But my cable might fail during the test precisely.
Vlf cable test report.
Commissioning test for hv underground cable up to 33kv swp sp0407 field instruction sp0407c01 hv cable commissioning test report form sp0407c04 commissioning tool hv cables up to 33kv sp0506.
In the first step a go no go statement is sufficient.
Ieee 400 2 establishes some suggested test voltages and times.
The vlf test instrument should be solidly grounded before connecting up any cables.
Very low frequency is the preferred method over 60hz for two reasons.
There are no leakage current readings to take.
The hv test lead outside shield conductor is connected to the concentric neutral ground point of the cable under test.
Once partial discharge is triggered in a defect under the test.
Perform the test as instructed to make best use of vlf technology.
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.
The main conductor of the hv test lead is then connected.
Vlf cable testing is the cutting edge technology for proof testing of fully operating medium voltage cables and the detection of faulty ones.
This report concluded there is no distinguishable difference between failure rates on test for the common vlf test frequencies of 0 05 hz and 0 1 hz from data obtained through laboratory.
If a vlf test is too low in voltage and or too short in duration more harm than good may result.
The vlf cable testing time varies from 15 to 60 minutes.
Connecting a vlf test instrument to a cable refer to ieee 400 2 for safety guidelines.
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.
If a cable can t hold 2 3 times normal voltage.
Hv cable commissioning test report page 2 of 2 form sp0407c01 ver 10 ergon energy corporation limited abn 50 087 646 062 1 sheath test criteria new hdpe sheaths.
Dc leakage currents tell little about the cable quality a cable either holds the test voltage or fails.
The device under test must withstand a vlf very low frequency ac voltage for a preset testing time without flashover.
Working at heights poles ladders swms002.
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.
When vlf withstand testing cable the proper test voltage and time duration are critical for the success of the test.
Cable length size 250m 500m 1000m 2000m 11kv or less mω 400mm2 250 125 60 30 185 240mm2 300 150 75 37 35mm2 500 250 125 62 22kv or more mω.
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.
Substation primary plant and secondary systems field testing swp swms001.
That is the point of vlf testing.
At a typical vlf frequency of 0 1hz it takes 600 times less power to test the same cable compared to 60 hz.
