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Since the instrument has only two relays, and eight possible uses for those two relays,
there may be times when a relay is being asserted by more than one alarm. The relay actions
fall into three categories: Momentary; Transient; and Persistent. A Momentary action, as
the name implies, closes the relay for only a moment, then opens the relay. The Tap Change
Acknowledge is the only Momentary use of a relay. A Transient action is one that keeps the
relay closed as long as a condition remains valid. As soon as the condition goes away, the
relay will open. The High Tap & Low Tap Alarms and the FA 25 and FA 27 Error
Alarms are the only Transient uses of a relay. A Persistent action is one in which the relay
remains closed until it is manually reset by the operator. The Total Tap Change Count
Alarm, On-Tap Alarm, Up-To & Down-To Change Alarms, Pass Through Neutral
Alarm, One Direction Change Alarm are Persistent uses of a relay.
Relay Assertion Priority: Any Persistent relay action takes priority over any
Transient or Momentary action. The Tap Change Acknowledgement Relay can not be
assigned to the same relay as another alarm.
3.2.1 Tap Change Acknowledgement Relay
The 1250-LTC can momentarily close a relay contact following every detected tap
position change. The user can program a delay time of 0.1 to 9.9 seconds, which causes the
relay to wait before asserting. The user can also program a duration time of 0.1 to 9.9
seconds, which causes the relay to hold its assertion before turning off.
Use the OP 3, tCrLY, ACKRLY command to choose which relay output (OFF, LO
or HI) will be asserted following every tap position change. When this value is set to “OFF”
this function is disabled. Do not assign another alarm to the same relay assigned to for
Tap Change Acknowledgement. Use the OP 4, tCrdL, ACKDLY command to set the
delay time. Use the OP 5, tCrLt, ACKHOLD command to set the duration time.
3.2.2 High Tap Relay and Low Tap Relay
The 1250-LTC can close a relay contact when the LTC moves beyond programmable
upper and lower position limits. When the LTC tap position value reaches the Low Relay
limit, the assigned Low Tap Relay turns on, the appropriate Relay LED will light up, and the
alarm code “LOtAP” will be displayed momentarily. When the position value rises above the
Low Relay limit, the Low Tap Relay & LED will turn off and the alarm code will not be
displayed. When the tap position value reaches the High Relay limit the assigned High Tap
Relay turns on, the appropriate Relay LED will light up, and the alarm code “HItAP” will be
displayed momentarily. When the value falls below the High Relay limit, the High Tap Relay
& LED turn off and the alarm code will not be displayed. The user can separately program
which relays will assert for the upper and lower position limits.
Use the OP 15, rL Lt, LTLMT command to set the Low Tap Relay Limit and the
OP 17, rL Ht, HTLMT command to set the High Tap Relay Limit. Use the OP 16, LtrLY,
LTRLY command to select which relay (OFF, LO or HI) asserts when the Low Tap Relay
Limit is reached. Use the OP 18, HtrLY, HTRLY command to select which relay (OFF, LO
or HI) asserts when the High Tap Relay Limit is reached. These are Transient relay actions.
When these values are set to “OFF” this functions are disabled.
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