Bird protector-related issues on medium voltage overhead networks

Abstract

In the last few years bird protection became a more and more important aspect on medium voltage overhead lines. Injuries of birds related to electrocution endanger both the health of the different species and the reliability of the grid as well. International standards and national regulations based on the opinion of different associations for wildlife protection are often been accepted without any detailed inspection of equipment to be installed on the network. There are many types of insulators, cross-arms and poles even in a specific section of a medium voltage power line. The same type of rigid bird protector installed on them can easily increase the risk of failures caused by the wrong way of application or installation. A rigid bird protector - especially in case of rainy weather conditions or fog - acts as a floating object near the phase conductors. This electrode distorts the electric field distribution even in case of normal operational conditions and increase the risk of flashovers on the surface of the insulators caused by an overvoltage wave in the conductors. Use of conductor and insulator covers are also questionable from the aspect of live-line maintenance (LLM): inspection of working site became impossible and electrical and mechanical condition cannot been estimated at all. Operations with the hot stick method - which is a widely used LLM technique for example in Hungary - became especially difficult. Inspection of different bird protective equipment from electrical aspect is a very important question to keep the operation of medium voltage grids as reliable as possible. In the High Voltage Laboratory of Budapest University of Technology and Economics calculations, finite element simulations of electric field and potential on complex 3D CAD models and a set of measurements have been executed to inspect the exact effects of these equipment from the aspect of the reliability of the grid. Experimental studies in Hungary show that many failures are related to rigid bird protectors. There are often detectable marks on the surface of both the phase conductors and insulators. There are many bird protector-related switch-offs on the territory of different Hungarian DSOs, so the clarification of unexplained questions about this practical topic is urgent and become more and more important.