Page 231 - Practical Power System and Protective Relays Commissioning

Protection Relays Chapter | 18 231

IEDs. The stub protection in a breaker-and-a-half application. With the
breaker-and-a-half configuration an operating mode is possible whereby
the feeder is out of service while both CBs in the diameter remain closed.
This is the case when DS1 is open, while CB1 and CB2 are closed in the
SLD is shown in Fig. 18.6.29.

FIGURE 18.6.29 Stub protection in a one-and-a-half circuit breaker busbar arrangement.

All faults in the zone between CB1, CB2, and DS1 are stub faults. The
stub protection boundary is defined by the location of the CTs, as shown
above.

18.6.11 AUTORECLOSING FUNCTION IN DISTANCE RELAY
This relay is used in a distance protection scheme to reclose the lines auto-
matically after transient faults trip by distance relay.

18.6.11.1 Autoreclosing Important Definitions

Eighty percent up to ninety percent of transmission line faults are transient
faults. This provides a need to use an autoreclosing system. There are basic
terms and definitions in autoreclosing systems as follows:
Arcing time:
The time between the instant of separation of the CB contacts and the
instant on extinction of the fault arc.
Closing impulse time:
The time during which the closing contacts of autoreclosing relay are made.
Closing time:
The time from the energizing of the CB closing circuit to the making of
the CB contacts.