Programmable Reset Characteristics; Idmt Characteristics - Toshiba GRE110 Instruction Manual





= ×

( )
t TMS


I



Is
where:
t = operating time for constant current I (seconds),
I = energising current (amps),
Is = overcurrent setting (amps),
TMS = time multiplier setting,
k, α, c = constants defining curve.
Nine curve types are available as defined in Table 2.1.1. They are illustrated in Figure 2.1.2.
In addition to the above nine curve types, OC1 and EF1 can provide user configurable IDMT
curves. If required, set the scheme switch [M∗∗∗] to "C" and set the curve defining constants k, α
and c. The following table shows the setting ranges of the curve defining constants. OC2 and EF2
for stage-2 also provide the same inverse time protection as OC1 and EF1.
IEC/UK Inverse Curves
(Time Multiplier = 1)
1000
100
10
1
0.1
1 10
Current (Multiple of Setting)

Programmable Reset Characteristics

OC1 and EF1 have a programmable reset feature: instantaneous, definite time delayed, or
dependent time delayed reset. (Refer to Appendix A for a more detailed description.)
Instantaneous resetting is normally applied in multi-shot auto-reclosing schemes, to ensure correct




k
(1)
+

c

α
− 
1 


100
10
LTI
NI
1
VI
EI
0.1
100
Figure 2.1.2 IDMT Characteristics
 9 
IEEE/US Inverse Curves
(Time Multiplier = 1)
1 10
Current (Multiple of Setting)
6 F 2 T 0 1 7 2
MI
VI
CO2
CO8
EI
100