The measurement of electrical energy consumption has a huge economic importance. Through the development of electric energy market, the importance of measurement accuracy and traceability is further emphasised. Accurate electrical power standards are required in the calibration of energy meters. At VTT MIKES, measurements of electrical power at 50 Hz are traceable to SI units through a sampling power standard. Calibrations are performed using either single-phase or three-phase measurements. Typical devices that we calibrate are electrical power meters and converters.
At VTT MIKES power laboratory, the traceability of electrical power at 50 Hz is based on direct voltage from a Josephson standard and resistance realised by a quantum Hall equipment. The sampling power standard consists of two 8½ digit voltmeters, which are accurately synchronised. Currents smaller than 20 A are converted to voltages using specially constructed shunt resistors, whose resistance values are traceable to the quantum Hall resistance standard. The same measurement equipment with a current sensor based on a Rogowski coil is used to measure currents and current ratios up to 8000 A. The measurement uncertainty of the VTT MIKES power reference equipment is 0.005 % at its best.
The methods and equipment of VTT MIKES power laboratory represent international top quality. The high quality of measurements is verified by taking part in international comparison measurements together with national metrology laboratories from other countries. VTT MIKES is also an active member in different expert working groups at international level and takes part in national as well as international joint research projects. Several projects are in the European Metrology Research Programmes EMPIR and EPM.