Circuit Breaker Measurements - DEMA CPM 310 G User Manual

Circuit Breaker Measurements Menu
Main Screen » Menu »
Measurements » CB
Measurements
As shown on the image above,
the ∑A and ∑A 2 values on the
measurement menu is shown in
scientific notation. E.g., 12745 E4
means 12745 x 10 4 .
Circuit Breaker Measurements Menu
used by statistical and diagnostic means; therefor all
values displayed on the menu can be reset when
needed. Values that are shown on the menu are listed
and explained in the following paragraphs.
Opening Time
Monitors the latest tripping time of the circuit breaker.
In order to use this feature, the following are required:
 Cabling a programmable input to a normally open
auxiliary contacts of the CB,
 Assigning "52a" to the programmable input.
Supervising the tripping time of the CB is of high
importance to make sure that the CB mechanism is in
good condition and the CB works within the expected
trip time delay interval and would not jeopardize the
selectivity scheme. Note that the measurement is
effective only when the opening / tripping command is
carried out over the relay.
Closing Time
Monitors the latest closing time of the circuit breaker.
In order to facilitate this feature, the following are
required:
 Cabling a programmable input to a normally open
auxiliary contacts of the CB,
 Assigning "52a" to the programmable input,
 Assigning "Close CB" function to any of the
programmable outputs.
Supervising the closing time of the CB is of high
importance to make sure that the CB mechanism is in
good condition. Note that the measurement is effective
only when the closing command is carried out over the
relay.
Open Numerator
Trip operations conducted via CPM 310 G is counted
and displayed on this field.
∑A (R, S, T)
These measurements are the summation of the RMS
current values at tripping moment. ∑A measurements
should be compared to the ∑A limit value
characteristics supplied by the manufacturer for CBs
with I > 52 kV.
r
∑A 2 (R, S, T)
These measurements are the summation of the RMS
current-square values at the tripping moment. ∑A
measurements should be compared to the ∑A
value characteristics supplied by the manufacturer for
CBs with I ≤ 52 kV. □
r
- 92 -
is intended to be
2
2 limit