分布式光伏接入对变压器中性点过电压特性的影响研究OACHSSCD

Aims:This paper aims to quantify the impact of distributed photovoltaic(PV)integration on the neutral-point overvoltage of 110 kV ungrounded transformers and to assess the adaptability of the coordinated protection scheme composed of a protective gap and a metal oxide arrester(MOA).Methods:A 110 kV transmission system model with distributed PV was established in the alternative transients program-electromagnetic transients program(ATP-EMTP);and the neutral-point overvoltage responses under typical fault conditions were simulated and analyzed.Results:Distributed PV integration significantly changed the distribution characteristics of neutral-point overvoltage.Under single-phase-to-ground faults,sustained current feeding from PV raised the neutral-point voltage from 41.8 kV to the critical gap discharge range of 43.6～72 kV,markedly increasing the risk of gap maloperation.Under two-phase disconnection faults,PV suppressed the overvoltage amplitude.But the voltage dropped from 72.02 kV into the same critical range,reducing the reliability of gap operation and increasing the risk of insulation coordination failure.Under lightning faults,PV integration had little influence on the transient neutral-point overvoltage.Conclusions:The conventional fixed-gap protection scheme is no longer fully suitable for the more complex voltage behavior introduced by PV integration.The proposed controllable gap strategy based on amplitude-time dual criteria can effectively avoid maloperation and failure-to-operate risks in the critical range.