A review of protection systems for distribution networks embedded with renewable generation

Abstract

The rapid growth of grid-connected embedded generation is changing the operational characteristics of power distribution networks. Amongst a range of issues being reported in the research, the effect of these changes on so-called 'traditional protection systems' has not gone without attention. Looking to the future, the possibility of microgrid systems and deliberate islanding of sections of the network will require highly flexible distribution management systems and a re-design of protection strategies. This paper explores the envisaged protection issues concerned with large penetrations of embedded generation in distribution networks extending into auto-reclosure and protection device coordination. A critical review of recently reported protection strategies for grid-connected only and microgrid operation is also undertaken. The outcome is a list of recommendations to achieve microgrid protection adequacy in future networks. AbstractThe rapid growth of grid-connected embedded generation is changing the operational characteristics of power distribution networks. Amongst a range of issues being reported in the research, the effect of these changes on so-called 'traditional protection systems' has not gone without attention. Looking to the future, the possibility of microgrid systems and deliberate islanding of sections of the network will require highly flexible distribution management systems and a re-design of protection strategies.This paper explores the envisaged protection issues concerned with large penetrations of embedded generation in distribution networks extending into auto-reclosure and protection device coordination. A critical review of recently reported protection strategies for grid-connected only and microgrid operation is also undertaken. The outcome is a list of recommendations to * Corresponding author Tel. +61 2 42392397 NOTICE: this is the authors' version of a work that was accepted for publication. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. achieve microgrid protection adequacy in future networks.

Progress on Protection Strategies to Mitigate the Impact of Renewable Distributed Generation on Distribution Systems

“…The protection philosophy of TN applies directional and distance protection fundamentals to identify the faults, even in the case of various fault current sources [50]. Prior of radial feeders been connected to the DG, directional features must be well-thought out due to the fact that traditional overcurrent relays are incapable of sensing bidirectional current flows.…”

“…Despite the benefits of DOCRs, the authors in [50,55] highlighted their drawbacks in terms of cost, fault current and unwanted tripping. Mitigating the protection impact using this strategy will increase the cost when the protection components had become double in that it requires two relays, two current transformers and two circuit breakers for each DG embedded in a DN.…”

“…Another disadvantage is the false tripping impact at the upstream feeder end, which may occur when DG feeding faults on adjacent feeders which are using the NDOCR. Therefore, it is recommended that directional elements are featured in all OC relays in distribution lines connected with DGs with setting on forward operation only to block the fault from adjacent feeders [50].…”

“…all OC relays in distribution lines connected with DGs with setting on forward operation only to block the fault from adjacent feeders [50].…”

A Comprehensive Review of Protection Schemes for Distributed Generation

“…Reference [65] shows how overcurrent relays with no directional elements can cause coordination problems. This is depicted in Figure 15.…”