Hitachi Relion 670 Series Applications Manual page 160

Section 8
Current protection
Document
revision
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8.4.2 Identification
Function description
Two step residual overcurrent protection EF2PTOC
8.4.3 Application
The two step residual overcurrent protection EF2PTOC is used in several applications in the power
system. Some applications are:
• Earth-fault protection of feeders in effectively earthed two-phase railway supply system.
Normally these feeders have radial structure.
• Back-up earth-fault protection of transmission lines.
• Sensitive earth-fault protection of transmission lines. EF2PTOC can have better sensitivity to
detect resistive phase-to-earth-faults compared to distance protection.
• Back-up earth-fault protection of power transformers.
• Earth-fault protection of different kinds of equipment connected to the power system such as
shunt capacitor banks and others.
In many applications, several steps with different current operating levels and time delays are
needed. EF2PTOC can have up to two, individual settable steps. The flexibility of each step of
EF2PTOC is great. The following options are possible:
Non-directional/Directional: 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 functionality may be necessary. Note that for
directional operation additional logic in the IED configuration tool is needed.
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 operate time of the
different protections. To enable optimal co-ordination all overcurrent protections, to be co-ordinated
against each other, should have the same time characteristic.
154
Product History
revision
2.2.4 -
2.2.4 -
2.2.5 • The harmonic restraint function changed to freeze the definite and IDMT timers.
• Modes Forward and Reverse were included in both the settings DirMode1 and
DirMode2.
• Previously called setting t2 had its name changed to tDef2 for more clear
understanding.
2.2.6 -
2.2.6 -
IEC 61850
identification
© 2017 - 2023 Hitachi Energy. All rights reserved
IEC 60617 ANSI/IEEE C37.2
identification device number
51N_67N
2(IN>)
IEC15000229 V1 EN-US
Railway application RER670
1MRK506375-UEN Rev. N
M14881-1 v7
M12509-12 v11
Application manual