Negative-sequence overcurrent element application and coordination in distribution protection

Negative-sequence overcurrent elements do not respond to balanced load and can thus be set to operate faster and more sensitively than phase overcurrent elements for phase-to-phase faults. It is demonstrated that on a radial distribution system negative-sequence overcurrent elements need only be coordinated with downstream phase overcurrent devices for phase-to-phase faults. Coordination for other fault types is then achieved with no further analysis required. The effects of negative-sequence load current and open phase conductors on negative-sequence overcurrent elements are discussed.<>