With the decision to construct the smart grids around China, the power line communications (PLC) on the low-voltage (LV) distribution networks have become one of the potential technologies to commute the information between the end users and the power provider. In order to provide communications services with different priorities under the smart grids environment, it is a must to design a completely new PLC system with variable information rate, which means understanding of the LV PLC channel characteristics become vital. This paper presents the measurement results of channel properties of LV PLC systems after giving a general overview of the topologies for the typical LV distribution networks in China. The testing results show that the main reason influencing the reliable communication of high-speed data of power line is the attenuation of the high-frequency signal, which exhibits more obviously in the branch of power line. It is almost impossible to use the frequency range from 10 to 20 MHz for the reliable communications from distribution transformer to end user, so it must be solved with the aid of such means as the repeater and the modulation schemes. Considering the signal's attenuation, the lower frequency range from 2 to 10 MHz is more suitable for the high-speed data access system. Based on the general topologies of the LV distribution networks, a new method with the help of the reflection matrix based on the multiconductor transmission line theory is proposed to model the channel transfer functions, taking into account of the source inner impedance matrix. The simulation results fit the measured data quite well and verify the feasibility of the proposed modeling scheme.

Transmission Characteristics of Low-Voltage Distribution Networks in China Under the Smart Grids Environment

Narrowband power-line communication (PLC) over distribution networks is gaining the attention of researchers, as a communication medium in future power grids. This paper investigates the application of narrowband PLC in smart distribution grids, starting from a historical overview on the accomplished technological progress and continuing with a comparison of the advantages and drawbacks of PLC technology to other smart-grid communication solutions. The analysis shows that narrowband PLC applications are best suitable for medium-voltage (MV) networks, due to the vast and complex geographical extent. The channel and topological characteristics of MV distribution networks are examined for different operational states and configurations, since they are important for the optimal design and implementation of the PLC infrastructure. The analysis is also extended to an existing overhead MV distribution network with distributed-generation units. The obtained results and the proposed methodology are useful and comprehensive tools for the efficient implementation of PLC technology in future smart grids.

Application of Narrowband Power-Line Communication in Medium-Voltage Smart Distribution Grids

Power-line communications (PLC) have gained a lot of scientific interest over the past years. In this paper, a practical noise model is proposed that best describes the noise conditions on an orthogonal frequency-division multiplexing PLC system. The noise present on a power-line system is divided in five categories which are grouped into two classes: 1) the generalized background and 2) the impulsive noise. In this paper, all of the components comprising the noise are precisely depicted on a computer simulation system. The statistical properties regarding all component parameters are taken into account and used in our model. By this way, the real conditions on a PLC channel can be portrayed in the most precise way. This model is tested on a PLC channel and its performance in terms of bit-error rate versus the E b/N 0 value is obtained. For reasons of completeness, we examine how two of the model's components affect the system's performance by altering their vital parameters. In order to accomplish this, we take various values for these parameters and we check their influence on the system. Furthermore, we apply a popular noise model, such as Middleton's noise model and we compare the performance obtained by both noise models.

Modeling the Noise on the OFDM Power-Line Communications System

Power-line communications (PLC) have proven to be susceptible to the next-generation power transmission/distribution systems with end-to-end communication capability, considered as a revolutionary and evolutionary regime of existing power grids More importantly, with recent advancements in PLC technological regulation, standardization and certification have spurred a lot of interest in the field of advanced communication and control technologies for heterogeneous networks These advancements are expected to greatly enhance efficiency and reliability of future power systems with renewable energy resources, as well as distributed intelligence and demand response (DR) programs As various national and international organizations have started to draw PLC regulations, standards and technologies for countries, these standards intend to determine important criteria such as bandwidth, modulation types, channel coding schemes, operating frequency and electromagnetic capability limits from fixed indoor/outdoor applications to smart grid (SG) applications Depending on the worldwide PLC regulation, standardization and technological developments, security schemes built around them can become interoperable from a standard point of view, but still have incompatible configurations or different maturity levels, or include non-standardized PLC functions Moreover, the PLC based systems/solutions for renewable energy integration, are also surveyed in terms of distributed-power system (DPS) and distributed energy resources (DERs) units monitoring/controlling and management purposes Thus, a particular section is dedicated to PLC based systems/solutions utilization of renewable energy sources (RESs) in SG covering all aspects of a monotype and hybrid energy plants Finally, the survey is carried on by reviewing the most recent and comprehensive articles to highlight the importance of PLC in a logical way in the smart grid for readers

Power-line communications for smart grid: Progress, challenges, opportunities and status

This paper considers broadband transmission via the overhead medium voltage (MV) grid. The MV broadband over power lines (MV/BPL) channels considered are three-phase overhead MV lines above lossy plane ground. To determine the end-to-end transfer function of any MV/BPL configuration the scattering matrix method is adopted. Various topologies of MV/BPL transmission channels have been studied with regard to their end-to-end signal attenuation and capacity. The analysis and relevant simulations reveal that broadband transmission via MV power lines depends drastically on the MV grid topology and the power constraints imposed to suppress electromagnetic interference to other services. A modification to the fixed spectrum allocation/all-protection model to regulate BPL emission is proposed employing power masks adaptive to locally existing wireless services.

