Toshiba GR 200 Series, Instruction Manual

Page: 200 / 1563

6F2S1915 (0.46)
GRZ200 (Soft 031 & 032)
- 179 -
in section (v).
(iii)
Operate time of IDMT
The dependent time in the IDMT is defined by Equation (2.6-4). (ref IEC 60255-151):
𝑡(𝐼) = 𝑇𝑀𝑆 × {[
k
(I I
s
⁄ )
α
− 1
] + c}
(2.6-4)
where:
t = operating time for constant current I (seconds),
I = energizing current (amperes),
Is = earth fault current setting (amperes),
TMS = time multiplier setting,
k, α, c = constants defining curve.
The nine pre-programmed standard characteristic curve are defined in Table 2.6-2. In
addition, one original (user-programmable) curve can be applied. One curve can be chosen for
each EF stage. Figure 2.6-3 illustrates these characteristic curves. For example, the user
should set one for the scheme switches [
EF1-Timer
]. (That is, “
IEC-NI
” is for IEC Normal
Inverse, “
IEC-VI
” for IEC Very Inverse, “
IEC-EI
” for IEC Extremely Inverse, “
UK-LTI
” for UK
Long Time Inverse, “
IEEE-MI
“ for IEEE Moderately Inverse, “
IEEE-VI
” for IEEE Very Inverse,
“
IEEE-EI
” for IEEE Extremely Inverse, “
US-CO2
” for US CO2 short time inverse, “
US-CO8
” for
US CO8 inverse, and “
Original
” for user-programmable characteristic.)
In the IDMT operation, the user can also program the characteristic using time-
multiplier-setting (TMS) for the required operate time. For example, the IEC characteristic is
selected, the user can set the TMS value using the setting [
EF1-TMS-IEC
] (incidentally, the
default value of the TMS is 1.00). The other TMSs are also available by the [
EF1-TMS-UK
],
[
EF1-TMS-IEEE
], [
EF1-TMS-US
] and [
EF1-TMS-ORG
].
Table 2.6-2 Constants for IDMT
Curve type
(IEC 60255-151)
Curve Description k α c
A IEC Normal Inverse (IEC-NI) 0.14 0.02 0
B IEC Very Inverse (IEC-VI) 13.5 1 0
C IEC Extremely Inverse (IEC-EI) 80 2 0
- UK Long Time Inverse (UK-LTI) 120 1 0
D IEEE Moderately Inverse (IEEE-MI) 0.0515 0.02 0.114
E IEEE Very Inverse (IEEE-VI) 19.61 2 0.491
F IEEE Extremely Inverse (IEEE-EI) 28.2 2 0.1217
- US CO8 inverse (US-CO8) 5.95 2 0.18
- US CO2 short time inverse (US-CO2) 0.02394 0.02 0.01694