Abstract: The unconventional measurement transformer for protection and/or measurement equipment of a three-phase electricity grid delivers digital information representative of a voltage or of a current of an electricity line by making use of optical sensors that are provided in sufficient number to achieve a certain amount of redundancy in the measurement paths. The output paths of the optical sensors are processed by digital processing means to validate said voltage or current digital information by a majority vote. Advantage is taken of features specific to three-phase high voltage and to the performance of such optical sensors to reduce the number of optical sensors required in an unconventional measurement transformer to obtain a degree of redundancy.