Vlf Cable Test Set

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Vlf cable test set.

When comparing this figure to power frequency ac or 0 1 hz vlf cos rectangular the tree growth rate is only 2 2 5 9 and 3 4 7 8 mm h. There are no rules of thumb to be used. 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.

Hva28 td vlf test set at a glance. The hv test lead outside shield conductor is connected to the concentric neutral ground point of the cable under test. The hva28td vlf high voltage test set is an ultra compact lightweight 0 1 hz vlf cable tester with integrated tan delta diagnostics. Critically the test object still receives the alternating sinusoidal voltage that would be supplied through everyday use but the size of the test equipment is.

Subsequent work by the cdfi has shown there to be no significant change in the efficacy of a vlf test conducted over the frequency range 0 1 to 0 01 hz when the ieee 400 2 voltages and times are used. At a typical vlf frequency of 0 1hz it takes 600 times less power to test the same cable compared to 60 hz. Very low frequency is the preferred method over 60hz for two reasons. Ground cable figure 4.

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. Connection setup for a vlf cable connecting a vlf test instrument to a cable refer to ieee 400 2 for safety guidelines. The vlf cable testing time varies from 15 to 60 minutes. The vlf test instrument should be solidly grounded before connecting up any cables.

Because vlf testing supplies a working frequency of 0 1hz as opposed to the 50 60hz usually required for live transmission the physical size of the vlf test set is massively reduced. Vlf cable test voltages and time durations are set by ieee standard 400 2 2013. Ieee 400 2 establishes some suggested test voltages and times. 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.

These numbers result from many years of vlf field use and research.