Mitigating the Impact of Distributed Generations on Relay Coordination Using Fault Current Limiters

TL;DR

This paper proposes using unidirectional fault current limiters in tie-feeders to reduce short-circuit currents caused by distributed generation, preventing relay setting changes and improving grid protection.

Contribution

It introduces a novel placement strategy for unidirectional fault current limiters in tie-feeders to maintain protection settings in grids with distributed generation.

Findings

UFCL placement prevents relay setting changes

The method is effective across six different scenarios

Reduces short-circuit currents to acceptable levels

Abstract

The use of distributed generation resources, in addition to considerable benefits, causes some problems in the power system. One of the most critical problems in the case of disruption is increasing short-circuit current level in grids, which leads to change the protection devices settings in the downstream and upstream grid. By using fault current limiters (FCL), short-circuit currents in grids with distributed generation can be reduced to acceptable levels, so there is no needed to change the protection relays settings of the downstream grid (including distributed generations). However, by locating the FCL in the tie-feeder, the downstream grid is not more effective than the upstream grid and thus its reliability indices also will be changed. Therefore, this paper shows that by locating the unidirectional fault current limiter (UFCL) in the tie-feeder, the necessity of changing in the relay protection settings of upstream grids is prevented. In this paper, the proposed method is implemented, and its efficiency is reported in six scenarios.