS
43
5.14
5.14.1 Type Test ............................................................................................ 43
5.14.2 3.9.2 Routine Tests.............................................................................. 43
5.14.3 Special Tests ....................................................................................... 43
5.15
MAINTENANCE AND OPERATION
44
5.15.1 Maintenance and Operating Tools ....................................................... 44
5.15.2 Maintenance and Operating Instructions.............................................. 45
5.16
DOCUMENTATION
45
5.16.1 Language ............................................................................................ 45
5.16.2 Type Test Reports ............................................................................... 45
5.17
MANUALS AND DRAWINGS
45
5.18
PACKAGING, TRANSPORTATION AND HANDLING
46
REQUIREMENTS FOR THE WORKS SUPPLIED BY THE CONTRACTOR
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
1
GENERAL
1.1
Scope
a. This requirements specification provides for the manufacture, testing before
despatch, supply, delivery to site, off-loading, erection, site testing and
commissioning and handover after commissioning to the power station.
b. Each panel is completed with all the necessary connections, interconnecting
wiring, fuses, supporting steelwork, hold down bolts, guards, labels and
accessories to make a complete functional assemble in the case of a
complete switchboard and in the case of additional panels to be connected to
existing 6,6kV boards as per this this specifications.
c. The specifications define the requirements for:
-
Specific design and specifications of the switchgear,
-
Safety of personnel and equipment with regards to the use of this
switchgear,
-
Specific design and technical, operation of the switchgear,
-
Maintenance and return to service of the switchgear.
d. If the Contractor cannot supply the equipment offered in Schedule B at the
time of delivery the next bigger size of equipment that is available is supplied
at no extra cost to the Employer.
e. The switchgear is of the withdrawable type, internal arc classified (IAC) of the
modular design with air-insulated busbars for the use on 3-phase systems
rated at 50Hz.
f.
1.2
Components used in the switchgear are designed, manufactured, installed
and tested in accordance with the manufacturer’s specifications and
requirements with these specifications supplementary.
Equipment to be supplied and installed
a. 6,6kV Ash Water Return Plant Boards 1 & 2
-
Install two (2) 6,6kV Boards consisting out of six (6) panels each, to be
installed inside the Ash Water Return Pumphouse near the Ash Water Return
Dam. Each board are equipped with busbar compartment, circuit breaker
compartment and cable compartment internal arc protection. The protection
is in compliance with Eskom Standard 240-56357424, MV and LV Switchgear
Protection Standard.
b. 6,6kV Station Boards 3 & 4
-
Install one 6,6kV, 630A, complete panel, equipped with a 6,6kV, 630A circuit
breaker on 6,6kV Station Board 3. The panel shall be equipped with busbar
compartment, circuit breaker compartment and cable compartment internal
arc protection. The protection is in compliance with Eskom Standard 24056357424, MV and LV Switchgear Protection Standard.
REQUIREMENTS FOR THE WORKS SUPPLIED BY THE CONTRACTOR
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
-
Install one 6,6kV, 630A, complete panel, equipped with a 6,6kV, 630A circuit
breaker on 6,6kV Station Board 4. The panel shall be equipped with busbar
compartment, circuit breaker compartment and cable compartment internal
arc protection. The protection is in compliance with Eskom Standard 24056357424, MV and LV Switchgear Protection Standard.
c. 6,6kV Sub-Station Boards 1, 2, 3 & 4 – ABB Uniflex Type
-
Replace all eight Ash Pump Motor 6,6kV VC’s on 6,6kV Sub-Station Boards
1, 2, 3 & 4 with 630A, SF6 VCB’s including the protection relays (Eskom
Standard 240-56357424, MV and LV Switchgear Protection Standard) and
internal arc protection as for circuit breaker panels. The 6,6kV panels of the
ash pumps will remain in its current position.
-
Replace all eight Sluice Pump Motor 6,6kV VC’s on 6,6kV Sub-Station
Boards 1, 2, 3 & 4 with 630A, SF6 VCB’s including the protection relays
(Eskom Standard 240-56357424, MV and LV Switchgear Protection
Standard) and internal arc protection as for circuit breaker panels. The 6,6kV
panels of the ash pumps will remain in its current position.
d. 6,6kV Sub-Station Boards 1, 2, 3 & 4 – ABB Uniflex Type
-
1.3
Install one x 630A, 6,6kV panel on each of 6,6kV substation boards 1, 2, 3 &
4 to supply the 6,6/0.4kV Aeration Transformers 1, 2, 3 & 4 to be installed on
Units 1 to 8 ash hoppers.
Applicability
This specification is applicable to the 6,6kV switchgear and controlgear at
Camden Power Station.
1.4
References
References are discussed under the Works Information, Section 2 of this
enquiry document.
2
NORMAL AND SPECIAL SERVICE CONDITIONS
The switchgear is to be used as per the Schedule A of these specifications.
3
DEFINITIONS AND ABBREVIATIONS
IEC – International Electrical Commission
SANS – South African National Standards
NPS – Negative Phase Sequence
PPS – Positive Phase Sequence
ZPS – Zero Phase Sequence
THD – Total Harmonic Distortion
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
4
RATINGS AND OPERATING CONDITIONS
4.1
Panel Ratings
a. The switchgear and control gear ratings and operating conditions, its auxiliary
equipment is in accordance with SANS 62271-200, the stipulations of Eskom
requirements and standards as provided in Schedule A.
b. Thermal ratings are as per these stipulations of this document and its
attachments. Panels are fully type and routine tested at the specified ratings.
c. The motor starting currents and number of starts per hour as specified are
taken into account when the temperature rise limits are verified or tested.
4.2
Ratings - Switching Devices
a. The circuit breakers are rated for the continuously carrying the circuit breaker
current rating as specified in Schedules A & B at the specified altitude for an
ambient temperature of 40°C.
b. The circuit breakers are rated for all the current ratings of the circuit breaker
in the service position within the fully assembled and functional unit.
c. The circuit-breakers shall be capable of interrupting, making, latching against
and able to withstand the specified fault duties at the maximum specified
voltage.
d. The circuit-breaker shall be classified as Class E2 in accordance with SANS
62271-100 without reclosing. Auto-reclosing is not required.
e. The circuit-breaker shall be classified as Class M2 in accordance with SANS
62271-100.
f.
Earthing devices shall be classified as Class E2 in accordance with SANS
62271-102, as a minimum.
g. Earthing devices shall be capable of enduring a minimum of 2000 mechanical
operations.
h. The short-circuit withstand current rating and insulation level of an earthing
device shall match that of the panel. The duration for the test will be 3
seconds.
i.
4.3
The connection between the earthing device and the panel earth bar shall be
designed to withstand the panel short-circuit withstand rating for same
duration.
Rated Voltage
The rated voltage is in accordance with SANS 62271-200, this specification
and the values as per Schedule A.
4.3.1 System normal power supply conditions
The extremes of these parameters can occur simultaneously:

Voltage
± 5%

Voltage imbalance
NNPS voltage up to 0.02 of nominal
PPS voltage

ZPS voltage component can
1% of the PPS
REQUIREMENTS FOR THE WORKS SUPPLIED BY THE CONTRACTOR
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
be up to
4.3.2
Circuit Breaker Auxiliary Coils
- Shunt-closing release – Between 85% and 110%
- Shunt-opening release – Between 85% and 110%
- Under-voltage release – below 35% of the rated voltage
4.3.3 Harmonic Voltage Distortion
a. The harmonic distortion of the supply voltage under normal operation is as
follows:
-
The Total Harmonic Distortion (THD) of the voltage can be up to 5% of the
fundamental component.
-
The voltage waveform can contain harmonic components up to the 100th
harmonic.
-
The amplitude of any individual component can be up to 1% of the
fundamental component.
4.3.4
System abnormal power supply conditions
The following are typical operating characteristics which can occur on
auxiliary supplies.
4.3.4.1 Power supply abnormal operating characteristics
a. The supply voltage frequency can reach limits of up to 52,5 Hz and fall as
low as 47,5 Hz. This condition can last for up to six hours.
b. The amplitude and duration of temporary abnormal voltage operating
characteristics which can occur on the power supply are as follows:
4.3.4.2 Short duration abnormal conditions
a. Short duration under voltage conditions arise either due to a loss of
supply or the supply voltage being depressed due to a short circuit on the
network.
4.3.4.3 Loss of power supply
a. When the supply is disconnected, the supply voltage either drops rapidly
to 0% of nominal value or is sustained at low amplitude at a reduced
frequency because of back generation of electrical drives.
b. The initial voltage amplitude during these conditions are less than 80% of
the nominal value and decay with a time constant of up to 1,5 seconds.
c. The time duration from loss of supply until supply restoration is between 1
second and 1,5 seconds.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
4.3.4.4 Short circuits
a. Depression of supply voltage due to short circuits can result in voltages
as low as 0% of nominal value. The duration of the drop can be up to 1
second.
4.3.4.5 - Overvoltage’s
a. Over-voltages with a amplitude of 110% of nominal value can occur for up
to 10 seconds.
4.3.4.6 Medium duration power supply deviations
a. Voltage depressions of medium duration can be caused by the switching
of load such as induction motors.
b. The supply voltage can fall as low as 75% of nominal value and the
duration of this depression can be up to 10 seconds.
c. An alternative source of this abnormal condition is when power swings
occur after a severe disturbance on the network.
d. The supply voltage amplitude oscillates at a frequency between 0,2 and 2
Hz.
e. In this case the voltage can fall as low as 65% of nominal and can rise up
to 110% of nominal during a swing.
f.
The voltage does not fall below 70% for longer than 0,5 seconds.
However, these oscillations, or repeated abnormal voltage conditions, can
continue for up to 60 seconds.
4.3.4.7 Long duration power supply deviations
a. Long duration abnormal supply voltage conditions usually originate from
operating the plant at its limits.
b. The supply voltage can be up to 110% of nominal value and can drop as
low as 90% of normal value.
The duration of such abnormal conditions is up to 6 hours.
