Grigoris K. Papagiannis

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

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.

Load profiling in the deregulated electricity markets: A review of the applications

This paper provides a state of the art survey on the load profiling applications in the deregulated market. The survey is focused on topics like tariff design, load forecasting and various power distribution issues. The procedure of the formulation of the load profiles is analyzed, as well as the algorithms used for the aforementioned procedure. Furthermore, the paper presents the two general models that are used in load profiling, namely the area (or regional) and the category (or the consumer-group-related) model. The strength and weaknesses of each model are discussed. Finally, the authors contribute to the existing load profiling literature by introducing a clustering algorithm that is used in other clustering applications. The algorithms performance is compared with a set of algorithms that have been proposed and the results are discussed.

Earth return path impedances of underground cables for the two-layer earth case

The influence of earth stratification on underground power cable impedances is investigated in this paper. A rigorous solution of the electromagnetic field for the case of underground conductors and a two-layer earth is presented. Analytic expressions for the self and mutual impedances of the cable are derived. The involved semi-infinite integrals are calculated by a novel, numerically stable, and efficient integration scheme. Typical single-core cable arrangements are examined for a combination of layer depths and earth resistivities, based on actual measurements. The accuracy of the results over a wide frequency range is justified by a proper finite-element method formulation. The differences in cable impedances due to earth stratification are presented. Finally, a simple switching transient simulation is examined to evaluate the influence of the earth stratification on transient voltages and currents.

A systematic approach to the evaluation of the influence of multilayered Earth on overhead power transmission lines

The influence of earth stratification on overhead power transmission line impedances is investigated in this paper. A systematic comparison of existing approaches is done, while results are also obtained using a finite-element method formulation. A novel numerical integration technique is proposed for the calculation of the infinite integrals involved. Typical single- and double-circuit line configurations are examined for a combination of layer depths and earth resistivities over a wide frequency range. The influence of the layer depth is also investigated. Results show significant differences from those, corresponding to the case of homogeneous earth. Using the multilayered earth return impedances in transient simulations, the transient responses show that differences occur mainly in cases of asymmetrical faults, justifying the need for a detailed earth model implementation.

A one-step finite element formulation for the modeling of single and double-circuit transmission lines

A method is presented, by which a finite element method (FEM) formulation is used for the direct computation of overhead transmission line series and sequence impedances. The method is applied in single and double circuit line configurations of arbitrary geometry, giving results in perfect agreement with those available from classical calculation methods. The new method can easily handle cases of nonhomogenous and/or irregular terrain, where classical methods may fail.

Earth Return Impedances of Conductor Arrangements in Multilayer Soils—Part II: Numerical Results

The influence of earth stratification on the conductor impedances is investigated in this paper. The generalized expressions for the self and mutual impedance of conductors in the multilayer earth case, which have been derived in a companion paper, are implemented on typical overhead power transmission lines and underground single-core power cable arrangements for discrete and exponential variations of earth resistivity. The accuracy of the results over a wide frequency range is justified by a proper finite-element method formulation. The differences in the impedances due to earth stratification are presented. The influence of the earth stratification on the actual transient responses of the conductor arrangements is also investigated.

Impedances and Admittances of Underground Cables for the Homogeneous Earth Case

A general formulation for the calculation of the influence of the earth return path on the impedances and the admittances of underground multiconductor power cable arrangements is presented in this paper. The expressions for the self and mutual earth correction terms are derived by a rigorous solution of the electromagnetic-field equations. The involved semiinfinite integrals are calculated by using a suitable numerical integration technique. The propagation characteristics of a single insulated conductor and of a typical three-phase single-core cable arrangement are investigated and are compared to the corresponding ones obtained by other approaches. Finally, the cable parameters calculated by the proposed method are used in a simulation of a fast transient in a three-phase single-core cable.

Low-Voltage Distribution Line Performance Evaluation for PLC Signal Transmission

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.

Calculation of overhead transmission line impedances a finite element approach

In this paper, the finite element method (FEM) is used to calculate the frequency dependent series impedance matrix of an overhead transmission line. A novel approach is proposed, leading from FEM results to the direct computation of the symmetrical components impedance matrix of any single or double circuit transmission line. Results show excellent agreement with those obtained by classical computation methods. Test cases examined include impedance calculations in the presence of certain terrain irregularities in the line neighborhood, such as a line by a mountain side of variable slope, a line inside a canyon or a line near a water region.

Medium Voltage Network PLC Modeling and Signal Propagation Analysis

PLC technology applications in medium voltage (MV) distribution networks are mainly related to the monitoring, control and metering applications. The CENELEC A band provides adequate transfer rate for such narrow band PLC applications. Scope of this paper is to present simulation results concerning NPL signalling on MV distribution networks. Cases of underground cables, overhead lines and distribution transformers are examined. All simulations have been done using the Electromagnetic Transients Program (ATP-EMTP). Results seem to be consistent with transmission line theory and modal wave propagation, showing standing wave signal voltage profiles along the lines. The case of an aerial MV distribution network is also examined for different frequencies and loading conditions, including open-ended lines, transformers, compensation capacitors and combinations of them.