Thyrite A New Material for Lightning Arresters

A new material has been developed which is peculiarly adapted for use in lightning arresters. It is physically similar to dry process porcelain and it can be made in any shape that can be successfully moulded. The manufacturing processes have been perfected so that the electrical and mechanical characteristics can be duplicated or varied as desired within practical limits. This material, which is called thyrite, does not follow Ohm's law, for each time the voltage is doubled the current increases 12.6 times. The ratio of change of current to change in voltage is constant over ranges of current of 10,000,000 to one. This means the resistance decreases as the current and voltage increase. The resistance at any particular value of voltage or current is fixed by the physical dimensions of the piece. It is slightly lowered at high temperatures but returns to normal when cooled. The resistance does not depend upon the rapidity of current or voltage change and it is unaffected by long service. Because of these definite characteristics of thyrite the action of lightning arresters can be accurately calculated for the first time. Thyrite is now being used experimentally in three types of lightning arresters. The station type is made in 11.5-kv. sections, each one containing its own gap unit so that no series arrester gap is required. These gap units have the desirable property of sparking over at practically the same voltage irrespective of wave front. The 11.5-kv.