Abstract
The integration of distributed generation (DG) into a distribution network changes the network’s topology. Three-stage current protection for a radial distribution network cannot meet the requirements of relay protection for a distribution network with DG. A directional relay that is based on the positive sequence fault component (PSFC) can effectively identify faults in the positive and negative directions and can be used to solve the adaptability problem with three-stage current protection in a multi-source distribution network. However, DG and the traditional generators have different fault characteristics and are affected by different control strategies, which may lower the sensitivity of a directional relay based on the PSFC or even cause mal-operation. Focusing on this problem, this paper proposes an improved directional relay that is adapted to a distribution network with inverter-interfaced generation (IIG) integration. The improved scheme divides the operation zone of the directional relay based on the PSFC into sensitive and insensitive areas. If the result of a phase comparison is located in the insensitive area, further identification is needed according to a comparison of the current amplitudes. Simulation experiments are carried out based on PSCAD/EMTDC, and their results verify the correctness of the proposed scheme.
Highlights
In recent years, with the development of distributed generation (DG) technology, DGs have become widely used in the distribution network
If the result of the phase comparison is located in the insensitive area, the direction of the fault is further determined according to the result of the current amplitudes comparison
The fault characteristics in inverter-interfaced generation (IIG) are different from those in a conventional synchronous generator, which may lower the sensitivity of the directional relay based on the positive sequence fault component (PSFC)—or even cause its mal-operation
Summary
With the development of distributed generation (DG) technology, DGs have become widely used in the distribution network. The three-stage overcurrent protection, which is applied to the single-ended network, is not suitable for such scenarios [1,2,3,4,5,6] To solve this problem, the traditional directional overcurrent protection (DOP), which utilizes the phase relationship between the voltage and the current to identify the direction of a fault, is proposed [7,8,9,10,11,12,13]. In view of the low sensitivity or mal-operation of the directional relay based on the PSFC for a distribution network with IIGs, this paper proposes an improved directional relay.
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