NR Electric PCS-9611, Instruction Manual

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3 Operation Theory
PCS-9611 Feeder Relay
3-35
Date: 2014-04-08
current (I
2
/I
1
). This will be affected to a lesser extent than the measurement of negative sequence
current alone, since the ratio is approximately constant with variations in load current. Hence, a
more sensitive setting may be achieved.
At the moment when the circuit breaker is closed, because the three poles of the circuit breaker
are discrepant for a very short time, and if the broken conductor protection is enabled, it is easy to
make the broken conductor protection pick up, and it will restore after the load current is stable.
The logic diagram is as shown below. The ratio of I
2
/I
1
is calculated and is compared with the
threshold and if the threshold is exceeded then the delay timer is initiated.
I
2
/I
1
> [50BC.I2/I1_Set]
[50BC.Blk]
[50BC.En]
[50BC.Op]
[50BC.St]
[50BC.En1]
&
t
BCP
0
Figure 3.8-1 Logic diagram of the broken conductor protection
Where:
[50BC.I2/I1_Set] is the ratio setting of the broken conductor protection;
“t
BCP
” is the setting [50BC.t_Op], the time setting of the broken conductor protection;
[50BC.En] is the logic setting of the broken conductor protection;
[50BC.En1] is the binary signal for enabling the broken conductor protection;
[50BC.Blk] is the binary signal for blocking the broken conductor protection.
3.8.2 Broken Conductor Protection Settings
All the settings of the broken conductor protection are listed in the following table. For the
information about the common explanation of the settings, see Section 7.3 .
No. Menu text Explanation Range Step
1 50BC.I2/I1_Set
The ratio setting for the broken conductor
protection
0.10~1.00 0.001
2 50BC.t_Op
The time setting for the broken conductor
protection
0~200s 0.001s
3 50BC.En
The logic setting for the broken conductor
protection
0~1 1
4 50BC.OutMap
The output matrix setting of the broken conductor
protection
0x00000 ~
0xFFFFF
1
3.9 Breaker Failure Protection
3.9.1 Breaker Failure Protection Theory
The circuit breaker failure protection is specially applied for re-tripping the circuit breaker, when