Direct current lightning tests on Optical Ground Wires

Abstract

In the last 19 years, the Mexican Federal Electricity Commission (CFE), proprietary of the transmission lines in all the country, has proceeded to replace its conventional overhead earth wires by Optical Ground Wires (OPGW) which is expected to lead to a better incentive. Indeed, those wires include in addition to the traditional protection aspect against atmospheric discharges, the ability to remotely control and operate the grid as well as passing telecommunications. The OPGW's are designed based on the electrical and mechanical specifications required by the end user to fit a given application. Nevertheless, the position of the wire at the top of the transmission towers is to protect the power phases below against lightnings. Therefore, the designer should guaranty its physical integrity as well as its additional functionalities under any atmospheric conditions which can be realized through direct current lightning tests as defined by the national specification given in CFE E000-21-2011 and the international standard IEC 60794-1-2. In addition, it is necessary to define the polarity applied during the tests in order to obtain a representative level of damages found in the field. Implementations of the this specification and the international standard has been carried out and various tests have been conducted on OPGW's for the Mexican utility grid. The results have been compared to actual damages found in the field.