Verification & testing
Measuring insulation resistance
How to verify that the insulation is sound
The insulation resistance measurement shows whether there are weaknesses or faults in the insulation between conductors and to earth. It is a fixed part of the testing and must be carried out with the installation disconnected from the load.
Make the circuit dead and disconnect the load
The measurement is carried out without voltage and with the loads disconnected. If the load is not disconnected, you measure the appliances instead of the installation itself, and the result will be misleading.
Protect sensitive electronic equipment
The test voltage is a DC voltage that can destroy electronics (LED drivers, dimmers, controls, surge protection). Disconnect or short-circuit such equipment before you measure, so that it is not damaged and does not pull the measurement result down.
Choose the correct test voltage
For ordinary installations with a nominal voltage up to 500 V (e.g. 230/400 V), measure at 500 V DC according to table 6.1. Select the test voltage on the insulation tester before you start.
Test voltage500 V DC (≤ 500 V circuits)Measure between the live conductors
Measure the insulation resistance between the phases and between phase and neutral. A low value here reveals moisture, pinched cables or faults in joints.
Measure between live conductors and PE
Then measure between each live conductor and the protective conductor (PE). It is this measurement that reveals insulation faults that can cause dangerous touch voltage on exposed parts.
Assess against the requirement of min. 1 MΩ
The insulation resistance must be at least 1 MΩ per circuit (table 6.1). The requirement has been tightened compared with the previous 0.5 MΩ. If a circuit is below the limit, the fault must be found and rectified before the installation is energised.
Minimum requirements1 MΩ per circuitValues just above the limit may signal emerging moisture or insulation problems — investigate them.
Record the results in the verification report
Record the measured insulation resistance for each circuit in the verification report together with the test voltage and date. The measurements are part of the statutory documentation for the verification.
Source
Based on DS/HD 60364-6, table 6.1 (elsikkerhed.dk/krav-til-verifikation).
Videos from NDLA
Video guide· Norwegian speech
Isolasjonsmåling
Source
NDLA
«Isolasjonsmåling» · Creator: Esteban Panza
License: CC BY-SA 4.0 · Original at NDLA ↗
Shown unaltered in the original language with the source's own subtitles. The video shows Norwegian practice — the method is often the same, but rules and standards may differ from the Danish ones.