Micom P721, Technical Manual

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User Guide P72x/EN FT/C21
MiCOM P721/P723 Page 11/38
The different electrical system alarms are listed below:
Alarm Signification
[95] SUP + phase fault
indication Phase bus-wire supervision alarm (phase A, B or C).
[95] tSUP + phase fault
indication Time delayed phase bus-wire supervision alarm (phase A, B
or C). This alarm acknowledges [95] SUP alarm.
[87] DIFF + phase fault
indication Phase segregated high impedance current differential
protection alarm (phase A, B or C).
[87] tDIFF + phase fault
indication Phase segregated high impedance current differential
protection alarm (phase A, B or C). This alarm
acknowledges [87] DIFF alarm.
[95N] SUP Earth bus-wire supervision alarm.
[95N] tSUP Time delayed earth bus-wire supervision alarm. This alarm
acknowledges [95N] SUP alarm.
[87N] DIFF Earth high impedance current differential protection alarm
[87N] tDIFF Time delayed earth high impedance current differential
protection alarm. This alarm acknowledges [87N] DIFF
alarm.
[87CZ] check zone Check zone input. This alarm appears after [95] tSUP.
Buswire shorting Buswire shorting information.
tAux 1 / tAux2 / tAux3 /
tAux4 t AUX1, t AUX2, t AUX 3 and t AUX 4 time-out. These alarms
can be inhibited using CONFIGURATION/ALARMS menu
tEquation A to H t Equation A, B, C, D, E F,G and H
CB Failure (50BF) Circuit breaker failure indication (the CB does not trip on tBF
time. tBF can be set under the AUTOMAT. CTRL/CIRCUIT
BREAKER Fail menu.
Logical output relays
latched At least one output relay is latched.
Maintenance Mode The relay is in maintenance mode.
Relay Hardware or Software Warning Messages
Any software or hardware fault internal to MiCOM relay generates a "hardware/software
alarm" that is stored in memory as a "Hardware Alarm". If several hardware alarms are
detected they are all stored in their order of appearance. The warning messages are
presented on the LCD in reverse order of their detection (the most recent first and the oldest
last). Each warning message is numbered and the total stored is shown.
The user can read all warning messages pressing
c
, without entering the password.
It is not possible to acknowledge and clear warning messages caused by internal relay
hardware or software failure. This message can only be cleared once the cause of the
hardware or software failure has been removed.
The control of the WARNING LED (LED 3) is directly assigned to the status of the warning
messages stored in the memory.
If the internal hardware or software failure is major (i.e. the relay cannot perform protection
functions), the WARNING LED (LED 3) lights up continuously.
−
major fault: Protection and automation functions of the equipment are blocked. In this
condition, the protection relay detects the corresponding fault and activates RL0 Watch
Dog relay (35-36 terminals contact is closed).
For instance: the “DEF. ANA” fault (fault in the analog circuit channel) is considered as a
major fault because the protection functions will not operate correctly.