Management of transmission power lines in heavily polluted environments

• Authors: J.M. George, Sediver France
• Title: Management of transmission power lines in heavily polluted environments
• Presented at: RVPAI 2019, XXXII Reunión Internacional de Verano de Potencia, Aplicaciones Industriales y Esposición Industrial IEEE – 16-19 July 2019, Acapulco, Mexico

Abstract

Airborne dust or coastal salt contamination of overhead line insulators can seriously compromise the performance of a transmission line, either AC or DC, generating potential heavy financial losses and additional maintenance costs.

This paper will review the basic concepts required for understanding the contamination process, the tools available for their evaluation and the classical mitigation methods.

Beyond the usual approach where engineers will search for the optimum leakage distance, the last decades have shown the limitations of composite insulators often considered as the only way out. While pollution performance is one of the benefits of this technology using hydrophobic silicone housings time has shown that ageing and failure risks were a major problem in the long term. More recently silicone coated glass insulators have been used in progressively larger volumes and this paper will review the key aspects and performances of this approach to pollution as well as the most recent service experience. Since this technology is gaining more and more interest it becomes a priority for utilities and engineering to be able to select the best coated insulators with meaningful requirements and testing protocols. This paper will suggest ideal elements addressing this need based on a large spectrum of laboratory and field results.

Classical evaluation and mitigation of contamination require usually an outage during which either samples are periodically taken down to measure the pollution level or preventive line washing at predefined intervals is performed. Ideally information on the condition of the string of insulators should be more useful if provided on a real time basis without disturbing the system. This would allow maintenance action at the proper time without any risk or unnecessary premature spending. Innovative techniques for real time evaluation of the condition of a string of insulators are now possible thanks to smart insulators capable to communicate in real time their pollution condition.

This paper will describe the fundamental aspects of this IoT technology where the insulator itself produces a diagnostic. Instead of measuring the level of contaminants through physical sampling on a string, this development will concentrate directly on the consequence of the environment on the performance of the string by measuring the actual leakage current. Using wireless communication technologies, the data is transferred to a dedicated server where the information will be analysed and presented to the end user with a diagnostic of risk of pollution related flashover. Such processes imply a detailed knowledge of the signature of each type of insulator in terms of leakage current since threshold values depend upon shape and profile. Actual examples will demonstrate this aspect.

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