can be chosen very low. As it is required to detect ground faults in the transformer
winding, close to the neutral point, values down to the minimum setting possibilities
can be chosen. However, one must consider zero-sequence currents that can occur
during normal operation of the power system. Such currents can be due to un-
transposed lines.
In case to protection of transformer windings not feeding residual current at external
ground faults, a fast low current step can be acceptable.
9.5
Four step directional negative phase sequence
overcurrent protection NS4PTOC (46I2)
GUID-E8CF8AA2-AF54-4FD1-A379-3E55DCA2FA3A v1
9.5.1
Identification
GUID-E1720ADA-7F80-4F2C-82A1-EF2C9EF6A4B4 v1
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Four step negative sequence
overcurrent protection
NS4PTOC
I2
4
4
alt
IEC10000053 V1 EN-US
46I2
9.5.2
Application
GUID-343023F8-AFE3-41C2-8440-1779DD7F5621 v2
Four step negative sequence overcurrent protection NS4PTOC (4612) is used in
several applications in the power system. Some applications are:
•
Ground-fault and phase-phase short circuit protection of feeders in effectively
grounded distribution and subtransmission systems. Normally these feeders have
radial structure.
•
Back-up ground-fault and phase-phase short circuit protection of transmission
lines.
•
Sensitive ground-fault protection of transmission lines. NS4PTOC (4612) can
have better sensitivity to detect resistive phase-to-ground-faults compared to
distance protection.
•
Back-up ground-fault and phase-phase short circuit protection of power
transformers.
•
Ground-fault and phase-phase short circuit protection of different kinds of
equipment connected to the power system such as shunt capacitor banks, shunt
reactors and others.
1MRK 504 163-UUS A
Section 9
Current protection
Transformer protection RET670 2.2 ANSI
549
Application manual
Summary of Contents for RELION RET670
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