Quantifying the effect of differential insulation on double circuit back flashover performance using the leader progression model

[1]

A common mitigation strategy to reduce backflashover and improve overall lightning performance is to reduce tower footing resistance. [2] However, this approach is not always feasible due to site-specific constraints, highlighting the need for alternative mitigation strategies to improve transmission line lightning performance.

The literature indicates that differential insulation using insulator units of different lengths has been employed to reduce double circuit backflashover rates, with varying degrees of success.

[2], [3] This paper examines the impact of utilising arcing horns on one (1) circuit of a 500 kV double circuit transmission line that will be constructed in Australia. The backflashover rate will be assessed by simulating strikes to earth wires on the tower using an electromagnetic transients’ program.

The impact to both single circuit and double circuit back flashover is discussed. Additionally, several sensitivity cases are assessed, including arcing horn gap length and footing resistance, to assess effectiveness of arcing horn installation. As the proposed transmission line has not been constructed yet results regarding the actual performance are not available for comparison and will form part of future works.

Traditionally, implementation of differential insulation on double circuit towers has been done by increasing the number of insulator units on the phases of one (1) circuit. This is discussed in

CIGRE TB063, this paper expands on the idea of differential insulation by considering arcing horns as an alternative implementation method.