A MEMS-Based Electric Field Sensor for Measurement of High-Voltage DC Synthetic Fields in Air

Measurement of the electric fields of high-voltage direct-current (HVDC) transmission lines is essential for safety and reliability of power systems. However, air breakdown and corona discharge at the vicinity of HVDC lines create ion flows that induce a charging effect to measurement equipment, causing significant measurement errors. This paper reports an MEMSbased sensor to measure the HVDC fields coupled with ion flows. It consists of two identical chambers and two MEMS electric field sensors that are placed at different levels in the chambers. The chambers use a shielding metal to prevent ion flows from accumulating on the MEMS sensors inside, and thus the electric fields inside the chambers can be measured by the MEMS sensors. The relation between the electric fields inside and outside the chambers is established, and the HVDC fields coupled with ion flows are obtained by using the relation and the measured fields inside the chambers. The design, fabrication, assembly, and test of the MEMS-based sensor are given in detail. The measurement results show that the sensor is able to measure HVDC electric fields coupled with ion flows.

I. Introduction

High-voltage, direct-current (HVDC) systems are superior to alternating current (AC) systems for long-distance electric power transmission in terms of technical merits, safety problems, economic consideration, and environmental issues [1], [2]. Continuous pursuing to low loss in transmission lines has led to the voltage of DC transmission systems to 800 kV. High voltage requires measurement or monitoring of the electric fields close to HVDC transmission lines to ensure safety, predict stability and failure, and diagnose reliability of the power transmission systems [3]. For example, it is necessary to accurately acquire the electric fields near HVDC transmission lines after installing to ensure the safety of passengers and equipment [4]. Changes in the electric fields around transmission lines caused by damage, failure or degradation of insulators can be used to predict reliability problems. Measuring electric fields with distributed wireless sensor networks is essential to smart grids towards highly reliable power systems with intelligent conditioning of production and distribution of electricity [5]–[7].