Search

To further mitigate the BER error floor of M-ary differential chaos shift keying modulation for impulsive noise, a low-cost high-reliability coded modulation scheme without equalizations is desirable for impulsive noise. In this paper, a protograph-based low-density parity-check coded MDCSK-based bit-interleaved coded modulation scheme is proposed for the scenario with impulsive noise. Considering the Gaussian distribution of protograph extrinsic information transfer and the benchmark of coding design, the U-shaped non-coherent capacity is derived with optimal code rate for square MDCSK, showing that the code rates are stable with E_b/N_0 increasing but still much lower than that of DS-16DQAM at code rate >0.145. The derived joint probability density function can be considered as approximately a Gaussian distribution, which is used to improve the impulsive noise fitted PEXIT. Finally, a new code under a novel principle is designed for better bit error rate performance based on the improved PEXIT analysis. Both PEXIT analysis and simulation results demonstrate that the proposed scheme achieves a better BER than that with a traditional scheme, and suggesting a research approach based on simple methods. This basic research work provides a guide to establish a framework and optimize the performance of transmission systems over practical power line communication.

A distributed zero-sequence-current (ZSC) carrier signal injection via current transformer (CT) is proposed for underground cable single-phase-to-ground fault location in neutral isolated medium voltage (MV) distribution networks. High-frequency ZSC carrier signal is directly injected to a high-voltage underground cable of an energized distribution network via CT. The injected carrier signal travels along the cable to the receiving center in the substation, and is processed for quick fault line selection and fault location. No external power supplies or signal generators are needed due to the self-contained nature of the injector. The device can be constructed as a sleeve to be mounted around the underground power cable. This permits economical retrofitting to existing installations of power line communication (PLC) devices. In this paper, the operational principle and the application considerations for such an injection device and fault location tricks are explained, followed by the theory behind the proposed technique. Finally, MATLAB based numerical simulations are performed and a low-voltage prototype is tested to verify the validity of the proposed approach.

This paper proposes three different black-box models for a 10-kVA 7.967 kV–120/240 V distribution transformer that is suitable to narrowband power line communication studies. One is valid in the 3–500 kHz range, while the remaining two are simpler models valid for the CENELEC band (3–148.5 kHz). The models are represented as equivalent circuits derived from the rational approximation of the transformer admittance matrix using either phase- or modal-domain theory. All parameters needed for their implementation in electrical circuit solvers are given. Validation is performed not only in frequency domain, but also in time domain, with the application of voltage signals that excite the 3–500 kHz and 3–148.5 kHz frequency bands uniformly. The models are shown to accurately predict the attenuation and distortion of signals transferred through the transformer for a wide range of load conditions for both downstream and upstream signal transmission. Signal attenuation is shown to be load dependent, frequency dependent, and sensitive to the considered transmission path (downstream or upstream).

This paper presents and discusses the results of analysis and experimental studies of the metrological characteristics of Rogowski coils made in high density interconnect printed circuit boards technology. The purpose of the research and analysis was to determine the possibility of their use in the metering units of automated electrical power systems. Particular emphasis is placed on the formation of the resonant characteristics as well as to provide suitable resistance to external interfering electromagnetic fields. This allows, inter alia, the use of Rogowski coils for detection of interfering transmissions power line communication high-frequency conductive currents. Based on the obtained results, conclusions and recommendations for practice are formulated.

The business of distribution system operators is rapidly evolving as the distribution grid is hosting more distributed energy resources. Technology for monitoring, control, and protecting the grid is progressively pervading the lower segment of the network. These changes require a performing communication infrastructure to enable data exchange among the control centers of the grid. The 7th Framework Program European Project INTEGRIS proposes a hybrid infrastructure—based on broadband power line (BPL), Wi-Fi, and fiber optics (FO)—to enable services for grid management. This mix of technologies provides a balanced tradeoff between investments and benefits, meeting most of the requirements of the smart grid. This paper investigates the technologies that could be adopted and describes the experimental assessment performed in an operational environment in Italy. Using this installation, transfer time, time synchronization accuracy, dependability, and throughput are evaluated and analyzed over a long-term campaign. Results show that the FO is the best communication media, able to provide a two-way latency of 3 ms (95 percentile), whereas BPL has a two-way latency of 57 ms (95 percentile —4 hops). Those results confirm that a careful selection of the technologies is required to satisfy requirements of smart grid.

