MEASURING INTERFERENCE AND HARMONIC CURRENTS

A common problem in electrical engineering is the measurement of small high frequency interference currents or low strength higher order harmonics in the presence of a large fundamental current.

With traditional methods of current measurement the primary transducer, often a CT or hall effect device, has to be of sufficiently large rating to not saturate in the presence of the fundamental component. Thus the primary transducer is expensive, bulky and in combination with the power analyser or oscilloscope often without the resolution necessary to measure these small higher frequency currents accurately.

o the coil size can be specified independently of measured current.
o the fundamental current component cannot damage the transducer and the Rogowski coil does not suffer from magnetic saturation.
o it is straightforward modification to tune the bandwidth to attenuate the fundamental components and enhance the sensitivity to provide a large signal to noise ratio at those frequencies of interest.

PEM Ltd has supplied a number of such transducers for applications in the traction industry. One example is an RCTi used in the facilitation of EMC assessment of a new national railway - this is the subject of the following press release from PEM - RCTi measuring interference currents.pdf.

If you think that your current lies outside the capabilities of our standard ranges, please Contact Us giving as much information about your requirement as possible and we will be happy to investigate the possibility of a special design.