Page 71 - Practical Power System and Protective Relays Commissioning

68 Practical Power System and Protective Relays Commissioning

Primary current injection in transformer bay to check the circuit continu-
ity in secondary circuits.
Stability test of busbar protection at the same time. These latter two items
will be explained elsewhere in this book.

5.7.3 Secondary Tests

Secondary injection of all transformer protection relays.
Check voltage regulator relay with the tap changer operation.
Check all alarm circuits.

5.7.4 Tripping Tests

All tripping matrix of high voltage circuit breakers to be tested by actuat-
ing the relays which issue the tripping signal from the source.
All tripping matrix of low voltage circuit breakers to be tested by actuat-
ing the relays which issue the tripping signal from the source.
Intertripping signals tests between high and low voltage side of
transformer.
Transformer mechanical relays tripping tests simulation, such as winding
temperature, Buchholz relays, etc.

5.7.5 Load Test
Before energizing the transformer circuit bay, we connect the transformer
bay to an empty busbar in the substation. With the acceleration of overcur-
rent relay to have a fast trip for any fault, (This means to reduce the time
delay setting of the overcurrent relay) also to measure the voltage in second-
ary of the transformer bay circuit and the reference circuit in substation this
means measure between R Phase of transformer circuit and R Phase of refer-
ence circuit it should read zero also for the other two phases Y and B also
phase rotation should be checked before loading the transformer. This will
be explained later in commissioning tests.