Connections; 1.Protection Signal Routing - ABB REX 521 Technical Reference Manual, Standard Configurations

1MRS 751802-MUM
11.2.4.
11.2.4.1.
Protection Relay
Technical Reference Manual, Standard Configurations
The needed time for blocking includes:
Start time of the relay +
(40 ms)
The set operate time of a back-up protection stage 3I> of the incoming feeder can be
calculated as follows:
Time grading +
The time grading includes (definite time):
2 X Tolerance of the + Operation time
relays' operate times
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 LV-side incoming feeder to
the relay of the HV-side in-feeder. Notice that in this application example the CBFP
function is only operating in the HV side of the transformer, but fault current will be
fed from the other direction as well if the fault is between the LV- and the HV-side
circuit breakers of the transformer feeder.
The settings for the overcurrent protections can be found in:
Main menu\Protection\3I>->\ 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\.

Connections

All the necessary settings for the connections and signal routings can be set via the
Relay Setting Tool or the local HMI.
Protection signal routing
The settings for the protection signal routing can be implemented as described in the
second application example (chapter 9.2.). In this application example two different
trip signals are used: Trip 1 for opening the circuit breaker of the incoming feeder
and Trip 2 for opening the circuit breaker of the transformer feeder. In this
application example separate power output relays are used for Trip 2 and CBFP
(circuit-breaker failure protection) function.
Input delay on the relay
to be blocked
(10 ms)
Operate time of the
protection relay of the bus
sectionalizer
+ Retardation time
of the CB of the relay
REX 521
+ Retardation time +
(30 ms)
+ Saturation and delay
margin
Margin
(20 ms)
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