Hello Toby
Could somebody please explain the difference between pressure testing and
insulation resistance testing of HV cables.
And how is the pressure testing actually done and what do the results
actually mean ?
You do not say where you are in the world and this sometimes effects the
answers to this type of question, but in the UK Pressure Testing implies
applying a voltage to a cable for a short time which exceeds working voltage.
This is usually done with dc even on ac cables, and the result of the test is
either success or failure depending on whether the cable survives or fails.
There will usually be a measured leakage current, but it is not regarded as
important. It is usually done once only as a test when commissioning a cable.
Insulation Resistance testing usually involves testing an HV cable at a lower
voltage, and measures the insulation resistance of the cable at this
voltagae. If done regularly and carefully with guard electrodes the readings
can give some indication of how a cable is detiorating with age. Personally I
would not use it because of the difficulties of ensuring all readings were
done under the same conditions, and the data management needed to keep
meaningful records, but it some places it may be a legal requirement.
John
