A Traction Power Supply System (TPSS) supplies electricity for train propulsion on electrified railways. In many countries, electrified railways have single-phase low-frequency AC power systems fed by frequency converters (FCs). Outages of power will significantly weaken the TPSS, cause operational problems and ultimately lead to traffic disruption in the form of speed reduction, train delays, or cancellations. The aim of this study is to propose an approach to analyse the reliability of power conversion capacity to discover the reasons for ‘loss of load”. The paper assumes train delays are caused by converter outages, shortages of reserve power capacity for unexpected train loads, or a combination of the two. It considers the availability performance of the converter station and evaluates the reliability of the conversion power capacity. It proposes a power-traffic factor (PTF) to aggregate and quantify train power demands. The PTF can be related to the availability of traction power capacity and will identify areas with risks of power shortages. The study finds the shortage in power leading to train delays in some regions of the system is due to a shortage of reserve power capacity

The increased interest in electrified railways can be explained by their huge capacity, high efficiency, and low pollution. Today’s electrified railway is expecting higher demands for electric power for increased speeds, increased traffic volume capacity, and heavier freight loads. This will in turn impose greater demands on railway infrastructure managers to increase the overall capacity of their railways without traffic disruption. The increasing demand for railway transportation services is having a significant effect on important stakeholder requirements, such as safety, punctuality, dependability, sustainability and costs. This in turn is affecting railway practices in the areas of operation, maintenance, and modernisation.The traction power supply system (TPSS) is one of the most important parts of the electrified railway system due to its responsibility for providing a continuous and adequate electrical power for electric railway vehicles and its great impact on the availability performance. The TPSS provides the railway with power either directly with low-frequency generators or indirectly via frequency converters (FCs). In the converter-based electrified railway network, frequency converter stations represent the generation system which converts the electric power from the three-phase 50 Hz public grid to electric power for the single-phase 16.7 Hz traction grid. Obviously, any operational problems in the FCs will cause an unavailability of traction power capacity and consequently entail operational problems for trains, resulting in speed reduction, train delays, or cancellations. Shortages of traction power may occur due to a loss of capacity or a shortage of reserve capacity. The installed capacity should be capable of meeting the system load in the case of unexpectedly large loads, in the event of one or more FC units not being in service due to forced outages or scheduled maintenance, or when a combination of these scenarios takes place. The purpose of the research for this thesis has been to develop methodologies and tools for availability evaluation and improvement of FCs and the traction power capacity, in order to prevent and mitigate outage events through optimal decisions for improvement. To fulfil the stated purpose, empirical data have been collected from reporting databases, interviews, and documents. Examples of the data gathered are train delay statistics, failure statistics, and electrical measurements. The data have been analysed on two different levels, the FC type level and the FC station level, as well as by applying theories related to RAM analysis. The study has addressed issues regarding availability performance as follows: improvement of data reporting system planning, reliability modelling, evaluation of availability performance, and, finally, identification of effective ways to reduce shortages of traction power. The analysis outcome has revealed the areas where resources must be invested for improvement to reduce and prevent loss of load due to capacity outages.

Reliability, availability and maintainability analysis is one of the most important tools for measuring system performance. The performance of a traction power supply system (TPSS) can be measured using the data collected from frequency converters, as these converters constitute the main part of the TPSS. The quality of the collected data should be good enough to provide the correct and complete information necessary for assessment of frequency converter performance. Many methods can be used to assess the performance of converters such as neural networks, fuzzy logic and standards. The IEEE 762 Standard offers a methodology that can provide key performance indicators for power generation units. This standard has been chosen for its widespread acceptance and applicability. To be able to evaluate a converter’s performance, IEEE 762 indexes should be calculated using data such as the downtime, reserve shutdown hours and service hours. Therefore, the purpose of this study is to assess the performance of the Swedish TPSS frequency converters using IEEE 762, and to assess the quality of data by inspecting their compatibility with this standard. In this study, an application has been developed to generate the missing information and to calculate the indexes provided by the standard, in order to evaluate the power converters’ performance. A case with sample data is also discussed in this paper.

The purpose of this paper is to survey the unavailability of the two main types of converters used in the Swedish traction power supply (TPS) system, i.e. the rotary and the static converter. The number of outages and the outage rate has been used to analyze and compare the unavailability of rotary and static converters. The mean cumulative function (MCF) has been used to analyze the number of outages and the unavailability trends, while the forced outage rate (FOR) concept has been used to analyze the outage rates.

The study shows that the outages due to converter failure occur at a constant rate by calendar time at most of the converter stations, while very few stations have an increasing or a decreasing rate. It has also been found that the static converters have a higher number of outages and a higher outage rate by calendar time compared to the rotary converter types.

The results of the study show that combining the number of outages and the forced outage rate gives a better view of the converters’ performance, and provides support for the maintenance decision. In fact, using one of them alone does not reflect reality. Comparing these two indexes is also helpful in identifying the areas where extra resources are needed to improve maintenance planning and where improvements can reduce the outage in the TPS system.