Determination of the fundamental frequency components by tracking voltage and current phasors

Recently, problems arose with actions of protection relays in MV systems (6 kV) on occurrences of arcing faults. Most of these faults are results of the isolation damaging and they begin as earthing faults. The earth faulted current depends on the connection of the transformer's neutrals. The earth faulted currents that are bigger than nominal currents are identified by overcurrent elements in respective phases. In occasion when the earth faulted current is smaller than working currents, more sensitive protective relays are needed which are created on the basis of measuring zero sequence components of voltages and currents, for the purpose of the fault identification. Protecting relays for these aims require overcurrent protective relay for the identification of short-circuit currents and the arcing fault detector, which will identify the low currents. These protective problems can be solved by used a microcomputer, what is described in this paper. 6 refs, 1 fig