Download Type LFAA 103 Mesh Corner Unit

Type LFAA 103
Mesh Corner Unit
Features
● Automatic isolation, delayed
automatic reclosure (DAR),
ferroresonance suppression
● Selectable 0, 1, 2 or 3 mesh
circuit breakers
● Selectable 0, 1 or 2 line
disconnectors and 0, 1 or 2
transformer disconnectors
● Ferroresonance schemes F2A, F2B
and F3
● Timers are independently
adjustable
● Scheme logic options can be
selected
● User-friendly inbuilt keypad and
menu system
● Built-in test facilities
● Scheme documentation via ladder
diagram
Benefits
● Wider choice of scheme logic
options
● Suitable for mesh stations
● Simplified commissioning via
inbuilt test feature
● Greater setting flexibility
2
Figure 1: LFAA 103 with hinged front cover open.
Application
Primary Circuit Description
The LFAA 103 (Mesh corner unit MCU) provides for the automatic
reclosure of circuit breakers, the
automatic isolation of persistently
faulted plant and the suppression of
ferroresonance, following a fault on
the system.
As shown in Figure 2, the maximum
circuit configuration of a mesh corner
comprises three HV circuit breakers
CBX, CBY and CBZ at the common
node of which are two feeders and
either two banked transformers
feeding onto the LV busbars or two
grid transformers. Each mesh breaker
(CBX, CBY, CBZ) has its associated
disconnectors (MXA, MXB, MYA,
MYB, MZA, MZB) either side, and the
feeder circuits have a disconnector
(LDA, LDB) on the line side of the
mesh corner. The banked transformers
each have a disconnector (HDA, HDB)
on the HV side and where LV busbars
are being fed, an LV circuit between
the transformer and the busbars.
Equipment is provided on the basis of
one MCU per mesh corner. Although
each MCU is an autonomous unit,
interunit communication guarantees
co-ordinated control of a complete
mesh system.
A typical single switch system would
require two MCUs; a two switch
system, three MCUs, and three and
four switch systems, four MCUs. Once
the initial system has been installed
(minimum two corners) additional
corners can be installed and
commissioned on a corner by corner
basis.
There may be a mesh disconnector
between the transformer tee-off and
the mesh corner.
The items controlled by the mesh
corner unit are the mesh circuit
breakers, line disconnectors
(if motorised) and the transformer
disconnectors. The LV circuit breakers
are controlled by an independent unit
with which the mesh corner unit is
intended to interface.
Plant type L circuits
These are typically overhead lines for
DAR REQUIRED functions and cable
circuits for DAR NOT REQUIRED
functions. Inputs from the plant voltage
transformer monitoring relays are
used as a voltage reference. Delayed
automatic reclosure facilities are
provided for two circuits of plant
type L, referred to as line A and line B.
Plant type H circuits
These are typically transformer feeders
for DAR REQUIRED functions and
transformers or reactors for DAR NOT
REQUIRED functions. Inputs from the
plant voltage transformer monitoring
relays are not required as a voltage
reference. Delayed automatic
reclosure facilities are provided for
two circuits of plant type H, referred
to as trans A and trans B.
Description - Scheme
Scheme initiating enabling conditions
Automatic isolation is initiated by
protection operation. Delayed
automatic reclosure is initiated by
protection operation and a line
voltage reference up to the point of
trip. Automatic reclosure for a specific
breaker is enabled provided that:
– the circuit breaker is closed prior
to the protection operation
– the operation of the breaker is not
inhibited
– automatic reclosure for that circuit
breaker is not switched out of
service and is not locked out.
Figure 2: Maximum configuration.
Scheme Operation
Plant type L circuits
DAR REQUIRED
If the incident line remains dead,
mesh breaker CBX will reclose to
charge the line. If the line becomes
live during the dead time of the
reclosing breaker, the breaker will
revert immediately to closure with
synchronism check. If the circuit trips
within the reclaim time, following the
dead bar/dead line closure, no
further reclosure on to the faulty circuit
will be attempted, instead the faulted
circuit will be isolated by opening
disconnector LDA for line A or LDB for
line B, provided that DAR is selected
in service. The mesh will then be
restored by closing CBX, CBY and
then CBZ.
If DAR is selected out of service, the
mesh circuit breakers will be locked
out to prevent reclosure by associated
units.
DAR NOT REQUIRED
If the incident circuit trips on fault, no
reclosure on to the faulted circuit will
be attempted. The faulted circuit will
be isolated by opening the
disconnector LDA for line A or LDB for
line B.
