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Author: thpapad
Type: Document
Downloaded: 125 times
Date: 2017-11-03

MIMO-OFDM Narrowband-PLC in Distribution Systems: Impact of Power Transformers on Achievable Data Rates

Description:
Power-line communication (PLC) is gaining a renewed interest, due to the smart grid (SG) emerging communication requirements. Among other communication technologies, PLC is a very efficient and feasib... see morele solution, especially for the extended SG distribution networks. However, it is very challenging to consider both the medium- and low-voltage parts of the distribution network as a whole communication medium, due to the attenuating effects of distribution transformers, limiting PLC applicability. In this paper, data transmission through distribution transformers is investigated by means of multiple-input multiple-output (MIMO) narrowband power-line communication (NB-PLC) system, utilizing orthogonal frequency-division multiplexing (OFDM) technology. Multi-conductor distribution line and measurement-based transformer models are developed to characterize the MV-LV PLC channel. In addition, OFDM signal processing techniques are applied to enhance the achievable data rates. The transmit power budget and bit allocation across the OFDM sub-channels of the spatial beams are optimized to maximize the data rate through the distribution transformer. The achievable data rates are calculated and systematically analysed for different scenarios to investigate the effects of the distribution lines, connected loads, noise models, etc. Results reveal the superiority of the proposed MIMO design against the traditional SISO systems. In addition, the possibility for an extensive and reliable application of MV-LV PLC communications through distribution transformers is shown.

Tag(s): Distribution lines, distribution transformers, MIMO-OFDM, power-line communication, smart grids

Author: n.sene
Type: Publication
Date: 2015-10-22

Fault Current Limiters in Industrial Power Systems

Description:
The concept of saturable core fault current limiter (FCL) is relatively known nowadays. It usually consists of two reversely magnetized cores per phase to effectively limit the fault current passively... see more and immediately upon its inception. In this paper prospects of application of fault current limiters in industrial power systems will be considered. Industrial power systems (distribution networks) are widespread and include a number of various electrical appliances. The power systems development (addition of new power plants, interconnections, etc.) may lead to more intense short circuit currents at the fault location. Furthermore, industrial systems may possess on-site generation which can increase fault current levels as well. All these factors might require appropriate upgrades of industrial system electrical equipment (especially switchgear) or special operating procedures (for instance avoiding parallel operation). Another alternative is the installation of fault current limiters. In this light, a series of simulations were carried out in order to observe the impact of fault current limiters on short circuit currents in an industrial power system using the EMTP-RV software program.

Keywords: saturable core fault current limiter (FCL), industrial power system, induction machine, EMTP; fault current analysis, medium voltage

Tag(s): saturable core fault current limiter (FCL), industrial power system, induction machine, EMTP; fault current analysis, medium voltage

Author: n.sene
Type: Publication
Date: 2015-04-02

Short-Term Scheduling of Active Distribution Systems

Description:
The latest distribution management systems tend to incorporate optimization functions for the short-term scheduling of the various energy and control resources available in the network (e.g., embedded... see more generators, reactive power compensators and transformers equipped with on-load tap changers). The short-term scheduling procedure adopted in the paper is composed by two stages: a day-ahead scheduler for the optimization of distributed resources production during the following day, an intra-day scheduler that every 15 minutes adjusts the scheduling in order to take into account the operation requirements and constraints of the distribution network. The intra-day scheduler solves a non-linear multi-objective optimization problem by iteratively applying a mixed-integer linear programming (MILP) algorithm. The linearization of the optimization function and the constraints is achieved by the use of sensitivity coefficients obtained from the results of a three phase power flow calculation. The paper shows the application of the proposed approach to a medium-voltage 120 buses network with 10 dispatchable generators and 2 transformers equipped with on-load tap changers.

Authors: A. Borghetti, M. Bosetti, S. Grillo, M. Paolone, F. Silvestro

IEEE Bucharest Power Tech Conference, June 28th - July 2nd, Bucharest, Romania

Tag(s): Distributed generation, operation of distribution networks, MILP.

Author: n.sene
Type: Publication
Date: 2015-04-02

Indirect Lightning Performance of a Real Distribution Network with focus on Transformer Protection

Description:
The paper applies the Monte Carlo procedure proposed by the Authors to evaluate the indirect lightning performance of a real medium-voltage distribution network, which includes feeders and laterals, p... see moreoles, secondary substations and surge protection devices. Such a procedure allows inferring the amplitude of lightning-induced voltages at any point and any phase of the network. The analysis presented in this paper aims at assessing the expected mean time between failures of each MV/LV transformer caused by indirect lightning strikes.
A heuristic technique has been specifically developed to reduce the computational effort despite the non-linear response of the network enhanced by the presence of surge arresters.

Authors: Alberto Borghetti, Fabio Napolitano, Carlo Alberto Nucci, Fabio Tossani, Gilnei J. G. Dos Santos, Donorvan R. Fagundes, Gustavo P. Lopes, Manuel L. B. Martinez

2014 International Conference on Lightning Protection (ICLP), Shanghai, China

Tag(s): induced voltages; distribution networks; Monte Car lo method; lightning protection; MTBF.

Author: n.sene
Type: Publication
Date: 2015-04-02

Selection of MV/LV Transformers to be Protected by Surge Arresters against Indirect Lightning Overvoltages

Description:
The papers addresses the problem of locating surge protective devices in a medium voltage distribution network by means of an accurate computer model for the calculation of lightning induced overvolta... see moreges and a Monte Carlo statistical procedure. The indirect lightning performance of small network cells of different configuration are evaluated and used as a benchmark for the validation of the surge arrester locations provided by a genetic algorithm procedure. The obtained results appear useful for the lightning protection design of networks
with complex topology.

Authors: Alberto Borghetti, Fabio Napolitano, Carlo Alberto Nucci, Fabio Tossani, Gilnei J. G. Dos Santos, Donorvan R. Fagundes, Gustavo P. Lopes, Manuel L. B. Martinez

2014 International Conference on Lightning Protection (ICLP), Shanghai, China

Tag(s): distribution network; surge arresters; lightning protection.