Impact of First Tower Earthing Resistance on Fast Front Back-Flashover in a 66 kV Transmission System

Abdullah H. Moselhy, Abdelaziz M. Abdel-Aziz, Mahmoud Gilany and Ahmed Emam
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Abdullah H. Moselhy: Smart Power Company, 10-A/4 Takseem El Laselky, New Maadi, Cairo 11742, Egypt
Abdelaziz M. Abdel-Aziz: Electrical Engineering Department, Faculty of Engineering, Al-Azhar University, Cairo 11651, Egypt
Mahmoud Gilany: Electrical Power Engineering Department, Faculty of Engineering, Cairo University, Giza 12613, Egypt
Ahmed Emam: Electrical Power Engineering Department, Faculty of Engineering, Cairo University, Giza 12613, Egypt

Energies, 2020, vol. 13, issue 18, 1-20

Abstract: Lightning stroke on a transmission tower structure is one of the major reasons that results in high voltages at the tower arms due to the excessive lightning current flowing through the transmission tower to earth. The Surge voltage seen at the tower cross arm on the first tower close to a substation is the worst case. If this voltage is higher than the withstand level of the insulator string, the insulation of substation equipment will be exposed to transient over-voltage called fast front back-flashover (FFBF). The peak of this transient overvoltage is affected by the value of the system’s earthing resistance. This paper studies the effect of reducing the grounding resistance of both the surge arrestor (SA) and the first transmission line tower adjacent to a 66 kV substation on FFBF. Three case studies using PSCAD/EMTDC software are presented to simulate the variation of the potential sire at the substation equipment with different resistance values for the first tower and SA earthing resistance. The paper also addresses the economic protection system for solving the problem of transient overvoltage. The study proves that the proper design of the first tower grounding system enhances the safety of the system and reduces the cost for the grounding system to the minimum.

Keywords: back-flashover; insulation coordination; fast front transient study; footing resistance; lightning impulse withstand voltage; PSCAD/EMTDC (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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