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Anexa. Specificatie tehnica comutator incarcasat de 11 KV
2.2.1 Switchgear:
The switchboard shall be indoor totally enclosed metal-clad type with either
horizontal or vertical draw out, vacuum circuit breaker. The busbars shall be of
hard drawn high conductivity copper bars, air insulated and Heat Shrink
Sleeve covered for busbar Insulation . Suitable moulding should be used to
shroud the joints. The switchboard shall be of robust construction and shall be
unaffected, in whole or in part, by the forces imposed by short circuits or other
fault currents, operation, installation, vibration or changes in temperature. The
switchgears must be capable of withstanding 11 KV line to earth fault current
indefinitely under emergency conditions. The switchgear shall be strictly in
accordance with B.S: 5227 or IEC 60298 unless specified otherwise herein. The
busbars on all switchboards shall be arranged to permit future extension at
each end. Phase rotation and colour markings shall be in accordance with BSS
158. All instruments, instrument transformers, other components and
compounds used in 6 the switchgear and in the circuit breakers shall comply
with the appropriate and latest British Standard Specification or at least
equivalent to it. The switchgear shall be fully interchangeable. The switchboard
shall be arranged for bottom entry of 11 KV cables and pilot cables as shown in
drawing No. MB/7/634. The circuit breaker compartment of the panel shall be
provided with front door. The circuit breakers shall have 3 positions, viz.,
SERVICE, TEST and ISOLATED. In the test position, it should be possible to
close the door of the circuit breaker chamber.
2.2.2 Earthing Gear:
Provision shall be made for earthing of the power cables of each unit. The
earthing arrangement shall be one of the following:
a) Through the circuit breaker by the method of transfer position without the
necessity of any loose attachments or devices (i.e. integral earthing)
b) Through a fault making earth switch fully interlocked. The switch shall be of
the quick-make-break type. Visual checking of the earthing switch shall be
possible through transparent covers. However, the earthing switch chamber
shall be vermin proof and dust protected. Earthing devices shall be fully
interlocked with the circuit breaker and shall be capable of closing on full short
circuit current corresponding to 25 kA at 12 KV without sustaining any
damage or endangering the operator. The short time current rating must not be
less than 25 kA for 3 seconds. Type test certificate for earthing devices should
be submitted. Earthing device shall be operated from front of the panel and to
be marked clearly.
2.2.3 Duty of Plant:
a) Rating:
All current carrying parts of the switchgear including current transformers,
isolating contacts, busbars, connections and joints shall be capable of carrying
their specified rated current continuously under Kuwait Climatic conditions
and the temperature rise in Kuwait shall comply with B.S. 5311 and 159 and
any other applicable relevant British Standard Specification. Tenderers shall
state the B.S.S. ratings alongside the Kuwait rating in each case.
b) Circuit Breakers:
The circuit breaker shall be of the vacuum type and shall have guaranteed
rupturing capacity of not less than 25 kA at 12 KV and must conform to BS
5311 taking into account the climatic conditions of Kuwait. The circuit breaker
should be capable of carrying full short circuit current associated 7 with the
above fault level at 12 KV for a duration of 3 seconds without any damage. All
live parts of C.B should be completely insulated when it is plugged in service
position. One circuit breaker shall be tested for 75 KV. Impulse withstand
voltage at no extra cost.
c) Normal Rating:
630 Amps shall be normal continuous rating under Kuwait worst temperature
conditions.
2.2.4 Operation:
Hand charged spring closing mechanism shall be provided. An indicator shall
be fitted clearly indicating whether the spring is in the „charged“ or
„uncharged“ state. Closing to be affected by means of a 50 volts D.C. spring
coil, through a local barrel type control switch. Tripping shall be by means of a
50 volts D.C. shunt trip coil. Manual trip also is to be provided.
