This study was used to identify potential arc flash risk when electrical operatives manually switched and / or isolating the wind turbines from the distribution system. The project was used to assess the potential arc flash risk at the 15MW windfarm’s 20KV and 690V equipment. The wind energy convertors (WEC’s) on site generated power at 690V. The wind power generated by the turbines was then stepped up and exported to the distribution network at 20kV. The challenge here was to take into account multiple network feeding arrangements and the WEC’s contribution to the sites overall prospective arc incident energy levels.
Using an advanced power systems software package, SKM, the wind farm’s electrical network was modelled and scenario analysis was performed to simulate the worst case arc incident energy levels on site. Due to the nature of the network, significant time was spent reconfiguring the electrical model to ensure all potential network feeding arrangements were captured. Scenario analysis was imperative in identifying the worst case arc flash risk to electrical operatives.
"The results from this study showed that the risk to electrical operatives is as great on windfarms as it is in large manufacturing facilities. This was witnessed through the high prospective arc incident energies found at both MV and LV distribution levels."
Arc flash hazard analysis demonstrated that there were several locations on site that were considered to be extremely dangerous. Due to the limited settings available on the WEC TXFR supply relay the high prospective arc incident energies could not be mitigated against through protection setting adjustments. Because protective setting adjustments could not be implemented, alternative control measures were recommended. This included remote switching and isolating the LV equipment through the upstream MV circuit breakers.