Wideband Synchronous Measurement-Based Detection and Location of High Impedance Fault for Resonant Distribution Systems With Integration of DERs

The increasing integration of distributed energy resources (DERs) into the distribution system has caused interference with the signals stimulated by high impedance faults (HIFs). Many existing HIF detection or location methods that are only based on the superficial nonlinearity features of signals rather than the deep laws, will become invalid. This paper proposes a detection and location scheme for HIFs by theoretically analyzing the relationships between signals and systems. By establishing the equivalent circuit of a resonant distribution system, an online method to calculate the kernel system parameters is proposed, based on which an adaptive criterion for HIF detection is provided. In this way, the ability to detect HIF is adequately exploited and independent of DER influences. The method is able to detect HIF over 8.5 $\text{k}{\Omega }$ under common operating conditions. Furthermore, the nonlinearity of HIF is analyzed by deriving laws about how wideband signals distribute in the system. The $3^{\mathrm{ rd}}$ harmonic component of zero-sequence signals is proved to be superior in HIF location in terms of signal content and discrimination, which is also demonstrated to be valid under the influence of DER harmonic injection. On this basis, a HIF location method utilizing the $3^{\mathrm{ rd}}$ harmonic zero-sequence signals is proposed. The effectiveness of the method and its robustness to the DER interference are validated by simulated and field HIFs in 10kV systems.

I. Introduction

Integration of distributed energy resources (DERs) into distribution systems has become a prevailing trend to cope with the growing concerns of environmental problems [1]. The structure and characteristics of systems are changed with the increase of DER capacities, probably causing traditional protection schemes to lose their reliability [2]. High impedance fault (HIF) is a challenging fault type in the medium-voltage (MV) distribution network, and protection schemes for them have been studied for forty years but are still not well solved [3]. Generally, HIFs are regarded as single-line-to-ground faults as they occupy the vast majority in practice. They occur in the form of a line coming into contact with a high impedance ground surface or tree and forming a dielectric breakdown (arc). Several forest fires recently happening in Australia (2009), the United States (2018), and China (2020) [4], [5] have been demonstrated to result from HIFs and caused significant damage. In a DER-integrated distribution system, the weak HIF features will be further complicated, and badly needed to develop more reliable HIF protection methods considering such scenarios.