4.4
Rated Insulation level
The rated insulation level is in accordance with SANS 62271-200, this
specification and the values as per Schedule A.
4.5
Rated Frequency level
The rated frequency level is in accordance with IEC 62271-200, this
specification and the values as per Schedule A.
4.6
Rated Normal Current and Temperature Rise
The rated normal current and temperature rise is in accordance with SANS
62271-200, this specification and the values as per Schedule A.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
4.7
Rated Short-time Withstand Current
The rated voltage is in accordance with SANS 62271-200, this specification
and the values as per Schedule A.
4.8
Rated Peak Withstand Current
The rated peak voltage withstand current is in accordance with SANS 62271200, this specification and the values as per Schedule A.
4.9
Rated Duration of Short Circuit
The rated duration of short circuit is in accordance with SANS 62271-200, this
specification and the values as per Schedule A.
4.10 Rated Supply Voltage of Closing and Opening Devices and of
Auxiliary and Control Circuits
The rated supply voltage of closing and opening devices and of auxiliary and
control circuits are in accordance with SANS 62271-200, this specification and
the values as per Schedule A.
4.11 Rated Supply Frequency of Closing and Opening Devices and of
Auxiliary Circuit
The rated supply frequency of closing and opening devices and of auxiliary
circuit is in accordance with SANS 62271-200, this specification and the values
as per Schedule A.
5
DESIGN AND CONSTRUCTION
a. The new boards, replacement of VC’s with SF6 VCB’s and additional panels
are of the indoor type, trunk type circuit breaker, being able to be removed
from the breaker compartment by means of a trolley (Withdrawable) and
internal arc classified AFLR for 1 second in accordance with the requirements
of SANS 62271-200.
b. The switchboards are of the modular design to allow for air insulation and the
subsequent addition of identical panels. The design allows for human safety
and as little as possible time to RTS in the case of an internal arc fault.
c. The new switchgear and controlgear are of the behind-closed-door operation.
d. Circuit breaker trolleys are supplied with the boards to allow for the removal
of circuit breakers with regards to maintenance and isolation activities.
e. The switchgear and controlgear are clearly marked as per this specification
with the ratings to which the equipment has been type tested. Ratings shall
be displayed as per SANS IEC 62271-1, section 5.10.
f.
CT labels are displayed in the LV compartment and inside the cable
compartments.
g. Oil filled circuit breakers, voltage transformers are not acceptable due to the
risks and dangers attacked to oil filled medium voltage equipment.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
5.1
Switchgear and Controlgear
5.1.1
General
a. The new 6,6kV Ash Water Return Plant Boards 1 & 2, the additional Uniflex
6,6kV panels are of the metal-enclosed type switchgear and control gear, of a
proven design and fully type tested. The design of the switchgear and
controlgear complies with the requirements of this specification and the
following:
-
Schedule A – attached to Annexure 1. The contractor completes
schedule B of the attachment to Annexure A.
-
Schedule C – attached to Annexure 2. Type-testing requirements.
-
Schedule D – Attached to Annexure 3. Maintenance requirements.
-
Schedule E – attached to Annexure 4. Design requirements as per
the switchgear schedules.
b. The switchgear is rated at 25kA, therefor no exhaust duct or arc absorber will
be required.
c. All moving parts in the switchgear and switchgear panels haves a
maintenance interval of a minimum of 1 year or 5000 operations. Of
particular concern are the busbar shutters and other moving parts during
racking in and out of the switchgear.
d. Panels are designed to contain internal arcing faults and to direct arcs and
gasses arising from these up and away from the operator.
e. Additional safety measures provided by the Contractor are noted in Schedule
B.
f.
Circuit breakers and contactors are mounted in the switchboard with the
same type of finishing.
g. All access doors and covers to live compartments are padlockable.
h. Multi-tier mounting of switchgear is not permissible.
i.
5.1.2
On the new 6,6kV Ash Water Plant Boards 1 & 2, all incomer and
interconnector circuits (Panel, panel covers and panel doors) are powder
coated “RED”.
Operating Service Requirements
Compliance with the power stations operating philosophy and conditions is the
minimum requirement. The requirements of 32-846 “Operating regulations for
high voltage systems” are mandatory. In addition to the requirements, the
following normal and abnormal conditions apply during which all the safety
requirements of the Internal Arc Classified (IAC) switchgear and controlgear are
met:
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
a. All substations are unmanned, but access to the substations is being
carried out at regular intervals for inspection purposes, operating and
fault finding.
b. Nobody is allowed on switchgear that is energised.
c. A fault can occur during the operating which includes the removal of
trunk type switchgear from the disconnected, earthed or test position to
the connected position or vice versa.
d. An earth can be applied to a live circuit.
e. A low voltage compartment fault finding actions can be performed with
the switchgear and controlgear in the live state.
f.
Voltage transformers can be racked out with the switchboard in the live
state.
g. A cable can be terminated in an isolated cable compartment with the
switchboard being alive (Includes busbars and adjacent circuits).
5.1.3
Internal Arc Classification
a. The 6,6kV switchgear, vacuum circuit breakers and controlgear are
designed to confine the internal arc for fault currents as specified in
Schedule A attached to Annexure 1.
b. The design of the new boards is such that all direct arcs and gasses
arising from these faults are guided upward away from personnel. Care
in the design is taken to prevent the gases from exiting on the sides of the
end panels of the boards.
c. Each power compartment is able to withstand and contain the internal
fault arc and shall release the pressure upwards, without the arc
spreading or pressure released into any other power compartment.
d. Each functional unit is designed to contain the arc without spreading it to
any other functional unit.
e. The design of the switchgear and controlgear is safe at the front, on the
sides and at the back to enable operating while the switchgear is in
operation.
f.
Internal arc type testing in the circuit breaker and busbar compartment ar
carried out, with the low voltage compartment door open. This reason
being to enable safe fault finding, operating and maintenance access to
the low voltage compartment while the circuit breaker and busbar
compartments are alive. Due to the internal arc classification and for
maintenance purposes, no voltage transformers or earthing switches are
installed within the pressure relief area on top of any functional unit.
g. Where cable terminations are protruding the floor, a fire seal with a rating
2 hour are maintained. The seal is at least 50mm thick.
h. For switchgear and controlgear with circuit breakers supplied from two
independent supplies, the design prevents an internal arc to spread from
one side of the circuit breaker connecting arms to the other side of the
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
circuit breaker connecting arms (circuit breaker in service position but
open position and both sides of the circuit breaker alive from two
independent supplies). If the design does not comply with this
requirement it shall be highlighted in the deviation schedule.
5.1.4
i.
The designation of the IAC classification in terms of SANS 62271-200 is
AFLR and the test current is equal to the busbar short circuit current
specified in Schedule A attached to Annexure 1 and the internal arc
duration for any internal arc is 1 second.
j.
If arc eliminator technology is available, it can be offered.
Segregation of Compartments
5.1.4.1 General
The following is the minimum with regards to segregation of compartments:
a. Circuit breakers (Withdrawable or not).
b. Main busbars.
c. Low voltage compartment including low voltage cabling.
d. Power cable termination compartment (Including earth switch and cable
VT).
e. Busbar earthing g device compartment.
f.
Busbar VT compartment.
5.1.4.2 Low Voltage Compartments
a. The low voltage compartments are located in the front top section of the
functional unit.
b. The design of the LV compartment are such that it will house all the
protection, control and monitoring functionalities as specified in this
specification.
c. The HMI (Human Man Interface) are located on the compartment door and all
other facilities are accessible from the front of the panel.
d. The compartment door has a swing frame design and is adequately
supported by means hinges.
e. The LV compartment doors design allows for control/protection cabling from
the top or bottom of the panel.
5.1.4.3 Power Cable Compartment
a. The power cable termination and cable current transformer are accessible
from the cable compartment.
b. The design of the compartment is such that the power cable terminations and
current transformers can be easily disconnected/removed/replaced with the
busbars in the energised state.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
c. The power cable compartment complies with SANS 876 and provides for
three-core cable terminations.
d. The stipulations of ORHVS 32-846 are taken into account when the cable
compartment is designed.
e. The design is such that a fault/flash-over in this compartment shall not
damage to rear power cable compartment or rear power cable compartment
cover.
5.1.4.4 Main Busbar Compartment
a. The main busbar compartment houses the main busbars and the busbar
support structures.
b. The main busbar compartment is only accessible if the provisions of OHVRS
32-846 are met.
5.1.4.5 Circuit Breaker Compartment
a. Each panel is equipped with a circuit breaker compartment to house the
circuit breaker.
b. The design of the circuit breaker compartment is such that only circuit
breaker with the same ratings can be interchanged into a circuit breaker
compartment.
c. Circuit breakers are of the withdrawable type and the circuit breaker
compartments are designed to cater for this requirement.
d. Circuit breaker compartments are operator-accessible as per interlocking
requirements.
5.1.4.6 Busbar Earth Device Compartment
a. The busbar earthing device compartments are special-accessible
compartments that requires the switchgear board to be isolated from all
points of supply and castle key system are required to release the busbar
earth before the busbar earth can be applied. The isolation requirements of
ORHVS 32-846 and GGR 992 are mandatory.
b. The design of the busbar earth is mechanically sound and rigid, of the fixed
type and with all indications and limit switches to indicate the position of the
busbar earth.
c. The busbar earthing device is in the same panel as the busbar VT.
d. The busbar earth is operated from the front of the panel.
e. The lockout system that is installed is such that the incomer circuit breakers
cannot be engaged without the busbar earth in the “OFF” position.
f.
Withdrawable busbar earth is not acceptable.
5.1.4.7 VT Compartments (Busbar and Cable)
a. VT’s are of the withdrawable type.
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b. The VT’s are housed in it’s own panel/compartment.
c. Access to the VT’s whilst in the energised position are not possible.
d. The switchboard must be isolated to remove the busbar VT. This must be
incorporated in the design of the switchboard.
e. The cable VT’s cannot be accessed without isolating the circuit to which the
cable VT is connected. This must be incorporated in the design of the
switchboard.
