Electronic Voltage Transformers And The Harmonic Voltage Measurements

In power systems, it is necessary to detect power parameters timely. First of all, we need to measure current and voltage accurately. This paper aims to measure voltage and harmonic voltage in power grid.With voltage level increasing in power grid and the development of intelligent﹑digital device, traditional voltage transformer is hard to meet the developmental requirements of modern power system in voltage level and output mode. This paper chose the capacitance divider as voltage sensor after analyzing the advantages and disadvantages between conventional voltage transformer and new electronic voltage transformer. Electronic voltage transformer is composed of capacitance divider and signal processing circuit. It proportionally transforms the high voltage to lower and available digital signal for power equipment. Firstly, this paper analyzes the performance of capacitance divider on 220kV. Secondly, it processes output voltage of capacitance divider using signal processing circuit so as to response the true voltage parameters. Thirdly, it transforms the analog signal to digital optical signal which can be used by digital device for satisfying the development of modern power system.Power electronic device have been widely applied with rapid development of power electronic technologies. Therefore, harmonic pollution is becoming more and more serious. This paper discusses harmonic voltage measurement on the basis of research on electronic voltage transformer. We chose the capacitance divider as harmonic voltage sensor and FFT with strong operability and practicability as the analytical method of harmonic measurement. Furthermore, we analyze the problems of spectrum a and spectrum leakage, then put forward some methods how to avoid and reduce them.Electronic voltage transformers based on capacitance divider on 220kV has passed the total type tests in Quality Inspection and Test Center for Equipment of Electric Power; we make the performance tests of Harmonic voltage measurement device in the laboratory.