Areva MiCOM P521 - Page 17

Update Documentation P521/EN AD/B21
MiCOM P521 Page 15/24
MiCOM P521
+
Vdc
Trip Order
RL1
52a
Opto-input
2
6
Trip Coil
- Vdc
P0038ENb
Figure 22: Trip coil monitoring
Example 2
In this example both the 52a and 52b auxiliary contacts are available, the MiCOM
P521 relay monitors the whole of the trip circuit when the CB is closed and part of the
trip circuit when the CB is open. When the circuit breaker is open the supervision
current bypasses the trip coil via the 52b contact, thus trip coil supervision is not
provided whilst in this condition. If the circuit breaker is open, a fault in the trip path
will only be detected on CB closing, after the tSUP delay time (typically set to 400ms).
In this example resistor R1 needs to be placed in series with the 52b contact to
prevent damage if the trip contact (RL1) is latched, stays involuntarily closed, or a
long trip pulse time is programmed.
MiCOM P521
+
Vdc
Trip Order
RL1
52a
Opto-input
2
6
Trip Coil
- Vdc
P0039ENb
52b
Resistor R1
Figure 23: Trip coil and auxiliary contact monitoring