ACB-I
7
A I R C I R C U I T B R E A K E R
Short time protection has two modes:
1. Inverse time protection: when the fault current exceeds setting current value of denite time, if it is curve(1 ∼ 5),
controller protects according to the curve (1 ∼ 5) of overload long time delay, but the speed 10 times of it. (In
other words, it equals to the tenth of the delay tripping time, which computed from the overload long time curve
expression.) If it curve6, then calculate the inverse time delay tripping time from the expression of short-circuit
shot time delay curve 6 characteristic.
2. Denite time protection: when the fault current exceeds denite time current setting value, controller protects as
denite time delay setting value.
Note : If setting current value of inverse time sets on the position of "OFF" or if denite t
ime setting current value
is less than or equal to inverse time setting current value, then controller protects according to denite
time protection, and the inverse time trip automatic avoidance. If denite time works, tripping time of the
short time delay is greater than or equal to setting value of denite time delay, no matter denite time or
inverse time. Else, denite time exits, delay tripp
ing time of inverse time protection would not restrict by
denite time delay setting value.
Current setting value of inverse time and
denite time
Ir2=Ir1× … 1.5 ∼ 15 ＋ OFF (Exit)
Operating characteristic
≤ 0.9 Ir2 : no tripping
>1.1 Ir2 : delay tripping
Setting value of denite time delay: ts
ts (s) 0.1 ∼ 1( 0.1 interval)
Precision ±10%
Inverse time protection feature
1 ∼ 5 curves are the same overload long time delay, but curve speed is 10 times.
Curve 6 characteristic express: Ts=64ts/ N2 that is
Ts=ts x (8lr1/l)2
Inverse time thermal memory
(15 min, clean out when power o)
Standard+ OFF
4.1.1.2 Short-circuit short time-delay protection features
Table 2 for reference of technical parameters of Short-circuit short time-delay protection features
Table 2: Technical parameters of Short-circuit short time-delay protection features
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