ABB REX 521, Техническое справочное руководство, стандартные конфигурации

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1MRS751802-MUM Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
The time grading includes (definite time):
As an example the time grading can be:
2 x 25 ms + 50 ms + 30 ms + 20 ms = 150 ms
Back-up protection can be realized with the circuit-breaker failure protection
function of the protection relay. A fast back-up function can be achieved because the
safety margin can be omitted when setting the CBFP time. The CBFP function
requires external wiring from the protection relay of the bus sectionalizer to the relay
of the in-feeder.
The settings for the overcurrent protections can be found in:
Main menu\Protection\3I>\ … \3I>>>\Setting group 1\
where
the parameters
Operation mode
,
Start current
and
Operate time
for
the function can be set. In
Main menu\Protection\3I>\Control
setting\
can for example the
Drop-off time
and the length of the trip signal
Trip pulse
be set. The data of the three last operations, start or trip, are recorded
and the values of the most recent operation can be found in
Main menu\Protection\3I>\Recorded data1\…3\
.
11.3.3.2. Synchro-check function
In this application example where the synchro-check function is used for ensuring
the condition between two busbar sections fed by own transformers, the voltage
difference between busbar sections is the most important criterion. The synchro-
check function does not allow the circuit breaker to be closed if the voltage
difference is too high. If the voltage difference is high, the inrush current between
the busbar sectors can be too high. In an application where a generator is connected
to one of the busbar sectors other criteria are also important and the need for the
synchro-check functionality is unavoidable.
The synchro-check function can be used in two different operating conditions. The
most typical case is one where both sides of the circuit breaker to be closed are live
and thus the synchronism is always checked before the circuit breaker is given the
permission to close. In an other situation one or both sides of the circuit breaker to
be closed are dead and, consequently, the frequency and phase differences cannot be
measured, in which case the relay checks the energizing direction.
Operation criteria of the function are:
• Voltages must be in accordance with the energizing direction.
• In cases “Live-Dead”, “Dead-Live” and “Dead-Dead” no other conditions are
checked.
• In the case “Live-Live” also the following must be fulfilled:
•
∆
U< dU setting
•
∆
f< df setting
•
∆
ϕ
< dphi setting
2 X Tolerance of the
relays’ operate times
+ Operation time
of the CB
+ Retardation time
of the relay
+ Saturation and delay
margin