Areva MiCOM P225, Technical Manual

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User Guide P225/EN FT/B11
MiCOM P225 Page 41/52
4.11.10 The LATCH TRIP ORDER submenu: Latching of the trip output relay
In this menu, the user selects which functions are to maintain the output relays energised
when an order is generated by these functions.
Therefore, when one of the functions set as latching issues a trip signal via output relay RL1,
the relay remains energised after the end of the trip signal. It will be necessary to come and
acknowledge the P225 in order to switch off the output relay RL1.
N.B.: – Latching of the output relays is optional for each of these functions.
The user can chose whether to assign these functions to the “ trip
output relay latching facility ”.
– There are 3 possible ways to acknowledge the P225, and thus
switch off the output relay RL1 in the event of latching:
- press
the " pushbutton,
- send an acknowledge order to the configured logic input
on “ EXT RESET ”
- send a acknowledge remote order via the communication
network (order given by a supervisor)
– On loss of auxiliary power, the output relay drops back. On return
of auxiliary power, the output relay is re-energised, independently
of the fault status (still present or cleared).
4.11.11 The CB FAIL sub-menu: Breaker failure protection
The breaker failure function is used to quickly detect that a circuit-breaker has not opened
(phase fault currents still present) after a trip signal.
This function is based on a "I<BF" current threshold and on a "tBF" time-delay; these two
settings can be configured by the user.
If this function is commissioned by the user, it is activated every time relay RL1 issues a trip
command.
The "tBF" time-delay is initiated upon energisation of output relay RL1. Then, for each
phase, the MiCOM relay detects the first crossing of the current out of the zone created by
"
I
<BF". Upon detecting this crossing, the MiCOM relay initiates another time-delay with a
fixed value equivalent to 20 samples.
The relay sampling value is 32 samples/cycle. Therefore, the duration of the fixed time-
delay is 12.5ms at 50Hz and 10.4ms at 60Hz As long as this 12.5ms timer is running, the
relay checks whether the current leaves the current zone again. Where the current is not
suppressed by the circuit breaker pole, it will come out of the zone after a half cycle, ie. 16
samples (10ms at 50Hz).
The relay restarts the 20 sample timer each time it detects that the current comes out of the
preset current zone "
I
<BF".
For each 20 sample window the relay checks that when the current leaves the zone it does
so in the opposite direction to the previous crossing:
•
If there is no opposed current crossing, then the relay decides that the circuit breaker
pole is open.
•
If there is a current crossing opposed to the previous crossing, then the relay decides
that the circuit breaker pole is still close.
At the end of the tBF time-delay, the relay checks the state of each breaker pole (according
to the principle described above). If one or several poles are not open, the MiCOM relay
issues an alarm message: "CB FAIL".