Provided that DAR is selected in
service, the mesh will be restored,
otherwise DAR on the mesh breakers
will be locked out.
INTERTRIP
The receipt of an intertrip signal from
a remote station will initiate and then
inhibit the delayed automatic reclose
of mesh circuit breakers for the period
of time during which the intertrip
signal is received. If the intertrip
signal is maintained for a period of
time in excess of the intertrip receive
timer settings, the associated line will
be isolated by opening LDA for line A
or LDB for line B and then the mesh
restored.
3
Figure 3: Relay block diagram.
Plant type H circuits
INTERTRIP
DAR REQUIRED
The receipt of an intertrip signal from
a remote station will initiate and then
inhibit the delayed automatic reclose
of mesh circuit breakers for the period
of time during which the intertrip
signal is received. If the intertrip
signal is maintained for a period of
time in excess of the intertrip receive
timer settings, the associated line will
be isolated by opening HDA for Trans
A or HDB for Trans B and then the
mesh will be restored.
Following a fault on the feeder
section, if the mesh corner remains
dead and provided that DAR is
selected in service, mesh breaker CBX
will reclose to charge the transformer
feeder. If the mesh corner becomes
live during the dead time of the
reclosing breaker, the breaker will
revert immediately to closure with
synchronism check. If the transformer
circuit trips within the reclaim time
following re-energisation, no further
reclosure on to the faulty circuit will be
attempted; instead the faulted
transformer circuit will be isolated by
opening disconnector HDA for Trans
A or HDB for Trans B provided that
DAR is selected in service.
The mesh will then be restored by
closing CBX, CBY and then CBZ.
If DAR is selected out of service, the
mesh circuit breakers will be locked
out to prevent reclosure by associated
units.
DAR NOT REQUIRED
The faulted transformer is immediately
isolated by opening the disconnector
HDA for Trans A or HDB for Trans B.
Any reclosure sequence for the
transformer LV circuit breaker is
locked out and any reclosure
sequence on the associated banked
line of the transformer plant is
inhibited until isolation of the faulted
transformer is complete.
Provided that DAR is selected in
service, the mesh will be restored.
Otherwise, DAR on the mesh breakers
will be locked out.
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Mesh Corners
FERRORESONANCE
Facilities are provided to either
prevent the re-energisation of circuits
while in a ferroresonant condition, by
locking out the mesh and LV circuit
breakers, or to suppress
ferroresonance, by opening the
appropriate disconnectors. Any two
disconnectors may be assigned
ferroresonance suppression facilities.
DAR REQUIRED
Delayed automatic reclosure facilities
are provided for the re-energising of a
faulted mesh corner. Automatic
isolation of any associated plant type
H circuits is immediately initiated.
If DAR is selected out of service any
plant type H will be isolated, and then
DAR on the mesh circuit breakers
locked out.
DAR NOT REQUIRED
The faulted mesh corner is
immediately isolated by opening the
plant type L and plant type H
disconnectors and then locking out
DAR on the mesh and LV circuit
breakers.
COMMON RECLOSE LOCKOUT
A signal to cancel reclosure of mesh
and associated LV circuit breakers is
given. This signal is relayed to
adjacent mesh corner units.
SWITCHING IN/OUT OF SERVICE
AUTOMATIC ISOLATION and
DELAYED AUTOMATIC RECLOSE can
be switched in or out of service from a
remote point. DELAYED AUTOMATIC
RECLOSE may only be switched into
service while AUTOMATIC ISOLATION
is in service. When AUTOMATIC
ISOLATION is out of service, the OUT
OF SERVICE amber indicator lights on
the front of the MCU.
Indications and Alarms
The MCU has four light emitting
diodes (leds) on the front panel for
indications and alarms. The top two
(red and amber) are in four groups:
– status alarms 1
indicated by the red led being
stably lit. This group includes
lockout conditions and a
ferroresonance alarm.
– compound alarms
indicated by the red led flashing.
This group includes the plant DBI
alarms.
– status alarms 2
indicated by the amber led being
stably lit. This group includes the
plant and MCU inhibited alarms.
– change alarms
indicated by the amber led
flashing. This group includes the
switchgear failure alarms.
The alarms are enabled when the
appropriate condition occurs in the
ladder logic, and can then be read
without removing the MCU front
cover, by a combination of keystrokes
on the ACCEPT/READ and
SELECT/RESET keys on the relay front
panel.
