An Innovative Relaying Scheme for Protection of AC Microgrid Feeders Using Incremental Negative Sequence Power

The detection of high-impedance faults (HIFs) in microgrid feeders is a serious issue due to low fault current levels during HIFs. This issue becomes especially problematic when microgrids are operating in an islanded mode integrated with inverter-based distributed generators (IBDGs). This paper proposes an innovative relaying scheme for the protection of microgrid feeders using incremental negative sequence power. After a fault occurs, the negative sequence voltage and currents are collected at the ends of the protected feeder and then its incremental values are measured. After that, incremental negative sequence real power is obtained at the ends of the feeder to obtain the proposed relaying feature, i.e., a ratio of the sum of incremental negative sequence real power$(\Delta \mathbf{RSNSP})$. The$\Delta\mathbf{RSNSP}$is defined as the ratio of the sum of incremental negative sequence real power at the two ends of the feeder to the minimum of the powers among the ends. Simulation studies on a modified IEEE 13-bus system have shown that this scheme can detect HIFs and low-impedance faults (LIFs). It has been rigorously tested under various operating conditions, like variations in fault inception angles, faults during islanding, simultaneous faults, evolving faults, composite faults, capacitors, and load switching. This scheme is not only fast and accurate but also performs well even in noisy conditions, changes in topologies (i.e., radial or mesh), synchronization errors, and transient faults. A comparative chart comparing its performance with other recent schemes is also included. Finally, the scheme is also validated on a real-time simulator which proves that the proposed scheme can work effectively under various fault conditions.