Page 355 - Practical Power System and Protective Relays Commissioning

350 Practical Power System and Protective Relays Commissioning

Subchapter 20.6

Busbar Protection Testing and
Commissioning

20.6.1 SECONDARY INJECTION TEST FOR THE
DISCRIMINATING ZONE

The most used scheme is a high-impedance differential protection.
1. Pickup test of busbar protection modules
Put the busbar protection out of service during this test—this means
the buswires will be short-circuited and trip links will be opened.
Inject the current to each module of the busbar protection to check
the pickup value, which should be 6 5% of the normal pickup setting of
the relay.
2. Pickup test of the breaker failure module if it is attached to the Busbar
protection system
Inject this module with current and check the pickup value is within
6 5% of the nominal pickup value. This is done after opening the trip
link of the Breaker Failure (BF) system of the substation.
3. Time test measurement of BF relay
Simulate a BF initiation signal and inject a current above the relay
setting, then allow BF time and check the operation of the BF trip—
normally it is set to 125 ms. Check that the measured time is 6 5% of
the time set on the relay.
4. Busbar isolator image test (refer to Fig. 20.6.1).

FIGURE 20.6.1 Busbar discrimination test of fault location.