The Way of Reducing Current Values in Optical Ground Wires at Asymmetrical Faults on Overhead Transmission Lines

Georgiy Egamnazarov

doi:10.1515/ecce-2016-0007

Abstract

Abstract Given the fact that the installing costs of an optical ground wire on overhead lines directly depend on its cross-section, which in turn depends on the level of fault current it should withstand, in order to reduce these current values in the optical ground wire, I suggested performing its isolated descents from the end towers of the line with its transition to an optical cable. The research was carried out on the example of a 500 kV overhead line in the National Electric Power Grid. The Method of Symmetrical Components for calculating asymmetrical fault currents was not used; therefore, calculations were carried out on the base of presenting the line as a multi-wire system for the considered case as a five-wire system (optical ground wire, steel ground wire, and three phase wires). Such approach allows taking into account the initial asymmetry of the line parameters and modeling any kind of asymmetrical faults. The analyses of calculated results were performed. The conclusive evidence that the optical ground wire isolated descents from the end towers of the line give the possibility of reducing the level of maximal fault current distribution values in it and therefore its cross section, is presented.

Highlights

In recent years, the suspension of optical fiber composite ground wires on overhead power transmission lines (PTL), known as optical ground wires (OPGW), is becoming increasingly popular.OPGW serves two purposes [1]: 1) to replace a conventional ground wire (GW), to protect the transmission system from lightning, and to serve as a conductive medium for carrying fault currents to ground; 2) to provide telecommunications capacity utilizing optical fibers
Given the fact that the project costs on installing OPGW directly depend on the OPGW cross-section, which in turn depends on the level of fault current it should withstand, the solution for reducing these current values by performing its isolated descents with its transition to an optical cable from the end towers of the line was studied
The isolated descent of OPGW allowed decreasing the values of currents in it – this approach helped to reduce the cross section of OPGW and, as a result, to save costs on the project stage

Summary

INTRODUCTION

The suspension of optical fiber composite ground wires (the IEEE standard) on overhead power transmission lines (PTL), known as optical ground wires (OPGW), is becoming increasingly popular. Given the fact that the project costs on installing OPGW directly depend on the OPGW cross-section, which in turn depends on the level of fault current it should withstand, the solution for reducing these current values by performing its isolated descents with its transition to an optical cable from the end towers of the line was studied. It was proved that this solution gives the possibility of reducing the level of fault current distribution values in OPGW and, of decreasing its cross section, allowing to save the total costs of the project. This approach on the example of the 500 kV PTL Sirdarya–Novoangren in the National Electric Power Grid was implemented and analyzed. The matrices for the second and the third section of the line are not presented as they are too space consuming

THE PRINCIPLE OF FAULT CURRENT CALCULATIONS

A B C phases

ANALYSIS OF THE RESULTS

CONCLUSION