What is the purpose of VLF testing?
Very Low Frequency testing for Medium Voltage and High Voltage cables is a method for verifying the integrity of the cable insulation. 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.
Is VLF testing destructive?
Is the VLF test destructive? VLF hipoting is not destructive to good insulation and does not lead to premature failures like DC voltage testing. Using VLF does not cause degradation of good insulation nor aggravate defects too small to be triggered into PD under the test voltage.
How do you test a XLPE cable?
ALL (XLPE and Paper Lead) cable shall be tested with a VLF alternating voltage whose waveform shall approximate a sinusoidal waveform of frequency 0.1 Hz. NOTE: VLF is the preferred method for testing ALL types of cables.
What is VLF kit?
VLF cable testing (Very Low Frequency) is a technique for testing of medium and high voltage (MV and HV) cables. Traditionally DC hipot testing was used for field testing of cables, but DC testing has been shown to be ineffective for withstand testing of modern cables with polymer based insulation (XLPE, EPR).
What is VLF Tan Delta testing?
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. 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.
How do you test for partial discharge?
When problems occur in medium and high voltage electric equipment, such as partial discharge and corona, it will produce sound waves that can be detected by Ultrasonic Testing. Performed without disrupting plant or facility operations, Ultrasonic Testing is a nondestructive, noninvasive predictive maintenance tool.
Is VLF testing AC or DC?
AC
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. This kind of test is suited for testing high capacitance loads such as cable and rotating machinery. This is a pass fail test i.e. bad cable will fail during testing rather than in service.
Is standard for tan delta test?
The frequency range for tan delta test is generally from 0.1 to 0.01 Hz depending upon size and nature of insulation. There is another reason for which it is essential to keep the input frequency of the test as low as possible. As we know, That means, dissipation factor tanδ ∝ 1/f.