Voltage Changes in Case of 6–10 kV Overhead Line Phase Wire Breakage in 6-10/0.38 kV Electic Network

Abstract

The phase wire breakage of an overhead line is the common damage in electric networks with 6–10 kV voltage. To set a protection in case of a phase wire breakage, the negative and zero sequence voltages are used as an information parameter. The protection device itself is installed either at the end of the 6–10 kV overhead line or at the side of a low voltage step-down transformer with 6–10 / 0.38 kV voltage. To select the information parameter, to obtain its quantitative characteristics and to determine the protection installation location, the investigations using a MATLAB/Simulink computer model, a physical model in the laboratory and experimental electric network are carried out. The article provides the results of the negative and zero sequence voltages research and shows the expedience of using the negative sequence voltage as an information parameter and justifies the installation of a protection device at the side of a low voltage step-down transformer with 6–10/ 0.4 kV voltage. The article shows that the negative sequence voltage more fully characterizes the phase wire breakage of 6–10 kV overhead line than the zero sequence voltage and information on the negative sequence voltage can be obtained on both the side of a high and the side of a low voltage of the 6–10 /0.4 kV step-down transformer.