System studies of voltage dips resulting from energisation of MV wind turbine transformers

A typical wind farm consists of several wind turbines, each operating at less than 1kV and connected to the MV grid system via a turbine transformer. When the turbine transformers are energised, the grid system will see a transient phenomenon called “inrush current” and voltage dips/fluctuations on the local grid system will result. Severe voltage dips can cause fluctuations of certain types of lights resulting in customer complaints. System studies of voltage dips caused by energisation of turbine transformers for three proposed MV wind farm sites connected to 33kV distribution networks have been undertaken using PSCAD software and are described in this paper. Site measurement data was obtained for one of the three sites for verification purposes. The results of the system studies, recommended mitigation measures to overcome any unacceptable voltage dips and energisation switching sequence for each wind farm site are contained in the paper.