5.1.4.8 Service Continuity Classification
The loss of service category for the new switchboards is LSC2B in accordance
with the requirements of SANS 62271-200.
5.1.4.9 Partition Class
a. Partition class of the new switchboards is class PM as per SANS 62271-200.
b. The circuit breaker compartments are equipped with busbar and cable
shutters that will close when the circuit breaker is withdrawn and open when
the circuit breaker is racked in.
5.1.4.10 Special labelling for Internal Arc Proof Switchboards
a. Functional units (Switchboards) are so designed that the blow (Due to internal
fault) will be to the top of the functional unit to satisfy IAC requirements, then
the switchboards are equipped with labels to provide warning messages to
persons working on the panels/switchboards.
b. The following labels are displayed:
-
“DO NOT CLIMB ON THE SWITCHGEAR WHEN ENERGISED”. The
labels are installed on the rear and sides of the switchboards. The
amount of labels is dependent on the length of the panel and approval
from the employer about the amount of signs is obtained.
-
“DO NOT STEP ON PRESSURE RELIEF FLAPS”. This sign is displayed
on every functional unit of the switchboard on top of the flap.
c. Warning labels are red lettering on a white background.
d. The size of the signs is such that it can be clearly seen when a person is
standing in the upright position.
5.1.4.11 Cooling
a. The use of forced cooling is not allowed.
b. Cooling of the switchgear is natural dispersion through the switchgear metal
structure.
5.1.4.12 Degree of protection
a. Minimum required degree of protection for the functional units is IP41.
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b. Minimum required degree of protection for the external housing units is
IP3XB.
5.1.4.13 Panel Fasteners, Doors and covers
a. Fasteners used in the functional units are the same material and construction
that was used in the Type Tested panels. No deviations.
b. When a fastener is also a locking mechanism, provisions are made for a
padlock with dimensions as per Eskom drawing 0.00-002839.
c. If lift off covers is part of the design with regards to the cable compartment, it
is designed such that a mechanical interlock will prevent the cover from being
removed. The caver can only be removed when a cable earth is applied.
d. All circuit breaker compartment or VT compartment doors are equipped with
a front window that is part of the type testing for internal arc compliance. The
window is part of the type and routine test certificates and seal tightly to
prevent moisture and dust ingress.
e. All cable compartments covers other that those housing a cable VT is fitted
with bolted covers.
f.
Empty compartments in busbar extension dummy panels are fitted with
bolted covers.
g. Where doors are fitted on empty compartments, the doors are padlockable.
5.1.4.14 Corrosion Protection
a. Steelwork shall be corrosion protected in accordance with the specification
240-75655504, Corrosion Protection Standard for new Indoor and Outdoor
Eskom Equipment Components, Materials and Structures from Steel
Standard.
b. The colour of the final coating shall be in accordance with SANS 1091.
5.1.4.15 Colour Coding
a. Colour coding of the new boards is Local B32, Imported RAL 2000.
b. The incomer circuits and the switchboard interconnectors are coded “RED”.
5.1.4.16 Busbars and Connections
a. The main busbars compartment and connections inside the busbar
compartment are of the air insulated type and the clearances do not
compromise the specified voltage withstand levels.
b. Busbars and connections are covered up with insulating shrouding.
c. The busbars are supplied as per the type tested arrangement, including any
additional insulation shrouding that were used.
d. Cables are not allowed to be used for busbars or busbar connections inside
the circuit breaker, voltage transformer or inside busbar compartments.
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e. All busbars are marked in such a way that they are easily identifiable as to
the phase or pole they are connected to when covers are removed. The
phase identification marking material is not easily removable.
f.
It is recommended to use heat shrink tube for marking however, the material
used for marking the busbars is subject to Eskom acceptance.
g. Busbar connections are made with at least two bolts and the overlap is
sufficient to ensure ample mechanical strength and joint conductivity and is
having the same electrical characteristics as the main busbar. The busbar
connections match those of the type tested panel.
h. Silver tinted or tinted copper joint interfaces are preferred for connections on
busbars.
i.
The busbar compartments and where possible busbar connections are
sealed to avoid ingress of contaminants that might degrade the connection.
j.
Design information relating to the type tested and routine tested busbar
components is made available during tenders to clarify the materials,
manufacturing method, design and manufacturing location for these
components.
5.1.4.17 Spouts, Bushings and Insulators
a. Moulded type bushings and spouts are used as connections between circuit
breaker and busbars (Cable side and Main busbars side).
b. The permissible levels of partial discharge are in accordance with SANS
62271 – 200.
c. All type and routine test documentation is made available during tenders to
clarify the materials used, manufacturing method, design and manufacturing
locations for these components.
5.1.4.18 Insulating Materials
a. The insulation material are identical (Same material characteristics and size)
to the material used during voltage withstand and temperature rise type
testing.
b. Insulating materials can be used in areas where the insulation level criteria
cannot be met with air as an insulating medium.
c. Where insulation on busbars is required, it is of the heat shrink type and
correct size with non-static characteristics.
d. Where insulating barriers are required, the material used is of a non-static
type.
e. Where covers on main power connections are used, they are of the correct
size, easily removable and of robust insulating materials to allow ease of
inspection and maintenance.
f.
Clamping covers with robust insulating bolts and nuts are preferred as to not
disturb the busbar connection when the busbars are inspected.
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5.1.4.19 Auxiliary Wiring
a. The wiring, terminals, lugs, identification and installation shall be in
accordance with 0.00-10341, Sheets 1 to 4 and the requirements of this
specification.
b. All current transformer circuits are wired with PVC 7 strand 4mm² (or multi
strand 2,5mm²) copper wire. The control and voltage transformer circuits are
wired such that the voltage drop does not exceed 1,5% under any conditions.
c. CT and VT wiring shall be coloured as per the phase - red, white, blue and
black (neutral).
d. CT wiring: Wiring between the current transformer and the low voltage
compartment terminals shall be coloured as per the phases – red, white, blue
and black (neutral) with wire numbers.
e. VT wiring: Wiring between the voltage transformer and the first fuse shall be
coloured as per the phases. After the first fuse the AC wiring shall be all black
with wire numbers.
f.
Bus wiring associated with control and voltage transformer circuits is sized to
ensure that voltage limits specified in Schedule A and the current carrying
capacity are not exceeded during the most onerous duty cycle.
g. Alphanumeric ferrule codes are provided on all wire ends shown on the
standard current transformer and voltage transformer circuits and on all bus
wires. All LV wiring is done as per drawing 0.00-10341, Sheets 3 & 4.
h. Bus wiring is terminated on one side of the terminals only. The wiring from
the left panel is the rear lug and that from the right panel the front lug. This
leaves one side of the terminals free for individual panel use only. If more
than two wires are required to be connected on the bus wiring side of the
terminal, an extra set of terminals is placed next to the first two, with bridge
pieces to provide connection points.
i.
Ferrules with wire identification numbers read from left to right (the right way
up) on vertical terminal strips and from top to bottom in all other cases (refer
to drawing 0.00-10341, Sheets 3 & 4). The wire numbering rules as stated in
of NRS 003 are not applicable.
j.
Stripping of insulation is done in such a way that conductors are not
damaged. The stripping tool is of the type that permits the length of the strip
to be pre-set.
k. The crimping tool does not release the termination during normal operating
until the crimp is correctly formed.
l.
All wire ends are terminated using crimp type lugs as detailed on drawing
0.0010341, Sheets 3 & 4. Not more than two conductors are connected to
any single side of a terminal.
m. For control wiring each wire tail is of sufficient length to reach the allocated
equipment plus an additional length of 50mm to facilitate changes in wiring.
The slack appears as close as possible to the component in the form of a
loop.
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n. Wiring presents a neat appearance and is braced and placed in PVC trunking
to prevent vibration and the possibility of forces being exerted on termination
arrangements. Where only a few wires have to be braced (excluding panel
doors) ‘wash line’ supports are used, no stick on plastic bracing supports is
allowed.
o. Wires to plant and material on swing doors are so arranged as to give a
twisting motion and not a bending motion to wires.
p. Wiring passing from the control panel to the control cable compartment does
not pass through live compartments. The totally enclosed metal duct is easily
accessible and metal ducts passing over the top of the cable/busbar
compartment must have removable top (not side) covers.
q. Wires passing through holes in compartments are protected by means of
neoprene grommets. Bevelling of sheet steel is not acceptable as a
substitute.
r.
Wiring which are passing through a live compartment ie cable, busbar etc;
are totally enclosed within a metal duct. Where this wiring is connected to
current transformers adequate protection is provided. Protection for CT and
VT wiring are discussed with the employer and approval is obtained from the
employer.
s. Control wire sheaths are coloured as follows:
-
Black for AC circuits
-
Grey for DC circuits
-
CT and VT wiring are coloured as per the phase - red, white, blue and
black (neutral). After the first fuse the AC wiring is all black.
Dielectric (insulation withstand) test of all wiring is conducted using
2,5kV to earth for 60 seconds.
-
5.1.5
Power Cable Entry and termination
5.1.5.1 Power Cable Termination
a. The cable compartments are adequately sized to allow for termination in air.
b. The distance between cable termination points and adjacent structures within
the compartment shall be in accordance with SANS 876.
c. Provision shall be made to allow for the termination of multiple cables per
phase. It is required to always provide one termination flag per cable to be
terminated.
d. Allowance shall be made inside the cable compartment to install the
termination kits for XLPE MV cables of the same voltage rating as the panel,
unless otherwise specified.
e. All cable fixing bolts and cable lug fixing holes are provided. This
arrangement, together with that for fixing the cable lug to the busbar dropper
tail, is clarified with the Employer prior to proceeding with manufacture.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
f.
Provision is made for terminating all 6,6kV cables using heat shrink
terminations. Cable lug fixing holes are provided as per drawing 0.00/10341,
sheets 1 & 2. Heat shrink termination kits and cable lugs do not form part of
this contract. This arrangement, together with that for fixing the cable lugs to
the busbar dropper tails, is discussed with the cabling contractor prior to
proceeding with manufacture. This arrangement is to the Employer’s
acceptance.
g. The distance from the gland plate or floor to the terminal points is adequate
to allow crossing of cable cores for correct phase sequencing.
h. With three core MV cables, adequate depth in the cable termination
compartment is provided to allow for tandem cable entry rather than side-byside entry.
i.
