The model of microprocessor-based earth fault relay protection for distribution networks with isolated neutral is developed. For computer model realisation it was used Matlab application Simulink.
The protection model algorithm allows to identify the feeder, which has the highest earth fault current, to eliminate false tripping during inrush capacitive current, to eliminate false tripping during self-start of electric motors, to disable the damaged feeder. A method of increasing sensitivity of relay protection is presented.
The protection model includes current and voltage orthogonal components formers, voltage filter, current filters, zero-sequence current relay, voltage relay, comparative module to identify the the highest earth fault current, locking module to avoid false tripping during inrush capacitive current, locking module to avoid false tripping during the self-start of electric motors, an executive module.
The model principle of operation is based on identification of zero-sequence current by the symmetrical components method and the protection tripping conditions.
The protection testing is presented. It is based on the Matlab-based programmable laboratory stand, which is representing a part of an electrical system. This system include three phase electrical source, transmission lines, current and voltage transformers, electrical loads, shorting plug and developed earth fault relay protection.
Waveforms of the protection model testing are received. The work finds application both in laboratory and for scientific purposes.


Relay protection, modelling, Matlab, simulink, earth faults, real-time mode, zero-sequence current.

Issue number: 3
Year: 2016
UDK: 621.311.078
Authors: Kurmazova N. A.

About authors: Kiselev D.N., Candidate of Technical Sciences, Assistant Professor, e-mail:, Ershov Yu.A., Graduate Student, Engineer, e-mail:, Siberian Federal University, 660041, Krasnoyarsk, Russia.

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