ABB Remote I/O RIO600 Installation And Commissioning Manual page 116

Section 6
Commissioning
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GUID-10A31995-3BC8-4F02-9384-5AD774869A66 V1 EN
Figure 62: Earth-fault in an isolated network
Directional earth-fault detection in a compensated network
In compensated networks, the capacitive fault current and the inductive resonance coil
current compensate each other. The fault detection cannot be based on the reactive
current measurement, since the current of the compensation coil would disturb the
operation of the relays. In this case, the selectivity is based on the measurement of the
active current component. The magnitude of this component is often small and must
be increased by a parallel resistor in the compensation equipment. When measuring
the resistive part of the residual current, the relay characteristic angle (RCA) should
be set to 0° and the operation criteria to "IoCos" or "Phase angle".
the simplified equivalent circuit for a compensated network with an earth-fault in
phase C.
B C
ΣI
01
C
0
ΣI
02
I
ef
1MRS757488 H
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0
ΣI
02
Figure 63 illustrates
Installation and Commissioning Manual
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RIO600