P521/EN AD/B21
Update Documentation
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MiCOM P521
COMMISSIONING AND MAINTENANCE (P521/EN CM/B11)
9.3.2
Protection comms fault
As soon as a problem with the protection comms is detected the operation of the
main protection is stopped. All other protection elements continue to operate and
those selected as backup in the current setting group will be enabled.
Message:
“COMMS ALARM CH1”: communications channel failure detected.
Cause:
Hardware or software failure of the communications card.
Hardware failure of the communications module retained in the case when the active
part is withdrawn.
Failure of the relay at the distant end of the communications link.
Failure of a device in the communications path or break in the communications link.
Live parts exposed within the P521 case, when the P521 module is
removed.
Action:
Determine the location of the failure using the P520L loopback test box
(see Accessories section).
Initiate a loopback test on the back of each of the relays. If the protection comms
alarm resets then the fault is with the communications link not the relays. The relays
should assist with diagnosing the location of the fault by indicating the faulty path (Tx,
Rx or both). If the protection comms alarm does not reset on one relay it is likely that
the relay is faulty. To diagnose if the fault is in the active part (withdrawable part) of
the relay or the protection communications card, remove the relay and plug in the
P520L loopback test box as shown in Figure 2. It is recommended that the battery is
tested, before inserting the test box, by selecting battery test and checking that the
green LED illuminates. With the loopback tester inserted select “Loopback Test” using
the selector switch and ensure that the green LED illuminates. Initiate a loopback test
from the remote relay so that the comms signal passes through the local relay
communications card. If the comms fail alarm on the remote relay disappears, then
the protection comms card is functioning correctly, hence the problem is with only the
active part. If the comms fail alarm does not reset then the local protection comms
card is faulty.
