Method and apparatus for digitally measuring electrical power

A method and apparatus for digitally measuring electrical energy consumption parameters from a transmission line carrying alternating current. Current flowing in the conductor is sampled at multiple times which are independent of the current phase. Using an appropriate microcomputer, this sampled current is analytically filtered by expressing the current with Fourier Series using only selected harmonics thus eliminating those harmonics which define noise. An approximation of the power and power consumption is then computed by multiplying the current as expressed in Fourier Series and a voltage measurement from the conductor to obtain a power reading, and the power reading is summed to obtain a number value proportional to the energy consumption. Even harmonics and high frequency harmonics may be eliminated in the Fourier expression of the current derivative to further simplify computer computations and required hardware, and the magnetic rate of change pickup and the voltage pickup are preferably filtered to remove unwanted noise.