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.
Description:
Designs built or presented during the webinar of the series Studies from A to Z on Transient Recovery Voltage
Models built:
- Rating TRV envelop (IEC 62271-100 / C37.010 - 2011)
- CP / ... see moreFD lines
- Thevenin equivalent of a network
Description:
Designs built or presented during the webinar of the series Studies from A to Z on Lightning stroke analysis.
Models built:
- Metal Oxide surge arrester (IEEE working group 3.4.11)
- To... see morewer model for fast-front transients.
- Footing resistance of towers (with ionization effect)
- air-gap leader (Area Criterion Model and equal area integration (Cigre))
- FD lines
- Substation equipment
- Parametric studies
- Corona
Description:
The paper deals with the evaluation of the indirect-lightning performance of overhead distribution networks. The novelty of this contribution is that it takes into account the inherent complexity of d... see moreistribution networks. These networks are indeed characterized by a plurality of lines (main feeder and laterals) and also by the presence of typical power components (e.g., transformers and surge arresters); they consequently differ considerably from the straight line configuration generally adopted in this type of studies.
To accomplish such an evaluation we have extended the general procedure already presented in a previous paper based on the use of the LIOV code along with the Monte Carlo method. The extended procedure combines the advantage of the LIOV-EMTP computer code—that allows the calculation of lightning-induced voltages in complex distribution networks—with a heuristic technique specifically developed and integrated in the Monte Carlo routine in order to reduce the computational effort. The application of the proposed procedure to a set of distribution overhead networks characterized by different topologies, but all of the same length, shows that, in general, the usual single straight-line approach may result into a misestimation of the indirect-lightning performance. The paper also analyzes and discusses the influence of both the line terminations, and the position of the line poles.
Authors: Alberto Borghetti, Senior Member, IEEE, Carlo Alberto Nucci, Fellow, IEEE, and Mario Paolone, Member, IEEE
IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 24, NO. 4, OCTOBER 2009
Description:
For the accurate statistical assessment of the lightning performance of distribution lines one needs to
take into account the presence of protection devices such as surge arresters and shielding ... see morewire/neutral
groundings. Indeed, the presence of those devices can significantly modify the indirect lightning
response of the overhead line and, therefore, the relevant lightning performance.
In particular, this paper aims at investigating the impact of the presence of surge arresters on the
indirect lightning performance of overhead distribution lines having realistic configuration.
Specifically, reference is made to typical Italian distribution lines. The investigation is performed with
the help of a statistical procedure developed by the authors – based on the Monte Carlo method and of
the use of an accurate modelling/calculation tool for the induced surges – that has been recently
compared with one proposed in the IEEE 1410 Std for the same purpose, and shown to be more
complete and suitable for the problem of interest. The paper also aims at investigating the influence of
the presence of surge arresters on the indirect lightning surges transferred through power transformers.
Such an additional investigation is performed by means of a suitable high-frequency power
transformer mode integrated with the lightning-induced computation tool.
Authors: A. Borghetti, F. Napolitano, C.A. Nucci and M. Paolone - University of Bologna, Italy
CIGRE – Colloquium Cavtat - Application of Line Surge Arresters in Power Distribution and Transmission Systems
Description:
Accurate evaluation of the response of overhead distribution lines to lightning electromagnetic pulse (LEMP) represents an important aspects in insulation coordination of distribution network. The imp... see morerovements of the accuracy of such an analysis call for the extension of the field-to-transmission line coupling models from single straight lines to multi-conductor/branched and complex systems. This paper deals with the description of a new interface between the LIOV (Lightning Induced OverVoltage) code and the EMTP-RV software. In particular, the paper illustrates the treatment of the boundary conditions – on which the link with the Augmented Nodal Analysis Technique adopted by the EMTP-RV is based – together with the main aspects related to the numerical integration of the Agrawal and al. LEMP-to-transmission line coupling model adopted in the LIOV code.
The proposed interface aims at improving the simulation capabilities of the previous version of the LIOV-EMTP, namely this new version completely removes the disadvantage of the time-delay associated to the use of a short Bergeron’s line needed to link the LIOV code with the EMTP. Additionally, this new version of the LIOV-EMTP code takes advantages of the Augmented Nodal Analysis Technique implementation in EMTP-RV. Comparison with experimental results is also presented in order to verify the accuracy of the proposed interface.
Authors: A. Borghetti, F. Napolitano, C.A. Nucci, M. Paolone, J. Masheredjian, F. Rachidi
29th Conference on Lightning Protection 23rd – 26th June 2008 Uppsala, Sweden
Description:
The paper deals with the analysis of the possible correlation between cloud-to-ground lightning discharges and relay operations inferred by using the experimental data obtained means of a measurement ... see moreset-up, installed on an Italian MV distribution network, and a statistical procedure based on the coordinated use of the Italian Lightning Location System (LLS) CESI-SIRF, the monitoring systems of protection manoeuvres and an advanced simulation tool for the calculation of lightning induced overvoltages. The procedure takes into account the uncertainties related to the estimation of lightning stroke location and current amplitude provided by the LLS. The experimental set-up, composed by a distributed monitoring system, is able to measure a-periodic voltage transients characterized by a frequency content up to 4 MHz. Three of these units have been installed in the feeder of a three-phase overhead distribution network with a total length of 21 km. The same feeder is protected with overcurrent and zero-sequence relays whose operations are recorded by a monitoring system with a 10-ms sampling time. The data collected during one year of operation of the experimental set-up have been analyzed together with the data collected by the LLS for a 144 km2 area covering the equipped feeder and its surrounding area, in order to account for all direct and indirect lightning events that may have caused a relay intervention. The data have been also used to test the calculation model. The paper eventually reports the results of the correlation analysis carried out using the mentioned procedure, which is used to evaluate the probability that a specific event, detected by the LLS and time-correlated to relay operation, may have been the cause of a flashover in the network.
