Directional Over Current Relay Working Principle 1b731d

Directional Over current relay working principle. Directional phase protection equipment is used on a radial network for substations supplied simultaneously by several sources. In order to obtain good continuity of service, it is important that a fault affecting one of the sources does not cause all the sources to trip. The required selectivity is achieved by installing phase directional protection equipment on the incomer of each of the sources.

A phase element connected Ia Vbc B phase element connected Ib Vca C phase element connected Ic Vab

Directional Over current relay working principle Directional overcurrent This type of directional relay is made by combining overcurrent protection equipment with an equipment to measure the phase displacement between the current and the polarisation variable Vbc. Tripping is subject to the two following conditions: - the current is greater than the threshold & - the phase displacement between the current and the polarising Volage Vbc, defined by the characteristic angle, is in the zone between +90° and 90°.