Influence of Quality of the Electric Energy on Reliability of Electrical Supply Systems

The problem of electric power quality is currently aggravated due to increase in nonlinear, unbalanced and abruptly variable loads capacity. The range of loads is expanding both in the industrial and the household sectors. Growth of renewable power sources also affects the electric power quality. The most significant negative effects of electric power quality degradation are: increased energy loss; decrease in the service life of electric installations insulation; malfunctions, errors and failures in the operation of relay protection and automation, telecommunications and microprocessor technology. As a result, the reliability of power supply systems is compromised and normal performance of electrical receivers and consumers is disrupted. The number of accidents and power system disturbances caused by degradation of electric power quality is increasing. Annual losses due to low electric power quality amount to hundreds billions of rubles. Non-sinusoidality, imbalance, voltage deviation and the way, they affect reliability indices of elements and power supply systems were addressed in the paper. The impact of electric power quality on power supply systems reliability was described. Dependencies between power quality indices and probability of failures and non-failure operation were identified. It was shown, how sudden and gradual failures of electrical equipment and networks depend on power quality. It was determined, that with power quality indices higher than normal, reliability of power supply is negatively affected. Examples were presented, which show quantitative decrease in power systems reliability indices in conditions of power quality distortion. The identified dependence between power supply systems reliability indices and power quality indices allows acting promptly, to avoid situations, that can lead to undersupply and interruptions in power supply due to low power quality.