R and C measurement scenarios
The resistance and capacitance of your power system affects
your device’s measurements.
The diagram below shows the insulation resistance R and the leakage capacitance C of the power system.
The following situations may occur on an installation. The gray arrows represent the preferred route for the IMD injection signal.
| R and C value | Equivalent circuit diagram | Impact on measurements | Significance of R | Significance of C |
|---|---|---|---|---|
| R Weak (in the event of a fault) | Most of the injection signal goes into R. Throughout the duration of the insulation fault, the R measurement is inaccurate. Measuring C is difficult, particularly if C is weak. | Significant measurement for the installation. | Obtaining a measurement of C is of no significance when there is an insulation fault. | |
| Medium C, medium R | The injection signal is shared between R and C. R and C can be measured correctly. | Significant measurement for the installation. | Significant measurement for the installation. | |
| R and C high | The injection signal that goes into R is weak. It becomes difficult to measure R and is completely impossible in the case of very high C values. C is measured correctly. | Obtaining an accurate measurement of R is not important, as the system is in good condition. | Significant measurement for the installation. An excessively high C value corresponds to the maximum limits of an IT system. Above 60 μF (150 μF with filtering of 160 seconds), the product is outside of its operating range and fails. |