Alstom MiCOM P545 - 3.5.2.2 Scheme 2 PSL; 3.5.3 TCS scheme 3; 3.5.3.1 Scheme description

Application Notes P54x/EN AP/La4
MiCOM P543, P544, P545 & P546
(AP) 6-65
AP
3.5.2.2 Scheme 2 PSL
The PSL for this scheme (Figure 23) is practically the same as that of scheme 1. The main
differen
ce being that both opto inputs must be off before a trip circuit fail alarm is given.
P2229ENa
0
400
Drop-Off
Opto Input
&
50
0
Pick-up
NC Output Relay
0
0
Straight
User Alarm
LED
Latching
Figure 24 PSL for TCS scheme 2
3.5.3 TCS scheme 3
3.5.3.1 Scheme description
P2231ENc
Trip
R3
R2
R1
Opto
P54x
Circuit Breaker
Trip
Coil
52a
52b
Trip
Figure 25 TCS scheme 3
Scheme 3 is designed to provide supervision of the trip coil with the breaker open or closed,
but unlike schemes 1 and 2, it also provides pre-closing supervision. Since only one opto
input is used, this scheme is not compatible with latched trip contacts. If circuit breaker
status monitoring is required a further 1 or 2 opto inputs must be used.
When the breaker is closed, supervision current passes through the opto input, resistor R2
and the trip coil. When the breaker is open current flows through the opto input, resistors R1
and R2 (in parallel), resistor R3 and the trip coil. Unlike schemes 1 and 2, supervision
current is maintained through the trip path with the breaker in either state, therefore giving
full pre-closing supervision.
As with schemes 1 and 2, resistors R1 and R2 are used to prevent false tripping, if the opto-
input is accidentally shorted. However, unlike the other two schemes, this scheme is
dependent upon the position and value of these resistors. Removing them would result in
incomplete trip circuit monitoring. The table below shows the resistor values and voltage
settings required for satisfactory operation.
Auxiliary voltage
(Vx)
Resistor R1 & R2
(ohms)
Resistor R3
(ohms)
Opto voltage
setting
48/54 1.2 k 0.6 k 24/27
110/250 2.5 k 1.2 k 48/54
220/250 5.0 k 2.5 k 110/125