A Practical Method for Nondetection Zone Estimation of Passive Anti-Islanding Schemes Applied to Synchronous Distributed Generators

Abstract

Unintentional islanding detection is a primary requirement for the interconnection of synchronous distributed generators (DGs). For this purpose, voltage and frequency-based relays are largely employed due to their low cost and simplicity However, these devices are not totally reliable due to their associated nondetection zone (NDZ). The NDZ is an effective tool to evaluate the performance of these relays against islanding occurrence. In this context, this paper presents a simple and practical analytical method to estimate the NDZ of frequency and voltage-based relays without relying on numerous, time-consuming electromagnetic transient (EMT) simulations. The main contribution is that one can easily estimate the NDZ of these protection systems based on a few analytical expressions. The effectiveness and generality of the analytical method are verified by comparing its results with those obtained by repeated, intensive EMT simulations for different power distribution networks and different relay types.