2.2.5 Live Parts Isolation and Shutters:
Each switchboard must be provided with approved means of isolation of circuit
breakers and circuits, and to be complete with automatic shutters to screen off
all live parts. The shutters for the feeder and busbar spouts shall be operated
independently and must be suitable for the arduous Kuwait conditions without
any deformation. The switchgear must be fully interlocked to prevent
unauthorized or mal-operation. Safety of personnel and continuity of supply
are the prime considerations.
2.2.6 Racking Equipment:
A wheeled carriage for the removal of the circuit breaker from a switchboard
shall be an integral part of the circuit breaker (cassette type circuit breakers
shall not be accepted). Suitable external guide rails shall be provided for fixing
in the substation floor in front of the switchgear for guiding the circuit breaker
during its removal from the board.
2.2.7 Cable Boxes:
a) Power Cables:
Each cable dividing box on the feeder units shall be suitable to receive 3x300
sq. mm. AL or CU/SC/XLPE/SC/SWA/PVC 11 KV cable and each cable
dividing box on the transformer units shall be suitable to receive 3x185 sq.
mm. CU/SC/XLPE/SC/SWA/PVC 11 KV cable. 8 The boxes shall be designed
with ample dimensions with removable bottom gland plate and back cover
to facilitate jointing and to allow crossing of cores without damage to
insulation. All the boxes shall be bolton-type. Suitable Brass Compression
Cable Glands shall be provided. The vertical distance between the cable crutch
and the cable connection terminals shall not be less than 570 mm in any case
for all feeder/transformer cable dividing box. The gland plate for the power
cable should be at least 350 mm above the ground level. The terminations shall
be designed for the use of Heat/Cold shrinkable Terminations.
b) Multicore cable cabinet:
The 11 kV switchgear shall be provided with multicore cable cabinet on the
back of each panel. The cabinet shall be capable to receive either 16-core,
polyethylene insulated and sheathed, „steel wire armoured and overall PVC
sheathed“ pilot cables or multicore cable from common integrated device or
pressure relief valve from transformer room.
2.2.8 Current Transformers:
Current Transformers may be either air insulated type or cast resin type.
Current transformers shall be so rated that they will not sustain any damage
by the through fault currents expected on a system level of 25kA at 12 KV. All
secondary windings shall be one ampere unless otherwise specified. Current
transformers shall be capable of withstanding full short circuit current for 3
seconds without distress or damage. Proper barrier is to be fixed in between
the C.T. Chamber and the cable termination box.
2.2.9 Circuits:
Each circuit breaker will control either (a) a feeder circuit or (b) a power
transformer circuit.
2.2.10 Protection:
a) Feeder Circuits.
Each feeder circuit shall be protected by „UNIT FEEDER PROTEECTION“
comprising of Solkor RF feeder protection using relays and associated
equipment manufactured by M/s. A. Reyrolle & Co., Hebburn, Durham,
England. The current transformers shall be of ratio 9 400/300/1A, of 15 VA
capacity and class X accuracy, and they shall have characteristics matching
with the current transformers already connected to the system. A separate
400/1 current transformer of class 1 accuracy shall be provided for metering
purposes. The through fault current shall be 25kA at 12 KV. Alternatively, unit
feeder protection (other than Solkor RF feeder protection) manufactured by
other companies may be offered. However, the unit feeder protection should
match with solkor RF of M/s. A. Reyrolle and guarantee for the performance of
these relays should be submitted. M/s. A. Reyrolle are discontinuing
manufacture of cable differential relay type „Solkor R“ both 5 KV & 15 KV and
instead producing new version of cable differential relay called Solkor „RF“ for
both 5 KV & 15 KV insulation. For feeder circuits the existing Solkor „R“ 5 KV
relays can be used with the new type Solkor „RF“ 5 KV relays by means of
changing four links internally in the Solkor “RF” relay and these shall be
carried out by the contractor of this tender without any extra cost.
b) Transformer Circuits:
Each transformer circuit shall be protected by non-directional over current and
earth leakage relays. The overcurrent relays shall be of the inverse definite
minimum time lag type (IDMTL). The relays shall have a current setting of 50 –
200% in steps of 25 %. The time setting shall be 3 seconds at 10 times plug
setting with time multiplier setting at 1 and shall be adjustable between zero
and unity and shall have characteristics to BSS. The earth leakage relay shall
also be of the inverse definite minimum time lag type (IDMTL). The relay shall
have a current setting range from 10% - 40% in steps of 5 % and time setting
adjustable from zero to unity and time setting shall be 3 seconds at 10 times
plug setting with time multiplier setting at 1, having characteristics to BSS.
