Accurate measurements of electrical power at various points of a power grid is becoming more important and, at the same time, is getting more difficult as the old power distribution model of a few, large power generating stations and a multitude of relatively linear loads is replaced by a newer model containing a multitude of smaller, and to some degree unpredictable power sources, as well as a multitude of not always linear and often smart (essentially also unpredictable) loads. Embodiments of the invention provide for high accuracy voltage, current and power measurements of quasi-stationary and stationary waveforms in single and multiple phase power systems. Precision AC voltage, current, phase, power and energy measurements in power networks may be measured with current ranges from 1 mA to 20 kA and voltage ranges from 1V to 1000 kV and in a frequency range from a few hertz to one hundred kilohertz.