7SG15 MicroTAPP Description of Operation
©2013 Siemens Protection Devices Limited
Chapter 1 Page 20 of 38
For an incorrect tap change, Figure 14, where the mechanism over-runs, or continues to operate, a new control
signal AND/OR ‘in progress’ is detected before the internally generated reclaim time has expired. The tap change
has not satisfied rule 3 above, and a further tap position change will result in a lockout signal and the TIP LED will
flash.
Raise/Lower
TPI
Lock Out
Time
In Progress
Runaway Condition
Next cycle starts before
Reclaim time end
IP Indication
Figure 14
The runaway prevention unit also protects against a runaway situation during push button operation. Unwanted
lockouts in manual control are prevented by avoiding further operations until the "In Progress" LED is
extinguished.
If a lockout is required the relay can be configured to operate contacts both for lockout and alarms. Output
contacts can be used for the tripping of a mechanically latched contactor or the permissive operation normally
open contactor.
6.2.2 Tap Change Incomplete
If a ‘raise’ or ‘lower’ signal is sent to initiate a tap change operation and the operation is not completed, then the
relay can be configured to issue an alarm and lockout the tap-change motor power supply. For a tap change
operation to complete, a pulse must be seen at the ‘In Progress’ Status Input and the indicated tap position must
change.
6.2.3 Limit of Tap Change Range
If the tap changer is on either the top or bottom tap position, an "End of Tap Range" alarm is issued. Further tap
changes will be inhibited if they attempt to drive the tap changer beyond its extreme positions.
6.2.4 Tap Not Achievable
If the tap changer is on either the top or bottom tap position and the voltage goes out of the Dead-band in such a
direction that a corrective tap change would be required beyond the tap changer extreme positions, a "Tap not
achievable" alarm will be issued.
