x/EN AP/Na7
-22 MiCOM P74
Resistor R1 is an optional resistor that can be fitted to prevent maloperation of the circuit
breaker if the opto input is inadvertently shorted, by limiting the current to <60mA. The
resistor should not be fitted for auxiliary voltage ranges of 30/34 volts or less, as satisfactory
operation can no longer be guaranteed. The table below shows the appropriate resistor
value and voltage setting (OPTO CONFIG. menu) for this scheme.
This TCS scheme will function correctly even without resistor R1, since the opto input
automatically limits the supervision current to less that 10mA. However, if the opto is
accidentally shorted the circuit breaker may trip.
Auxiliary Voltage (Vx) Resistor R1 (ohms)
Opto Voltage Setting with
R1 Fitted
24/27 - -
30/34 - -
48/54 1.2k 24/27
110/250 2.5k 48/54
220/250 5.0k 110/125
Note: When R1 is not fitted the opto voltage setting must be set equal to
supply voltage of the supervision circuit.
TABLE 1:
SCHEME 1
OPTIONAL R1
OPTO INPUT
RESISTOR VALUES
4.2.2 Scheme 1 PSL
Figure 3 shows the scheme logic diagram for the TCS scheme 1. Any of the available opto
inputs can be used to indicate whether or not the trip circuit is healthy. The delay on drop off
timer operates as soon as the opto is energized, but will take 400ms to drop off/reset in the
event of a trip circuit failure. The 400ms delay prevents a false alarm due to voltage dips
caused by faults in other circuits or during normal tripping operation when the opto input is
shorted by a self-reset trip contact. When the timer is operated the NC (normally closed)
output relay opens and the LED and user alarms are reset.
The 50ms delay on pick-up timer prevents false LED and user alarm indications during the
relay power up time, following an auxiliary supply interruption.
FIGURE 3: PSL FOR TCS SCHEMES 1 AND 3
To Next Page
Loading...
