P54x/EN AP/La4 Application Notes
(AP) 6-64
MiCOM P543, P544, P545 & P546
AP
P2229ENa
0
400
Drop-Off
Opto Input
&
50
0
Pick-up
NC Output Relay
0
0
Straight
User Alarm
LED
Latching
Figure 22 PSL for TCS schemes 1 and 3
3.5.2 TCS scheme 2
3.5.2.1 Scheme description
Figure 23 TCS scheme 2
Much like scheme 1, this scheme provides supervision of the trip coil with the breaker open
or closed and also does not provide pre-closing supervision. However, using two opto inputs
allows the relay to correctly monitor the circuit breaker status since they are connected in
series with the CB auxiliary contacts. This is achieved by assigning Opto A to the 52a
contact and Opto B to the 52b contact. Provided the Circuit Breaker Status is set to 52a
and 52b (CB CONTROL column) the relay will correctly monitor the status of the breaker.
This scheme is also fully compatible with latched contacts as the supervision current will be
maintained through the 52b contact when the trip contact is closed.
When the breaker is closed, supervision current passes through opto input A and the trip
coil. When the breaker is open current flows through opto input B and the trip coil. As with
scheme 1, no supervision of the trip path is provided whilst the breaker is open. Any fault in
the trip path will only be detected on CB closing, after a 400 ms delay.
As with scheme 1, optional resistors R1 and R2 can be added to prevent tripping of the CB if
either opto is shorted. The resistor values of R1 and R2 are equal and can be set the same
as R1 in scheme 1.
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