SURGE CURRENT BACKFLOW PREVENTION CIRCUIT INCLUDING TRIPLE-POLE SPD ELEMENT, AND COUNTER SYSTEM

PROBLEM TO BE SOLVED: To protect the DC circuit of a high voltage power circuit, a low voltage power circuit, a lighting circuit, a storage battery circuit, and a communication circuit against backflow of surge current, by mounting a triple-pole SPD element on the breaker in a distribution board, receptacle, an OA tap receptacle, and the circuit of an electronic substrate, respectively, because the triple-pole SPD element can be used as a discharge element for high voltage although it is compact, and can be mounted in an electronic substrate, and in which a surge current flowing through a cable can be entirely made nearby earth connection through series parallel connection element of triode element.SOLUTION: An element formed by laminating a plurality of zinc oxide elements 1a, the lowest voltage and the response start voltage of which can be adjusted, are made to a double-pole element by arranging an electrode integrating an electrode plate 1b and a lead rod 2 at both ends of the element 1. A triple-pole element 1 is formed by connecting the minus poles of double-pole elements in series. A triple-pole SPD element is constituted of a triple-pole discharge element 1a of a grounded center element as an intermediate pole, and positive and negative poles laminated thereon and bonded thereto.