Primary measuring device for measuring a current effective power

A method of determining a calibration factor for a measurement of an effective power in a primary circuit of a power transmission system, the method comprising:

• setting a predefinable working point by setting a predefinable input voltage and a predefinable working frequency;
• at the working point, generating a power ratio with a low effective power and a high apparent power;
• and
• determining the calibration factor as a cosine value of a phase shift (ϕcal) and/or as a holding time (Tcal) for a known reference (ϕref).

A method of calibrating a measured value, the method comprising:

• detecting a current (Imess), a voltage (Umess), and a phase shift (ϕmess) between the current (Imess) and the voltage (Umess) in a primary circuit;
• carrying out a power measurement by evaluating the detected current (Imess) and the detected voltage (Umess);
• correcting the detected current (Imess) and/or the detected voltage (Umess) via a cosine value of the detected phase shift (ϕmess) between the detected current (Imess) and the detected voltage (Umess) and/or a holding time (Tcal) to generate a corrected value (Ikorr) of the detected current and/or a corrected value (Ukorr) of the detected voltage;
• calculating a power value with the corrected value (Ikorr) of the detected current and/or with the corrected value (Ukorr) of the detected voltage;
• and
• provisioning the calculated power value as a current effective power (Pkorr).