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1VAC388793-MB A
TCC300
User Manual
continue operating the regulator with this failure until it can be repaired. The alarm
however, will remain in effect as long as the failure conditions exist.
Reaching a Physical Tap Limit Set in the Regulator
When the tap limit is reached, motor power is physically disconnected from the raise or
lower motor windings in the direction of the tap limit and operation in that direction cannot
occur.
This scenario removes motor power from the raise or lower motor winding when the
associated physical tap limit is reached. There is no negative consequence of this
occurring when the Motor Seal-in Failure Block feature is disabled. With the Motor Seal-
in Failure Block feature enabled however, the control cannot detect the difference
between Reaching a Physical Tap Limit and a Motor Seal-in Switch failure, so it must
block and alarm.
The unidirectional nature of the block is designed for this scenario as well as a Motor Seal-
in Switch failure to allow operation of the regulator in the opposite direction when needed.
Alarming in this condition can provide the user with information that there may be a
settings error or an upstream Fixed Tap Transformer may be tapped incorrectly as a
regulator should not normally need to issue a raise or lower command when at its physical
limit.
When Motor Seal-in is selected in the control the Motor Seal-in Failure Block feature and
the input to the Abnormal Tap Position alarm are enabled by default. The user may choose
to disable the Motor Seal-in Block feature. However, the input to the Abnormal Tap
Position alarm is always enabled when Motor Seal-in is selected. The feature includes the
following:
Abnormal Tap Position Alarm Input
The Motor Seal-in Failure Block feature provides an input to the "Abnormal Tap Position"
alarm. This input is actuated on the first occurrence of a tapchange coincident with no
motor seal-in current detected for 15 seconds.
Motor Seal-in Failure Alarm
The Motor Seal-in Failure Alarm is actuated on the second occurrence (either direction)
of a tapchange coincident with no motor seal-in current detected for 15 seconds. This
alarm can be reset by the user from the Human Machine Interface (HMI), from the
TCC600® "Alarms" dialog screen or via SCADA. The alarm is also reset when a
successful tapchange operation occurs (motor seal-in current detected) in either direction.
Motor Seal-in Failure Block
The Motor Seal-in Failure Block is actuated on the second occurrence of a tapchange
coincident with no motor seal-in current detected for 15 seconds in either direction. The
block will be in effect in the direction that produced the second Motor Seal-in Failure
Section 6
Configuration
349
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