The large amount of differentiated quality-of-service traffic generated by modern smart grids necessitates efficient scheduling schemes for the uplink traffic. This paper proposes a cross-layer time-division multiple access scheduling scheme destined for broadband power-line communications (BB-PLC)-access networks. The scheme determines the topology of the smart-grid communications (SGC) PLC trees formed across the power grid, identifies the noninterfering segments in the tree graph, and schedules the uplink transmission. The scheme is based on appropriately adjusting the injected power of the SGC tree nodes following a graph-based distributed approach in the attempt to enhance slot reuse. The scheme has been tested and assessed for typical SGC networks deployed in rural and urban areas, considering both aggregated and nonaggregated SGC traffic. The relevant simulations verify that by reducing the interference due to PLC transmission, the proposed adaptive power-control-based scheme can significantly minimize the injected power, enhance throughput, and reduce delay on an SGC cell basis. The reduction in schedule length depends drastically on the maximum-allowed injected power and the topology of the SGC tree and may reach 70% when combined with data aggregation.

This paper discusses the channel gain characteristics of a two-conductor power-line communication system under a given transient analytical model. The channel frequency responses are derived with different transmission-line lengths and terminal loads. Compared with previous works on power-line communication, the transient model can more accurately describe the variation of the channel frequency responses, especially when transients occur on the transmission line. Simulation results show higher accuracy is achieved compared with the results under the traditional lumped-circuit π model.

The implementation of power-line communication systems requires detailed knowledge of the channel properties, such as transfer function, noise levels, and channel capacity in order to assess the services that can be provided. In this paper, the interference scenario on overhead medium-voltage power distribution lines caused by external electromagnetic (EM) fields is examined by focusing on the noise induced. The external EM fields are considered to be the main source of occurring noise and a novel method capable to calculate the corresponding noise levels is presented. The proposed method is compared to other existing models and its strengths are highlighted. The effect of the induced noise to the overall data capacity of the power-line communication channel is examined. Eventually, the influence of several parameters, such as the magnitude and direction of propagation of the external EM field, network topology, earth's EM properties, and different levels of emissions suggested by various organizations are investigated.

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.

Shield wire segmentation has been used for quite some time as an effective method for reducing transmission-line power losses, with most segmented shield wire applications on extra high-voltage lines utilizing phase-to-phase power-line carrier (PLC) coupling. As transmission system efficiency becomes more of a priority, some utilities may consider applying segmented shield wires to lower voltage lines, such as 115-kV and 230-kV lines, which most often utilize single-phase-to-ground PLC coupling. Thus, knowledge of the effects of segmented shield wires on PLC signal attenuation for various coupling methods would be useful to relay engineers. The purpose of this paper is to present a generalized method to model transmission lines for signal attenuation calculation at PLC frequencies, with special consideration given to shield wire connections. Terminating impedance and phase wire transposition are considered as well. The modeling method presented is validated with field measurements. In a companion paper, signal attenuation results considering the effects of various parameters are analyzed.

A previous paper has been written on the generalized modeling method of overhead transmission lines for use in power-line carrier (PLC) systems. Knowledge of the effects of shield wires on PLC signal attenuation for various coupling methods would be useful to relay engineers. In addition to the effect of the coupling method on PLC signal attenuation, other problems, such as resonance conditions resulting in high signal attenuation may also occur depending on the PLC signal frequency and the length of the shield wire segments. Therefore, the purpose of this paper is to provide awareness to relay engineers of problems that may arise when applying PLC systems on transmission lines with segmented shield wires.

The aim of this paper is to develop a complete model of a power-line communication (PLC) system operating on a medium-voltage (MV) network. The core-shield configuration was chosen for signal transmission in the power cables. In order to validate the developed model experimental, the medium-voltage network of the Favignana island was used to carry out detailed testing. The transmission was performed between two transformer substations in the presence of mains voltage (i.e., 24 kV). ST7540 FSK power-line transceivers, together with capacitive coupling interfaces, were used for the transmission and the reception of the communication signal. The correlation between the experimental measurements and the simulation results would appear to validate the use of the developed model for the analysis of MV transmission channels.

