Micom P631, Technical Manual

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3.26 Measuring-Circuit Monitoring (Function Groups MCM_1 and
MCM_2)
The measuring-circuit monitoring function featured by the P631 will detect faults
in the secondary circuits of the CTs. Measuring-circuit monitoring functions
MCM_1 and MCM_2 are permanently assigned to the transformer ends monitored
by the P631.
Function group MCM_1 will serve as an example to illustrate the operation of the
measuring-circuit monitoring functions. The same will apply to function group
MCM_2.
3.26.1 Enabling or Disabling Measuring-Circuit Monitoring
The measuring-circuit monitoring function can be enabled or disabled using
setting parameters. Moreover, enabling can be carried out separately for each
parameter set.
64Z5186A
Parameter
set 1
set 2
set 3
set 4
MCM_1:
Enable PSx
081 038
082 038
083 038
084 038
MCM_1:
Enabled
[ 036 194 ]
MCM_1:
Enable PSx
[ * ]
1
0
0: No
1: Yes
0
0: No
1: Yes
MCM_1:
General enable USER
[ 031 146 ]
1
Fig. 3-123: Enabling or disabling measuring-circuit monitoring
3.26.2 Measuring-Circuit Monitoring
The negative- to positive-sequence current ratio is used as a criterion for
measuring-circuit monitoring. The measuring-circuit monitoring function is
triggered when the set ratio value, I
neg
/I
pos
, is exceeded and either the negative-
or the positive-sequence current exceeds 0.02 I
nom
. After the set operate time-
delay has elapsed, a warning is issued.
The measuring-circuit monitoring functions can be used to detect broken
conductors on the CTs' primary sides.
●
The functions can now be blocked individually via input signals set at
MCM_x: Blocking EXT.
●
When the triggering condition is met an instantaneous starting signal is
raised: (MCM_x: Starting).
In the following logic diagram, the measuring-circuit monitoring function is
displayed using function group MCM_1 as an example.
P631 3 Operation
3-156 P631/EN M/R-11-C // P631-310-650