Power Quality Event Analysis in 25 kV 50 Hz AC Railway System Networks

Power quality (PQ) phenomena characterizing the voltage and current signals of railway electricity networks differ from those present in transmission and distribution electricity grids. Presently, there are no standardized procedures focused on PQ measurement techniques explicitly for railway applications. This paper evaluates whether the standard power quality measurement algorithms used in monitoring 50 Hz electrical grids are sufficient for an accurate evaluation and classification of PQ parameters of voltage dips, swells and interruptions present in 25 kV AC railways. An algorithm is presented to better characterize different types of interruption, distinguishing between causes due to network configuration or by other factors. For voltage dips and swells it is also shown that a smaller window size (less than 1 cycle) produces a more accurate estimate of the disturbance magnitude and duration. The two methods are verified against recorded signals of pantograph voltage and current. Recommendations are therefore provided for PQ measurement algorithms for AC railways.