Losses in Porcelain Insulators

Losses in Porcelain Insulators. — In an article on this subject by R. M. Triese in the Elektrotechnische Zeitschrift, it is stated that porcelain insulators may be regarded as small capacities, the two sides of which are formed by the holder (earth) and the wires respectively, the dielectric being the porcelain. In certain tests, a large number of insulators connected in parallel were suspended head downwards in a bath of water connected to one terminal of the testing transformer, the surface of the water being level with the neck of the insulator. The holes in the insulator, provided for the iron supports were filled with water, and electrical contact with the other pole or the transformer was made by means of metallic chains dropping in the holes. In Tables I and II are recorded the results of the tests. Table I refers to an insulator of an older type, possessing a double petticoat and weighing 3.44 lbs., while Table II concerns a modern type of insulator with four petticoats and weighing 2 lbs. Both types withstood approximately the same disruptive tension. The frequency of the testing current was 50 cycles per second.