Toshiba GR200 Series Instruction Manual page 277

Table 2.14-2 Constant value at each setting of IDMT curve
Set item
IDMT
User-programmable
(Original)
Reset feature
The user should set the time for resetting. Figure 2.14-3 shows that examples of the pick-up
and the drop-off relevant to both the fault occurrences and the operation time. The value of the
time counter furnished in the OVG1 element is incremented if faults occur.
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 OVG1 element is paralyzed in the reset time
set by [TOVG1R].
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 OVG1 element will issue a trip command after a certain delay.
After issuing the trip command, if a series of fault completely disappears after issuing the trip
command, the value of the time counter will be expired after the reset time [TOVG1R].
When the user requires resetting the operation of the OVG1 element immediately, setting
zero for the settings [TOVG1R] is needed. Consequently, when a voltage falls below the reset
threshold (drop-off), the operation of the OVG1 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 2.14-3 Faults occurrences and reset operation when IDMT being applied
k
1
0.00000 – 500.00000
by 0.00001 step
Intermittent fault
T
3
Trip level
T T
1 1
T
2
Increment process in time
counter
- 256 -
a
1
0.00000 – 10.00000
by 0.00001 step
Series faults
Tripping
T
1
Value maintenance of time counter
6F2S1915 (0.46)
C
0
0.00000 – 10.00000
by 0.00001 step
Relay operation reset
T
1
T
2
Reset of time counter
GRZ200 (Soft 031 & 032)