Four Step Residual Overcurrent Protection, Zero, Negative Sequence Direction Ef4Ptoc (51N/67N) - ABB REC650 Applications Manual

Section 6
Current protection
6.4
6.4.1
6.4.2
106
Four step residual overcurrent protection, zero,
negative sequence direction EF4PTOC (51N/67N)
Identification
Function description
Four step residual overcurrent
protection, zero or negative sequence
direction
Application
The four step residual overcurrent protection, zero or negative sequence direction
EF4PTOC (51N_67N) is used in several applications in the power system. Some
applications are:
• Ground-fault protection of feeders in effectively grounded distribution systems.
Normally these feeders have radial structure.
• Back-up ground-fault protection of subtransmission and transmission lines.
• Sensitive ground-fault protection of transmission lines. EF4PTOC (51N_67N) can
have better sensitivity to detect resistive phase-to-ground-faults compared to distance
protection.
• Back-up ground-fault protection of power transformers with ground source at
substation.
• Ground-fault protection of different kinds of equipment connected to the power
system such as shunt capacitor banks, shunt reactors and others.
• Negative sequence direcitonal ground-fault protection of feeders with PTs connected
in Open Delta connection from which it is not possible to derive Zero sequence
voltage.
• Negative sequence directional ground-fault protection of double-circuit medium or
long transmission lines with significant mutual coupling.
In many applications several steps with different current pickup levels and time delays are
needed. EF4PTOC (51N_67N) can have up to four, individual settable steps. The
flexibility of each step of EF4PTOC (51N_67N) is great. The following options are
possible:
IEC 61850 IEC 60617
identification identification
EF4PTOC
2
IEC11000263 V1 EN
1MRK 511 286-UUS A
ANSI/IEEE C37.2
device number
51N/67N
Application manual