Authors: A. Borghetti, F. Napolitano, C.A. Nucci, M. Paolone, M. Bernardi, F. Rachidi, K. Yamabuki
Description:
Monitoring units for the measurement of high frequency voltage transients have been in operation at three different busses of an Italian medium voltage (MV) distribution feeder, mainly composed by ove... see morerhead lines, in March 2007 – August 2008. The feeder is located in a region characterized by a high ground flash density value (4 flashes/km2/yr); many of the recorded voltage transients may be correlated with the lightning events detected for the same region by the Lightning Location System (LLS) CESISIRF. The paper presents some experimental results obtained using the monitoring units and their comparison with computer results obtained using a LIOV-EMTP model of the considered MV feeder. A procedure aimed at achieving the best fit between measurements and calculations, which takes into account the uncertainties associated with LLS data, is also presented.
Authors:A. Borghetti, F. Napolitano, C.A. Nucci, M. Paolone, M. Bernardi, W. Schulz
X International Symposium on Lightning Protection, 9th-13th November, 2009 – Curitiba, Brazil
Description:
The aim of the paper is to analyze overvoltages in overhead distribution lines induced by nearby lightning return stroke currents taking into account also the conductive coupling between the lightning... see more current injected into the soil and the line’s grounding system. Experimental results obtained in 2003 at the International Center for Lightning Research and Testing (ICLRT) in Florida have shown that significant currents were coupled with an overhead experimental line through its grounding system by nearby rocket-triggered lightning.
The paper first proposes a conductive coupling model between the lightning current injected into the soil and the nearby line grounding system, then presents the incorporation of such a model into the LIOV-EMTP computer code. The paper finally presents an experimental validation of the proposed models by making reference to results obtained during the above-mentioned triggered-lightning campaign.
Authors: F. Napolitano, M. Paolone, A. Borghetti, C.A. Nucci, F. Rachidi, V.A. Rakov, J. Schoene and M. A. Uman
Description:
The assessment of the lightning performance of a compact configuration of MV overhead lines that is expected to be adopted in the near future by an electricity distribution company in a Brazilian regi... see moreon characterized by high keraunic levels is presented. The compact configuration is characterized by the presence of an unenergized wire that has the main function to sustain the spacers of the phase conductors. As the wire could be periodically grounded, the paper analyses its effectiveness in reducing the overvoltages due to indirect lightning. The results are compared with those relevant to a conventional configuration of MV overhead lines now adopted by the same distribution company. The effects of the presence of surge arresters along the line are also analysed.
Authors: F. Napolitano, A. Borghetti, D. Messori, C.A. Nucci, M.L.B. Martinez, G.P. Lopes, J.I.L. Uchoa
Description:
The following example demonstrates the coupling effect between 3 adjacent transmission lines.
The case study consists of the implementation of a third transmission line next to two existing... see more lines. The data of the geometrical configuration are entered in the DATA LINE module and are stored in the "line_couplin_CP.lin". The generated model was obtained using the CP option and are loaded to the CP m-phase module using the data included in the "line_coupling_CP_rv.csv" file. The results are very close to the measurements provided in "H.W. DOMMEL ET AL, CASE STUDIES FOR ELECTROMAGNETIC TRANSIENTS, P.1,1991".
Description:
Authors:
A. Xémard, P. Baraton, B. Bressac, N. Qako, J. Mahseredjian, G. Simard, J. Ribeiro, R. Tarafi, A. Zeddam.
Abstract:
LIPS (Lightning Impact on Power Systems) is a toolbo... see morex based on EMTP (DCG version) and devoted to the calculation of the failure rate of apparatus due to lightning. This software covers direct and induced lightning. It has been developed in a partnership project between France Telecom, Hydro-Québec and électricité de France. The induced lightning nearby the electrical system. It is based on the following computational steps:
1) For each overhead line and underground cable of the electrical system, two equivalent current sources are calculated in the frequency domain, representing the illumination of the conductors by external electrical field due to lightning. These sources are evaluated in the frequency domain, taking into account the variation of the parameters of lines and cables with frequency. The conductivity of the ground is taken as finite. The modal theory is applied in the case of multi-conductor cable or line.
2) The equivalent sources are converted into time-domain and then included in an EMTP representation of the system allowing a time-domain transient computation. this approach and follow by comparisons between induced overvoltages calculated by LIPS and results from the literature.
