Applications and discussions of arc flash protection relay as a main busbar protection in MV switchboards

Minimizing the operational personnel´s injury and the damage to the power equipment when an arc flash fault occurs in a MV switchboard has always been a major concern to the utilities protection engineers. This paper summarized the last 10 years application and operational experiences of arc protection in MV switchboards of substations in China. The different aspects of power distribution configuration and applications are discussed in relation to the arc protection. Key protection issues, such as recommendations of current and light settings, reliability of the light sensors, selectivity of the arc protection relays, the pros and cons of the arc protection relays in comparison with the traditional busbar differential protection relays, etc. are also discussed. Finally, two successful arc protection operations are reported and discussed. The paper concludes that as an alternative protection to the busbar differential protection, the arc protection relay can be cost effectively and widely used in the MV switchboards of substations with high speed, flexibility, reliability and selectivity. Particularly the arc protection relays are suitable for retrofitting of existing MV switchboards of the substations where no busbar main protection has been installed in almost all the MV switchboard of the substations in China.