A system that measures a high electric voltage on an electrical transmission line has an electro optical voltage transducer sensor connected between the electrical transmission line and ground for providing in response to the measured high electric voltage a Sin optical intensity signal and a Cos optical intensity signal. The system also has a signal processor that operates in a first state to digitally process samples of the Sin and said Cos optical intensity signals. The process samples are used to provide a representation of the high electric voltage on the transmission line. The representation can be used for one or more of metering, relaying and transient capture.