Computation of the zero-wire current under an asymmetric nonlinear load in a distribution network

Abstract

Recently the electrical receivers with a nonlinear volt–ampere characteristic have increased significantly in utility electrical networks. The authors suggest applying a detailed account of their characteristics to analyze asymmetric/non-sinusoidal operating mode on an external electrical network. This paper is devoted to the problem of calculating the current level in a zero wire with an asymmetric operating mode of utility electrical networks containing such electrical receivers. A simulation model of the 0.4 kV network section of the urban electrical networks of Dushanbe has been developed. It is shown that a consideration of the higher harmonic components of the zero-sequence current is required, which is not a multiple of three. An algorithm for calculating the harmonic component of the zero-wire current has been also developed to determine the heating temperature of a cable. The obtained results make it possible to correctly select the cross-section of the zero wire of the cable line in the 0.4 kV distribution network for feeding a non-sinusoidal/asymmetric load.

Keywords

• Asymmetry
• Electric receiver
• Higher current harmonics
• Modeling
• Nonlinear load
• Non-sinusoidality