Section 4
1MAC050144-MB C
Protection functions
172
615 series ANSI
Technical Manual
Figure 76:
Ground-fault situation in an isolated network
Directional ground-fault protection in a compensated network
In compensated networks, the capacitive fault current and the inductive resonance coil
current compensate each other. The protection 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
means of a parallel resistor in the compensation equipment. When measuring the resistive
part of the zero sequence current, the relay characteristic angle (RCA) should be set to 0
degrees and the operation criteria to I
0
cos(
φ
) or phase angle.The figure below describes
how ground fault current is defined in compensated neutral networks.
A
B
C
C
0
-
ΣI
01
ΣI
02
-
ΣI
02
I
ef
R
0
0
V
0
V
0
V
Summary of Contents for 615 Series ANSI
Page 1: ...Relion Protection and Control 615 series ANSI Technical Manual ...
Page 2: ......
Page 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Page 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Page 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Page 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Page 711: ...Section 16 1MAC050144 MB C Glossary 704 615 series ANSI Technical Manual ...
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