Is “virtual” measurement permitted? In other words, is it permitted to measure anything other than active power and calculate the power value from it?

As long as the calculation of active power meets the measurement accuracy requirements for active power, it is permitted. For example, it is permitted to measure voltage and current separately and calculate the corresponding active power via physical connections.

If a calculation model is used for active power, it is important that the final calculated value meets the measurement accuracy requirements. This includes the entire chain from sensor, via transducer, to prediction model. The greater the uncertainty of the model itself, the more stringent the requirements placed on the accuracy of the measurement sensors.

If calculated measurement values are applied, the actor must report on how the requirements are fulfilled and submit documentation that confirms this reasoning. Particular emphasis will be placed on the calculation model and its accuracy.