ABB 615 series Technical Manual page 855

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1MAC059074-MB A

615 series ANSI

Technical Manual

Open CT circuits create extremely high voltages in the circuits, which

may damage the insulation and cause further problems. This must be

taken into consideration especially when the protection functions are

When the reference current is not connected to the protection relay, the

function should be turned off. Otherwise, the FAIL output is activated

when unbalance occurs in the phase currents even if there was nothing

wrong with the measurement circuit.

Reference current measured with core-balanced current transformer

CCM compares the sum of phase currents to the current measured with the core-balanced

GUID-DA7A48EF-0F07-4665-9A09-87188E5A9982 V2 EN

Connection diagram for reference current measurement with core-

balanced current transformer

Supervision functions

protection relay

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