Description
2.6 Protection system
3VA molded case circuit breakers with IEC certificate
Manual, 03/2019, A5E03603177010-03
77
Ground-fault detection in balanced systems
The three phase currents are evaluated using vectorial summation current.
3VA trip unit variants
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ETUs 3-series: ETU330 (LIG)
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ETUs 5-series: ETU560 (LSIG)
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ETUs 8-series: ETU860 (LSIG)
3-pole molded case circuit breaker in balanced systems:
Ground-fault detection in unbalanced systems
The neutral conductor current is measured directly and in the case of 3-pole molded case
circuit breakers only for the ground-fault protection, but in the case of 4-pole circuit breakers
the neutral conductor current is also evaluated for the neutral conductor protection.
The trip unit calculates the ground-fault current using the three phase currents and the
neutral conductor current for the vectorial summation.
3-pole molded case circuit breaker in unbalanced systems, 3-pole 3VA with external N
transformer:
3VA trip unit variants, 3-pole 3VA2 with external N transformer
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ETUs 5-series: ETU560 (LSIG)
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ETUs 8-series: ETU860 (LSIG)
