Rogowski Coil - Disadvantages

Disadvantages

This type of coil also has some disadvantages over other types of current transformers.

• The output of the coil must be passed through an integrator circuit to obtain the current waveform. The integrator circuit requires power, typically +/-15Vdc. Traditional split-core current transformers do not require integrator circuits. The integrator is lossy, so the Rogowski coil does not have a response down to DC; neither does a conventional current transformer.

• The full-scale output of a properly designed Rogowski coil is typically a few hundred microvolts, or perhaps a few millivolts. At 1% of full scale, which is a typical test point in standards like IEC 62053-22, the output can be as low as a few microvolts. Measuring signals this small in an electrically noisy environment, such as an electrical cabinet for a high-power photovoltaic inverter, can be extremely challenging. Because of these very small signals, and the plastic enclosures often supplied for integrators, the Rogowski coil-integrator combination can be highly susceptible to electromagnetic interference.

Due to these disadvantages, Rogowski coils are primarily used when ease-of-installation is a high priority. Traditional or split-core current transformers are used when accuracy, noise immunity, and currents during power quality events are a high priority.