The third led (amber) is the out of
service indication.
The fourth led (green) is the relay
healthy indication.
Test facilities
The LFAA relay provides the customer
with the facility to test the following
parameters:
– to read the state (i.e. on or off) of
each input to, and output from, the
relay.
– with the front cover removed, and
the relay out of service, the state
of each relay can be changed.
Description-Hardware
The MCU is housed in a 4U (178mm)
high case suitable for either rack or
panel mounting. The MCU uses plugin modules which are individually
tested and calibrated in the factory.
If necessary, modules can be
exchanged without any need to
recalibrate the relay.
A power supply module converts
power from a dc supply to internal
voltage rails.
A power failure monitoring circuit with
alarm output contact is provided.
contains non-volatile read/write
memory (EEPROM) for settings and
relay status information, read/write
memory (RAM) for temporary data,
and read-only memory (ROM) for the
system and application software. The
system software resides in one pair of
ROM devices, and the application
software in another, separate pair.
By appropriate programming of the
application ROM, either standard or
special auto-reclose requirements can
be satisfied.
and testing output relays, are only
available when the cover is removed
and can be blocked under certain
specific conditions. See the Service
Manual and Scheme Description for
details of the conditions under which
the commands are blocked. Five pushbuttons, arranged in a cruciform
pattern, become accessible when the
front cover is removed; four of these
act as cursor keys for selecting
commands or altering parameters in
an easy to follow menu approach.
The power supply module converts the
auxiliary dc voltage into the regulated
dc voltage rails required by the relay.
High efficiency and isolation from the
auxiliary supply are achieved by the
use of a switching dc/dc converter.
A power fail monitoring circuit with
two alarm output contacts is included.
The SET key at the centre is used to
confirm entry of new settings.
A parallel socket can be used to send
information about the relay to a
parallel printer. In addition, test points
within the relay can be monitored on
the parallel socket.
Remote communications
User Interface
The front panel operator interface,
shown in Figure 4, consists of a 2 row
16 character alphanumeric liquid
crystal display (lcd) together with a
seven push-button keypad. With the
relay cover in position only the
SELECT/RESET and ACCEPT/READ
keys are accessible. Using just these
two keys, it is possible to view system
details, view (and clear) alarms, view
counters, view settings, view the status
of all opto-inputs and output relays
and perform a timer test. A menu
approach has been adopted such that
the operator, using the lcd, can easily
and efficiently access a whole range
of useful information.
All menu options may be configured
on a PC and then transferred into the
Mesh Corner Unit via its RS232C
serial communications port. Sockets
are provided on the front of the relay
for temporary connection and on the
rear for permanent connection. The
rear socket can also interface with a
modem for communication over a
suitable link, for instance a telephone
line.
Security related commands, such as
changing settings, resetting counters
Three status input modules receive
external plant status and protection
equipment status signals via optoisolated inputs.
Three output relay modules are
provided.
A 16 bit microprocessor is used for
sequence control and timing functions.
It interfaces with the opto-isolated
inputs and output relays via an
address/data bus. A block diagram is
shown in Figure 3. Input and output
connections are shown in Figures 5
and 6 respectively.
The microprocessor module also
Figure 4: Operator interface.
5
Figure 5: External connections to opto-isolator inputs.
6
Figure 6: External outputs contacts wiring.
7
Description-Software
The relay software is divided into
three main groups: the system
software, the logic controller software,
and the scheme logic.
The system software is independent of
the application and is common to all
multi-modular hardware applications.
It consists of various diagnostic,
debugging, input/output, and multitasking handling facilities. It provides
a common software environment,
within which different application
programmes can be developed and
operated.
The scheme logic is the application
programme, defining how a relay
performs; it is presented in the form of
a ladder diagram. The ladder is an
easy to follow application diagram,
consisting of contacts, timers, counters
and output relays. This approach
means that the user does not need to
understand complex programming
languages in order to understand the
relay application. Each relay scheme
is fully documented including a copy
of the ladder diagram appropriate to
that scheme.
The logic controller operating system
interfaces between the system
software and the scheme logic of the
application programme. It processes
the status input information, updates
the relay outputs and controls the
operator interface.