142 with 100/1, 15 VA, class 10 P 10 current transformer. The over current
relays shall be equipped with high set instantaneous current elements having
setting of 8 Ins. to 20 Ins. and with steps of 2 Ins. and ending with infinity.
Trip contacts from common integrated safety device and/or PRV from the
transformer shall be wired for tripping the circuit breaker through suitable
inter-trip relay (three elements) with a 50 volts supply and mechanical hand
reset flag indication. 10
2.2.11 Intertrip Circuits:
The existing system has a number of Ring Main substations that will require
intertripping relays to be installed on the feeder panels covered by this tender
in case these are installed between or adjacent to those existing substations.
Therefore, each feeder C.B. panel shall have space and connection facilities for
a possible future addition of an intertripping relay of Reyrolle flush type No.
B12 or similar suitable for use with a 50 V D.C. supply. Necessary provision for
intertripping relay space and auxiliary contacts shall be arranged for such
requirements. These panels can be pre-drilled and fitted with blanking plates
for this purpose.
2.3 11 KV Ring Main Units:
2.3.1 Switchgear:
The 11 KV Ring Main Units shall consist of two on-load switches for feeder
control and one fuse-switch for transformer control. The switchgear shall be of
the totally enclosed metal-clad type of robust construction and shall be
unaffected in whole by the forces imposed by short circuits or other fault
currents, vibrations, changes in temperatures, etc. The switchgear shall be
with insulating and arc extinguishing media of SF6 insulating gas or vacuum.
In case of SF6 insulated switchgear, tenderers shall give the maximum rate of
leak per year and this shall not exceed 0.2% per year, for vacuum insulated
switchgear, tenderers shall give rate of loss per year if applicable. In case of
vacuum insulated switchgear, tenderers should explain clearly in their offers,
how the degree of vacuum is maintained and whether the switchgear is
suitable for periodical checking of vacuum. The impulse withstand voltage for
the switchgear and the switches shall not be less than that specified in the
relevant IEC recommendation. The bus-bars shall be of the hard drawn, high
conductivity electrolytic copper and of adequate section. All current carrying
parts of the switchgear including current transformers, isolating contacts, busbars, connectors and joints shall be capable of carrying their specified rated
currents continuously under the worst climatic conditions encountered in
Kuwait. The temperature rise of any part of the switchgear shall be well within
the limits as specified in the relevant IEC recommendations taking into
account the climatic conditions of Kuwait. In each case, the Tenderer shall
state the equivalent IEC ratings and Kuwait ratings. 11 The switchgear shall be
designed for easy inspection and maintenance and shall be fully interlocked to
prevent unauthorized or mal-operation. Safety of personnel shall be the most
important factor to be considered in the design of the switchgear. Partitions
and barriers shall be provided between adjacent panels of the switchgear and
between various compartments to prevent any internal fault spreading to
adjacent unit or compartment. In case of increase of SF6 pressure resulting
from internal failure, SF6 switching is applicable, bursting disc/s shall be
provided for pressure relief. The Tenderer shall state the appropriate degree of
protection according to relevant IEC recommendations. Ring switch and switch
fuse shall also be suitable to perform five (5) full load switching operations at
atmospheric SF6 gas pressure. Test reports from independent laboratory
should be furnished with the offer in this respect. Built in pressure gauge shall
also be provided for continuous indication of SF6 gas pressure. Each switch
unit shall be provided with a name plate suitably dimensioned consisting of
metal picture frame fitted with a drop in traffolite circuit label (laminated white
ground with black letters).
