Abstract: Switching devices for switching high voltages for cable testing by applying high voltage to a cable test sample and for discharging the cable test sample, wherein at least one device for switching a high voltage is connected to a negative high voltage source, and at least one identically embodied device for switching a high voltage is connected to a positive high voltage source. Said switching devices are distinguished in particular in that an increased voltage can be switched with a semiconductor switch. For this purpose, at least one electrically conductive heat sink having at least one printed circuit board with at least one semiconductor switch is arranged in an electrically insulated manner in a housing. The printed circuit board is a thermally conductive insulator between the semiconductor switch and the heat sink, to which and/or through which flows a coolant.

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: In order to locate a cable fault in a cable, a testing apparatus applies a test signal to the cable so as to induce an electrical oscillation. The testing apparatus includes a voltage source that generates the test signal, which e.g. ignites an electrical arc at the cable fault or applies a voltage surge to the cable, to cause the electrical oscillation. The apparatus further includes a measured signal evaluation device to measure the resulting oscillations in the time domain or the frequency domain, and carry out a spectral analysis in the frequency domain, so as to automatically determine the location of the fault preferably from the total phase rotation of the signal, the phase rotation of the reflection at the first cable end, the phase rotation of the reflection at the cable fault, and the imaginary part of the propagation constant of the signal in the cable.

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.