Publication: Electrical Review and Western Electrician
Chicago, IL, United States
Much trouble has been experienced in properly insulating storage batteries, especially on high-voltage circuits. The ordinary glass insulators give satisfactory results in many cases, but where the circuit is grounded there is a tendency to a leakage of current over the surface of the insulators, especially when the latter have become coated with dust and acid. This leakage sometimes sets up electrolytic action which may eventually corrode through the lining of the tank.
The Electric Storage Battery Company has developed a new type of oil insulator which is described in its bulletin No. 126 recently issued. Previous experiments with oil insulators have not been very satisfactory, but the present design has proved so efficient that it is being used in many new installations, especially where the voltage is higher than 220 volts, or where one side of the circuit is grounded. The design of this insulator is shown by the cross section given in the accompanying illustration. The glass body is provided with a circular trough which is partially filled with oil and covered by a cap of lead alloy, which is so designed as to exclude spary and other foreign matter from the oil space. It also serves to protect the oil from the effects of splashing when the floor is washed. The lead cap fits as closely as possible over the outer rim of the insulator, but without coming in contact with it, and the upper edge of this rim has a protecting lip to further protect against entrance of moisture. The oil chamber is of sufficient depth to provide for the accumulation of any foreign matter or water which may leak in. While refilling will seldom be necessary, provision has been made for it by a small hole in the cap. The insulator rests on a heavy lead washer in order to distribute the weight more uniformly. Some of these insulators have been in service for a number of years under extreme conditions, and in no case has electrolytic action been noted.