engleski

Relay protection of isolated, compensated and low- resistance grounded distribution networks

This thesis consists of a theoretical background of the relay protection schemes in distribution networks that will be activated if the fault occurs. Different methods of the star point grounding in isolated, compensated and low- resistance distribution networks as theirs advantages and shortcomings, considering network topologies and other influences, are described also. Here are shown two relay types ; Siemens’s 7SJ62/64 and ABB’s REF615 relay. Both of them are using cos(ϕ)/sin(ϕ) and V0(φ)/I0(φ) measurements due to fault. They are applicable in each of these networks individually. They are used in radial, meshed and looped networks. Both of them can determine fault direction and location. A sensitive, directional ground varmetric element is the classic solution for the ground fault detection in isolated systems. Relay selects automatically the best directional element to use for each particular fault and system condition in low-resistance grounded distribution network. The wattmetric method is the most widely used solution for ground fault detection in compensated systems.

relay protection ; distribution network ; isolated ; low-resistance ; grounding ; Petersen coil ; ground faults

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