Impact of Temperature on Nonlinearity of Voltage Transformers in Harmonics Measurement

The aim of the study here presented is to evaluate how temperature variations affect the metrological performance of inductive voltage transformers (VTs) in harmonic measurements. The analysis specifically targets the harmonics up to 1 kHz, where measurements using VTs can be challenging due to their nonlinear behavior. In fact, recent scientific literature has evidenced that when a VT operates under distorted conditions, the harmonics at its secondary side are not simply a scaled version of those injected. Instead, they are a combination of the injected harmonics and the spurious ones generated by the iron core due to its B-H curve. This phenomenon has been investigated in laboratory under controlled conditions, and the specific techniques have been proposed to compensate for it. However, no studies have analyzed the impact of temperature variation on this phenomenon and, consequently, on the introduced errors. This article addresses this open issue through experimental activities on two different VTs using a high-accuracy reference setup. Results show that, for different temperatures, the measured VT harmonic errors can differ up to an order of magnitude, indicating that this influence quantity cannot be neglected.