Hi-POT test during regular maintenance
Hi-POT test during regular maintenance
(OP)
Is there any merit to conduct HI-POT on the autoreclosers during periodic maintenance? Some vendors maintenance manuals recommends it and some leave it for users to decide. Our challenge is most of our reclosers are mounted on the poles so conducting Hi-POT on these reclosers is bit of challenge. And we are already during insulation resistance tests.
Talk To Other Members
RE: Hi-POT test during regular maintenance
I have the following opinion for your consideration.
1. Insulation resistance (IR) and Dielectric over-voltage (DOV) tests are conducted for difference purposes. IR on insulation resistance, while DOV determines NO flash-over over the Creepage or Clearance distance.
Note: high Voltage can flash-over over the creepage/clearance distances having high insulation resistance.
2. Different voltage level, leakage current and duration etc.
a) IR is conducted at say <1kV dc up to <8kV dc. Reading in M Ohm or G Ohm. Test Voltage is not very critical, usually <8kVdc. Leakage current is Not shown, but is taken into the R= E/I indicated resistance value. Duration is not very critical, say 10s is good enough; if PI and DAR are not considered. No hard defined pass/failed value, there are some guide lines though, not below certain minimum value. The value is used for "trending" over a period say 12 months or longer etc.
b) DOV is conducted at much higher Voltage in AC or DC. The Voltage value is dependent on the voltage rating of DUT. Leakage current is NOT critical/ignored. Duration is usually 60s. Pass/failed criterial is based on NO flash-over at the test Voltage within 60s.
3. Suggestion: In view of the site installation limitations, carry out IR say every 6 monthly; but DOV on yearly.
Che Kuan Yau (Singapore)
RE: Hi-POT test during regular maintenance
Muthu
www.edison.co.in
RE: Hi-POT test during regular maintenance
1. Agreed on the accessibility, but...
a) IR can be carried out easily with a say <8kVdc hand crank insulation high resistance meter say about <3kg. Cost of instrument is very low. Most technicians are competent to carry out the test at site
b) DOV test involves much higher Voltage and equipment, especially with AC instead of DC. The total equipments set up may easily be in the range of >100kg !. It needs LV AC power supply, which may not be available at site/in the field.
2. Opinion: In view of the logistic, cost of equipment, competence of the technician, it is NOT recommended to conduct DOV shorter than say 6 months, unless under special reasons. However, IR test on every 6 monthly is NOT excessive.
Che Kuan Yau (Singapore)