GE BUS1000 Instructions Manual page 20

3. OPERATION PRINCIPLES
3.7.2. OPERATION
The testing element, which may be optionally provided with bus differential protection, has been designed to
check the alarm and differential units, during maintenance.
In the alarm and differential units test it is not necessary to disconnect the protection through its OFF button.
The TEST button itself is, as a step prior to the application of test current, in charge of disconnecting the
trips and not allowing for reset until all the elements in the trip circuits have not been reset.
Bear in mind that while doing the test there will come out the Differential Tripping signalling caused by the
test, and the Blocking signalling. Do not forget to reset the alarm and the differential modules, whose LED
will lit as a probe that each unit has no problem.
3.7.3. DIFFERENTIAL UNITS TEST:
The differential units test will be carried out separately in every phase and with the current level
corresponding to the restraint measured in the protection measuring terminals.
Set the AL - DIF selector to the DIF position and we shall then select the phase to be tested and the level
corresponding to the restraint, with the appropriate switches.
Once the previous adjustments have been carried out, push the TEST button and check that the selected
unit has operated and the unit trip signalling the corresponding LED remains lit.
3.7.4. ALARM UNIT TEST:
The alarm unit test will be carried out separately in every phase. Set the AL - DIF switch to the AL position
and we shall then select the phase to be tested with the phase selector switch. In this case the test current is
fixed and does not depend on the current level selector switch.
Once the previous adjustments have been carried out, push the TEST button and do not release it until the
unit operates (usually 10 seconds). Check that the unit selected has operated and the unit trip signalling
LED remains on.
3-8 BUS1000 Busbar Protection GEK-98514B