Toshiba GR-200 Series Instruction Manual page 95

Reset time for IDMT
(v)
Programming the reset time characteristic is available for the IEEE standard, US standard
and original (user-programmable) dependent time characteristic†. In the IEEE standard, for
example, the user can set DEP for scheme switch [SEF1-Rtimer]. The following equation
defines the reset time for the inverse-time-reset characteristic (ref. IEC 60255-151):
where:
t = time required for the element to reset fully after complete operation (seconds),
I = energizing current (amperes),
Is = threshold setting (amperes),
kr = time required to reset fully after complete operation when the energizing current is
zero
RTMS = time multiplier setting for resetting.
β = constants defining curve.
For setting RTMS for the IEEE standard, the user can use setting [SEF1-RTMS-IEEE]
(incidentally, the default value is 1.000). Similarly, setting [SEF1-RTMS-US] and [SEF1-RTMS-
ORG] are provided for the US standard and the original, respectively (For more information
w.r.t the values for the kr and β, see Table 2.4-2; Figure 2.4-4 shows the characteristic curves)
Table 2.4-2 Constants for inverse-time-reset characteristics
Curve Type
IEC 60255-151
A IEC Normal Inverse (IEC-NI‡)
B IEC Very Inverse (IEC-VI‡)
C IEC Extremely Inverse (IEC-EI‡)
- UK Long Time Inverse (UK-LTI‡)
D IEEE Moderately Inverse (IEEE-MI)
E IEEE Very Inverse (IEEE-VI)
F IEEE Extremely Inverse (IEEE-EI)
- US CO8 inverse (US-CO8)
- US CO2 short time inverse (US-CO2)
†Note: To select the inverse-time-reset characteristic, set [SEF1-Rtimer]=DEP.
Conversely set [SEF1-Rtimer]=DEF to select definite-time-reset characteristic.
Note: For the setting [SEF1-Rtimer]=DEP (inverse-time-reset), the integrated value will
be reduced in accordance to the magnitude of an energized current, when the
energized current is smaller than the setting [SEF1]. The reducing degree will be
determined with the reset curve characteristics defined in the standards.
Note: For the setting [SEF1-Rtimer]=DEF (definite-time-reset), the integrated value
kr
�� ( I ) = �������� × [
1 − ( I I
⁄ )
Curve Description
- 76 -
]
β
s
kr
sec
N/A
N/A
N/A
N/A
4.85
21.6
29.1
5.95
2.261
6F2T0200 (0.15)
(2.4-2)
β
N/A
N/A
N/A
N/A
2
2
2
2
2
GRE200 (1,2)