The effect of the van Staden wind farm on the power quality of the rural distribution network

Connection of wind farms to weak networks with a typically low X/R and short circuit ratio could result in a larger variation of voltage for corresponding variation in wind farm generation output. This variation in voltage could negatively affect the quality of electrical power in the vicinity of the connected wind farm. The analysis was based on actual on-site measurement data at individual consumers’ point of supply and the effect of the Van Stadens Wind Farm integration as seen by the consumers can be determined. It was found through statistical and correlative analysis that the voltage quality measured at the test sites were not negatively affected by the presence of generation at the Metrowind Van Stadens Wind Farm. The voltage was found to be more negatively affected by the load current drawn by the consumer at the test site and that it is foremost when the loading current was higher. No definitive evidence of an increase in voltage harmonics due to generation output or loading current was found. At two sites it was however found that the 7th order harmonic is eliminated or reduced by an increase in the generation of the wind farm above approximately 20% of maximum output. Power Factory simulations, using the Quasi Dynamic simulation tool, was performed to validate the voltage findings of the on-site power quality measurements and two things were clear from the simulations. Firstly the voltage at the point of connection has a strong negative correlation with the consumer loading current and means that the voltage will usually decrease with an increase in the loading current and vice versa. Secondly, as with the analysis of the on-site measurement results, it can be said that when current is low, then the generation output of the wind farm will have a proportional effect on the voltage. From the findings of the on-site measurements it was concluded that the wind farm did not have a negative effect on the test site consumers in the vicinity and the Power factory simulations confirmed the conclusions on the voltage analysis. It was also concluded that the local consumer load current has a larger effect on the local measured voltage than the generation output of the wind farm