A Closed-form Expression to Estimate the Uncertainty of THD Starting from the LPIT Accuracy Class

Abstract

Power quality is a wide-ranging and current topic that involves a huge effort from the scientific community. Power quality issues have to be avoided or solved in order to preserve the integrity of the network and its assets. To this purpose, several power quality indexes and measurement techniques have been developed and used by experts. This paper aims at solving the issue of having an uncertainty associated to the total harmonic distortion (THD) measurements. The idea is to obtain a close-form expression, which only requires the knowledge of the instrument transformer accuracy class, to estimate the mean value and the variance of THD. After the development of such an expression, it has been tested and stressed to confirm its effectiveness and applicability in a variety of conditions, and for harmonics up to 25th (of 50 Hz), defined by the standards.

The Accuracy of Evaluation of the Requirements of the Standards IEC 61000-3-2(12) with the Application of the Wideband Current Transducer

“…However, their metrological properties can be affected by the self-generation phenomenon caused by the non-linearity of the magnetization characteristic of the magnetic core [ 11 ]. This behavior is not observed with electronically controlled current transformers [ 12 , 13 , 14 , 15 , 16 ].…”

Closed-Form Expressions to Estimate the Mean and Variance of the Total Vector Error

“…Consequently, authors started from their previous experience on evaluating the uncertainty of typical parameters (THD [24] and residual voltage [25]) to obtain the TVE mean and variance.…”