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operation time. The UV1 element has a time counter that increases in response to the fault
occurrence and duration. This figure also shows the increment degree of the time counter for
the fault occurrences.
As for an intermittent fault (the former in the figure), the time counter does not reach
the trip level. In the other word, the UV1 element will be paralyzed in the reset time [TUV1R].
If a series of fault occurs, the time counter increase corresponding to the duration of series
faults. When the time counter reaches the trip level, then the UV1 element issues a trip
command after a certain delay. After issuing the trip command, if a series of fault disappears
completely, the operation of the UV1 element is expired after the reset time [TUV1R].
When the user requires resetting the operation of the UV1 element immediately, setting
zero for the settings [TUV1R] is needed. Consequently, when a voltage is recovered over the
reset threshold (drop-off), the operation of the UV1 element is reset promptly.
Condition fault occurrence
Fault observation by the relay
Issue of trip command
Incrimination of time counter
corresponding to the fault
duration.
T
: Resetting time set by the user
1
T
: Actual resetting time in the relay operation
2
T
: Time gap between fault occurrence and relay start time
3
Figure 2.13-3 Faults occurrences and reset operation when IDMT being applied
Miscellaneous functions
2.13.3
Blocking UV operation
(i)
Blocking the UV function may be required when a failure in the voltage transformer occurs.
In this case, the user shall set Block for scheme switch [UV1-VTFBlk]. Non (as a default) is set
for scheme switch [UV1-VTFBlk] in order that the UV function is not blocked by the failure.
Intermittent fault
T
3
Trip level
T
T
1
1
T
2
Increment process in time
counter
- 145 -
A series fault
Tripping
T
T
1
1
T
2
Value maintenance of time counter
6F2T0207 (0.01)
Relay operation reset
Reset of time counter
GRE200 (5,6)
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