GB299968A - Improvements in devices for testing and locating the defective insulators in electric power lines - Google Patents

Abstract

299,968. Berry, T. D. Sept. 28, 1927. Detecting, indicating, and locating faults.-An instrument for locating defective insulators in a high-tension power line consists of an insulating casing 1 divided into two chambers by a partition 6. In the lower chamber are situated the terminals 14, 15 of a spark gap, in parallel with which is a variable condenser comprising concentric cylinders 9, 10, the inner cylinder 10 being adjustable by means of a screw 11 and its portion being indicated on a scale 13 by a pointer 12 moving through a slot in the casing 1. The spark-gap terminal 15 is connected to the movable cylinder 10 of the condenser through the screw 11 and a spring 17, the screw 11 being also connected to an arm 4 carrying a brush 5 adapted to be contacted with the insulator under test. The terminal 14 of the sparkgap is connected with the stationary member 9 of the condenser and also with a member 20 carrying a detachable conducting rod 21 situated in the eletcrostatic field of the insulator under test. The effective length of the conductor 21 is variable by means of a sliding conducting tube 22 actuated by a member 24 extending through a slot in the casing, which is provided with a scale. The members 10, 22 are adjusted from hygrometer readings in accordance with the positions of these members at the point where sparking at the gap ceases are an indication of the leakage current. The passage of sparks across the gap sets up high-frequency currents in an antenna 25. which are rectified and amplified by means of a thermionic valve having means for indicating the filament current so that a constant degree of amplification may be ensured.