GE KVGC 202 - 6.4 Functional Alarms

K
VCG202/EN M/H11
Technical
Manual
KVGC202
6.3.2 Alarm indication
The alarm LED will flash when the password has been entered. It will be lit and remain
steady when an internal fault has been detected by its self test routine.
The alarm flags can then be accessed to determine the fault, provided the relay is still
able to perform this function. See chapter 3, Chapters 3.3.5 and 3.6 for more information
on alarm the flags.
6.3.3 Blocked indication
When the tap change operation is blocked (RaiseV and LowerV), it is indicated by a
CONTROL LED and a relay output contact (BLOCKED) allocated in the relay mask. The
tap change operation can be blocked for any of the following conditions:
- Tap change failure [Tfail)
- Number of tap change operations [TotalOps]
- Frequent tap change operations [FreqOps]
- Run Away protection [RunAway]
- Block logic input mask (0706) is manually initiated
The CONTROL LED will be flashing for any of the above conditions except for manual
blocking, for which it will illuminate continually. It is also lit permanently during tapping if
the inter tap delay time is set to zero for continuous tap change operation.
6.4 Functional alarms
A relay output should be allocated in the relay mask to give an alarm condition for any of
the functions described in this Chapter. The relay masks can be found in chapter 3,
Chapter 3.3.12. of this service manual. The logic diagram showing the logic for each of
the functions can be found in Appendix 2.
6.4.1 Raise/lower volts indication
Relay outputs can be allocated in the relay masks to give an indication for raise and lower
volts tap change.
6.4.2 Blocked indication
Relay output can be allocated in the relay masks to give an indication for the blocked
condition.
6.4.3 Undervoltage blocking (V<<)
If the system voltage falls below the undervoltage blocking setting value, the
undervoltage detector will operate and instantaneously reset the initial time delay thus
inhibiting the relay outputs to ‘Raise’ or ‘Lower’ tap change operations.
V<< output relay allocated in the relay mask will pick up the undervoltage blocking
condition to give the alarm indication.
The pick-up/drop-off ratios on the undervoltage blocking detection is +5% of the threshold
setting.
6.4.4 Undervoltage detection (V<)
The undervoltage detector block operations that would lower the voltage further thus
defining the minimum working limit of the transformer and allowing tap changes in such a
direction as to restore the regulated voltage.
V< output relay allocated in the relay mask will pick up the undervoltage detection
condition to give the alarm indication.
The pick-up/drop-off differentials on the undervoltage detectors is +1% of the threshold
setting.