24.3.3 CURRENT SENSE
Two of the six relays for Phase A, K3 and K4 are intended to trip a power utility breaker. The current in the con-
tacts of these relays is monitored by relays K9 and K10, which will activate if a current of 250 ma or greater is
present in the trip relay. The current sense inputs, A_SENSE1 and A_SENSE2, are debounced in the Actel. If
current is present while a trip is active and the trip release is programmed for current sense, the Actel will keep
the trip relay energized until the sense current goes to zero. The relay will remain energized even if the trip is no
longer active as long as the sense current continues to be present. This is
required to keep the contacts in the
trip relay from burning out. External relays in the substation are intended to remove the current in the trip relay
after the breaker contacts open.
24.3.4 CURRENT SENSE ALARM
A serial message is sent to the supervisor board over a single wire (SV_DAT) JP1-23. The system clock from
the supervisor JP1-7 is used to clock messages from the Single Pole Chassis to the supervisor. If the current
sense input to the ACTEL ( A_SENSE1 or A_SENSE2 ) is active without any trip signal in at A_IN, the current
sense alarm for Phase A will be active in 32 ms. This could only happen if there is a hardware failure in the Sin-
gle Pole Chassis. This alarm will always be active if a current is sensed for 500 ms or longer.
The supervisor will not accept the signal as an alarm unless it is read twice. If the pulses are not present for
more than 500 ms, the supervisor will issue an alarm indicating a problem in the Single Pole Chassis. The clock
may have failed or the connector may have been unplugged. The missing serial messages will indicate a bro-
ken connection or board failure.
24.3.5 TARGETS (See note below)
If a trip input from the back plane lasts for more than 1ms, the “TRIP” LED is latched on. In addition, if a sense
current input from one of the current sense relays lasts for more than 4 ms, the “TC1” or “TC2” LED is latched
on. This will be a record of a trip or a sense current, after the trip has released or the sense current has been
turned off. The target LEDs can be reset by pressing the reset button on the display controller. The reset will
cause a three-second LED test which causes all LEDs to turn on for 3 seconds. If the trip is not active or if the
sense current is not active, the LED targets will turn off. If the sense current is still on, the targets will not be re-
set.
NOTE
A Target is a visual indicator, such as an LED, which remains ON after the event has occurred.
24.3.6 TARGET DOWNLOAD
When the Single Pole Chassis is first turned on, the active targets, current sense targets, three pole/ single pole
and trip release code stored in the display controller are sent down to the Single Pole Chassis. A trip may have
occurred and the power to the unit was turned off. When the power is turned on again, the target information is
still present in the display controller. The Single Pole Chassis does not have battery backup to save the targets
and must get the beginning target status from the display controller. After the power is on, any new target infor-
mation is latched from the trip and sense current signals as described in the TARGET section above.
24.3.7 POWER SUPPLY CIRCUITS
The +15, -15 and +5 volt supplies are monitored by the trip disable circuitry. If any of the supplies are not pre-
sent, trip is disabled since the relays do not have power to operate.
RFL 9300 RFL Electronics Inc.
August 25, 2000 24 - 7 (973) 334-3100
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