Compensation of Nonlinearity of Voltage and Current Instrument Transformers

partially_open11This paper aims at characterizing and improving the metrological performances of current and voltage instrument transformers (CTs and VTs) in harmonic measurements in the power system. A theoretical analysis is carried out to demonstrate that, due to the iron core nonlinearity, CT and VT output signal is distorted even when the input signal is a pure sine wave. Starting from this analysis, a new method for CT and VT characterization and compensation is proposed. In a first step, they are characterized in sinusoidal conditions and the harmonic phasors of the distorted output are measured; in the second step, these phasors are used to compensate the harmonic phasors measured in normal operating conditions, which are typically distorted. The proposed characterization and compensation techniques are called SINusoidal characterization for DIstortion COMPensation (SINDICOMP). Several experimental tests, using high-accuracy calibration setups, have been performed to verify the proposed methods. The experimental results showed that the SINDICOMP technique assures a significant improvement of CT and VT metrological performances in harmonic measurements.restrictedopenCataliotti, Antonio; Cosentino, Valentina; Crotti, Gabriella; Femine, Antonio Delle; Cara, Dario Di; Gallo, Daniele; Giordano, Domenico; Landi, Carmine; Luiso, Mario; Modarres, Mohammad; Tine, GiovanniCataliotti, Antonio; Cosentino, Valentina; Crotti, Gabriella; Femine, Antonio Delle; Cara, Dario Di; Gallo, Daniele; Giordano, Domenico; Landi, Carmine; Luiso, Mario; Modarres, Mohammad; Tine, Giovann

Processing techniques for metrological improvement of low-cost smart meter hardware solution for IEC 61000-4-7 Class I harmonics measurements

The work investigates the feasibility of harmonic analysis implementation on smart meter microcontroller devices, according to IEC 61000-4-30 Class A and IEC 61000-4-7 Class I requirements. The final aim was to evaluate to what extent Class I harmonic analysis can be integrated into existing low-cost hardware platforms for smart metering, which normally have limited hardware features, especially concerning the ADC and the possibility of varying the sampling frequency with high resolution, according to the power system signal frequency. An extended experimental characterization is carried out on a case study device, aimed at analyzing its performances in terms of both measurement accuracy and computational burden. To increase metrological ADC behavior and decrease computational costs, sampling strategies and optimized interpolation algorithm have been implemented and tested verifying the feasibility of harmonic analysis implementation on smart meter microcontroller devices, according to IEC 61000-4-30 Class A and IEC 61000-4-7 Class I requirements

A Novel Approach to Current Transformer Characterization in the Presence of Harmonic Distortion

The current transformer (CT) performance under distorted waveform conditions are usually characterized by means of the frequency response test. In this paper a new way to characterize CTs, closer to real operation conditions, is proposed. The harmonic phase angle and ratio errors are measured using a nonsinusoidal current composed of fundamental and one harmonic with adjustable phase shift. The new method was tested by determining the performance of two metering class CTs commonly used by the Italian power company. The errors measured using the proposed approach are larger than the ones obtained with the frequency response. This result suggests that the frequency response approach for the evaluation of CT performance under distorted waveform conditions is not a reliable method

A smart measurement network for optimization of electrical grid operation

The electrical grid was historically created to collect large amounts of energy from generating stations and distribute them to a large number of consumers.With the advent of diffused generation, mainly produced from renewable energy sources, this classical view of the electrical grid must be completely revised. A new control system, which integrates electronics and telecommunications, is now required. Therefore, the aim of the paper is the development of a new smart measurement network, which allows the optimization of the management of a Smart Grid with a wide presence of power generation from renewable sources and decentralized storage systems

Measurement Issues for the Characterization of Medium Voltage Grids Communications

This paper is focused on the measurement issues and procedures for the characterization of medium voltage grids for narrowband power line communications (NB-PLCs), in the perspective of the use and integration of such technology into smart grids communication networks. The fundamentals are given for the characterization of the PLC channel, by means of noise and attenuation measurements. Suitable procedures are also developed for the characterization and modeling of the power system components in the frequency range of interest. Furthermore, the complete model of the PLC system is experimentally validated in a real case stud

Simulation of a Power Line Communication System in Medium and Low Voltage Distribution Networks

The aim of the paper is to study the influence of the power transformer on signal transmission in the case of a power line communication (PLC) system in a overhead Medium Voltage (MV) power network. A model of the PLC system was carried out by means of the Simulink® software. A distributed parameter MV overhead line, two power transformers, the signal coupling networks and the receiving and transmitting line coupling interface of a ST7540 FSK powerline transceiver were included in the model. The performances of the complete PLC communication system are evaluated for different line lengths by means of the attenuation computed as ratio between the received and transmitted voltage signals