DEVELOPMENT OF THE MEANS TO IMPROVE A SELECTIVE OPERATION OF THE DIFFERENTIAL-PHASE BUSBAR PROTECTION IN CASE OF CURRENT TRANSFORMERS SATURATION ; РОЗРОБКА ЗАСОБІВ ПІДВИЩЕННЯ СЕЛЕКТИВНОСТІ ДІЇ ДИФЕРЕНЦІЙНО-ФАЗНОГО ЗАХИСТУ ЗБІРНИХ ШИН ПРИ НАСИЧЕННІ ТРАНСФОРМАТОРІВ СТРУМУ

An important problem in the field of development and technical improvement of the functional features of relay protection devices used at the electric power stations and power grids is a problem concerning with providing selective operation of these devices in the steady and transient emergency conditions and other modes under which the possible a saturation of the magnetic systems of measuring current transformers, to which are connected relay protection. The purpose of this paper is a development of the algorithmical means to increase selective operation of differential-phase busbar protection of switchgears of power stations and power grids in off-normal and emergency conditions in case of operation with saturation of current transformers. The paper analyzes the possible current transformer saturation conditions, and the functioning of the differential-phase busbar protection of switchgears in these conditions. According to the results of investigations a common feature for the above conditions was identified by authors. It is a presence of no-current pauses in the secondary circuits of saturated current transformers having some duration which is determined by the conditions and the degree of its saturation. The presence of no-current pauses at the secondary circuits of saturated current transformers for one of the bays that are connected to a common busbar and the lack of these pauses for other bays with unsaturated current transformers can lead to unselective operations of differential-phase busbar protection using the operational algorithm which is based in determining the duration of pauses in the impulse signals created from a half-waves of secondary currents. This feature ware taken as the basis for the development of a functional algorithm of operation of differential-phase busbar protection, the use of which increases the selectivity of the protection in case of a deep saturation of current transformers of one or more bays. The diagram and explanations of developed algorithm operation were given in ...