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Directional Ground Overcurrent Relays have been an essential component in protection of transmission lines for as long as any of us have been around. Their role has been to provide protection for ground faults by applications that have included an instantaneous element in combination with an inverse time overcurrent element. Recent years have seen a rapid evolution in transmission line protective relays to microprocessor based transmission relays that provide a wide variety of functions that include both phase and ground impedance relay elements. The widespread availability of ground distance protection has led many companies to de-emphasize, or even stop using, directional ground overcurrent protection. This evolution has also resulted in a significant portion of existing DGOC relays that have not been regularly evaluated or maintained to assure proper settings and applications.
Date of Conference: 11-14 April 2011