1MRS751802-MUM
REX 521
207
Protection Relay
Technical Reference Manual, Standard Configurations
The needed time for blocking includes:
The set operate time of a back-up protection stage 3I> of the incoming feeder can be
calculated as follows:
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 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\
.
11.2.4.
Connections
All the necessary settings for the connections and signal routings can be set via the
Relay Setting Tool or the local HMI.
11.2.4.1.
Protection signal routing
The settings for the protection signal routing can be implemented as described in the
second application example (see Section 9.2. Incoming feeder, Basic B01). 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.
Start time of the relay
(40 ms)
+ Input delay on the relay
to be blocked
(10 ms)
+ Retardation time
(30 ms)
+
Margin
(20 ms)
Time grading
+
Operate time of the
protection relay of the bus
sectionalizer
2 X Tolerance of the
relays’ operate times
+ Operation time
of the CB
+ Retardation time
of the relay
+
Saturation and delay
margin
Summary of Contents for REX 521
Page 1: ...Protection Relay REX 521 Technical Reference Manual Standard Configurations ...
Page 2: ......
Page 12: ...12 ...
Page 22: ...22 ...
Page 62: ...62 ...
Page 72: ...72 ...
Page 128: ...128 ...
Page 132: ...132 ...
Page 172: ...172 ...
Page 198: ...198 ...
Page 249: ......
