Methodology and accuracy for non-invasive detection of switching transient overvoltages from compensation coils connected to power transformers

Peter A.A.F. Wouters (Corresponding author), Armand van Deursen, Mischa Vermeer

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Abstract

Transient voltages from (dis)connecting compensation coils near high voltage transformers are studied. Non-invasive sensors are needed in order to exclude any influence by the measurement equipment on the overvoltage magnitude. This study describes results from open-air capacitive sensors as part of a differentiating/integrating measurement system. Its bandwidth
(up to 10 MHz) allows to record large detail in the switching events. However, the coupling strengths and the cross-couplings inherent to the use of air capacitive sensors need to be determined. Calibration based on symmetric phase voltages during normal operation supplies part of the information. Three methods are compared to supplement this knowledge for establishing the complete coupling matrix between phase conductors and sensors. One method employs estimates from the system configuration, in particular, its symmetry. The other techniques extract information from fast transient events within the responses for both switching on and off. The decoupled waveforms from different methodologies align within their confidence bounds and predict the maximum overvoltage magnitudes within an accuracy of 5% when employing information from the fast transients. Based on measurements performed on two compensation coils, both tested three times, larger overvoltages occurred during energisation compared to de-energisation with maximum amplitude exceeding three per unit.
Original languageEnglish
Pages (from-to)173-181
Number of pages9
JournalIET Science, Measurement & Technology
Volume14
Issue number2
DOIs
Publication statusPublished - 1 Mar 2020

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