Patent US 6,236,949

A sensor apparatus for monitoring voltage and/or current in an electric circuit and a system for monitoring voltages and currents in a system wherein electricity is distributed in a plurality of circuits. A sensor apparatus is associated with each phase conductor in each of the circuits. The sensor apparatus senses the electricity in the phase conductor and provides a digital output that is representative of the sensed electricity in the phase conductor. The digital output preferably includes phasor data for the sensed phase conductor. The monitoring system includes a plurality of such sensor apparatuses. The plurality of sensor apparatuses are coupled to a digital data network that provides for the exchange of sensed data among nodes on the digital data network. On a node of the network, phasor data from some of the plurality of sensor apparatuses are summed or otherwise processed to obtain phasor data representative of a plurality of the circuits.