Provision is made to allow for the bolting of cable lugs of multiple cables to
adequately spread termination points with no more than two cables bolting to
one point i.e. one on the front and one on the back of the termination bar.
j.
Earthing of cable core screens and wire armouring to the earth bar is
provided for.
5.1.5.2 Gland Plates
a. Gland plates are of adequately thickness, cover the total area in the bottom
of the panel, and are mechanically sound and rigid for the cable size.
b. The gland plates are adequately bolted to provide a mechanical sound and
rigid installation.
c. If single core cables are used, the gland plates are manufactured from
aluminium.
d. Number of gland plates for medium voltage cables is required as clarified with
the Employer prior to proceeding with manufacture.
5.1.5.3 Cable Entry Arrangements
a. Cable entries are in accordance with the minimum requirements as per the
SANS 876: distance from terminal centre line to gland plate or cable clamp (if
applicable).
b. Any through wall plates or gland plates mounted between the bushing centre
line and cable clamps, are a minimum distance of 800mm from the bushing
centre line to the through wall plate or gland plate to allow for standard
Eskom three core cable terminations, unless otherwise specified.
c. The provisions of Eskom document 240-56227573, Air-Insulated
Withdrawable AC Metal-Enclosed Switchgear and Control Gear for Rated
Voltages above 1kV up to and including 52kV Standard, Section 5.1.15.3
applies.
5.1.5.4 Vermin and Fire Proofing of Cable Compartment and LV Compartment
a. All cable termination compartments are designed to be sealed off with a 2
hour fire retardant material of at least 50mm thick at floor level, after the
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
cables have been installed, to ensure the IAC integrity of the cable
compartment is maintained.
b. The space provided beneath the switchgear panel in the trench or cable rack
allows for the installation of fire retardant material, to the extent that during an
internal arc in the cable compartment, no pressure release or any smoke or
heat to the front of the panel, the rear of the panel, into the cable trench, onto
the cable rack or tunnel or any adjacent compartments and functional units
will be possible..
5.1.6
Earthing
a. Holes in the switchgear panels provided for connecting the station earth to
the switchboard earthing bar inside the switchgear panels.
b. The switchboard earth bar does not protrude the side walls of the outside last
panel.
c. Provision is made for the switchboard earth bar to be connected to the station
earth mat at least at both ends of the board.
d. If the switchboard exceeds 15m in length, it is connected to the station earth
in at least three places.
e. The earth bar is adequately sized to carry the total fault current of the
switchboard. For any earth bar, it is required to provide 25mm wide earth bar
with a suitable thickness calculated to provide an equivalent fault current
carrying capacity of at least 200A/mm2.
f.
5.1.7
All doors and covers shall be earthed to ensure that the touch potential does
not exceed the safe values as specified in the SANS 10142, Part 1 & 2 and
OHS Act 85 of 1993.
SPECIAL CONSIDERATION FOR INTERNAL ARC PROOF DESIGN
a. Pressure relief flaps in a power compartment are designed such that the
gasses are not directed to any other compartment during an internal arc fault.
b. Each functional unit contains the arc without spreading it to any other
functional unit.
c. Due to the internal arc classification and for maintenance purposes, no VTs
or earthing devices are installed within the pressure relief area on top of any
functional unit.
d. All switchboards with a fault rating of 31.5kA and above are equipped and
type tested with exhausting ducts to channel the hot gasses generated by
internal arc fault to the outside of the substation. All applicable type test and
routine test reports and type test videos are provided during tender
evaluations.
e. The design of switchboard with a fault rating below 31.5kA allows for venting
to the inside of the substation switchgear room subject to Eskom’s
acceptance. In such a case, proof of type test reports and type test videos
are submitted for Eskom tender evaluations.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
f.
Substations with soft ceilings and/or windows, venting is directed to the
outside of the substation via the exhausting duct.
g. IAC requirements are upheld while working in the low voltage compartment.
Hence, the channels or conduits between the power compartments and the
low voltage compartments are sealed accordingly and type tested with the LV
compartment door removed.
5.2
Protection
5.2.1
General
a. The contractor designs the protection system in conjunction with these
stipulations, specifications and submits to Eskom for approval.
b. The standard circuit design facilitates the integration of signals from the
CT’s and VT’s and the interface with circuit breakers to perform various
functions such as protection, control, alarm and monitoring.
c. The IED that can perform at least control, indication and protection
functionalities is used.
d. The IED is also linked to the circuit breakers and earth switches for intertripping and interlocking functions where required.
e. The control circuit is protected as per proven Eskom practice. The
Contractor ensures that there is adequate co-ordination grading between
the mcb’s in the control circuit and also the feeder from the DC supply.
5.3
Intelligent Electronic Devices
5.3.1
Design and Construction
a. Protection schemes for all the power circuits (i.e. incomers, feeders and
others) consist of IEDs constructed as a 19 inch rack mountable unit or
according to Contractor's standard arrangement. No terminals are provided
on the 19 inch rack. Where required, the tails are suitably ferruled with a
minimum length of two meters.
b. All IEDs are equipped with screen or display facility to allow for human
interface. The contents are clearly visible from a distance of 2m and at an
angle of 30° from either side. This display is of the Liquid Crystal Display
(LCD) with anti-glare and non-blinking properties. The IED’s display makes it
possible for the mimic of the circuit protected by the device to be illustrated
on the display. The mimic shows as a minimum the status of circuit breakers
(ON or OFF), status of earth switches, position of circuit breaker (connected
or disconnected) and electrical parameters (voltage, current, power, etc.) for
a particular circuit. The mimic should also display an interlock on a device if
present.
c. Provision is made for the local control of the breakers to be performed from
the associated IED using an integrated control pad for local test purposes
during maintenance only.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
d. LED’s are required for indication of the operation of the alarm and protection
functions within the IED and are an integral part of the device. The allocation
of the LED’s to the different functionality is configurable to allow for flexibility
during the engineering phase.
e. Split face IED’s, whereby the digital display is mounted on the door of the LV
compartment and connected to the main processing unit by means of fibre
optic cable, are preferred.
f.
The devices are equipped with ports to allow for access to information via a
communication link. These ports have the capacity that matches the data
transfer requirements for the associated communication bus.
g. A label stating the firmware version is fixed to all IED’s. Information regarding
the estimated data retention time of the storage medium used in the IED’s is
provided to the Employer.
5.3.2
Functions
a. The protection, control, indication and data capturing functionalities are
provided by the IED’s.
All functions, settings and internal logic are
programmable through the IED software and a personal computer (PC),
except where otherwise stated.
b. The Contractor specifies and gives written details of protection functionalities
that are inherently part of their IED’s but are not required by the performance
specification.
c. A single IED is able to provide all the required main and back-up protection
functions for the scheme in question as a minimum. The control and
indication functions are also incorporated in the IED’s.
d. The integration of the auxiliary functions such as the DC Fail and Trip Circuit
Supervision (TCS) functions within the device is preferred. The IED’s have a
self-monitoring function of both integral hardware and software that is done
on a continuous basis. Any fault or irregularity is immediately alarmed to an
output contact.
e. The random switching of the DC auxiliary supplies at high rate does not affect
the functionality of the IED.
Where required, the internal battery
requirements for numerical IED’s (i.e. battery lifetime, type of battery etc.) is
stated on a label attached to the front of the numerical device.
f.
Unless otherwise specified, all IED’s are provided with manual-reset
operation indicators for each function of the IED. These do not operate until
the IED’s have operated. Resetting is accomplished without opening the
case.
g. The IED’s have disturbance or event recording and data logging capability
with the integral storage media. The information stored in the IED is
accessible via the communication port. Information regarding the estimated
data retention time of storage medium of the IEDs is provided to the
Employer.
h. All IED’s have the capability to perform control, indication or monitoring,
interlocking and data transfer functions via a communication bus. The IED’s
communication capability complies with IEC 61850 standard.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
5.3.3
Software
a. Software installed on the IED’s for event or disturbance recordings, data
logging, settings and marshalling or configuration is accessible via a
dedicated communication link using engineering tools. This software allows
information to be downloaded in COMTRADE format in accordance with IEEE
C37.111-1991. All software required to perform the marshalling and settings
of the IED’s is contained in one package.
b. The Contractor supplies evidence, on request, in the form of reports from a
mutually acceptable third party that an adequate formal specification for the
software has been produced. The specification is based on a requirement
document and comprehensive risk analysis. The software is formally verified
to ensure that it matches its specification.
c. All software purchased on any contract and subsequent software upgrades
supports the latest Microsoft Windows operating system. The Contractor
informs the Employer of any and all new releases. The latest software
version is always compatible with the installed base of IED’s, which originally
were compatible with the previous version of software that was compatible
with the previous Microsoft Windows operating system. For example, if the
existing software is only compatible with Windows 95, it is upgraded to
Windows 7 (the latest Microsoft supported operating system).
d. All software and firmware are backward and forward compatible (i.e. the
software for this contract is such that all future versions of software will be
compatible with the installed base of IED’s).
5.3.4
Analogue Voltage and Current Inputs
a. The current inputs of the devices are rated at 1A.
b. Where required, the voltage inputs are rated at 110V AC, unless otherwise
stated.
c. The IED is also provided with the digital inputs for the control and indication
functions as determined by the schemes.
d. The configuration of the inputs is programmable. The minimum number of
inputs required is provided in the C&I Interface Signals for MV Switchgear.
5.3.5
Output Contacts
a. All output contacts of the IED’s have self-resetting capabilities, except for
those linked to master trip and lockout functions, which have manual-reset
capabilities.
b. Each protection scheme has at least two output contacts for tripping.
c. The IED is also provided with the digital outputs for the control and indication
functions as determined by the schemes.
d. The configuration of the device’s outputs is programmable. The minimum
number of outputs required is provided in the C&I Interface Signals for MV
Switchgear. Where required, some of the trip, alarm and indication outputs
are channelled via the communication ports.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
e. DC Fail and under voltage protection functions are facilitated by normally
closed contacts. All other relays have normally open contacts.
