Availability and Reliability Performance Analysis of Traction Frequency Converters - A Case Study

The frequency converter is one of the main parts of the traction power supply system (TPSS) and converts adequate traction power from the power company to the electric vehicle. In the Swedish railway network, this system comprises around 133 frequency converters with a total capacity reach of 1,295 MVA and covers around 9,543 km of electrified railway. The aim of this article is to evaluate and compare the reliability, availability and maintainability (RAM) performances of the ten models of converters used in the Swedish railway system. The key performance indicators introduced by the IEEE Std 762 methodology have been used to measure and compare the RAM performance of the converters. Moreover, the mean cumulative function (MCF) has also been used for the monitoring and comparison of the field reliability of converters versus the operating time, capacity factor and converted power. The study shows that, in general, both the static and the rotary types have a high level of availability ranging from 97%-99%. The results also show that the TGTO model (a static type) has the lowest RAM performance among all the models. In addition, it has been found that using IEEE Std762 or the MCF alone does not always provide a complete answer. Therefore, the study suggests using both the IEEE Std762 and the MCF methodology to arrive at a more realistic result. The study has shown that the MCF based on the capacity factor gives a good result compared with the results obtained using the MCFbased on the operating time and on the converted power as a measure of the usage intensity