Power-frequency dielectric withstand test

AC Hi-Pot Withstand Test Report Format, Free PDF

A report form for AC high-voltage withstand tests, with a capacitive current check so you know before you start whether your test set can supply the load.

  • Free
  • No sign-up
  • A4, 2 pages
  • Formulas and limits included
Preview of the AC Hi-Pot Withstand 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

  • Equipment details, basis for the test voltage, test set and trip current setting
  • Eight test lines with IR before, test voltage, hold time, leakage current, trip or flashover, IR after and result
  • A capacitive current check: expected current I = 2πfCV against the test set rating
  • Page 2: commonly used test voltages, the largest capacitive load a 25 mA or 50 mA set can carry at 1 to 5 kV, and a safe test sequence
  • Safety notes, discharge and earthing steps

How it was checked

The maximum load table is calculated from I = 2πfCV at 50 Hz and was checked against an independent calculation. Test voltages on page 2 are common practice shown as guides: take the test voltage from the equipment standard or the manufacturer. The 28 kV for 12 kV figure and similar MV values are shown for reference only.

Related

Common questions

What test voltage should I use for a hi-pot test on a motor?

For a routine factory test the common formula is twice the rated voltage plus 1000 V for one minute (IEC 60034-1), with 1500 V as the minimum. In-service re-tests commonly use a lower percentage. Use the standard or manufacturer value for your machine.

Why does a hi-pot test set trip on a long cable?

A cable behaves like a capacitor, so it draws a capacitive current even when the insulation is perfect. If that current is above the test set rating, the set trips. The form calculates the expected current and the table on page 2 shows the largest load each rating can carry.

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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Need the instrument as well?

CIE supplies insulation testers, earth testers, oil BDV testers, micro-ohm meters and relay test sets, with test certificate available on request.

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