Minimization of high harmonics in the current of a biasing controlled arc suppressing reactor

Abstract

Compensation of single-phase earth fault currents in 6- to 35-kV networks is one of the purposes of using arc suppressing reactors (ASRs). Nonlinear distortion current of the reactor contributes to the residual fault current, for which reason its minimization is a critical task during ASR design. Operation under the technical saturation mode of electrotechnical steel is a characteristic feature of biasing controlled ASRs. Moreover, the biasing current of the device contains the high harmonics components; the share of these components depends on the structure of the magnetic system and on the properties of the electrotechnical steel. This paper proposes an approach to optimization of the magnetic system of a biasing controlled ASR based on adjustment of the biasing characteristics of the magnetic core according to the results of experimental measurements of the harmonic composition of reactor currents within a wide biasing range. Analysis of the influence of the parameters of the combined shell–core magnetic system on the reactor distortion current is carried out. Results of experiments for obtaining a biasing characteristic aiming at calculation of the harmonic composition of the reactor current with minimum 10% error are given. An optimization calculation of the parameters of the RUOM reactor magnetic system sections was carried out that allowed reducing the distortion current to 4% within the whole control range (10–120%) of the reactor nominal power and to 1% within the range of 60–100% of the reactor nominal power.