Rapid voltage changes and their evaluation in comparison to IEC TR 61000-3-7 and EN 50160

Voltage characteristics in the Czech Republic distribution networks are monitored on a long-term basis according to EN 50160, using permanently installed voltage quality analysers that comply with the requirements of IEC 61000-4-30 for class A instruments. Rapid voltage changes (RVCs) are monitored and evaluated, however, EN 50160 does not provide all necessary details to detect RVCs and distinguish them from voltage fluctuation. The definition of RVCs and the method for separating RVCs from voltage dips and swells are in IEC 61000-4-30, nevertheless the RVC setting is not unique. The magnitude and number of RVCs are detected and stored, but only if the voltage changes do not exceed the limits for voltage dips or swells. RVC, including compatibility and planning levels, are also addressed in IEC TR 61000-3-7, but individual emission limits are not specified. Moreover, according to clause 10.5 the worst case is assessed, i.e. the emission limit is applied for 100% quantile. The paper presents results of the measurement campaign in the public distribution networks, including RVCs monitoring, and shows that the IEC TR 61000-3-7 RVC indicative planning levels are very frequently exceeded, yet customers complaints don’t practically occur. The aim is to discuss the suitability of settings for RVCs in IEC TR 61000-3-7 and the need to adopt newer procedures based on experience of other countries.