Passband and baseband transmissions are two competing transmission schemes for power-line communication (PLC) orthogonal frequency-division multiplexing (OFDM) systems. The advantage of the former is that it is simpler to implement for digital circuits as it needs the half-size inverse fast Fourier transform/fast Fourier transform. As will be shown, there are synchronization errors, such as carrier frequency offset (CFO) and sampling frequency offset (SFO) that degrade the performance of passband transmission. On the other hand, baseband transmission is expected to be less complex in an analog circuit implementation and to be affected by only SFO, since it does not need up-down conversion. Both CFO and SFO are caused by the frequency errors of the reference clocks in the transmitter and receiver. In this paper, signal-to-interference-plus-noise ratios and capacities are considered in comparing the effects of synchronization errors in passband and baseband transmissions. The results indicate that the performance degradation of passband transmission is almost the same as that of baseband transmission in the presence of synchronization errors.

Even though the power line is a wired medium, its channel characteristics are very different from that of conventional wired media, such as telephone and Ethernet as it is not designed for communications. Some characteristics of the power-line channel are that of the wireless channel, so most power-line communication (PLC) schemes use the carrier-sense multiple access with collision-avoidance protocol, which is popular in wireless communications, for random access. In addition, the power-line channel has some characteristics that are absent in wired and wireless channels. In this paper, we design a new PLC media-access control (MAC) protocol considering two different types of power-line noise models: 1) impulsive noise (generated by on-off switching of electronic devices) and 2) background noise. When a transmission error occurs, the transmitter in our proposal adjusts its transmission rate according to the receiver's feedback and determines the contention-window size appropriately according to the current loading. Through extensive simulations, we verify that our proposed MAC scheme improves network throughput under various scenarios.

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.

Multipath phenomenon lies in the heart of power-line communication and leads to the reception of multiple replicas of the transmit signal at the receiver through various paths. Statistical knowledge of arriving paths is essential in order to evaluate performance of communication systems. First arriving path is distinguishable from the other paths in the sense that it experiences less reflection and less attenuation along its propagation path, giving it a favorable position regarding detectability. In this study, statistics of the first arriving path are initially investigated. It is shown that the first arriving path can be defined with log-Normal probability density function. It is seen that the mean of the approximating log-Normal variable decreases with an increasing number of branches between transmitter and receiver while its variance increases. The same finding is also observed when the maximum number of branches that extend out a branching node is increased. Although statistics of the first arriving path are emphasized more, statistical characterization of the other paths is discussed as well. Infinite bandwidth assumption in which all paths arriving at the receiver can be resolved is considered in the analysis. However, a brief discussion on the impact of finite bandwidth is given.

In this paper, a novel communication concept for sensors at an inverter-fed electric motor is proposed. The concept utilizes power-line communication and a motor cable in data transmission. The signal used in communication is inductively coupled to the motor cable. The supply power for sensing and communication at the electric motor is harvested from the motor-phase conductor with a current-transformer-based power supply. The proposed concept has numerous advantages, such as no galvanic connection to the motor power circuit, an opportunity to implement the concept afterwards without electrical installation, and reliable and battery-free operation. The operation of the concept is analyzed, simulated, and verified by laboratory measurements.

In this paper, two narrowband-interference (NBI) rejection methods are formulated for power-line orthogonal frequency-division multiplexing (OFDM) communications. The inherent NBI suppression capability of the OFDM system is improved upon through the application of a spreading sequence (i.e., IS-OFDM) and further improved through the utilization of NBI filtering implemented at the OFDM receiver. A block least-mean-square (BLMS) algorithm, called cyclic prefix BLMS (CP-BLMS), is constructed for time-domain NBI filtering and a corresponding fast BLMS (FBLMS) algorithm, called linear FBLMS (LFBLMS), is also presented which performs the NBI filtering in the frequency domain. The fast implementation reduces the computational burden of the additional filtering process for a large number of subcarriers without impact on filter performance. Both simulation and theoretical analysis demonstrate the bit-error rate improvement of the proposed approaches compared to previous methods. Numerical results from theoretical analysis also illustrate the speed advantage of the LFBLMS algorithm.

Advanced communication technologies has allowed the power-line communication (PLC) channel to be a transmission medium that enables the transferring of high-speed digital data over the classical indoor electrical wires. The development of PLC systems for Internet, voice, and data services requires measurement-based models of the transfer characteristics of the power-line network suitable for performance analysis by simulation. In this paper, a statistical-based and deterministic PLC channel frequency model was proposed. This model has the advantage of using only one parameter: the channel class. Related software is also developed. In this paper, this model is further improved to represent the measured impulse responses, and related software is developed. First, a PLC channel classification is realized, and an average magnitude and phase channel model by class is proposed. Second, the multipath behaviour of the PLC channel is introduced: a statistical-based channel magnitude generator is built, and a refined phase model is suggested. Finally, the related software is briefly described.