5.3.6
Testing of Devices
a. The protection devices are subjected to routine and type tests which cover at
least the tests recommended in standard 32-333. The program of routine and
type tests is submitted to the Project Manager for acceptance.
b. Unless otherwise specified, all IED’s are provided with suitable test facilities
for VT and CT circuits to enable tests carried out on the IED’s while in
position inside the panel without disconnecting any wiring or links. Test
facilities are provided in accordance with standard 240-56358929, Standard
for Electronic Protection and Fault Monitoring Equipment for Power Systems.
c. Two copies of all test certificates are submitted to the Employer for
acceptance on completion of the tests.
5.3.7
Buszone Protection Relay
a. The latest Eskom approved relay list applies and is adhered to with the
selection of the relay types.
b. Bus zone protection is implemented by utilising a numerical differential relay.
These devices comply with the requirements of 240-56358929, Standard for
Electronic Protection and Fault Monitoring Equipment for Power Systems as
a minimum.
c. Only a low impedance scheme is acceptable. The Contractor provides
details of the CT requirements. CT selection methodology is required to be
submitted to the employer for acceptance.
d. All devices are fitted with contacts which are self-resetting with exception of
the tripping function.
e. The devices are provided with hand-reset operation indicators for each of the
functions. The indicators do not operate until the relays have closed their
contacts. Re-setting is accomplished without opening the case.
f.
The protection schemes are provided with suitable test facilities to enable
tests to be carried out on the device while in position on the panel without
disconnecting any wiring.
g. The bus zone protection equipment is housed in separate panels designed to
accommodate 482.6mm (19 inch) type racks or the Contractor’s standard
arrangement. The panels are constructed in accordance with Eskom
Standard number 240-56358929, Standard for Electronic Protection and
Fault Monitoring Equipment for Power Systems.
h. Auxiliary power for the bus zone protection device will be provided by the
Employer at 220VDC nominal voltage rating from an external DC power
supply system. The AC power supply for the cubicle lighting will also be
provided by the Employer.
i.
DC line filters are installed in the bus zone system such that it protects the
electronic components against voltage spikes.
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5.4
Arc Detection System
5.4.1
Protection Relays
a. The arc protection function is provided by a device that accepts both light and
current signals as input. These signals are detected simultaneously to initiate
a trip and alarm.
b. The arc protection relay performs the high speed tripping of the supply circuit
breaker in the event of an arc fault when the current exceeds a pre-set
reference value. The device have a maximum sensor detection function
pulse delay time of less than 5ms and subsequently issues a breaker trip
pulse in a time of less than 10ms from fault inception. The total (including
breaker and arcing time) fault clearance time required is less than 100ms
from fault inception.
c. All devices are fitted with contacts which are self-resetting with exception of
the tripping function.
d. DC line filters are installed in the arc detection system such that they protect
the electronic components against voltage spikes.
5.4.2
Light Sensors
a. Arc detection is performed with light sensitive type elements located in the
respective switchgear chambers (including segregated busbars between
panels). The elements are installed in such a way that they completely cover
the space to be protected.
b. The light sensors are not triggered by external light sources such as camera
flashes or welding arcs.
c. The sensor has the degree of protection to operate within the boards’ internal
environmental conditions.
5.4.3
Monitoring
a. The internal arc protection system has a self-diagnostic (self-monitoring)
function that prevents the relays from operating if a system (i.e. devices and
sensors) fault is detected. It clearly indicates by means of an alarm indicator
the fault and the location thereof.
b. The system gives an indication of the fault location (i.e. which compartment
faulted) locally at the switchgear panel through an IED and remotely on the
dedicated engineering station.
c. The power supply modules are continuously monitored and should provide an
alarm in the event of failure.
5.4.4
Auxiliary Relays
a. Where required, the auxiliary relays are provided with the desired trip or
indication function with the operation time of less than 50ms. The auxiliary
relays must comply with the requirements of 240-56358929, Standard for
Electronic Protection and Fault Monitoring Equipment for Power Systems.
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b. Unless otherwise specified, all the relays are provided with manual-reset
operation indicator/s for the dedicated function. The indicator/s does not
operate until the relay has operated. Resetting is accomplished without
opening the case.
c. Each relay has at least two output contacts for tripping and two output
contacts for external alarms.
5.5
Protection Schemes
5.5.1
Motor Protection Scheme (Motors ≥ 1 MW)
a. Protection scheme is provided for all feeders to the MV motors with power
rating larger or equal to 1MW. Each scheme includes the following functions:
-
motor differential protection,
-
three-phase thermal overload protection,
-
three-phase definite time overcurrent protection,
-
three-phase IDMTL overcurrent protection,
-
definite time earth fault element,
-
IDMTL earth fault protection.
-
negative phase sequence protection,
-
three phase undervoltage protection,
-
motor stall protection element.
b. In addition, the schemes have binary Input/output (I/O) facilities as well as
analogue outputs. These input facilities are for external trip and close signals
and to enable thermistors to decrease the tripping time of the overload
elements. The trip outputs are latched.
c. The protection elements have setting ranges. The characteristic curves of
IDMTL overcurrent and earth fault protection elements conform to IEC
standards.
d. Thermal overload protection monitors the current flowing into the motor.
Based on these currents, it models the temperature inside the motor.
e. Negative phase sequence protection function is made available in the motor
protection scheme. This function protects the motor against overheating
caused by induced double frequency currents.
The negative phase
protection has an inverse and a definite time characteristics.
f.
Motor stall protection function is available in the motor protection scheme.
This function is preferably an overcurrent protection element set below the
locked rotor current and a time delay set to the stall capability time of the
motor. The time delay is adjustable over the range.
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g. Three-phase definite time undervoltage protection function is made available
in the motor protection scheme. This function does not operate for the loss
of a single-phase VT supply but only operates for the loss of all three phases
after a predetermined period. The undervoltage protection function trips the
motors for a sustained under voltage condition. The protection elements are
energized from voltage transformers with secondary of 110V phase-to-phase
and 63.5V phase-to-neutral. The elements are adjustable to operate in the
voltage ranges and have drop-off/pick-up ratios greater than 95%. Setting
adjustment is preferably continuously variable, but if adjusted in steps, these
do not exceed 10%. The time delay is adjustable over the range.
h. Other functions required in the motor protection scheme such as current
interlock, long starting time, etc. are indicated in.
i.
5.5.2
The Contractor provides output analogue signals (i.e. current and power)
from the IED’s. The Contractor provides separate measurement modules
(i.e. transducers) for both current and power. Alternatively, the measurement
modules are provided as an integral part of the protection IED in accordance
with 240-56535964, Generation MV and LV Protection Philosophy for Eskom
Power Stations. The Contractor also provides in the Rates Price Schedule
both the take out price for having separate measurement modules, as well as
the price for transducers provided as an integral part of the IED.
MV Interconnector Protection Scheme
a. Interconnector protection schemes include the following functions:
-
line differential protection,
-
three-phase definite time overcurrent protection,
-
three-phase IDMTL overcurrent protection,
-
definite time earth fault protection, and
-
IDMTL earth fault protection.
b. The overcurrent and earth fault elements (i.e. IDMTL or definite time) are set
as main protection for the interconnector and back-up protection for
downstream circuits.
c. The Contractor specifies and supplies the fibre optic or pilot wire cables,
which are suitable for the cable differential protection, to be installed by the
Employer.
Fibre optic links are preferred for differential protection
application.
d. A synchronism check facility is provided for the changing of power supplies
on a MV board, which is feeding from different sources. The synchronism
check facility measures the three phase voltage quantities from the cable and
busbar VT’s. Once the three voltages are the same, in phase, magnitude,
phase rotation and frequency, a closing signal is issued to the breaker of the
normal supply and an open to the alternative supply after a period not
exceeding 100ms. This is done to ensure the make-before-break operation.
Different set parameters are required.
e. A typical switching or operating procedure for the power transfer is as follows:
Close the unit supply breaker (with unit supply cable VT alive) to energize the
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busbar (busbar VT dead and station supply breaker opened with station
supply breaker cable VT dead). Vice versa is also applicable. This is a ‘Live
line’, dead bus charge.
f.
The protection elements have setting ranges. The characteristic curves of
IDMTL overcurrent and earth fault protection elements conform to IEC
standards.
g. The Contractor provides output analogue signals (i.e. current and voltage)
from the IED’s. These measurement modules are an integral part of the
protection IED in accordance with 240-56535964, Generation MV and LV
Protection Philosophy for Eskom Power Stations. The Contractor also
provides a takeout price for having separate measurement modules (i.e.
transducers) in the Rates Price Schedule.
5.5.3
Transformer Feeder Protection Scheme (Transformer < 10 MVA)
a. Protection scheme for the feeders of the transformer with the power rating
smaller than 10MVA includes the following functions:
-
three-phase definite time overcurrent protection,
-
three-phase IDMTL overcurrent protection,
-
definite time earth fault protection, and
-
IDMTL earth fault protection.
b. The IDMTL overcurrent and earth fault are set as main protection for the
transformer / feeder and back-up protection for downstream circuits.
c. In addition, the IED’s have binary input facilities. These input facilities cater
for external alarm and trip signals such as Buchholz, winding temperature, oil
temperature and pressure relief protection. A minimum of eight binary inputs
are required.
d. The protection elements have setting ranges. The characteristic curves of
IDMTL overcurrent and earth fault protection elements conform to IEC
standards.
e. The Contractor provides output analogue signals (i.e. current) from the IED’s.
These measurement modules are an integral part of the protection IED in
accordance with 240-56535964, Generation MV and LV Protection
Philosophy for Eskom Power Stations. The Contractor also provides a
takeout price for having separate measurement modules (i.e. transducers) in
the Rates Price Schedule.
