Multi-phase Converters with Rotating Magnetic Field for Power System Protection

This paper derives theoretical foundations for novel protective relaying system based on electromagnetic multi-phase converters with rotating magnetic field. The measurement circuit designed based on this principle can connect to the conventional voltage and current instrument transformers and utilize the fundamental laws of electromagnetism to generate output signals proportional to the magnitude of the voltage and current, as well as their combination, e.g. distance relay and symmetrical component filters. This is done without using digital signal processing, a microprocessor of any kind, or rotating parts, as in the case of electromechanical relays. The rotating magnetic field is obtained by using four windings in the primary circuit and performing the corresponding vector summation of the magnetomotive forces. A basic methodology to estimate the parameters for the rotating magnetic field converter is also presented in the paper.