JPS57149972A - Testing equipment for underwater dielectric strength of electric wire or the like - Google Patents

Abstract

PURPOSE:To detect the occurrence of the destruction of an electric wire, whose dielectric strength is tested, with high sensitivity by connecting a power-factor indicator to a testing transformer, and controlling the disconnection of a power source according to a power-factor. CONSTITUTION:A high voltage is applied through a testing transformer 3 to an electric wire 21 whose underwater dielectric stregnth is to be tested in a water tank 1. To the primary winding, etc., of the transformer 3, a current transformer 8 is connected in parallel and a current transformer 9 is also connected in series; those transformers 8 and 9 are connected to a power-factor detector 10. Then when a power-factor greater than a reference one is detected, electric power to the transformer 3 is cut off by a breaker 6 through a discriminating circuit 11, a breaker opening and closing circuit 12, etc. A system which acquires as a power-factor variation in capacity due to the destruction of the capacitive insulating coating of the electric wire 2 detects the generation of the destruction of the electric wire with the high sensitivity, and the test is interrupted by cutting off the electric power before the destruction progresses, thus searching for the cause, etc., of the destruction adequately.