Development of a novel single-phase auto-reclosing scheme for distribution network with integrated distributed generation.
Tan, Sock Fua
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According to G59 recommendation, the common practice adopted by utilities in the UK is to disconnect Distributed generators (DGs) immediately once a network fault is detected to prevent islanding operation and disruption of the operation of conventional auto-reclosing schemes. However, with the continuous increase of penetration of DGs into existing distribution networks, it is becoming increasingly important that DGs must support power networks during steady-state and fault conditions. It has been recognised that 80% of faults in distribution networks are temporary and most of them are single-line-to-ground (SLG) faults. This should give a strong incentive to find ways for maintaining DGs in service during temporary SLG faults as far as possible which would benefit utilities, DG developers and customers. The literature survey shows that no research work has been carried out to investigate a fault identification and phase selection algorithm suitable to be used in a novel single-phase auto-reclosing (SPAR) scheme, specifically suitable to distribution networks with DGs, for maintaining the continued operation of DGs during fault conditions. The work in this PhD has focused on investigating feeder protection requirements for continued operation of DGs in radial and ring overhead distribution networks with DGs, particularly the new requirements for operating an auto-reclosing scheme in networks with DGs. Simulation results obtained from this investigation have revealed that it is a possible to maintain continued operation of DGs that are based on DFIG and FSIG during temporary SLG faults in radial and ring operated networks. This is followed by investigating the development of an adaptive fault identification and phase selection algorithm suitable for a SPAR scheme in a power system with DGs. The proposed fault identification and phase selection algorithm uses only the three line currents measured at the relay point. The waveform pattern of phase angle and symmetrical components of the three line currents during the transient period following a fault condition is analysed using IF-THEN condition-based rules in order to determine the type of SLG fault. The verification test results have revealed that the proposed method can correctly detect the faulty phase within one cycle in a distribution network with DGs under various network operating and fault conditions. The work in this PhD has resulted in publication of papers (see Appendix I).