VLF CR28 kV – "Very Low Frequency" 0.1 Hz Test

In accordance with most regulations, cables and joints must be tested after installation or repair. For this test the break-down strength of the cable is tested. The portable VLF Test System 28 kV of SebaKMT can be used to test the cables in conjunction with the according local regulations for operating voltage levels up to 15kV for new cables and 22 kV for aged cables at 5 µ F cable capacity.

By using the patented SebaKMT 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 ageing of the cable insulation.

The VLF Test System 28 kV consists of a DC source which charges the test object up to the required test voltage level and an electronic HV switch which performs the regular 5 second interval polarity change.

The change over from one polarity to the reverse one is performed with the support of the switched rectifier, an inductivity (choke) and a capacitor which is made up of the internal 0.3 µ F and the cable capacity itself. The L / C resonance circuit produces a cosine shaped voltage with slopes identical to a 50 Hz sine wave.

The optional leakage current measurement permits a direct quality assessment during the test procedure.

Technical Features

• The VLF Test System 28 kV in two parts is a very powerful, universal and at the same time portable unit.
• Control and power module with approx. 25 kg individual weight.
• The patented change over principle in combination with the recycling of energy stored in the cable capacity results in a lower weight, less energy consumption and much higher test capacity in comparison to other methods.
• Optional module “leakage current measurement”.
• Optional module “data recording” for comfortable and easy on-the-spot recording of the test results.
• Optional automatic breakdown recognition.
• The high test capacity of 5 µ F permits the simultaneous testing of all three phases.
• The method is officially recommended by the two VDE Standards
0276-620 and 0276-621.
• The advantages of the VLF method with 0.1 Hz Cosine Square Wave Voltage are proven by extensive scientific research results, as well as in practical field experiences.
• VLF is the most efficient method to test PE and XLPE cables.

Scope of Delivery

VLF Test System 28 kVConsisting of:

• Control and power module
• Mains cable
• Earth cable 4 m
• HV-connection cable 4 m
• Accessory bag
• Operator manual

Optional

• Automatic breakdown recognition
• Leakage current measurement module
• Printer and/or data recording module