Precision loss measurement of reactive compensation components by sampling voltage and current

Achievable Accuracy in Industrial Measurement of Dissipation Factor of Power Capacitors

“…Recently, sampling techniques have reached maturity and offer a possible alternative to classical bridges [19][20][21]. In a sampling system, current shunts are used to convert the capacitive currents into a voltage that can be recorded by the sampling instruments as shown in Figure 3.…”

“…The raw digital data must be analyzed to determine the dissipation factor, usually by means of Fourier Transform methods, which establish the phase displacement at the fundamental frequency. The stated uncertainty of sampling techniques ranges down to about 0.002 %, although systems under development now approach 0.0001 % for the sampler [20]. Voltage divider and shunt do however present problems that are not yet well known, possibly limiting the performance of the measuring system to higher uncertainty than transformer ratio arm bridges.…”

“…In this way the estimate on achievable uncertainty will be state-of-art. The digital bridge [20] is a possible candidate to replace the ratio arm bridge, but does require shunts for very small currents, and will be prone to phase displacement errors due to capacitive loading, and it is not immediately clear if this is a better choice.…”