Dielectric strength of insulating oil, IEC 60156 style

Transformer Oil BDV Test Report Format, Free PDF

Record up to four oil samples on one sheet: six breakdown voltages each, with mean, lowest, highest, spread and a pass or fail against the limit for your voltage class. Page 2 has the procedure and the calculations.

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  • A4, 2 pages
  • Formulas and limits included
Preview of the Transformer Oil BDV Test Report form
Download the PDF formA4, 2 pages

Print it at 100 % on A4. Page 1 is the form you fill in. The next page is the worksheet and reference.

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What is inside

  • Sample and transformer details: ID, rating, oil type, where the sample was drawn, oil temperature, electrode gap and voltage rise rate
  • A table for six breakdowns on each of up to four samples, with rows for mean, lowest, highest, standard deviation and spread
  • A limit row and a pass or fail row, with the limit left for you to fill from your specification
  • Visual checks, oil condition options and a retest date
  • A worked example, the test sequence (sampling, rest, rate, repeats) and commonly quoted guide values by voltage class

How it was checked

Mean, standard deviation and spread are calculated from the formulas on page 2, and the worked example was checked against an independent calculation. The guide thresholds are common field practice marked as guides: take the binding limit from your specification, IEC 60422 or IS 1866.

Related

Common questions

How many breakdowns are taken in a BDV test?

The usual test takes six breakdowns on one filling of the cell, with the voltage raised at about 2 kV per second and a short rest between breakdowns, and reports the mean. Follow the standard your specification names.

What is the minimum BDV for transformer oil?

It depends on the voltage class and your specification. Commonly quoted field values for in-service oil with a 2.5 mm gap are 30 kV or more up to 72.5 kV class, 40 kV or more up to 170 kV, and 50 kV or more above that. The form leaves the limit box for your own value.

Using the form

  • Limits and constants come from the standards named above, as commonly quoted. Check them against the edition you work to, and use the stricter of those and your specification.
  • Where a value is a common guide rather than a limit from a standard, the form says so.
  • This is a calculation aid for qualified people. It does not replace the standard, the instrument manual or your site safety procedure.

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