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P746/EN TS/G31 Troubleshooting
(TS) 12-
10
MiCOM P746
TS
7. MAL-OPERATION OF THE RELAY DURING TESTING
7.1 Failure of output contacts
An apparent failure of the relay output contacts may be caused by the relay configuration;
the following tests should be performed to identify the real cause of the failure. Note that the
relay self-tests verify that the coil of the contact has been energized, an error will be
displayed if there is a fault in the output relay board.
Test Check Action
1
Is the Out of Service LED
illuminated? Illumination of this LED may indicate that the
relay is in test mode or that the protection
has been disabled due to a hardware verify
error (see Table 4).
2
Examine the Contact status in the
Commissioning section of the
menu. If the relevant bits of the contact status are
operated then proceed to test 4, if not
proceed to test 3.
3
Verify by examination of the fault
record or by using the test port
whether the protection element is
operating correctly. If the protection element does not operate
verify whether the test is being correctly
applied.
If the protection element does operate then it
will be necessary to check the programmable
logic, to ensure that the mapping of the
protection element to the contacts is correct.
4
Using the Commissioning/Test
mode function apply a test pattern
to the relevant relay output
contacts and verify whether they
operate (note the correct external
connection diagram should be
consulted). A continuity tester can
be used at the rear of the relay for
this purpose. If the output relay does operate then the
problem must be in the external wiring to the
relay. If the output relay does not operate
this could indicate a failure of the output
relay contacts (note that the self-tests verify
that the relay coil is being energized). Ensure
that the closed resistance is not too high for
the continuity tester to detect.
Table 6: Failure of output contacts
7.2 Failure of opto-isolated inputs
The opto-isolated inputs are mapped onto the relay internal signals using the programmable
scheme logic. If an input does not appear to be recognized by the relay scheme logic the
Commission Tests/Opto Status menu option can be used to verify whether the problem is in
the opto-isolated input itself or the mapping of its signal to the scheme logic functions. If the
opto-isolated input does appear to be read correctly then it will be necessary to examine its
mapping within the programmable logic.
Ensure the voltage rating for the opto inputs has been configured correctly with applied
voltage. If the opto-isolated input state is not being correctly read by the relay the applied
signal should be tested. Verify the connections to the opto-isolated input using the correct
wiring diagram. Next, using a voltmeter verify that 80% opto setting voltage is present on the
terminals of the opto-isolated input in the energized state. If the signal is being correctly
applied to the relay then the failure may be on the input card itself. Depending on which
opto-isolated input has failed this may require replacement of either the complete analog
input module (the board within this module cannot be individually replaced without
re-calibration of the relay) or a separate opto board.