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Harmonic Effects on Electromechanical Overcurrent Relays = Harmoniklerin Elektromekanik Aşırı Akım Röleleri Üzerindeki Etkileri

Author(s): K. Burak DALCI | Recep YUMURTACI | Altuğ BOZKURT

Journal: Dogus University Journal
ISSN 1302-6739

Volume: 6;
Issue: 2;
Start page: 202;
Date: 2005;
Original page

Keywords: Electromechanical | Relay | Harmonic | Overcurrent | Elektromekanik | Röle | Harmonik | Aşırı akım

The electromechanical overcurrent protection relays are designed to operate with sinusoidal current. The operation of protective relay with harmonic currents is not reliable. The literature on harmonics and relays covers mostly the theoretical studies. In this paper, the harmonic effects on operation of electromechanical inverse time overcurrent relay (ITOCR) were examined. Not common in existing studies, the behaviour of ITOCR was analysed with laboratory experiments for distorted waveforms. A type of induction disc relay was used as an electromechanical ITOCR in the experiments. The non-sinusoidal load currents that consist of different harmonic spectra were applied to ITOCR and these nonlinear-load currents were processed by a data acquisition card and a harmonic analysis programme in the computer environment. According to the experiment results, the pick up current and the operating time of the ITOCR increase proportionally to the total harmonic distortion (THD) value of the non-sinusoidal current. It is concluded that, this type of relay cannot protect the system reliably due to the harmonic components of current.
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