Abstract
In this paper, a methodology for determination of the optimal value of protection design parameters, i.e. tower footing resistance, insulation strength, and surge arresters’ rating in the planning stage of transmission lines (TLs) is presented. This method calculates the shielding failure flashover rate (SFFOR) of TLs, based on Electro-geometric model (EGM) of TLs, and the back flashover rate (BFR) of TLs, based on the Monte Carlo method, in which the accuracy of the proposed methodology has been verified by comparing the resultant results with those obtained with the use of the IEEE FLASH program. The proposed method can be directly used to achieve the minimum lightning flashover rate (LFOR) of TLs by the minimum investment cost. Also, it can be used, indirectly, for determination of the appropriate value of the footing resistance, insulation strength and arresters’ rating to satisfy any target number of LFOR that might be specified by the utilities or standards.
Highlights
The transmission lines (TLs) are exposed to lightning strokes in which the resultant overvoltages may lead to insulation failure and the transmission line outage [1]
The lightning flashover rate (LFOR) of the transmission line as a function of the design parameters is specified by summing the back flashover rate (BFR) and shielding failure flashover rate (SFFOR): LFOR (Ri,Ua,Ur)=SFFOR+BFR
As the transmission lines are divided into N regions, an analysis is performed for each region along with TLs, and suitable values for design parameters are computed
Summary
The transmission lines (TLs) are exposed to lightning strokes in which the resultant overvoltages may lead to insulation failure and the transmission line outage [1]. In the literature, the arrester rating is not considered as a design parameter to select the appropriate protection scheme. The proposed approach is a rough-straight method to evaluate the lightning performance of TLs considering the effect of the surge arresters installation along with TLs in addition to the conventional parameters, i.e., the footing resistance and insulation strength of insulator strings. The presented method could be useful for optimal placement of surge arresters along with TLs considering economic criteria. It is helpful for selecting the appropriate value of footing resistance, insulation strength, and arrester rating as protection design parameters in the planning stage of TLs
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