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Page 889 | Volume 3 | Chapter 43 | Lightning Protection

one plate to the other thus quickly destroying the plates and causing other more serious damage.

Ques. What provision is made to prevent the destruction of arresters by the line current?

Ans. Lightning arresters used on heavy duty circuits are designed to rupture the arc as soon as formed.

Fig. 1,042. - Diagram showing operation of variable gap arc breaker used on heavy duty lightning arresters.
Fig. 1,042.—Diagram showing operation of variable gap arc breaker used on heavy duty lightning arresters. When a lightning discharge passes across the gap to earth, the dynamo current follows it and energizes the magnet M, which attracts the short arm of the double lever, thus quickly jerking the terminal B away from C. The wider air gap thus interposed between B and C greatly increases the resistance which breaks the arc.

Ques. How is this done?

Ans. There are several methods, of which may be mentioned the variable gap method described in fig. 1,042, and the magnetic blowout method shown in fig. 1,043.

Ques. Where should lightning arresters be placed?

Ans. They should be placed as near as possible to the point where wires enter a building, and in an easily accessible place away from combustible material.



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