The portable VLF Test System 27 kV of Seba KMT can be used to test the cables in conjunction with the according local regulations for operating voltage levels up to 11 kV for new cables and 16 kV for aged cables at 3 uF cable capacity. By using the patented Seba KMT 0.1 Hz Cosine Square Wave Voltage, weak and for further operation critical spots in PE, XLPE but also in paper cables are brought to a controlled breakdown very fast without causing additional damage or aging to the cable insulation.
The VLF Test System consists of a DC source, which charges the test object up to the required test voltage level and the commutator unit, which performs the regular 5 second interval polarity change. The change-over from one polarity to the reverse one is performed with a switched rectifier, an inductivity (choke) and a capacitor, which is made up of the internal 0.3 uF and the cable capacity itself. The L/C resonance circuit produces a cosine shaped voltage with slopes similar to a 50 Hz sine wave.