5.5.4
MV Incomer Protection
a. Incomer protection scheme have the following functions:
-
three-phase definite time undervoltage protection,
-
three-phase definite time overcurrent protection,
-
three-phase IDMTL overcurrent protection,
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-
definite time earth fault protection,
-
IDMTL earth fault protection.
b. The overcurrent and earth fault protection is utilised to provide the required
current input for the arc detection interlock and also act as back-up protection
for downstream circuits.
c. A synchronism check facility is provided for the changing of power supplies
on a MV board, which is feeding from different sources. The synchronism
check facility measures the three phase voltage quantities from the cable and
busbar VTs. Once the three voltages are the same in phase, magnitude,
phase rotation and frequency, a closing signal is issued to the breaker of the
normal supply and an open to the alternative supply after a period not
exceeding 100ms. This is done to ensure the make-before-break operation.
Different set parameters are required.
d. A typical switching or operating procedure for the power transfer is as follows:
Close the unit supply breaker (with unit supply cable VT alive) to energize the
busbar (busbar VT dead and station supply breaker opened with station
supply breaker cable VT dead). Vice versa is also applicable. This is a ‘Live
line’, dead bus charge.
e. In addition, the IED’s have binary input and output facilities in accordance
with the scheme requirements for external trip signals.
f.
The protection elements have setting ranges. The characteristic curves of
IDMTL overcurrent and earth fault protection elements conform to IEC
standards.
g. The Contractor provides output analogue signals (i.e. current and voltage)
from the IED’s. These measurement modules are an integral part of the
protection IED in accordance with 240-56535964, Generation MV and LV
Protection Philosophy for Eskom Power Stations. The Contractor also
provides a takeout price for having separate measurement modules (i.e.
transducers) in the Rates Price Schedule.
5.6
Arc Protection Scheme
5.6.1
General
a. The system protects the segregated breaker, busbar and cable chamber
respectively in the case of an internal arc fault for air insulated MV
switchgear.
b. The main protection device is mounted on the board incomer panels with the
auxiliary devices in different panels as required.
5.6.2
Current Detection Methods
a. A three-phase CT connection from the board incomer or upstream feeder
overcurrent and/or earth fault function is provided together with an arc
sensing device (two-out-of-two measuring criteria). The current rating of the
input to the device is 1A.
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b. An overcurrent or earth fault signal is activated once the current on any one
phase exceeds the reference values. This function has the capability to
capture and display the three phase currents that caused the protection
operation. The system is able to provide arc protection with low fault currents
as well (i.e. smaller than 4kA fault current).
c. Detection of overcurrent conditions is implemented to increase the stability of
the detection system under normal conditions. This feature ensures that the
system does not act on incidents where light is emitted without the existence
of excessive current in the circuit concerned.
5.6.3
Circuit Breaker Failure Protection
a. The circuit breaker failure protection facility is provided by the arc protection
system to trip the upstream feeder circuit breaker in case of an incomer
breaker failure.
b. A time delay of 100ms is allowed for the main circuit breaker to operate
before the breaker fail protection operates the upstream circuit breaker.
c. The total tripping time does not exceed the switchgear internal arc test time,
Tt (as defined in SANS 62271-200).
5.6.4
Busbar Chamber Protection
a. The function of this application is to detect and clear internal arc faults in the
busbar chamber on a particular board. When any of the light sensors on the
board detect an arc together with an overcurrent or earth fault current on the
incomer feeder, it trips the incomer feeder, bus section breaker and all the
feeder circuit breakers of the relevant zone.
b. The internal arc detection devices are applied to overlap in the bus section
chamber, thus tripping only the faulty zone for an internal arc fault in the bus
section chamber.
5.6.5
Protection of Circuit Breaker Compartment
a. The function of this application is to detect and clear internal arc faults in the
circuit breaker chamber.
b. Where multiple tripping is required the arc sensing devices detect an arc
together with an overcurrent or earth fault current from the incomer feeder, it
trips the incomer feeder, bus section breaker and all the feeder circuit
breakers of the relevant zone.
5.6.6
Protection of Cable Termination Compartments
5.6.6.1 Feeders
a. The function of this application is to detect and clear internal arc faults in the
feeder cable chamber.
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b. Where multiple tripping is required the arc sensing devices detect an arc
together with an over current or earth fault current from the incomer feeder it
trips the incomer feeder, bus section breaker and all the feeder circuit
breakers of the relevant zone.
5.6.6.2 Incomers
a. The function of this application is to detect and clear internal arc faults in the
incomer cable chamber.
b. Where multiple tripping is required the arc sensing devices detect an arc
together with an over current from the upstream feeder it trips the upstream
feeder circuit breaker.
5.6.7
Buszone Protection Scheme
a. The bus zone protection scheme is designed to protect the breaker, busbar
and cable chamber respectively in the case of a three phase bolted fault for
air insulated MV switchgear. The protection scheme is based on basic
operation principles of low impedance differential current measuring system.
b. The function of the bus zone protection system is to perform fast clearance of
phase to phase and phase to earth faults. The supply breaker and all feeder
breakers are tripped in the event of a fault and current exceeding a pre-set
reference value.
c. A check feature such as integral circuit supervision is included to prevent
tripping of bus-zone protection if any of the current transformer circuits
become disconnected during normal load conditions. Alarm contacts operate
under these conditions to initiate a remote alarm.
d. A testing system, consisting of current isolation and measuring facilities at the
input from each current transformer, and facilities for short-circuiting the
current transformer circuits, when they are isolated from the protection
system, is included.
e. The detailed system description (i.e. specification, layouts and circuit
diagrams) and test procedures for the bus-zone protection system is provided
in the tender documents.
f.
The Project Manager may request the Contractor to check whether the bus
zone protection is stable under external fault conditions.
g. The protection CT core is fed onto standard switchgear terminals and then to
the CT test block and protection device measuring elements with overlapping
of the bus section CT cores.
h. The boards requiring single or double zone tripping.
5.6.8
DC Fail Function
a. DC Fail function is provided to monitor the DC supplies of all the protection
schemes at the last supply point.
This functionality can either be
incorporated in the IED, if a separate power supply is available, or a
dedicated auxiliary relay.
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b. The function allows for operating on loss of DC voltage. Alarm output signal
is also transmitted to the DCS system and indicated on the IED, if separate
suppliers are used.
5.7
Circuit Breakers
5.7.1
General
a. Circuit-breakers are of the triple-pole withdrawal type with visible indication of
the circuit breaker state, which is mechanically interlocked with the circuitbreaker.
b. The arc-quenching medium and/or insulation are of the type as specified.
c. No oil circuit breakers are acceptable.
d. Withdrawable circuit breakers are housed in a circuit-breaker compartment of
the panel. The design is of the behind close door design.
e. Emergency operating of the circuit-breaker complies with the behind close
door design.
f.
Total current interruption (break) time as defined in SANS 62271-100 is not
greater than the time duration specified, under all operating conditions.
g. Where circuit-breakers are used, the power connecting arms are fully
insulated. Bare copper as connecting arms are not acceptable.
h. Where bus-zone protection is required, the bus-section circuit-breaker design
shall allow for the installation of current transformers on each side of the bussection circuit- breaker.
i.
Where vacuum interrupters/SF6 are used in the circuit-breaker design, only
the type tested vacuum interrupter design or product specific code as per the
type test report designation shall be offered during tender evaluation.
j.
Circuit breakers are provided as per the scope of work of these
specifications.
5.7.2
Inter-changeability
a. Circuit breakers with the same current rating, type and auxiliary contact
configuration are interchangeable.
b. It is not possible to interchange a circuit breaker with a lower current rating
into a compartment with a higher current rating.
5.7.3
Circuit-breaker truck connections
a. Where the auxiliary connections between the circuit-breaker truck or trolley
and the circuit breaker compartment are made by means of flexible
connections, these are contained in a flexible conduit.
b. If metallic conduit is provided, this shall be covered by an approved insulating
material, however non-metallic robust flexible conduit is preferred.
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c. A means is provided to retain the flexible connection out of the path of the
circuit-breaker when the truck or trolley is inserted into and removed from the
circuit breaker compartment.
5.7.4
Shutters
a. Automatically-operated shutters are provided so that on racking out the
circuit-breaker, these shutters cover the busbar and circuit spouts
automatically and fully to prevent inadvertent contact with live busbars and
circuits.
b. Circuit spouts shutters are arranged to operate independently from the
busbar spout shutters.
c. These shutters are capable of being padlocked in the open and closed
position.
d. Shutters operate without lubrication and are constructed in such a manner as
to ensure fail-safe operation.
e. Shutter endurance and reliability is proven by type testing to the number of
operations as specified in Schedule A attached to Annexure 1.
f.
Busbar spout shutters are colour coded red and labelled with the word
“BUSBAR” in black letters at least 50mm high.
g. Circuit spout shutters are coloured yellow and labelled with the word
“CIRCUIT” in black letters at least 50mm high.
h. Shutters are of robust, rigid and durable design and is capable of the lasting
the live of the switchgear.
i.
5.7.5
Busbar and circuit shutters operate smoothly without the aid of lubricants.
Mechanisms
a. Mechanisms as per SANS 62271-1, SANS 62271-100, SANS 62271-102 and
SANS 62271-200 are provided.
b. All conventional circuit-breakers and actuator circuit-breakers electricallyoperated closing devices including mechanism charging motors are suitable
for operation at any voltage between 85% and 110% of nominal control
voltage measured at the terminals of the device.
c. The circuit-breaker closes correctly when an electrical closing pulse of 100ms
duration is applied to the closing coil.
d. The total power drawn by the closing coil, excluding closing solenoids, does
not exceed 1200VA per circuit-breaker.
e. All operating coils of solenoid coil contactors are continuously rated, and the
contacts are rated for a short duration in accordance with the current drawn
for the operating time.
f.
