Experimental Evaluation of Lightning-Surge Propagating in Distribution System and Customer's Facility-Surge Characteristics of Grounding Electrodes and Concrete Poles, and Lightning-surge in Customer's Facility-

Abstract

For the establishment of a more effective grounding design, it is necessary to clarify a transient behavior of a grounding system. In order to verify the current dependency of the grounding electrodes in a distribution system and the behavior of the lightning surges into customer's premise through the power lines, experiments were conducted using the 3 MV impulse voltage generator on a full-scale distribution system and a power line surge simulation mock-up constructed for this purpose. As a result, the behavior of the currents in the distribution system and the possible effects of mutual interference between grounding potentials were successfully identified. In addition, with the lightning surge flow, applied current and low-voltage grounding system parameters, it was possible to evaluate the magnitude of the lightning surges into customer's facility.

A study of lightning risk

“…The critical value, however, varies by several factors, for example, the cause of the damage which is the direct lightning hit or induced lightning, the lightning protection measures in the customer facility, and the grounding system of the customer facility. In order to clarify the effects of these factors quantitatively, several studies have been conducted energetically [14,15]. It has been reported that about 20% of currents of the direct lightning hits to distribution systems flow into a customer facility and the overvoltage generated on 45°F ig.…”

“…It has been reported that about 20% of currents of the direct lightning hits to distribution systems flow into a customer facility and the overvoltage generated on 45°F ig. 3 Lightning attractive area by the antenna of a house the equipments in a customer facility is larger with the T-T grounding system than that with the T-N grounding system [15]. With these results, it is possible to estimate the occurrence probability of lightning damage.…”

“…2. Occurrence probability of damage (a) Occurrence probability of damage by direct lightning hits to distribution systems When lightning directly strikes a distribution system, about 20% of lightning currents flow into a customer facility [15] and the currents distribute in the facility inversely proportional to the values of the grounding resistances [16]. The current flowing into an equipment is reduced by the number of equipments in the facility.…”

“…The current flowing into an equipment is reduced by the number of equipments in the facility. Considering the most severe condition that whole of the current flows into the same equipment, if the current exceeds a critical value of 3 kA [15], the lightning current is 15 kA. Because the occurrence probability of lightning current of more than 15 kA is about 80% [1], the occurrence probability of damage is considered to be 0.8.…”

“…(d) Occurrence probability of damage by direct lightning hits to the customer facility. It is reported that if a current of 3 kA flows into a TV antenna of a customer facility, protection circuits are broken down [15]. In other words, when lightning strikes a TV antenna of a customer facility, it is almost impossible to prevent damage of equipments in the customer facility.…”