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8. FINAL INSTALLATION AND COMMISSIONING
Leave the current circuits of the main transformers secondaries shorted until these currents are applied to
the differential protection.
8.5.
ARRANGEMENT AND PRELIMINARY LEADS
•
Check that the values of each of the Stabilization Resistance measured 250 ÿ.
•
Short out the Stabilization Resistance.
•
Disconnect the trips that go from the differential busbar protection and breaker failure protection, to the
circuit breakers of the Substation or Power Plant. It should be done by disconnecting the physical
elements (cables), or by the use of switching terminal boards .
•
Check that all the leads are down except for the d.c. power supply X1(+)-X2 (-) and X7(+)-x8(-) for the
control of the bar connection and disconnection of the feeders.
•
Disconnect the two differentials through their OFF buttons.
8.6.
TESTS WITHOUT LOAD
Carry out the acceptant test described in chapter 11.
Take into account that terminals mentioned in this chapter are referred to the set of drawings 226B6429. For
each scheme, depending on the arrangement of the substation or power plant, and the needs of each utility,
the identification and number of the terminals may defer from the ones that appear in 226B6429.
8.7.
TESTS WITH LOAD
The objective of this test with real load, is to verify if the protection is correctly balanced: the sum of all the
currents in the differential circuit is zero (0.0mV), and that all the polarities are correct.
This test uses the real currents that go through each circuit. Trips must be disconnected, for the differential
units it will be enough to push the red button, but for the breaker failure protection check that all the tripping
output terminals are brought down, so any mistake during the tests, will not cause a problem in the
Substation.
Connect feeder by feeder to differential A and verify:
• The magnitude of the current of restrain is increasing and corresponds to the sum of the absolute values
of all the currents connected to it.
• The differential current will increase or decrease weather the line currents are compensated or not.
• The voltage (ac) measured at the front of the panel DFI is proportional to the input current.
Upon connecting the last circuit, the value of differential voltage must be of the order of 0.0 mV, 3 milivolt as
maximum (upper values, indicate that there is a wrong connection). The alarm unit should be able to reset by
pushing the reset button, the LEDs on the DAL module should be off.
Now transfer all the feeders, one by one to differential B following the same steps as above, and check the
magnitudes of the current restrain and the differential current.
Upon connecting the last circuit, the value of differential voltage must be of the order of 0.0 mV, 3 milivolt as
maximum (upper values, indicate that there is a wrong connection). The alarm unit should be able to reset by
pushing the reset button, the LEDs on the DAL module should be off.
•
Arrange the differential according to the actual arrangement of the Substation, and check that the entire
alarm unit can be reset (no LED is on), and that the LEDs on the DDF modules are also off.
8-2
BUS1000 Busbar Protection
GEK-98514B
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