Page 225 - Practical Power System and Protective Relays Commissioning

Protection Relays Chapter | 18 225

FIGURE 18.6.24 Acceleration scheme.

The relay at end B will see the fault and send a signal to relay at end A
to switch the relay from Zone 1 reach to Zone 2 reach, the relay will trip
instantaneously but it will trip on Zone 2 reach with 500 ms if no signal is
received from remote end B—refer to scheme trip logic as shown in
Fig. 18.6.25.

FIGURE 18.6.25 Trip logic of acceleration scheme.

18.6.5.6 Blocking Overreach Transfer Scheme
In this scheme, the teleprotection signal is used to block tripping of the relay
at the remote end as shown in Fig. 18.6.26.
In this scheme, Z 2 is set to 120% overreach of the transmission line AB,
for fault F 1 at the remote end B, but outside line AB the fault will be
seen by Zone 3 in the reverse of relay at end B then a blocking signal is
sent to end A.