Effect of Grounding Resistance Connected to Surge Arresters in Power Distribution Lines on Lightning Surge Behavior Observed in Customer's Equipment

Abstract

SUMMARY In Japan, electric power companies have been spending large amounts of money on the construction costs and maintenance costs of low grounding resistances connected to surge arresters (Arrs) that are basically maintained below 30 Ω. In a recent study, it has been clarified that the rate of protection against direct lightning hits on distribution lines with an overhead ground wire (GW) hardly decreases, even if the grounding resistance of Arrs is high. However the installation of Arrs on a pole where a pole transformer (Tr) is mounted has not been considered, and in the case of a high grounding resistance, the lightning surge behavior observed in the customer's equipment has not yet been clarified. To examine the grounding resistance of Arrs, it is necessary to understand such behavior in the case in which the grounding resistance of Arrs is varied. In this paper, we clarified the relationship between the grounding resistance connected to Arrs and lightning surge behavior in customer's equipment. The result shows that the grounding resistance of Arrs installed on a pole with a Tr can be increased to some extent without decreasing the lightning protection level of the customer's equipment by the installation of a GW and the shortening of the interval between concrete poles with Arrs. A reduction in the cost of grounding construction can be expected.

Optimized Protection of Pole-Mounted Distribution Transformers against Direct Lightning Strikes

“…The protection level of MV transformers in a network depends on several factors, such as insulation level [4,5], protection devices (e.g., spark gap, surge arrester, etc.) [6,7], and grounding conditions [8], among others. More often than not, MV transformers are protected by spark gaps against lightning overvoltage [9].…”

“…Soil ionization results in decreasing the earthing resistance [24], i.e., under the ionization condition, the resistance is varied by the current. However, in most of the existing works on distribution networks, constant resistances were used to model the grounding resistance [8,25,26]. In [25], the importance of earthing resistance in the performance of surge-protecting devices installed in the LV terminal of the pole-mounted distribution transformer was investigated.…”

“…In this work, different constant ground resistances were considered in order to investigate the effect of grounding resistance size on phase-to-earth overvoltage amplitude under different lightning peak currents. In [8], by considering different constant grounding resistances of surge arresters and measuring the imposed voltage and current on the LV terminals, it was concluded that the lower the resistance, the better the protective functionality of the surge arrester becomes. Experimental results also emphasize the importance of low grounding resistance for better performance of protective devices such as surge arresters [12].…”