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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

Indirect-Lightning Performance of Overhead Distribution Networks With Complex Topology

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

Tag(s): LIOV-EMTP, lightning-induced overvoltages, lightning performance, power quality, distribution systems, overhead power lines.

Author: n.sene
Type: Publication
Date: 2015-04-01

DISPERSED ENERGY RESOURCES SCHEDULING FOR THE INTENTIONAL ISLANDING OPERATION OF DISTRIBUTION SYSTEMS

Description:
The paper presents an algorithm for the automatic optimal scheduling of dispersed energy resources (DERs) and of under-load tap changers (ULTCs) position. The aim of the scheduling problem consists in... see more the minimization of the voltage deviations with respect the rated value, of the DERs production deviation with respect the maximum efficiency point, and of the network losses.
The system incorporates also a procedure to facilitate the intentional islanding maneuver of the distribution network. The adopted approach is based on iterative solution of linear-constrained multi-objective optimization problems. The nonlinear power flow relationships are linearized by means of the calculation of sensitivity coefficients to small variations of the control variables (namely, controllable DERs power outputs and ULTCs positions). The algorithm is implemented in Matlab environment to exploit different solvers and suitably interfaced with EMTP-RV for three-phase power flow detailed calculations. In particular, two optimization solvers are adopted: the least square method and the goal attainment approach. The relevant results are compared using the IEEE 34-node distribution feeder as test case.

Authors: A. Borghetti, C.A. Nucci, M. Paolone, M. Bosetti

Tag(s): Dispersed generation, active distribution networks, islanding operation.

Author: n.sene
Type: Publication
Date: 2015-04-01

On the Mitigation Effect of Surge Arresters on the Lightning Performance of Overhead Distribution Lines

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

Tag(s): Lightning statistics, induced overvoltages, lightning performance of distribution lines, surge arresters, shielding wires groundings, Monte Carlo method.

Author: n.sene
Type: Publication
Date: 2015-04-01

AN ADVANCED INTERFACE BETWEEN THE LIOV CODE AND THE EMTP-RV

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

Tag(s): LIOV, EMTP-RV, LEMP