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This paper is an independent evaluation of problems encountered on railways when parts in signalling/train control systems are susceptible to intense, or impulsive electrical and electromagnetic effects. Impulse testing of the communication channels and analysis of responses are significant aspects of the design, build and proving of commercial and domestic digital and communication equipment. EMI and EMC issues may reduce performance. Observations and detailed measurements are the main ways to determine data error rate differences. The French Morane trials did achieve some good comparative results. There are other root causes and factors to consider in practice, train loadings, extreme weather, couplers, cable degradation, component wear and timing period failures occur. The purpose of this paper is to show complex and previously partial understood effect from DC traction GTO impulses can be capture and explained when manufacturers/designers, researchers, trained specialists and users cooperate and accept that both abnormal and normal behaviours of signalling/train control systems have to be addressed together.

The authors discuss the performance of an insulating system with floating electrodes, submitted to lightning impulse tests. The performance of a four conductor compact system was analyzed, for medium voltage networks, known as "spacer systems" and the performance of medium voltage gaps. For the spacer system, among the various conductor connections, those which presented floating electrodes were discussed. Experimentally, the influence of these electrodes was verified, with large dimensions, by comparison with standard systems without floating electrodes on the basis of the value of the critical flashover voltage and mainly on the value of the standard deviation of the critical flashover voltage.

High-end digital impulse analysing systems are becoming more and more accurate and surpass the relevant standard. Various performance data such as amplitude resolution and sampling rate are carefully checked for their influence on final accuracy or improvements in connection with sophisticated signal processing. As important as technical performance are frequent calibrations, which are also influenced by the quality standard ISO 9000. However, frequent calibrations are an expensive procedure. To minimise cost and work, a unique channel insert system has been developed. This channel insert system allows for an easy calibration procedure and a continuous device availability at 60% of the cost of conventional continuously operational systems.

Low voltage impulse testing (LVI) on power transformers can be used to detect winding movement, such as that caused by short circuits or by loss of winding clamping pressure. The technique is being developed to perform tests with transformers online. The techniques are described and results presented.