Research on single-phase grounding characteristics of low-resistance grounding systems with distributed generation

Abstract

The network-level characteristics of zero-sequence currents during single-phase ground faults in existing low-resistance grounding systems with inverter-interfaced distributed generators (IIDGs) remain unclear. Moreover, the influence of IIDG integration on conventional staged zero-sequence current protection has yet to be thoroughly investigated. Research on these fault characteristics and the applicability of traditional protection schemes is essential for developing effective protection strategies in IIDG-integrated power systems aand holds considerable practical significance. This paper uses the symmetrical component method to analyze the steady-state characteristics of single-phase ground fault zero-sequence current both before and after IIDG connection, as well as the applicability of traditional stage-type zero-sequence current protection. The results indicate that when a fault occurs on a line with IIDG grid connection, the zero-sequence current between the fault point and the Point of Common Coupling increases, while the zero-sequence current on other lines decreases. Conversely, when the fault is on a line without an IIDG, the zero-sequence current on the upstream line of the IIDG grid connection point and the upstream line of the fault point increases, while the zero-sequence current on other lines decreases. Consequently, the sensitivity of the zero-sequence protection Segment I on some IIDG-connected lines is reduced, and there is a risk of maloperation in Segment I or II of certain protection devices during external faults. Finally, a sub-area protection method is proposed to improve.. the single-phase ground fault handling capability of IIDG-integrated power systems.