Vlf Cable Testing Standards

In accordance with respective standards sine wave voltage is used for vlf testing.

Vlf cable testing standards.

The document uses the standard numbering system of ansi and ieee. While supplies to railways and aircraft may use 162 3 of 400hz it is still a sinusoidal voltage waveform. The preset test time in the range of 15 to 60 minutes is short and economical. A vlf test.

Ac is the standard used to transmit power worldwide usually at a frequency of 50 or 60 hertz. On february 19 2009 the american national standards institute approved the neta acceptance testing. However high capacitive loads as encountered with very long cable runs may require a lower frequency for the correct operation of test sets. Standard details very low frequency vlf withstand and other diagnostic tests and measurements that are performed using vlf energization in the field on shielded power cable systems are described in this guide.

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. Ieee 400 3 2006 ieee guide for partial discharge testing of shielded power cable systems in a field environment. Whenever possible cable systems are treated in a similar manner to individual cables. Vlf testing is performed with an ac hi pot at frequency ranging from 0 01 to 1 hz.

As higher voltage vlf equipment is developed standards may be adapted to increase the voltage level for application. Voltage levels are a multiple of the nominal voltage of the cable. These numbers result from many years of vlf field use and research. They are in the range of 1 5 u0 to 3 u0.

Vlf testing of cables is supported in iec 60502 up to 35 kv and in ieee 400 2 up to 69 kv. This combination of size and power makes very low frequency cable testing perfect for testing longer sections of cable and apparatus. The industry default standard vlf test frequency is 0 1hz. The most widely accepted test frequency is 0 1 hz however frequencies in the range of 0 0001 1 hz may be useful for diagnosing cable systems that exceeds the limitations of the test system at 0 1 hz.

During the test cables are subjected to a test voltage significantly higher than what they experience during normal operating conditions. Since 1989 revised editions of the acceptance testing specifications have been published in 1991 1995 1999 2003 and 2007. Ieee guide for field testing of shielded power cable systems using very low frequency vlf less than 1 hz. Ieee 400 4 2015.