Vlf Cable Testing Results

If a vlf test is too low in voltage and or too short in duration more harm than good may result.

Vlf cable testing results.

Its most frequently used to ac field test medium and high voltage cables and test rotating machinery like motor and generator coils. The benefits of vlf maintenance testing regular routine maintenance testing of aged cables has been demonstrated to reduce the chance of unscheduled failure to approximately 10 of the failure rate that might be encountered without such testing. Vlf testing uses very low frequencies as part of an ac cable maintenance routine. This kind of test is suited for testing high capacitance loads such.

Very low frequency vlf tan delta testing is a precise and non destructive method to provide information on the extent of ageing in cable insulation. Vlf testers are smaller and more practical than ac testers but output the same amount of power as a 50 hz mains device. Vlf testing is not only used for testing solid dielectric cable any application requiring ac testing of high capacitance loads can be tested using very low frequency. Vlf testing is a withstand test usually carried out at a frequency of between 0 1 hz and 0 01 hz rather than 50 60 hz.

This combination of size and power makes very low frequency cable testing perfect for testing longer sections of cable and apparatus. During the test cables are subjected to a test voltage significantly higher than what they experience during normal operating conditions. When vlf withstand testing cable the proper test voltage and time duration are critical for the success of the test. Approximately 12 of cables fail during the test and cable repair can then be done in a planned manner.

Once partial discharge is triggered in a defect under the test. Vlf tests at ieee 400 2 test levels do not damage cable systems good insulation but are used to degrade existing insulation defects to failure during the test rather than in service. The test applies an ac sinusoidal waveform at 0 1 hz frequency and measures the degree of real power dissipation or losses in a dielectric material. The test is conducted on entire drum of cable rather than a test sample length.

Vlf cable testers support iec 60502 and ieee. The major application is for testing solid dielectric cable per ieee 400 2 followed by testing large rotating machinery per ieee 433 1974 and occasionally for testing. The reasoning is that the low energy failure of the cable under test results in less collateral damage and a reduced likelihood of unplanned outages due to in. 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.

Compared to traditional ac dc hipot testing vlf cable testing methods are able to more easily determine the high voltage field of certain loads of high capacitance.