The Study on a New Method for Measurement of the Surge Voltage of 10/700 μs Based on Electric Induction of the Metal Slice

The accurate measurement of the transient fault voltage is helpful to the control, protection, condition monitoring, and evaluation of the power system. In this article, a simple and economical method for measuring the transient fault voltage based on the electric induction of a metal slice is proposed. The frequency spectrums of the transient fault voltage and the surge voltage of 10/ 700 μs are compared. The surge voltage of 10/ 700 μs is selected as the excitation source to mimic the transient fault voltage in the simulation and experiment. A simple coaxial experimental model for mimicking the gas-insulated switchgear (GIS) is built. Two schemes for the metal slice are designed and fabricated on the earthed enclosure. The equivalent circuit of the measurement system is established. The capacitance parameters in the equivalent circuit are calculated by the finite element method. Based on the equivalent circuit, the transfer relationship between the measured voltage and the induced voltage is given. The effect of the parameters of the equivalent circuit on the surge voltage measurement is discussed. The effectiveness of the method is verified by both simulation and experiment. The sensing part of the proposed method has the advantages of low cost and no insulation problems. The proposed method can be directly used in GIS.

I. Introduction

The surge voltage is a kind of transient overvoltage whose peak value exceeds the normal operating voltage, which may damage the power equipment and threaten the safe operation of the power system [1], [2]. The main sources of the surge voltage in power systems include external sources, such as lightning strikes, and internal sources, such as switching operations and system ground faults [3]. The surge voltage caused by lightning has the characteristics of wide impact range, long transmission distance, and a large amount of energy, and its rise time is microsecond level. The transient frequency of the surge voltage caused by the ground fault is usually between hundreds of hertz to tens of kilohertz. The transient fault voltage contains a lot of information about the fault, such as the type, location, direction, and duration of the fault, so it can be used for line protection. Therefore, accurately obtaining the waveform and data of the surge voltage is of great significance to the insulation design, lightning protection, and fault analysis of the power system [4]–[7].