Toshiba GR200 Series Instruction Manual page 285

Table 2.15-2 Values k, a, c for pre-programmable IDMT and user-programmable IDMT
Set item
IDMT
User-programmable
(Original)
Setting drop-off operation
The user should set the time for resetting in the IDMT characteristic. Figure 2.15-3 shows
examples of the pick-up and the drop-off relevant to both the fault occurrences and the
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 signal
after a certain delay. After issuing the trip signal, 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 2.15-3 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
- 264 -
a
1
0.00000 – 10.00000
by 0.00001 step
A series fault
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)