Study of Frequency Characteristics of a Voltage Sensor Based on System of Galvanically Coupled Bodies

Measuring voltage in electrical networks is an important task in ensuring its stable and uninterrupted operation. The design of a high-voltage measuring system of industrial frequency based on a system of galvanically coupled bodies is proposed. A mathematical model of a sensor with a matching device, including an instrumentation amplifier and an integrator, is described. The results of the conducted analysis of the frequency characteristics of the elements of the matching device are presented. The harmonic composition of the voltage at the output of each of the elements that make up the measurement system was measured and compared with the reference values. During the experiment, the adequacy of the mathematical model, as well as the correctness of the selection of elements, was confirmed. The results showed that the developed voltage sensor based on a system of galvanically coupled bodies with a matching unit meets the permissible requirements for the accuracy of high voltage measurement at least up to the 9th harmonic.

I. Introduction

An integral part of a modern electric power system are relay protection and automation devices, the purpose of which is to disconnect emergency sections of the power system in order to protect electrical equipment and ensure uninterrupted functioning of the electric power system as a whole [1]. The operation of relay protection and automation devices is based on information received from primary current and voltage sensors. Currently, there are three main types of voltage sensors used in the electric power industry: traditional electromagnetic measuring VTs, VTs based on capacitive dividers and optical VTs [2]–[7]. All of these primary converters have a number of known disadvantages [8]–[11]. A technological feature of the construction of existing voltage measurement systems based on VTs is galvanic isolation on the side of the measuring element.