DC hipot testing is used in shielded medium voltage cables to test the electrical safety of the insulators. This is to reduce the chances of someone being hurt or equipment getting damaged.
In DC hipot testing, a high voltage, usually more than 5 kilovolts, is applied to the test conductor then the leakage current is measured. Ideally, there is minimal leakage current due to the capacitance of the cable. A sudden rise in the leakage current while the test voltage is increased indicates a faulty insulation.
There are some things you should consider when performing the hipot testing to get an accurate reading:
- Make sure to ground all objects not to be tested.
- Ensure adequate clearance between tested terminals to prevent flash overs.
- Make sure terminals are free from dust, moisture and other contaminants.
- Ensure that the DC hipot tester has a clean filtered power supply. The reading may be impaired if the power line is fluctuating.
- Tests should be done on a cool dry weather. Humid or cold environments can cause an increase in leakage current, impairing your measurement.