Toshiba GR-200 Series Instruction Manual page 199

As for an intermittent fault (the former in the figure), the time counter will not reach the
trip level. In the other words, the operation of the OVS1 element is paralyzed in the reset time
set by [TOVS1R].
If a series of fault occurs repeatedly (the latter in the figure), and if the value of the time
counter reaches at trip level, the OVS1 element will issue a trip signal after a certain delay.
After issuing the trip signal, if a series of fault completely disappears after issuing the trip
signal, the value of the time counter will be expired after the reset time [TOVS1R].
When the user requires resetting the operation of the OVS1 element immediately, setting
zero for the settings [TOVS1R] is needed. Consequently, when a voltage falls below the reset
threshold (drop-off), the operation of the OVS1 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 2.16-3 Faults occurrences and reset operation when IDMT being applied
Miscellaneous functions
2.16.4
OVS operation blocked by the occurrence of VT failure
(i)
Blocking the OVS function may be required when a failure in the voltage transformer occurs.
In this case, the user shall set Block for scheme switch [OVS1-VTFBlk]. Non (as a default) is
set for scheme switch [OVS1-VTFBlk] in order that the OVS function is not blocked by the
failure.
Intermittent fault
T
3
Trip level
T T
1 1
T
2
Increment process in time
counter
- 180 -
Series faults
Tripping
T T
1 1
T
2
Value maintenance of time counter
6F2T0200 (0.15)
Relay operation reset
Reset of time counter
GRE200 (1,2)