Measurements and post-processing for achievement of electromagnetic transient interference models: Application to the signals provided by railway substations

This paper is focused on post-processing developments to automatically analyze measurement results and extract models of transient electromagnetic noises. The study presented in this paper is applied on the electromagnetic disturbances which are produced by the railway substations which supply the railway electrical infrastructure. Currents measurements were performed inside a substation in order to identify the harmonics and the transient signals which are created by the power devices of the substation. Finally, this paper suggests exploiting a time-frequency analysis and an adequate post processing to automatically detect transient signals. Results and concrete applications of these representations will be presented to automatically extract model of the transient noises present in the railway domain.

I. Introduction

The standard 50121 regulates the tests and limits which should be applied to whole vehicles by manufacturers of rail equipment [1]. Radiated emission measurements performed before commissioning of railway vehicles often highlight excessive emissions that correspond to resonance phenomena in the railway infrastructure [2]. These phenomena are generally observed between few kHz to few MHz. However, it is unclear whether the signals that excite these resonances come from vehicles or substations. In this context, we worked on a method of characterization of the signals supplied by the substations in order to extract model of the interferences produced by the sub-stations. Measurements were then performed inside sub-station in the time domain. However, the quantity of data collected and the variety of the measurement conditions made difficult the analysis. We then developed an analysis tool for studying the conducted interference characteristics between 10 kHz and 2.5 MHz, depending on nominal current provided by the substations.