Electrical diagnostics of high voltage devices via high resolution near field analysis

We here present our latest developments concerning an optical pigtailed electric field sensor dedicated to the monitoring and the analysis of medium and high voltage devices. This non invasive sensor allow to perform safely the electric field vectorial characterization in the closest vicinity of a device under test. The realized optical probe demonstrates here its potentialities for the diagnostic of a 25 kV monoconductor cable and is also exploited to analyse a default on a 100 kV insulator.

I. Introduction

Power transmission and distribution networks as well as power plants or electrical substations involve medium voltage (MV) or high voltage (HV) devices which have to be characterized or even monitored. Indeed, to ensure the quality and reliability of the power grid, the analysis of the electrical cables behaviour, of the insulators properties and more generally of MV and HV devices is required [1]. The related measurements are essentially performed using measurement transformers such as resistive or capacitive dividers in case of contact measurement or with metallic antennas for the contactless far field analysis [2], [3]. Such sensing techniques are limited firstly by the setting up constraints (e.g. galavanic connection to the high voltage device) and secondly by their inherent poor spatial resolution.