A normally-closed auxiliary contact is to be wired in series with the closing coil
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5.7.6
Tripping Devices
a. All conventional circuit-breakers and actuator circuit-breakers electric tripping
devices are of the shunt type, suitable for operating at any voltage between
85% and 110% of the rated control voltage measured at the device terminals.
b. Two normally-open auxiliary contacts in parallel are included per tripping
circuit in series with the trip coil.
c. Circuit-breakers design makes provision for the installation of a second
tripping coil as per the voltage specified. This second trip coil forms an
integral part of the design of the circuit-breaker complete with interlocking.
d. Circuit-breakers design makes provision for the installation of an under
voltage release coil as per the voltage specified.
e. This under voltage release coil forms an integral part of the design of the
circuit-breaker complete with interlocking operating below 35% of nominal
voltage.
5.7.7
Indicating Devices
a. A positive driven mechanical indicating device to show whether the circuitbreaker is open or closed is provided. The devices are labelled as follows:
-
ON or I - white lettering on a red background
-
OFF or O - white lettering on a green background
b. Lettering size shall not be less than 10mm, are easily readable and cannot be
removed unless force is applied.
c. The method of securing the labels is as per the requirements of this
specification.
d. Where the circuit-breaker position is not visible from the front of the panel, a
positive driven mechanical indicator is provided to indicate whether the
circuit-breaker is in the service or disconnected position, or state the position
of the integral-connected disconnectors, whichever is applicable.
e. All mechanical indicators shall be clearly visible from the front of the panel
and are type tested for the number of operations of the operating device to
prove the reliability of the indicating mechanism.
5.7.8
Auxiliary Contacts
a. Auxiliary contacts of the circuit breaker are readily accessible and the
preference is contacts with a pronounced wiping action.
b. Sufficient auxiliary contacts are provided as per the schematic drawings and
the requirements for spare contacts.
c. The spare contacts are easily convertible from normally open to normally
closed and vice versa and are wired to the outgoing control terminals.
d. Auxiliary contacts positively follow the action of the main contacts.
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e. Suitable arrangements are made to ensure that circuit-breaker auxiliary
contacts only signal the change of state when the circuit-breaker is in the
service and disconnected position.
f.
5.7.9
Where insufficient contacts are available, a continuously rated slave relay are
provided but is used for indication circuits only.
Control Connector
a. Control connectors are of the multi-pin design with removable pins for male
and female connectors.
b. Where connectors are of the off load design, this implies that the control
circuit are designed to take into consideration easy isolation of all supplies to
the circuit-breaker to connect or disconnect the control connector off load.
c. Control connectors have the facility to be coded to differentiate between
different circuit-breaker types, ratings and functions or protection schemes for
the same rated circuit-breakers.
5.7.10 Insulation Level
a. The insulation level of all circuit-breakers, busbars, busbar connections and
any other related components are in accordance with the values specified.
b. The use of insulation material barriers for phase segregation to increase the
insulation level are not acceptable if not type tested. Documented proof is
supplied to the employer.
c. No insulation material are used that may lead to material ageing and
degradation for the insulation levels specified over time, or may lead to partial
discharge of the panel due to ageing or possible dust collection.
d. Where insulating materials are part of the integral design of the switchgear,
the life expectancy is guaranteed by means of testing where applicable and
material data sheets for the prescribed installation conditions.
5.8
Earthing Devices
5.8.1
General
a. The switchgear design includes busbar and cable earthing devices as an
integral part of the associated functional unit/switchgear board.
b. Earthing devices are an earthing switch function except for cases where the
circuit-breaker is used as the earthing making device.
c. All earthing devices are operated from the front and outside of the panel. No
other method allowed.
d. Provisions are made for a mechanism that enables padlocking in both the
“ON” and “OFF” positions to inhibit operation of the earthing devices.
e. Interlocks are provided in accordance with SANS 62271-200.
f.
Earthing of cables or busbars via the enclosure and supporting structures are
be acceptable.
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g. The earthing device position indicator is visible from the front of the panel. A
positive driven mechanical indicating device to show whether the earthing
device is open or closed is provided.
h. Earthing devices are of sound and robust design.
5.8.2
Busbar Earthing Devices
a. Busbar earthing devices are provided for the main busbars of the switchgear
boards.
b. Busbar earthing devices are used to provide connection between all three
phases of the main busbars and main earth bar through isolating bushings
where applicable.
c. The busbar earthing device may not be mounted in the busbar compartment.
d. It is not possible to connect the main busbars to earth if the main busbars are
alive. Provisions are made to accommodate this requirement.
e. A positive driven mechanical indicating device to show whether the main
busbar earth is applied or not is provided. The devices are labelled as follows:
f.

ON or I - white lettering on a red background

OFF or O - white lettering on a green background
Lettering size shall not be less than 10mm, are easily readable and cannot be
removed unless force is applied.
g. The method of securing the labels is as per the requirements of this
specification.
5.8.3
Cable Earthing Device
a. Cable earthing switches are provided for all incoming and feeder, motor drive
and transformer circuit panels.
b. Interlocking is required for the cable earthing device to be applied before the
cable compartment door or cover can be opened.
c. Interlocking is also be provided for utilizing the cable live indication system
(VDS) to prevent closing of the earthing switch onto live cables.
d. Cable earthing devices are connected between all three phases of the cable
terminals and main earth bar.
e. A positive driven mechanical indicating device to show whether the cable
earth is applied or not is provided. The devices are labelled as follows:
f.
-
ON or I - white lettering on a red background
-
OFF or O - white lettering on a green background
Lettering size shall not be less than 10mm, are easily readable and cannot be
removed unless force is applied.
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g. The method of securing the labels is as per the requirements of this
specification.
5.9
ACCESSORIES
5.9.1
Current Transformers
a. Each functional unit is equipped with current transformers.
b. Current transformers comply with SANS 61869-2.
c. Current transformers are installed inside the associated functional unit such
that they are easily accessible and removable. Their mounting arrangements
are such that it does not interfere with the cable connecting arrangements.
d. The short-time withstand current rating of current transformers are not be
less than that of the associated circuit-breaker.
e. Secondary windings of current transformers are earthed at one point only.
f.
Each group of current transformers (i.e. protection, metering etc.) are earthed
to the earth bar using isolating links. The isolating links is not be removable
from the terminal.
g. All current transformers are of air-cooled design and the cooling is through
natural flow of air.
h. Additional rating plates made of a durable material are provided with
markings as per SANS 61869-2.
i.
The securing of the name plates is rigid and sound. Glue is not acceptable
as a medium to secure the nameplates.
j.
The information on the additional rating plates is duplicated from that
appearing on each current transformer and is located within the low voltage
compartment in a position giving easy visibility and on the inside of the cable
compartment.
k. The phase colour with which each current transformer is associated appears
beneath each rating plate.
5.9.2
Voltage Transformer
a. VT’s comply with SANS 61869-3.
b. VT’s are of the resin encapsulated type and air-cooled design. The cooling is
through natural flow of air.
c. VT’s are of the single-phase design, where applicable for motor starter
panels.
d. Busbar connected VT’s panels are of the withdrawable type and cable VT’s
are of the fixed type. No primary fuses are required for fixed type cable VT’s.
e. VT’s are interchangeable for individual phases.
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f.
The primary side of busbar connected VT panels are connected to the
busbars via adequately rated HRC fuses. It is not possible to gain access to
these HRC fuses with the VT in the service position.
g. The busbar connected VT is of the plug-in type and arranged such that it can
be isolated and removed without affecting the associated circuits.
h. When VT’s are withdrawn, the spouts are closable by means of automatic
shutters. The shutters shall have padlocking facilities.
i.
Provision are made to enable locking of the busbar connected VT in the
“service” position.
j.
All VT’s are star primary and star secondary connected.
earthed at both the primary and secondary star points.
The VT’s are
k. The circuit on the secondary side of the VT is protected with the use of either
fuses or mcb’s.
l.
The protection devices are mounted on the VT in order to include the wiring
from the VT to the LV compartment in the protected circuit.
m. The secondary fuses of the cable VT is easily accessible without any danger
of having to work in a live chamber. No fuses or mcb’s are fitted in a phasecircuit that is connected to earth.
n. The VT is connected to the earth bar by means of isolating links.
isolating links are removable from the terminal by use of a tool.
The
o. The links are accessible and safe to remove with the VT racked out.
5.9.3
Indicating and Measurement Instruments
a. All instruments are of the flush-mounting industrial type in accordance with
IEC 60051 for indicating instruments of Class 1.5 category.
b. Instrument test blocks/terminals are provided on the front of the relevant low
voltage compartment to facilitate connecting of external instruments in the
various current and voltage transformers secondary circuits.
c. Test blocks/terminals have terminal strips and links for performing the various
short-circuiting and bridging functions.
d. Test blocks/terminals have removable covers, which are secured in position.
e. The type of test block that will be used are approved by the employer.
f.
Transducers shall conform to IEC 60688.
g. Transducers are of the type approved by the employer and are available on
the market for the lifetime of the switchgear.
5.9.4
Selector Switches
a. Selector switch are of the pistol-grip type.
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b. The selector switches complies with 240-56358929.
5.9.5
Cable Live Indicators
a. Cable live indicators are installed on all outgoing and incoming cable and
transformer circuits.
b. Cable live indicators comply with SANS 61243-5.
c. Cable live indicators are of the fixed type.
5.10 Terminals
5.10.1 Material and Construction
Terminals are in accordance with 240-56358929, of the types as shown on
drawing 0.00-10341 Sheet 1 and 0.00-10341 Sheet 3 and adhering to the
limitations as indicated on the drawing.
5.10.2 Mounting
Rail mounted terminal blocks comply with the requirements for the
dimensions of mounting rails in accordance with 240-56358929.
5.10.3 Types
a. The terminal types are selected for voltage and current rating application in
accordance with Eskom document/drawing 240-56358929.
b. Instrument test blocks or terminals are provided in the relevant low voltage
compartment to facilitate connecting of external instruments in the various
current and voltage transformer secondary circuits.
c. The test block or terminals are accessible from the front of the terminal
without opening the low voltage compartment door.
d. Test blocks and terminals have terminal strips and links for performing the
various short-circuiting and bridging functions.
e. Test blocks and terminals are equipped removable covers, which are secured
in position.
