Accuracy and Reliability of Switching Transients Measurement with Open-Air Capacitive Sensors

Barakou Barakou,Steennis Steennis,Wouters Wouters

doi:10.3390/en12071405

Barakou Barakou, Steennis Steennis + Show 1 more

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https://doi.org/10.3390/en12071405

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Abstract

Contactless capacitive (open-air) sensors are applied to monitor overvoltages near overhead line terminations at a substation or at the transition from underground cables to overhead lines. It is shown that these sensors, applied in a differentiating/integrating measuring concept, can result in excellent characteristics in terms of electromagnetic compatibility. The inherent cross-coupling from open-air sensors to other phases is dealt with. The paper describes a method to calibrate the sensor to line coupling matrix based on assumed 50 Hz symmetric phase voltages and in particular focuses on uncertainty analysis of assumptions made. Network simulation shows that predicted maximum overvoltages agree within typically 7% compared to reconstructed values from measurement, also with significant cross-coupling. Transient voltages from energization of an (extra-)high voltage connection can cause large and steep rising ground currents near the line terminations. Comparison with results obtained by a capacitive divider confirms the intrinsic capability in interference rejection by the differentiating/integrating measurement methodology.

Highlights

IntroductionKnowledge on actual overvoltages from transients in electrical transmission systems can be very helpful to estimate optimal measures for overvoltage protection, to understand the background of problems (if any) and/or to estimate related degradation of electrical insulation
Knowledge on actual overvoltages from transients in electrical transmission systems can be very helpful to estimate optimal measures for overvoltage protection, to understand the background of problems and/or to estimate related degradation of electrical insulation
This paper describes applications based on open-air capacitive sensors as part of a D/I

Summary

Introduction

Knowledge on actual overvoltages from transients in electrical transmission systems can be very helpful to estimate optimal measures for overvoltage protection, to understand the background of problems (if any) and/or to estimate related degradation of electrical insulation Such transients arise e.g., from line energization and can cover a wide frequency spectrum [1]. The signal at the measurement cable end, characteristically terminated with 50 Ω, is basically the time-derivative of the phase-voltage as picked up with the open-air capacitive sensors. These sensors can be mounted in a short time without adaptation to the EHV (extra-high voltage) system.

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