Analysis of Ratio and Phase Errors over Time for Low Power Voltage Transformers

Future smart grids will increasingly rely on automated functionalities for the efficient management of the electric grid and of its assets. The reliable processing of the measurement data collected from the field will play thus a critical role. In such a scenario, the detailed knowledge of the metrological characteristics of the used sensors and of their behavior under specific operating conditions can be of paramount importance to properly design and tune management and control algorithms. In this paper, the goal is to analyze the characteristics of the measurement errors over time for instrument transformers typically adopted as voltage and current sensors. Such analysis is relevant to understand the properties of the measurement errors over time, given, for example, the large use of applications based on Kalman-filter theory or other approaches based on the dynamic processing of measurements over time. The paper presents laboratory tests performed on different Low-Power Instrument Transformers and discusses the statistical properties of the associated measurement errors.