High Voltage Vlf Testing Of Power Cables

This publication describes a laboratory test program conducted with the objective to develop a test that would replace the existing dc withstand test.

High voltage vlf testing of power cables. Some ofthe available test methods are listed below. Testing of high voltage cables manual horizon power 1st edition february 2013 prepared by field practices safety health. This kind of test is suited for testing high capacitance loads such. A very low frequency vlf withstand test is an ac withstand test usually carried out at a frequency between 0 1 hz and 0 01 hz.

A vlf test. Ac is the standard used to transmit power worldwide usually at a frequency of 50 or 60 hertz. The increased load capability in field applications in which 60 hertz is too bulky and expensive making it nearly impossible to test a cable of considerable length. The fundamental difference between ac and dc high voltage testing is the avoidance of space charge effects.

Vlf cable testing very low frequency is a technique for testing of medium and high voltage mv and hv cables. Vlf ac test voltages with cosinerectangular and the sinusoidal wave shapes are most commonly used. Very low frequency is the preferred method over 60hz for two reasons. The most commonly used commercially available vlf ac voltage test frequency is 0 1 hz.

Making them useful especially for field testing where transport and space can be issues. Direct current dc dielectric withstand voltage. This combination of size and power makes very low frequency cable testing perfect for testing longer sections of cable and apparatus. While supplies to railways and aircraft may use 162 3 of 400hz it is still a sinusoidal voltage waveform.

The article describes the methodology used to establish the voltage duration and magnitude of vlf 0 1 hz high voltage field tests suitable for crosslinked polyethylene xlpe insulated power cable. Power frequency 50 60 hz dielectric. Very low frequency vlf withstand testing is the application of an ac sinusoidal waveform generally at 0 01 0 1 hz to assess the quality of electrical insulation in high capacitive loads such as cables. Test sets typically operate at 0 1hz.

Ac is therefore recommended in most cable testing standards. Vlf systems are advantageous in that they can be manufactured to be small and lightweight. At a typical vlf frequency of 0 1hz it takes 600 times less power to test the same cable compared to 60 hz. Ac high voltage test equipment design vlf operation reduces the power required to load cables which present a capacitive load.

During the test cables are subjected to a test voltage significantly higher than what they experience during normal operating conditions.