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.

In this paper, we present a new approach to noise suppression for power-line communications based on orthogonal frequency-division multiplexing (OFDM). Previous work for wireless systems has suggested that augmentation of OFDM using spreading codes prior to modulation offers some narrowband interference (NBI) resistant capabilities. We present a study of the performance of such a system for power-line networks-well known to be affected by such noise. Termed interference suppression OFDM (IS-OFDM) and its counterpart NBI avoidance (NBIA), we also present a further modification of these techniques in order to improve NBI suppression performance. The proposed algorithm, orthogonal narrowband interference avoidance (ONBIA), avoids narrowband interference on contaminated subcarriers while preserving the orthogonality of the spreading code. Both theoretical analysis and simulation results demonstrate the improvements of ONBIA over the standard IS-OFDM and NBIA methods across a wide range of interference-to-signal ratios (ISR).

The optimal multilayer, multiobjective resource allocation model for multiuser and multitraffic orthogonal frequency-division multiplexing (OFDM)-based power-line communication (PLC) systems is analyzed with the restrictions of maximal total power, constant rates for every real time (RT) user, minimal rates for every non-real time (NRT) user, maximal upper limit of power and number of bits for every subcarrier in each OFDM symbol. A bit-loading lookup table resource allocation algorithm with rate- and margin-adaptation is proposed based on resource factor, which first assigns fairly Pareto non-dominated resources for all RT users according to resource factor so as to attain their constant rates, second computes the relevant remaining power and non-used subcarriers for every Pareto solution and assigns fairly them for all NRT users so as to attain their minimal rates, third also computes the relevant remaining resources and assigns them so as to achieve the maximal sum of the allocated rates for all NRT users, lastly selects out the globally optimal solution according to the order of partial information. Based on the typical power-line channel, the simulation results illustrate that the proposed algorithm outperforms the existed multiuser bit-loading greedy algorithm and it realizes better the multiple aims of resource allocation in OFDM-based PLC systems.

In this paper, we present a suboptimal integer bit allocation algorithm that minimizes power output for given user demands in multiuser orthogonal frequency-division multiplexing (OFDM) systems implemented in downlink transmission of power-line communication (PLC) networks. Assuming complete knowledge of a channel and the predetermined data rates for every user, the presented algorithm solves the power minimization problem analytically. The simulation results have shown significant advantages of this approach, especially in comparison with algorithms that deal with the problem of user data rate demands in an iterative manner. Compared to iterative algorithms, the proposed algorithm proves to be a much more effective solution regarding processing time and computational complexity. In addition, the losses in its power allocation efficiency due to its suboptimal approach remain very small in cases where the number of users does not exceed half the number of available subchannels.

This paper considers broadband signal transmission via three-phase overhead medium-voltage (MV) lines above the lossy plane ground. The established methods dealing with transmission along MV power lines are examined in terms of the end-to-end transfer function under various network configurations. The MV broadband over the power-lines transmission channel is investigated with regard to its spectral behavior, the usable bandwidth, and the end-to-end signal attenuation. It is found that the aforementioned features depend drastically on the number and type of branches existing along the end-to-end broadband over power-lines signal propagation.

Power-line communications (PLC) is a field that has raised a lot of research in the past years. In this paper, we introduce array codes into the PLC environment and we study the channel's performance. In particular, generalized array codes (GAC), as well as row and column array codes (RAC) are applied. We examine their performance by obtaining three different code rates from each category. Therefore, the (8, 4, 4), (12, 7, 4) and (16, 11, 4) GAC codes as well as the (9, 4, 4), (12, 6, 4), and (15, 8, 4) RAC codes are used, meaning that we obtain code rates of (1/2), (7/12), (11/16), and (4/9), (6/12), (8/15) respectively. In addition, for reasons of completeness, convolutional codes are also being applied under the same channel conditions. Moreover, we suggest a hybrid coding technique, which combines the (8, 4, 4) GAC and the (15, 8, 4) RAC code in order to meet the requirements of the PLC time-varying channel and improve its performance. Concerning the system's design, we take into consideration Zimmermann's model for the PLC channel. We apply Middleton's model for the channel's background and impulsive noise, while we also introduce a novel way of estimating the system's impulsive noise. Finally, the well-known transmission technique of orthogonal frequency-division multiplexing is used. The channel's performance is evaluated in terms of the bit-error rate for different Eb/N0 values via computer simulations.

