Geometrical properties of Rogowski sensors

The Rogowski coil is an important current sensing device because it is linear, robust, non-interfering, and safe. The standard theory indicates that wrapping the Rogowski around the measured current will give a unique signal, independent of relative positioning, and this is usually true if high precision is not sought. A new approach to the analysis of the Rogowski, based on the magnetic vector potential a rather than the flux density B, has proved fruitful in calculating the response in non-standard situations. In particular the geometrical dependence of the signal has been studied (a) when the measured current is very dose to the Rogowski (b) when the Rogowski is imperfectly wound (c) when the Rogowski was a deliberate gap for hookover. Multistranded Rogowski coils have been made that demonstrate these properties in practice. A further development is the use of Rogowski coils with different winding patterns to locate currents when their position is unknown, for example arcs inside a vacuum vessel