Areva MiCOM P441, Technical Manual

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P44x/EN AP/E33 Application Notes
Page 118/220 MiCOM P441/P442 & P444
Note that the combination of the Diff Phase and Bus-Line Delay settings can also be equated
to a differential frequency, as shown below:
•
Diff Phase angle set to +/-20
°
, Bus-Line Delay set to 0.2s.
•
The phase angle ‘window’ is therefore 40
°
, which corresponds to 40/360ths of a
cycle = 0.111 cycle. This equates to a differential frequency of:
0.111 / 0.2 = 0.55 Hz
Thus it is essential that the time delay chosen before an “in synchronism” output can be
given is not too long, otherwise the synchronising conditions will appear more restrictive than
the actual Diff Frequency setting.
The Live Line and Dead Line settings define the thresholds which dictate whether or not the
line or bus is determined as being live or dead by the relay logic. Under conditions where
either the line or bus are dead, check synchronism is not applicable and closure of the
breaker may or may not be acceptable. Hence, setting options are provided which allow for
both manual and auto-reclosure under a variety of live/dead conditions. The following
paragraphs describe where these may be used.
WARNING: THE SETTINGS VOLTAGE IN MiCOM S1 IS ALLWAYS CALCULATED IN
PHASE TO GROUND – EVEN IF PHASE/PHASE REF HAS BEEN
SELECTED.
If the threshold : live line has been set too high – the relay will never detect a healthy
network (as the line voltage is always measured below the voltage threshold). Without live
line condition, the distance protection cannot use the delta algorithms as no prefault
detection has been previously detected.
4.4.1 Dead Busbar and Dead Line
This mode is not integrated in the internal logic, however can be created using a dedicated
PSL:
(This facility with cells (Dead Line/Dead Bus) is available since version A3.0 model 05)
This setting might also be used to allow manual close with specific test conditions on the CB.
4.4.2 Live Busbar and Dead Line
Where a radial feeder is protected, tripping the circuit breaker will isolate the infeed, and the
feeder will be dead. Provided that there is no local generation which can backfeed to
energise the feeder, reclosure for live busbar / dead line conditions is acceptable. This
setting might also be used to allow re-energisation of a faulted feeder in an interconnected
power system, which had been isolated at both line ends. Live busbar / dead line reclosing
allows energising from one end first, which can then be followed by live line / live busbar
reclosure with voltages in synchronism at the remote end.
4.4.3 Dead Busbar and Live Line
If there was a circuit breaker and busbar at the remote end of the radial feeder mentioned
above, the remote breaker might be reclosed for a dead busbar / live line condition.