Cable testing with VLF voltage

All cable installations used in power engineering are subject to periodic inspections and diagnostic checks. Strength, voltage and operation tests constitute an integral part of routine measurements. The GK-Elektro company tests equipment and electric installations for maintenance and possible damaged component repair purposes. VLF mode voltage tests incorporated in operational cabling measurements are included in the company’s offering dedicated to equipment electric strength testing and electric cabling diagnostics. Diagnostic services also include leakage current measurements in tests run with trapezoidal voltage and leakage current measurements performed with slow-variable rectangular voltage.

Cable measurements with VLF voltage – specifications

Leakage current measurements during tests with VLF voltage are conducted in low frequencies equal to or below 0.1 Hz. Despite the fact that the frequencies are low, such tests are suitable for measuring voltage in high-capacitance facilities or long cabling sections. Cable damage or other fault locations are detectable to the same extent when performing cable tests with VLF voltage as it is the case of other voltage tests conducted at higher voltages.

Megger-measuring-kit-TDM-4540-P-TD-PD

Cable testing with VLF alternating voltage

Very Low Frequency (VLF) voltage is used to perform measurements on cables, generators and electric motors. While employing low-amplitude amperage, the necessary energy consumption is up to 500 times lower than for higher frequency measurements. Measuring instruments for the VLF system are also much lighter than higher amperage testing equipment that weighs several tonnes, which significantly affects, among other things, the costs associated with equipment transport. Therefore, cable tests with VLF voltage are suitable for fast and field-based diagnostic applications. However, when opting for this measurement solution, several basic parameters must be taken into account. The most important ones include the cable capacitance range, minimum and maximum test current amperage and load capacitance range at a given frequency. Thus the necessary differentiating factors for testing cables with VLF slow-variable alternating voltages can be determined.

Leakage current measurements

A leakage measurement is a test method consisting in detecting an electric energy “leak” that might be constitute hazard to life and health. Every electric device comes with a natural leakage value which, however, should not exceed certain standard and minimum values. Leakage current measurements facilitate determining the insulation wear degree or other electric equipment operating conditions. In order to measure these properties, a device is tested with trapezoidal voltage or multi-variable rectangular voltage.

Measurement system during a cable test with VLF voltage

Multi-purpose system for cable measurement with VLF voltage

Equipment used for VLF testing performs numerous functions including alternating and direct current measurements, as well as spot tests. A system for cable testing with VLF voltage facilitates testing for the tangent delta dielectric loss factor and partial discharges, which makes it a versatile measurement tool that can be used for any tests run on cables and electric equipment. Its functionality is also one of the factors determining the table testing with VLF voltage as the preferable and most frequently employed method for the MV cabling diagnostics.

Cable testing with VLF voltage – GK-Elektro offering

The GK-Elektro company specialises in installing electric systems and power supply sources. Our range of services also includes cable testing with VLF voltage and MV cabling diagnostics using the VLF method for industrial facilities. We conduct VLF voltage tests for long cables, and VLF voltage tests for short cables in small- and large-sized facilities with large-scale electricity consumption.