If the insulation is between 500 Ohms and 200 kOhms then the measurement of R and C will be correct. This is the configuration for most IT networks.

If the insulation is higher than 200 kOhms, it means that the network is really healthy. In this case, R will be underestimated. This is not a problem as the network is healthy.

If the insulation is lower that 500 Ohms, C will not be accurate. In this configuration it means that insulation is very bad, and there is a risk of fault. The main value that is interesting to know is the value of R, which is accurate.
The customer should fix his IT network to have a better insulation

Released for: Schneider Electric India