5.10.4 Wiring and Cable Lugs
a. Control wiring lugs and their application with different types of terminals are in
accordance with 240-56358929 and as detailed on Drawing 0.00-10341
Sheets 1 to 4.
b. Crimping on of power lugs are in accordance with BS 4579.
c. Crimping tools
specifications.
are
re-calibrated
according
to
their
manufacturer’s
d. The crimped area shall be equal to the conductor square area.
e. With the lug in position, no bare copper are visible after the crimp.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
f.
Wiring presents a neat and professional appearance.
5.11 Labels
a. All labels are in accordance with labelling specifications found in 0.00-10343
Sheets 1 and 2.
b. Labels are inscribed in English.
c. The content of the label shall be provided by Eskom following the relevant
plant codification standard.
5.12 Nameplates
a. Each switchboard is provided with a nameplate which complies with the
specifications found in 0.00-10343 Sheets 1 and 2.
b. The nameplate covers the following:
-
Manufacturer.
-
Date of manufacture.
-
Fault level of the board’s main busbars.
-
IP rating of the board.
-
Rating of the main busbars.
I
-
Rated voltage
Ur
-
Rated lightning impulse withstand voltage 2)
Up
-
Rated switching impulse withstand voltage 2)
Us
-
Rated power-frequency withstand voltage2)
Ud
-
Rated normal current
Ir
-
Rated short-time withstand current
Ik
-
Rated peak withstand current
Ip
-
Rated frequency
fr
-
Rated duration of short circuit
tk
-
Rated auxiliary voltage
Ua
-
Rated filling pressure (density) for insulation pre
(ρ re)
-
Rated filling pressure (density) for operation prm (
ρrm)
-
Alarm pressure (density) for insulation pae
(ρae)
-
Alarm pressure (density) for operation pam
(ρam)
-
Minimum functional pressure (density) for insulation pme
(ρme)
-
Minimum functional pressure (density) for operation pmm (ρmm)
kA
c. The nameplates are secured on the incomer circuit of each board.
d. The securing of the nameplates are done in such a way that force must be
applied to remove the nameplate.
e. Glue is not an acceptable method of securing the nameplates.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
5.13 SWITCHGEAR INTERLOCKING SYSTEMS
Mechanical interlocks are provided for the withdrawable circuit-breakers to
ensure that:
a. The circuit-breaker can only be engaged and disengaged to/from the service
position when the circuit-breaker main contacts are fully open.
b. The circuit-breaker can only be operated when it is in the service, or
disconnected/withdrawn position.
c. The circuit-breaker compartment front door is trapped in the close position
and cannot be removed/opened when the circuit-breaker is in the service
position and during racking of the circuit-breaker.
d. Integral earth switches, if fitted, cannot be closed unless the circuit-breaker is
in the disconnected position and cable VDS indication is dead.
e. Busbar selection in a switchboard, if applicable, is only possible when the
circuit-breaker is open.
f.
For flexible auxiliary connections, the multi-pin connector must be engaged
and the control supply switched on to enable the circuit-breaker to be placed
in the service position.
g. Circuit-breakers cannot be closed or racked into service position unless the
cable earth switch is in the open position.
h. Busbar earthing is only possible when all busbar supply, board
interconnecting circuit-breakers and circuit-breakers of transformer feeders
are in the disconnected position.
i.
With the circuit-breaker in the disconnected position and the circuit-breaker
compartment door open the circuit-breaker cannot be moved from the
disconnected position to the service position.
j.
The cable compartment door can only be open if the earth switch is in the
earthed position (i.e. earth switch applied).
k. The requirements for non-mechanical interlocks shall conform to required
operating philosophy presented by Eskom, defined schematic drawings and
SANS 62271-200.
l.
Where blocking magnets are used as part of the system interlocking, the
rating of the blocking magnets shall be continuously rated and shall comply
with the control voltage rating and variations.
m. Where electrical system interlocking is preferred, the details shall be
specified by Eskom.
n. Where castle keys are used, the provisions of these specifications are taking
preference.
-
The design of the castle key system are such that the incomer circuit
breaker, the interconnector circuit breakers of both boards and the
transformer circuits that are in a RM circuit must be isolated before a
busbar earth can be applied.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
5.14 Testing and Documentation of Test Reports
5.14.1 Type Test
a. Only type tested functional units are acceptable for use in this project. The
type tests are carried out on all types of functional units in accordance with
SANS 62271-200.
b. The electrical components affecting the performance of the functional unit
shall be type tested in accordance with the relevant parts of SANS 62271 and
other applicable standards. The components shall be tested to be in
compliance with Eskom specification.
c. CT’s shall be type tested in accordance with SANS 61869-2.
d. VT’s shall be type tested in accordance with SANS 61869-3.
e. Cable live indicators are type tested in accordance with SANS 61243-5.
f.
The tested functional unit and associated components are a credible
representation of the equipment under consideration.
g. Type test authorities for switchgear and controlgear are accredited in
accordance with ISO 17025.
h. All type tests are supplied to Camden Power Station to be verified and
accepted by Camden Power Station before manufacturing can start.
i.
It is the manufacturer and supplier responsibility to submit all type test reports
for the specific switchgear types and ratings offered.
j.
If the offered product is not 100% the same for the design, material,
manufacturing method and manufacturing location as was type tested, the
switchgear will not be accepted.
5.14.2 3.9.2 Routine Tests
a. Routine tests are performed on each of the functional units and associated
components.
b. Routine tests are conducted in a reputable testing facility that is acceptable to
Camden PowerStation.
c. Switchgear and controlgear are tested in accordance with the relevant parts
of SANS 62271.
d. CT’s shall be tested in accordance with SANS 61869-2.
e. VT’s shall be tested in accordance with SANS 61869-3.
f.
All the other components forming part of the functional unit are tested in
accordance with the applicable standards to prove functionality and
compliance with the relevant Eskom specifications.
5.14.3 Special Tests
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
The following special tests shall be performed on all types of switchgear
designs:
5.14.3.1 Mechanical Impact Test
The mechanical impact test is carried out on all types of functional units in
accordance with SANS 62271-200.
5.14.3.2 Partial Discharge Test
a. The partial discharge tests are carried out on all types of functional units in
accordance with SANS 62271-200.
b. Internal Arc Compliance with LV compartment door in the open position.
c. The internal arc tests are carried out in accordance with SANS 62271-200
with the LV compartment door open.
d. The duration of the internal arc test shall be 1 second.
e. The tests are carried out on all power compartments, which are busbar,
circuit-breaker and cable compartment.
f.
Type test authorities used to perform special tests are accredited in
accordance with ISO 17025.
g. All special tests compliance are verified and accepted by Camden Power
Station.
h. For prototype panels, full range of the required routine tests are conducted
and witnessed by Eskom.
5.15 MAINTENANCE AND OPERATION
5.15.1 Maintenance and Operating Tools
a. Any special tools or keys that may be required for maintenance, operating or
for adjustments are provided.
b. Handling equipment or trolleys are provided to facilitate the removal of the
mid-mount withdrawable devices from the panel.
c. The trolleys are of mechanical sound and robust design, equipped with
guards or guard rails to prevent the circuit breaker from damage when the
circuit breaker is withdrawn.
d. The trolley wheels are able to take up the full loading of the circuit breaker
and of durable material.
e. Two trolleys are supplied with each board.
f.
Special tools such as cable earth handles, racking in/out handles and panel
keys; the employer requires 3 for each board.
g. A tool cabinet is supplied with each board which will house the special tools.
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
5.15.2 Maintenance and Operating Instructions
a. The works instructions or procedures are provided to the employer by the
original equipment manufacturer (OEM) detailing descriptions of the
maintenance and operating work in accordance with BS 6626 and SANS
62271-1.
b. The procedures cover the requirements for maintenance and operating of the
equipment over the design life.
c. It is required during tenders to develop and submit to Eskom a failure mode
effect and criticality analysis (FMECA) to identify all maintenance
requirements and end of life criteria for the panel types offered.
5.16 DOCUMENTATION
5.16.1 Language
All documentation, including reports, manuals, etc. are in the English
language.
5.16.2 Type Test Reports
a. Type test documentation represents the design of the functional unit with
respect to the configuration, type and rating.
b. The information to be included in type test reports is in accordance with
SANS 62271-200.
c. The report of the type tested functional unit and associated components
reflect the equipment under consideration.
d. The type test report provided in full, containing all records of the tests
conducted as well as the drawings.
e. Softcopies are provided for all type test documentation.
5.17 Manuals and Drawings
a. The technical, training, maintenance and operating manuals are provided for
each type (e.g. for different ratings, voltage levels etc.) of a functional unit.
b. Technical manuals include all technical data, information on the switchgear
construction as well as the technical data and leaflets of each individual
component used in the switchgear provided and are subject orientated of the
plant installed.
c. Where generic manuals are provided, an addendum is provided indicating the
applicable project specific components.
d. Manuals and drawings are of a good quality and shall cover the following as a
minimum:
-
Technical descriptions of the equipment and component parts
-
General arrangement drawings
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CAMDEN POWER STATION 6,6kV SWITCHGEAR
-
Installation instructions with drawings or pictures
-
Operating and maintenance instructions for all components
-
Detailed parts lists (accompanied by exploded view type drawings clearly
detailing the part and uniquely identifying it)
-
Spare part ordering instructions
e. Any special instructions pertaining to storage as spare parts or as shelf life
are included in the maintenance manual.
f.
All drawings requested for component location, dismantling and re-assembly
for maintenance are included in the maintenance manual.
g. All special tools required for operating and maintenance of the equipment are
presented in a form of a schedule in the operating and maintenance manual,
respectively.
h. The content of the training manual shall be based on the content of the
technical, operating and maintenance manuals.
5.18 PACKAGING, TRANSPORTATION AND HANDLING
a. The functional units are suitable for handling and removal by providing
mechanisms for crane hooks.
b. The functional unit is suitable for handling and removal by providing
mechanisms to avoid damage to the functional unit.
c. During transportation the electrical components are packaged in such a way
that damage is prevented.
d. Components of the functional unit that are transported separately are marked
accordingly and shall be easily identifiable.
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