7SG15 MicroTAPP Description of Operation
©2013 Siemens Protection Devices Limited Chapter 1 Page 30 of 38
Auxiliary Target 2 Temporary change to target voltage.
This adjustment applies as long as the “Select Auxiliary Target 2” input is
active.
Auxiliary Target 3 Temporary change to target voltage.
This adjustment applies as long as the “Select Auxiliary Target 3” input is
active.
[102] Advanced Features
VT / CT Location On which side of Transformer VTs and CT are mounted.
Power Transformer Type Transformer is 3-Phase or Single Phase.
Controlled Voltage Point Which side of Transformer is to have its Voltage controlled.
Tap Spacing Voltage change for each tap step – allows voltage to be calculated on “other”
side of Transformer.
Nominal Tap Position Tap Position at which nominal Power Transformer Ratio is in effect - allows
voltage to be calculated on “other” side of Transformer.
Transformer Voltage Drop
Compensation
Allow for Voltage drop across Transformer windings.
Lowest Tap Direction of Tapping. Ratio specified as HV:LV.
Tap-Changer Location On which side of Transformer the Tap-Changer is mounted.
Voltage Target Adjustment
Step Size
Defines step % change in Target Voltage for each Voltage Target Adjustment
operation.
Voltage Target Acknowledge
Length
Length of Acknowledge pulse for completion of step change to Target
Voltage.
Reactive Stability Factor Allows Circulating Current compensation to be scaled down.
Voltage Monitoring
Overvoltage Alarm Level Alarm Level for voltages outside top of Deadband.
Undervoltage Alarm Level Alarm Level for voltages outside bottom of Deadband.
Overload Blocking Level Prevents Tap Changer operating during Overload condition.
Functional Outputs (mapable to hardware Plant Outputs)
Relay Healthy MicroTAPP is healthy.
If an alarm is to be sent, a normally-closed
contact should be used.
Instantaneous Alarm
Tap Raise Raise Command to Tap Changer.
Tap Lower Lower Command to Tap Changer.
Tap-changer Runaway Uncontrolled Tap Changer operation has
occurred. This output should be used to ‘trip’
the Tap Changer motor supply.
Instantaneous Alarm
Operation Permitted When used, this output should close when a
tap change is initiated by MicroTAPP and
open at the end of the tap change cycle. If the
tap changer operates incorrectly, for example
a Runaway occurs, the contact will open.
Voltage Control Alarm Voltage has been out of Deadband for
prolonged time.
Alarm after 15 minutes
U/V O/V Alarm Voltage is outside Undervoltage or
Overvoltage Alarm levels
Alarm after Alarm Time
setting
Overload Alarm Load is too high. Instantaneous Alarm
Control in Auto Automatic Voltage Control is in operation.
Control in Local Relay is in Local mode.
Ready for Switch-Out Relay is ready to be switched out of service.
If the Transformer is not switched out in the
next 5 minutes, the Relay(s) will revert to
normal operation.
Tap Incomplete Last Tap Change operation was not
completed.
Alarm after 5 minutes
Tap Count Alarm
Number of Tap Change operations has
exceeded pre-set figure.
Instantaneous Alarm
Sum of I
2
Alarm
Accumulated value of I
2
has exceeded pre-
set figure.
Instantaneous Alarm
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