Identification; Application - Hitachi Relion 670 Series Applications Manual

Section 8
Current protection
8.3.1

Identification

Function description
Four step negative sequence
overcurrent protection
8.3.2

Application

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 a 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.
In many applications several steps with different current pickup levels and time delays are needed.
NS4PTOC (4612) can have up to four, individual settable steps. The flexibility of each step of NS4PTOC
(4612) function is great. The following options are possible:
Non-directional/Directional function: In some applications the non-directional functionality is used. This is
mostly the case when no fault current can be fed from the protected object itself. In order to achieve both
selectivity and fast fault clearance, the directional function can be necessary. This can be the case for
unsymmetrical fault protection in meshed and effectively grounded transmission systems. The directional
negative sequence overcurrent protection is also well suited to operate in teleprotection communication
schemes, which enables fast clearance of unsymmetrical faults on transmission lines. The directional
function uses the voltage polarizing quantity.
Choice of time characteristics: There are several types of time characteristics available such as definite
time delay and different types of inverse time characteristics. The selectivity between different
overcurrent protections is normally enabled by co-ordination between the operating time of the different
protections. To enable optimal co-ordination all overcurrent relays, to be co-ordinated against each other,
should have the same time characteristic. Therefore a wide range of standardized inverse time
characteristics are available: IEC and ANSI.
126
IEC 61850
identification
NS4PTOC
© 2017 - 2023 Hitachi Energy. All rights reserved
IEC 60617 ANSI/IEEE C37.2
identification device number
46I2
I2
alt
IEC10000053 V2 EN-US
Phasor measurement unit RES670
1MRK511407-UUS Rev. N
GUID-E1720ADA-7F80-4F2C-82A1-EF2C9EF6A4B4 v1
GUID-343023F8-AFE3-41C2-8440-1779DD7F5621 v2
Application manual