54 6LE008146B
Protection functions
4.3 Short time delay protection against overcurrent
Adjusting the tsd time delay
Adjustment of the tsd time delay is done from the SHORT TIME DELAY PROTECTION
menu.
tsd adjustment
range (ms)
50 100 150 200 250 300 350 400 450 500 550 600
Non-tripping time
(ms)
25 75 125 175 225 275 325 375 425 475 525 575
Maximum tripping
time (ms)
100 150 200 250 300 350 400 450 500 550 600 650
Maximum break
time (ms)
120 170 220 270 320 370 420 470 520 570 620 670
An inverse time function I²t=K can be activated or deactivated when adjusting the short time
delay.
This I²t function makes it possible to improve selectivity with downstream devices. It activates
at the Isd threshold and works up to 10 x Ir.
Example use of the I²t function
lr
lsd
I (A
d
I
2
t
Circuit breaker 1: h3+
Circuit breaker 2: hw+
Circuit breaker 1
Circuit breaker 2
Activating the I²t function on circuit breaker 1 achieves total selectivity, otherwise selectivity
remains partial.
ATTENTION
The I²t function is deactivated by default. Activate it if selectivity needs to be improved.
Trip
command
t non-tripping
tsd time delay
maximum tripping t
maximum break time
Opening of
contacts
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