Field Trials for the Empirical Characterization of the Low Voltage Grid Access Impedance From 35 kHz to 500 kHz

Igor Fernandez,Noelia Uribe-Perez,David De La Vega,Asier Llano,Itziar Angulo,Amaia Arrinda

doi:10.1109/access.2019.2924253

Igor Fernandez, Noelia Uribe-Perez + Show 4 more

Open Access

https://doi.org/10.1109/access.2019.2924253

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Abstract

The access impedance of low-voltage (LV) power networks is a major factor related to the performance of the narrow-band power line communications (NB-PLCs) and, in a wider sense, to electromagnetic compatibility (EMC) performance. Up to date, there is still a lack of knowledge about the frequency-dependent access impedance for frequencies above 9 kHz and up to 500 kHz, which is the band where the NB-PLC operates. The access impedance affects the transmission of the NB-PLC signal, and it determines the propagation of the non-intentional emissions that may disturb other electrical devices, including malfunctioning or reduced lifetime of equipment. This paper presents the results of field measurements of the LV access impedance up to 500 kHz in different scenarios, with measurement locations close to end users and near transformers. The results provide useful information to analyze the characteristics of the LV access impedance, including variation with frequency, ranges of values for different frequency bands, and analysis of specific phenomena. Moreover, the results reveal a diverse frequency-dependent behavior of the access impedance in different scenarios, depending on the grid topology, the number of end users (that is, number and type of connected loads), and the type of transformation center. Overall, the results of this paper offer a better understanding of the transmission of NB-PLC signals and EMC-related phenomena.

Highlights

In the frequency range below 9 kHz, it is well known that the access impedance of LV networks is a major factor for setting Electromagnetic Compatibility (EMC) requirements
The results included in this paper provide further insight into this topic, with an empirical analysis based on field measurements of LV access impedance values
MEASUREMENT METHODOLOGY The measurement method used in the field trials has been developed by the TSR Group of the University of the Basque Country (UPV/EHU), for the characterization of the impedance of the LV electrical grid in the frequency range up to 500 kHz. This measurement method has been tested in the laboratory [11] and presented in CENELEC SC 205A Working Group 11 [12]. As these trials were planned in coordination with Iberdrola, the measurement methodology was adjusted to the frequency range of the narrow-band power line communications (NB-PLCs) technologies used by this DSO for Smart Metering services in the LV distribution network: 35 kHz - 500 kHz, for PRIME 1.3.6 [13] and PRIME 1.4 [14] transmission technologies

Summary

Introduction

In the frequency range below 9 kHz, it is well known that the access impedance of LV networks is a major factor for setting Electromagnetic Compatibility (EMC) requirements. Reference values for the network impedance are given in IEC/TR 60725 [1] for fundamental frequency and in the appendix to IEC 61000-4-7 [2], [3] for frequencies between 2 kHz and 9 kHz. By contrast, there is still limited knowledge about the access impedance and load impedances of LV grids for frequencies above 9 kHz. there are many EMC aspects. The impedance in the supply network affects the propagation of non-intentional emissions in this frequency band and, the possibly disturbing effects of these emissions to other electrical devices, including malfunctioning or reduced lifetime of equipment [3]–[5]. End-user equipment may represent a low-impedance path at frequencies used for NB PLC, resulting in attenuation of the intentional signal, which might

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