Research and Design of High Voltage Line Harmonic Detector Based on Electric Field Coupling Method

Abstract

New energy power generation relies on power electronic equipment, such as inverters. As a large amount of power electronic equipment is connected to the power grid, the power quality of the grid decreases, which causes voltage harmonics to exceed the standard. At present, the voltage harmonic measurement of the transmission line grid can only be indirectly measured in the substation by means of the Potential transformer (PT)/ Capacitor Voltage Transformer（CVT）cabinet. Due to the characteristics of PT/CVT and the wiring mode, the accuracy of harmonic voltage measurement is reduced, which seriously affects the accurate and true judgment of the voltage harmonics of the power grid. Therefore, we propose and design a new method based on field strength method for measuring voltage harmonic signals of high-voltage transmission lines. The method solves the problem of accurate measurement of 2-32 and 3-31 harmonics, and realizes direct measurement of voltage harmonic content of high-voltage transmission line through obtaining directly voltage harmonic signals by electric field coupling principle and applying fast Fourier transform (FFT), Hanning window algorithm to analyze and process harmonic measurement data. Besides, the actual test and measurement accuracy meets the national standard of 0.5 level requirement. The high-voltage line harmonic detector based on electric field coupling method provides a simple and fast method for harmonic detection of high-voltage transmission lines and has good practical value.