Technical Data
Auxiliary voltage rating
Auxiliary voltage Vx (1) (dc)
(Relay power supply)
Nominal (V)
24/27
30/34
48/54
110/125
220/250
Operative range (V)
19.0 - 32.0
24.0 - 40.0
37.5 - 65.0
87.5 - 150.0
175.0 - 300.0
Auxiliary voltage Vx (2) (dc)
(Opto-isolator supply)
Nominal (V)
24/27
30/34
48/54
110/125
220/250
Operative range (V)
19.0 - 32.0
24.0 - 40.0
37.5 - 65.0
87.5 - 150.0
175.0 - 300.0
Note:
Vx (2) may be different from Vx (1)
Burdens (maximum)
Vx (1) or
Vx (2)
(Volts)
24
27
30
34
48
54
110
125
220
250
8
Aux supply (W)
(No output
relays on)
8
8
8
8
8.5
8.5
8.5
9
10.5
11.5
Add to auxiliary supply burden (W)
Each input
0.025
0.030
0.030
0.040
0.060
0.090
0.110
0.150
0.250
0.350
Each output
RL0-RL7
RL8-RL13
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
Timers
Timer name
Limits
of settings (s)
Accuracy
greater of:
CBX dead bar time
CBX dead line time
CBX reclaim time
CBX DBI time
CBY dead bar time
CBY dead line time
CBY reclaim time
CBY DBI time
CBZ dead bar time
CBZ dead line time
CBZ reclaim time
CBZ DBI time
CB close pulse
LDA opening time
LDA DBI time
LDB opening time
LDB DBI time
HDA opening time
HDA DBI time
HDB opening time
HDB DBI time
Intertrip LDA
Intertrip LDB
Intertrip HDA
Intertrip HDB
CB operation timer
LDA operation timer
LDB operation timer
HDA operation timer
HDB operation timer
Ferroresonance
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
1.00 - 127
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
±2%
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
or
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
–10
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
+20ms
Contacts
Make and carry for 0.2s
Carry continuously
Break
7500VA
(30A or 300V ac or dc maxima)
5A ac or dc
ac 1250VA
dc 50W resistive
25W inductive, L/R=40ms
(subject to maxima of 5A or 300V)
Durability
Loaded contact
Unloaded contact
10,000 operations minimum
100,000 operations minimum
9
High voltage withstand
Dielectric withstand
IEC 255-5:1977
2kV rms for 1 minute between all case
terminals connected together and the
case earth terminal.
2kV rms for 1 minute between all terminals
of independent circuits, with terminals on
each independent circuit connected together.
1kV rms for 1 minute across open
outgoing contact pairs.
High voltage impulse
IEC 255-5:1977
Three positive and three negative impulses
of 5kV peak, 1.2/50µs, 0.5J between all
terminals of the same circuit (except output
contacts), independent circuits, and all
terminals connected together and case earth.
Electrical environment
High frequency disturbance
IEC 255-22-1:1988 Class III
2.5kV peak between independent circuits
and between independent circuits and
case earth.
1.0kV peak across terminals of the
same circuit (except metallic contacts).
Fast transient disturbance
IEC 255-22-4:1992 Class IV
IEC 801-4:1988 Level 4
EMC Compliance
89/336/EEC
EN50081-2:1994
EN50082-2:1995
Product Safety
72/23/EEC
EN61010-1:1993/A2:1995
EN60950:1992/A3:1995
4kV, 2.5Hz applied directly to
auxiliary supply.
4kV, 2.5kHz applied directly to all inputs.
Compliance with the European Commission
Directive on EMC is claimed via the
Technical Construction File route.
Generic Standards were used to
establish conformity.
Compliance with the European
Commission Low Voltage Directive.
Compliance is demonstrated by
reference to generic safety standards.
Atmospheric environment
Temperature
IEC 255-6:1988
Storage and transit -25°C to +70°C
Operating -25°C to +55°C
IEC 68-2-1:1990
Cold
IEC 68-2-2:1974
Dry heat
Humidity
IEC 68-2-3:1969
56 days at 93% RH and 40°C
Enclosure protection
IEC 529:1989
IP50 (dust protected)
Mechanical environment
Vibration
IEC 255-21-1:1988
10
Response Class 1
Figure 7: Case outlines.
Cases
Further Information
Type LFAA relays are housed in
multi-module MIDOS cases.
(See Figure 7).
Application notes:
Publication
R4099
Service manual:
Publication
R5936
Information required with
order
DARCOM user guide:
Publication
R5940
Type of relay
LFAA 103
Quantity required
Auxiliary supply voltages
Vx(1) and Vx(2)
Case mounting
Rack or panel
11