Optimization of overhead transmission lines insulation and grounding costs with respect to backflashover rate

Abstract

In this paper, the optimization of transmission insulation and grounding is performed considering two backflashover rate (BFR) evaluation procedures widely applied in the industry. The optimization approach is based on the Lagrange formulation introduced by Hileman in late sixties. This method used the old AIEE procedure to evaluate the BFR of transmission lines. Since then a number of BFR evaluation are available to determine BFR rates outperforming legacy procedures. Recently, the Hileman’s optimization method was updated using the EPRI two-point method to evaluate the BFR. However, despite the step-by-step EPRI method being still widely used in industry, stochastic simulation with specialized programs is becoming standard. Thus, in this paper, the insulation and grounding optimization methodology is updated using more adequate and recent BFR evaluation procedures such as the IEEE Std. 1243-97 and the Monte Carlo EMTP-based methods. Technical and economic results were compared with the existing optimization approach based on the EPRI two-point method using the EPRI 345 kV transmission line as test system. Results show that IEEE and EPRI methods yield equivalent results. The stochastic-based method (MC-EMTP) is more optimistic showing total and marginal insulation and grounding costs below the IEEE/EPRI methods.