A high accuracy reactive power and energy meter insensitive to frequency variations

Abstract

The application of a frequency-controlled powerto-pulse-rate conversion in a high accuracy instrument for reactive power and energy measurement at power frequencies is described. Test results show that the meter accuracy is better than 100 ppm regardless of frequency variation of +5% around nominal frequency.

A high performance frequency insensitive quadrature phase shifter and its application in reactive power measurements

“…it does not impose any restrictions on the choice of operating principle of watt/watthour meter used in the var/varh measurements. A meter based on this approach could be used as a reference for sinusoidal conditions while under nonsinusoidal conditions it has similar response as presented in [9].…”

“…This change should be equal to x / 2 exactly and be independent of the frequency of the input signals. A method presented in [8], [9] solves this problem by implementation of x/2 phase shifting circuit with frequency dependent amplitude response and frequency controlled analogue-topulse rate converter providing the output pulse train whose pulse-rate is proponional to the reactive power but insensitive to frequency variations.…”