Effect of temperature on the output

ABSTRACT: This paper describes the effect of temperature on measurements made using both rigid and flexible Rogowski coils. Temperature changes affect both types of coil by causing the coil former material to expand and by changing the resistance of the winding. With rigid coils it is possible to design a measuring system so that these two effects cancel each other out. With flexible coils, which are wound on a rubber-like former, the softness of the former makes a self-cancelling system more difficult to implement. We describe a theoretical model which attempts to explain the consequences of increasing the temperature of a flexible coil. The effect of temperature on the output of the coil is shown to depend on the relationship between the cross-section of the wire used for the winding and the cross-section of the 'return conductor' along the centre of the coil. The theory has been compared with actual measurements on a range of different coil designs and shows broad agreement. Whilst the theoretical model suggests how a coil could be designed to minimise temperature effects there are other practical constraints which have to be taken into consideration and the paper also considers these.