PRIMARY MEASURING DEVICE FOR MEASURING A CURRENT EFFECTIVE POWER

A measuring device for measuring current effective power in a circuit of a transmission system, including an evaluation device and a calibration device, the evaluation device having a connection for measuring current, voltage, and phase shift between the current and the voltage in the circuit, wherein the evaluation device and the calibration device are connected to one another, the evaluation device configured to measure power by evaluating measured current and measured voltage, the calibration device configured to correct the measured current and/or the measured voltage via a cos ( ) value of a measured phase shift between the measured current and the measured voltage and/or via a holding time, the evaluation device configured to calculate a power value with a corrected value of the measured current and/or a corrected value of the measured voltage, and the calibration device configured to make available the calculated power as the current effective power.