What is fault current or residual current measurement?
The vectorial sum of the individual currents of the phases (incl. N conductor) is measured via a residual current transformer. In the ideal insulation state, the vectorial sum should be zero. If a fault occurs in the consumer or in the supply lines, the fault current flows off via PE and the sum of the currents (differential current) is not equal to zero.
The measurement technology behind it (e.g. PQI-DE with feature D1) measures, detects and reports this error even with very small deviations. This ensures that a fault is detected at a very early stage and can be rectified before the system comes to a complete shutdown.
How does fault current occur?
If a deviation is detected with the residual current measurement, there may be various causes for the fault current:
- Defective components (such as switching power supplies)
- Insulation faults on electrical cables & connections
- Insulation faults on units
From a technical point of view, the measured residual current is not limited to the pure fault current! Switched-mode power supplies, filter technology and motor supply cables cause so-called leakage currents of the parasitic capacities or also leakage currents of the EMC filters.
Residual current measurement devices
Use as a permanently installed residual current monitoring device
The permanently installed PQI-DE measuring device offers many advantages over classic RCM measuring techniques on the market, in addition to the core tasks of disturbance fault recording and power quality monitoring according to EN 50160 and IEC 61000-2-4, also for monitoring the conducted EMC standards in your company.
Advantages of RCM measurement via PQI-DE:
- Fault recording
High-resolution fault records in case of exceeding/falling below alarm and warning thresholds - FFT for the detection of residual currents
The residual currents can be detected online/live as well as after recording via a spectral analysis up to 20 kHz! - Continuous recording in different interval classes
Measured values can be recorded in different averaging modes (200ms/ 3s / 10 min / 2h) - Reporting in WinPQ lite
Report with RCM and FCM selectable from free intervals!
Use as a mobile residual current meter
Our PQ-Box family consists of high-performance, portable mains analysers, frequency analysers, power meters and residual current meters that focus on user-friendliness and practicality.
Thanks to flexible current input measurement technology, you can also use our mobile power quality analysers as residual current measuring devices for residual currents up to 20 KHz.
Here is a practical application example:
Residual current measurement with a mobile PQ-Box 300
In a photography and design studio, located in a large industrial park, a residual current device (RCD) tripped very frequently. Due to the permanent power outtages, this company could not work reasonably on many days per month. Read here how we were able to fix this problem.
