抄録
Overvoltage generated by lightning is a threat to indoor electrical equipments in information-oriented and computerized society. Countermeasures for preventing the overvoltage on an indoor wiring are demanded. It is well known that low-voltage arresters and common grounding wires are effective for lightning protection. However, the effects of the position of the grounding point and the layout of the common grounding wire for controlling the overvoltage have never been investigated yet.
In order to propose an effective countermeasure using a common grounding wire, we have investigated the effects of the position of the grounding point and the layout of the common grounding wire on reduction of the overvoltage, using a full-scale test distribution line with a customer's facility and the EMTP analysis. Main results are as follows:
(1) A common grounding wire installed along the indoor wiring can reduce the overvoltage between the indoor wiring and the grounding more than that installed under the floor, when low-voltage arresters are installed at the panel board.
(2) One-point grounding of the common grounding wire at the panel board is more effective than multi-point grounding for preventing failure of surge protective devices.
