Abstract: An apparatus for testing a cable or other capacitive load object with a VLF alternating cosine square, rectangular or trapezoidal test voltage, includes one or two DC voltage sources and a switching arrangement controlled by a measuring and control unit, to produce the test voltage with alternating switched polarity. The apparatus further includes a choke coil serving as an energy store, which is controlled by a switching element to be activated if the voltage/time slope arising during the switch-over after a respective half-wave of the test voltage falls below a defined threshold value.

Abstract: A measuring apparatus is connected to a cable to perform testing and diagnosis of the cable. The measuring apparatus includes a voltage source, a resistance, a switch, and an inductance forming a charging circuit, and two anti-parallel thyristors or switched diodes together with the inductance forming a series resonant circuit loop. The apparatus produces a low frequency alternating voltage signal train including a low frequency test signal followed by a low frequency diagnostic signal. The diagnostic signal is a damped decaying signal oscillation in the resonant circuit connected to the test cable. At least one of the signals is bipolar. Both cable testing and cable diagnosis can be performed using the same single measuring apparatus in a single measuring procedure.

Abstract: An electrical pulse fed into an electrical cable, e.g. a power transmission or distribution cable buried underground, produces an acoustic signal, e.g. an arc-over or discharge noise, at a fault in the cable. This acoustic signal is detected and used to locate the fault. But the acoustic signal has interference noise superimposed on it, which makes it difficult to identify the acoustic signal in the noise-burdened received signal, and thus also makes it difficult or impossible to accurately locate the fault. To minimize or avoid the influence of interference noises, the relevant acoustic signal is identified in the received signal by comparing the received signal with predetermined sample data, such as signal patterns, characteristics or characteristic sets.

Abstract: An apparatus for testing a cable or other capacitive load object with a VLF alternating cosine square, rectangular or trapezoidal test voltage, includes one or two DC voltage sources and a switching arrangement controlled by a measuring and control unit, to produce the test voltage with alternating switched polarity. The apparatus further includes a choke coil serving as an energy store, which is controlled by a switching element to be activated if the voltage/time slope arising during the switch-over after a respective half-wave of the test voltage falls below a defined threshold value.

Abstract: An electrical pulse fed into an electrical cable, e.g. a power transmission or distribution cable buried underground, produces an acoustic signal, e.g. an arc-over or discharge noise, at a fault in the cable. This acoustic signal is detected and used to locate the fault. But the acoustic signal has interference noise superimposed on it, which makes it difficult to identify the acoustic signal in the noise-burdened received signal, and thus also makes it difficult or impossible to accurately locate the fault. To minimize or avoid the influence of interference noises, the relevant acoustic signal is identified in the received signal by comparing the received signal with predetermined sample data, such as signal patterns, characteristics or characteristic sets.