Introducing novel risk-based indicator for determining transmission line tower's backflashover performance

Abstract

Transmission line (TL) backflashover (BF) performance has been traditionally ascertained using a single number, the so-called backflashover rate, which is measured in number of BF events per 100 km-years. This paper aims at presenting a novel indicator for assessing performance of high-voltage TL tower’s ability for tolerating direct lightning strikes without provoking BF events. This indicator is also defined as a single number, which can be computed for any TL tower (by means of EMTP simulations) and measures, in a novel way, its tolerance against BF events. It is given in terms of the risk of the BF occurrence, which means it is statistical in nature and depends on the total sum of conditions governing the BF events. The BF risk, as an indicator, is obtained from the probability density function of the shield wire(s) incident lightning currents and the cumulative distribution function of the BF currents statistical distribution. Hence, it merges complete probabilities of obtaining lightning currents striking a tower with probabilities of those currents provoking BF events on that tower. This novel risk-based indicator can be related to the price of that risk and the associated investment costs, enabling the cost-effective optimisation solutions to the problems of TL arrester applications and station insulation coordination design. This seems appropriate, considering the fact that the investment in surge arresters and related protective measures is commonly perceived as buying insurance.

Petar Sarajčev

Full Professor | Department of Power Grids and Substations

Damir Jakus

Full Professor | Department of Power Grids and Substations

Researcher and a full professor at the Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture in Split. His research interests include power system optimization and planning, RES integration, electricity market modeling.

Josip Vasilj

Associate Professor | Department of Power Grids and Substations

Researcher and Associate Professor at the Faculty of Electrical Engineering, Mechanical Engineering, and Naval Architecture in Split, where he teaches courses related to engineering economics, power system analysis, power grids and machine learning. His research focus is the application of advanced numerical methods to problems in the analysis and planning of power system operations.