Vlf Cable Test Voltage

Vlf testing can be classified as a withstand or diagnostic test meaning it may be performed as a proof test for acceptance or as a maintenance test for assessing the condition of cable.

Vlf cable test voltage.

Acceptance test voltages are generally 2 5 3 times the line to ground system voltage. The most commonly used commercially available vlf ac voltage test frequency is 0 1 hz. Dc high voltage test set for paper lead cables. As higher voltage vlf equipment is developed standards may be adapted to increase the voltage level for application.

Output voltages are determined from the ieee 400 2 guide choosing rms or peak depending on the output waveform. A typical modern vlf test set has an output rating of 33kv peak sinewave 23kv rms and is capable of accommodating an output load of 0 5µf at 0 1hz i e. This combination of size and power makes very low frequency cable testing perfect for testing longer sections of cable and apparatus. Ac is the standard used to transmit power worldwide usually at a frequency of 50 or 60 hertz.

Vlf testing of cables is supported in iec 60502 up to 35 kv and in ieee 400 2 up to 69 kv. How long should a vlf test last. The device under test must withstand a vlf very low frequency ac voltage for a preset testing time without flashover. In the first step a go no go statement is sufficient.

Vlf testing is performed with an ac hi pot at frequency ranging from 0 01 to 1 hz. Task steps 5 1 on site risk assessment prior to performing this activity any hazards associated with prerequisite tasks at the worksite shall be identified and assessed. Unlike with dc voltage testing very low frequency is not destructive to good insulation and does not lead to premature failures. The vlf test can be used in a number of ways.

A channel tree growth rate with a 3u 0 test voltage at 0 1 hz vlf sinusoidal on field aged xlpe cables is 10 9 12 6 mm per hour mm h. Trusted for the most technically advanced portable and user friendly high voltage equipment on the market. Additional equipment for testing major cables very low frequency vlf high voltage test set for xlpe cables. Designs and manufactures industry leading high voltage test equipment for proof testing diagnostic testing high voltage breakdown testing and preventative maintenance testing.

Vlf ac test voltages with cosinerectangular and the sinusoidal wave shapes are most commonly used. Vlf cable testing is the cutting edge technology for proof testing of fully operating medium voltage cables and the detection of faulty ones. A typical 15 kv medium voltage cable in usa has an insulation thickness of 0 22 5 6 mm and therefore during a vlf test time of 30 minutes all defects within the cable should grow to failure. Vlf testers are smaller and more practical than ac testers but output the same amount of power as a 50 hz mains device.