2.3.2 On-load Switches:
The on-load switches shall be 400 Amps (Kuwait rating) and shall be suitably
rated to connect and interrupt the full load current of the respective circuit at
0.7 power factor lagging and also capable of making and breaking capacitive
currents at 0.3 power factor leading. The on-load switches shall be capable of
closing on to a full short-circuit making current not less than 50 KA peak
without resulting in any danger to the operator. Further, the short time current
rating shall not be less than 20 KA for 3 seconds. All Tenderers shall submit
evidence of tests carried out on on-load switches for this purpose. All Tenderers
shall confirm the above duties and shall submit evidence of tests carried on
these switches for this purpose. In case of SF6 insulated switchgear the onload and earth switches shall be filled with SF6 gas for insulation and arc
interruption. For vacuum switchgear the insulating and arc extinguishing
media for the on-load and earthing switches shall be vacuum. The switchgear
shall be equipped with a cable earthing switch on each on-load switch which
shall be suitable for closing on to a full short circuit making current of 50 KA
peak without resulting in any danger to the operator. Further, the shorttime
current rating must not be less than 20 KA for 3 seconds. All Tenderers shall
submit evidence of tests carried out on the earthing switches for this purpose.
12 On-load switch and earthing switch shall be fully interlocked and shall be
provided with spring-charged hand-operated mechanism and mechanical
indication of ON/OFF positions. Each cable dividing box on the on-load switch
unit shall be suitable to receive 300 sq.mm. aluminium (or Copper) conductor,
3-core 11 KV XLPE insulated single steel wire armoured and overall PVC served
cable. The cable end box shall be complete with brass type compression gland
and copper bonding strip to maintain earth continuity of wire-armouring. The
front and bottom covers of the cable box shall be a removable type. The vertical
distance between the cable crutch and connection terminals shall not be less
than 570 mms. The terminations shall be designed for the use of Heat
Shrinkable Terminations. For ease of operation and safety each on-load switch
shall have integral cable testing device in an easily accessible location and with
safety interlocks.
2.3.3 Fuse Switch :
The fuse switch shall be 150 Amps (Kuwait rating). The switching contacts
within the fuse switches shall be capable of making and interrupting full load
current at service voltage. The fuse switch shall also be equipped with 250V
tripping coil. They shall make and withstand short-circuit current until cleared
by the fuses. The fuses switch shall be equipped with tripping mechanism
which shall trip all three phases, if either one, two or three fuses have
operated. Mechanical „Fuse Blown“ indication shall be provided and shall be
visible without opening RMU cover/door. In case of SF6 insulated switchgear
the fuse/earth switch shall be filled with SF6 gas for insulation and arc
interruption. For vacuum switchgear the fuse/earth switch shall be vacuum
insulated type which also serves for arc interruption. The fuses shall be
mounted on detachable carriage to facilitate fuse replacement. Approach to
H.V. fuses shall be possible only when H.V. side of transformer is earthed and
both fuse terminals are isolated for safety. The fuse switch shall be equipped
with an earth switch for earthing the H.V. side of the transformers. The earth
switches shall be capable of closing on full short circuit current. Fuse switch
and its earth switch shall be fully interlocked. The H.V. fuses must
discriminate with the fuses on the low voltage side of the transformer.
Attention is drawn to the fact that the transformer’s summer load is mainly
motive and during severe surges or voltage dips, currents as high as 6 times
the full load current and persisting for approximately 2 seconds, are expected.
The fuse is not required to break the circuit under such conditions. The
Tenderer shall submit evidence of short circuit tests carried out on the
Fuseswitch and the earth switch, for the specified duties. 13
2.4 Type Tests:
The following type tests shall be carried out in accordance with the relevant
IEC/B.S.
Standards.
a. Mechanical performance test.
b. Temperature rise test.
c. Making capacity and breaking capacity tests.
d. Short- time current test.
e. Impulse voltage withstand test.