Toshiba GR 200 Series, Instruction Manual

Page: 293 / 1563

6F2S1915 (0.46)
GRZ200 (Soft 031 & 032)
- 272 -
Table 2.16-2 Values k, a, c for pre-programmable IDMT and user-programmable IDMT
Set item k a C
IDMT 1 1 0
User-programmable
(Original)
0.00000 – 500.00000
by 0.00001 step
0.00000 – 10.00000
by 0.00001 step
0.00000 – 10.00000
by 0.00001 step
Drop-off characteristic
The user should set the time for resetting in the IDMT characteristic. Figure 2.16-3 shows
examples of the pick-up and the drop-off relevant to both the fault occurrences and the
operation time. The UVS1 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 UVS1 element will be paralyzed in the reset time
[
TUVS1R
]. 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 UVS1 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 UVS1 element is expired after the reset time [
TUVS1R
].
When the user requires resetting the operation of the UVS1 element immediately, setting
zero for the settings [
TUVS1R
] is needed. Consequently, when a voltage is recovered over the
reset threshold (drop-off), the operation of the UVS1 element is reset promptly.
Figure 2.16-3 Faults occurrences and reset operation when DT being applied
Condition fault occurrence
Fault observation by the relay
Issue of trip command
Trip level
Incrimination of time counter
corresponding to the fault
duration.
T
1
T
1
: Resetting time set by the user
T
2
: Actual resetting time in the relay operation
T
3
: Time gap between fault occurrence and relay start time
Tripping
T
1
T
1
T
1
T
2
T
2
T
3
Intermittent fault A series fault
Relay operation reset
Reset of time counter Increment process in time
counter
Value maintenance of time counter