In this paper, we estimate the responses' upper and lower bounds of indoor power lines in the presence of electrical devices showing nonlinear behavior with respect to the mains voltage. These nonlinear loads produce short-time variations that are synchronous to the mains. Nonlinearities are modeled in the frequency domain as the sum of a nominal value impedance and of a number of elementary pulse-shaped terms with uncertain weights. The indoor power-line channel is modeled in the wavelet domain and sensitivity analysis with respect to the weights is performed by the adjoint circuit method. The proposed method allows fast and accurate evaluation of the bounds of the channel's response in the time and in the frequency domain, avoiding time-consuming Monte Carlo simulations. A measurement campaign on the power-line grid of a small apartment has shown the validity of the proposed method.

Power-line carrier (PLC) systems have proven to be susceptible to interference caused by harmonics produced by loads, such as HVDC converters, DC electric arc furnaces, static var compensators, and motor speed controllers. Previous work in this area has provided information regarding the nature and origin of harmonic frequency interference affecting PLC systems as well as discussion of problem mitigation. However, the information provided in this area is contained within a number of works. Therefore, the purpose of this paper is to summarize previous work in this area with the intent of providing a single and practically useful resource for field engineers and others responsible for the operation and maintenance of PLC systems used for communication over high-voltage transmission lines. Information provided includes a description of the nature and origin of harmonic frequency interference in PLC coupling systems, including field measurements. Susceptibility of different coupling systems to harmonic frequency interference is discussed. Methods for mitigating interference are also provided, including an example of interference mitigation on an actual coupling system on a 230-kV line. Finally, a relationship between harmonic frequency interference and standard harmonic distortion limits is discussed.

The aim of this paper is the development of a theoretical model of medium-voltage (MV) cables in the frequency range of 25-200 kHz, which can be easily implemented in the Simulink enviroment. Two transmission-line configurations: 1) line-ground and 2) line-line were considered. The model requires the knowledge of the transmission channel parameters in the frequency domain. Thus, a characterization of MV cables in the two transmission-line configurations by means of experimental measurements was performed on commonly used MV cables, RG7H1R, of different sections, 95 mm(2) and 185 mm(2) with an aluminum core and copper shielded. To validate the model, a comparison between the attenuation constant alpha measured and the one simulated for both configurations under study was carried out.

Power-line communications over the low-voltage networks is gaining the attention of researchers in both broadband and narrowband application areas. The transmission characteristics of the power-line carrier are very significant in signal propagation. This paper presents field test and simulation results concerning signal transmission on power lines in underground and aerial installations within the CENELEC EN 50065-1 B band. Field test results show the consistency to the transmission line theory and modal wave propagation. The well-known alternate transients program-electromagnetic transients program (ATP-EMTP) is used for the simulation of the transmission path. Simulation results, obtained for different operational cases and configurations, are compared to the actual measurements from field tests, showing satisfactory agreement. Finally, the proposed models are used in further investigations concerning the signal transmission.

In this paper, we consider an orthogonal frequency-division multiplexing (OFDM) communication system over a power-line channel (PLC) that exhibits cyclic short-time variations. In order to follow the cyclic channel variation, a blind estimation method is proposed. Simulations on an indoor PLC network show that the proposed estimation method is suited for following the short-time variation of the channel, achieving a better bit-error rate (BER) than a base pilot-aided method.

A new method of measuring the change in the average height above ground of horizontal high-voltage overhead transmission-lines (OHTLs) phase conductors is introduced. The new technique, called power-line carrier sag (PLC-SAG) for short, determines average overhead conductor height variations in real time by correlating sag with measured variations in the amplitude of signals propagating between power-line carrier (PLC) stations. The multifrequency PLC-SAG monitoring signals are injected onto the operational PLC system in the 50- to 500-kHz band, but without interfering with the operational integrity of the PLC teleprotection system. The feasibility of the method was examined using the theory of natural modes for multiconductor systems, and tested by extensive field experiments on two horizontal 400-kV lines operated in South Africa by Eskom. It is concluded that the average height of a horizontal OHTL can be tracked accurately for continuous periods by the PLC-SAG technique.