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Description
2.3 Protection system
2.3.5.7
Ground-fault protection GF
The ground-fault protection detects residual currents between the conductors and
grounded parts of the power distribution system. The ground-fault protection function
responds when the rms value of the ground-fault current exceeds the set tripping current
I
for the set delay time t
g
Ground-fault protection can be implemented either as a current-independent or a
current-dependent function.
The ETU300 LSIG electronic trip unit has a current-independent characteristic with a
fixed current setting.
The ETU600 electronic trip unit with the LSIG GFx option plug has a current-
independent or current-dependent characteristic curve with the following characteristics
for ground-fault protection:
• I
• I
• I
In the case of a current-independent characteristic curve, the circuit breaker trips when
the tripping current is exceeded after the set delay t
characteristic, the circuit breaker trips according to the inverse-time characteristic.
This protective function can also be used to detect intermittent ground faults. The
intermittent fault currents are totaled over a period of 5 s. The circuit breaker trips when
the total time of the short-time fault currents exceeds the set delay t
Intermittent detection can be switched off.
Characteristic with LSIG GFx option plug
58
.
g
t
2
t
4
t
6
. In the case of a current-dependent
g
.
g
3WA1 air circuit breaker
Equipment Manual, 02/2023, 92310000002-06
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