Capacity of Overhead Medium Voltage Power Line Communication Channels

This paper presents a statistical method to model the noise on 10-kV medium-voltage power networks. The cumulative distribution function of the Nakagami-m distribution is calculated and compared with the corresponding empirical cumulative probability distribution in time domain for both the total noise power and the noise power at certain frequencies. It shows that the Nakagami-m distribution offers an excellent fitting to the measured data. The noise spectrum is also analyzed and the exponential and Gaussian functions are used to fit the spectrum. All of the parameters of these fitting functions are random variables which follow the Nakagami-m distribution.

Statistical Analysis and Modeling of Noise on 10-kV Medium-Voltage Power Lines

This paper presents experimental research on the noise characteristics performed on 10-kV overhead power lines. The frequency range of interest is from 40 kHz to 2 MHz. The results show that: 1) The noise level of the 10-kV power networks depends on the power network structure, configuration, and loads. It is often higher than that of the low-voltage power networks. The noise power spectrum density usually follows the exponential distribution. However, if the power lines cross with the lines of higher voltage class power networks, the distribution is impacted by the noise from the higher voltage power network. 2) In the 10-kV power line, the noise at the power-supply side (head side) is a little higher than that at the receiving end (tail side) whereas the noise distributes uniformly. The system impedance at the busbar absorbs some noise power. 3) The noise level of phase-to-phase coupling is usually lower than or at least not greater than those of the related two single-phase-to-ground coupling, respectively

Research of Noise Characteristics for 10-kV Medium-Voltage Power Lines

Based on the typical topology and physical properties of a 10-kV power network, this paper first proposes a linear time-variant filter with additive noise to be the general channel model which takes into account the main problems that interfere with communications. Then it discusses the corresponding measurement methods. Next, for the first time in the related research area, the electrical loop wire was applied for the measurement of amplitude and phase responses of the transfer function H(f), which provides a better way to solve the problem of obtaining the phase response if the power line is relatively long. Also, the multitones method for the narrow-band fading measurement is put forward. Finally, it is concluded that moving the calibration reference plane of the network analyzer to a proper position improves the measurements efficiency and accuracy and these methods can be referred to in the 10-kV power-line channel study

Channel Model and Measurement Methods for 10-kV Medium-Voltage Power Lines

The general method to investigate the impedance characteristics with a network analyzer is discussed. The common properties of the impedance are studied based on two-months observation of two 10-kV medium-voltage power networks. Meanwhile, the difference of the impedance measured at the headside and tailside of a feeder, the impedance characteristic impacted by the operating mode of the power system, the time variance of the impedance, and the characteristic obtained from a different coupling mode are also studied carefully. The results show that the characteristic impedance is in correlation with the power system structure and its configurations, and its value is about several tenths of ohms. The input impedance varies scarcely with the time. The capacitor group connected to the bus has no influence on the input impedance. And the input impedances in common mode and differential mode are both symmetric. The impedance value in differential-mode coupling is higher than that in common-mode coupling

Research of Impedance Characteristics for Medium-Voltage Power Networks

Transmission properties of the power-line channels play a very important role in the reliability of signal propagations. This paper discusses the physical signal transmission property on the broadband power-line channels based on transmission-line theory, mode propagation theory and electromagnetic-field radiation theory. It also examines the carrier signal propagating through the multi-path line channel by empirical data. The correlations among the channel attenuation and frequency, length of the path, loads and branches are analyzed, respectively, and the path loss is calculated based on empirical data and linear regressive analysis. In the end, the impact of the radiation from carrier signals on the channel characteristic measurement is concluded

Yang Xiaoxian

Papers

Statistical Analysis and Modeling of Noise on 10-kV Medium-Voltage Power Lines

Research of Noise Characteristics for 10-kV Medium-Voltage Power Lines

Channel Model and Measurement Methods for 10-kV Medium-Voltage Power Lines

Research of Impedance Characteristics for Medium-Voltage Power Networks

Broadband transmission characteristics for power-line channels