| Summary: | In the framework of the <span style="font-variant: small-caps;">empir</span> projects <span style="font-variant: small-caps;">m</span>y<span style="font-variant: small-caps;">r</span>ail<span style="font-variant: small-caps;">s</span> and <span style="font-variant: small-caps;">w</span>ind<span style="font-variant: small-caps;">efcy</span>, <span style="font-variant: small-caps;">metas</span> developed a primary standard for electrical power using commercial off-the-shelf components. The only custom part is the software that controls the sampling system and determines the amplitude and phase of the different frequency components of voltage and current. The system operates from <span style="font-variant: small-caps;">dc</span> up to 9 kHz, even with distorted signals. The basic system is limited to 700 V and 21 A. Its power uncertainty is 15 μW/VA at power frequencies and increases to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.8</mn></mrow></semantics></math></inline-formula> mW/VA at 9 kHz. With the extension up to 1000 V and 360 A, the system reaches power uncertainties of 20 μW/VA at power frequencies, increasing to 510 μW/VA at 9 kHz. For higher voltages or higher currents, the same principle is used. However, the uncertainties are dominated by the stability of the sources. The voltage and current channels can also be used independently to calibrate and test power quality instruments. Thanks to a time-stamping system, the system can also be used to calibrate phasor measurement units, which are synchronised to <span style="font-variant: small-caps;">utc</span>.
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