Exchange Platform

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

VOLTAGE TRANSIENTS IN A DISTRIBUTION NETWORK CORRELATED WITH EVENTS IDENTIFIED BY A LIGHTNING LOCATION SYSTEM

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

Tag(s): Lightning, distribution network, LIOV, EMTP

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

Lightning-Induced Overvoltages Transferred Through Distribution Power Transformers

Description:
This paper deals with the calculation of lightning induced overvoltages on medium-voltage (MV) and low-voltage (LV) distribution networks taking into account the presence of MV–LV distribution trans... see moreformers and, in particular, the surge transfer through them. The influence of the high-frequency model adopted for the representation of the power transformer on the calculation results is analyzed, with regards to two different models, both identified and validated by means of laboratory measurements: namely, a simple π of capacitances, and the more complex one introduced by Morched, Marti, and Ottevangers in 1993. Accurate simulation results provide information on the adequacy of both models for the calculations of interest. Additional results, useful to evaluate the expected level of power quality and the benefits achievable by a proper installation of protection devices, are presented making reference to a realistic and complex configuration of an overhead distribution system

Authors: Alberto Borghetti, Atef Morched, Fabio Napolitano, Carlo Alberto Nucci, Mario Paolone,

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 24, NO. 1, JANUARY 2009

Tag(s): Lightning, distribution transformers, overvolatges

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

Transient recovery voltages in vacuum circuit breakers generated by the early-interruption of the inrush current of large motors

Description:
The switching of medium voltage electrical motors is typically realized by means of vacuum circuit breakers (VCBs) essentially in view of their elevated number of switching cycles. As known, switching... see more of VCBs generates important transient recovery voltages (TRVs)
that need to be properly evaluated in both VCB sizing and in the power system insulation coordination. As large medium voltage electrical motors are installed into plants typically controlled by means of Supervisory Control And Data Acquisition (SCADA) systems,
maneuvers that involve the motor inrush followed by its sudden de-energization (due, in general, to the intervention of an automatic diagnostic function), resulting into important TRVs, are not unusual. The paper aims at investigating the TRVs due to this specific type of
VCB switching by means of a model implemented in the EMTP-RV simulation environment. By making reference to a real plant, the validation of the implemented models is obtained by comparing the simulation results with some experimental transients provided by the plant data fault recorder. The paper finally discusses the adequacy of different countermeasures by analyzing their effectiveness for the TRVs limitation.

Authors: A. Borghetti, F. Napolitano, C.A. Nucci, M. Paolone, M. Sultan, N. Tripaldi

CIGRE - International Symposium “Assessing and Improving Power System Security, Reliability and Performance in Light of Changing Energy Sources” Recife, Pernambuco, Brazil, April 3-6, 2011
Topic 3 – System technical performance
Subtopic 3.5 – Switching and lightning transient on power systems. Impact on performance and measurements

Tag(s): Transient recovery voltages, vacuum circuit breakers, motor inrush currents, EMTP simulations

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

Interaction Between Grounding Systems and Nearby Lightning for the Calculation of Overvoltages in Overhead Distribution Lines

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

Tag(s): lightning induced overvoltages, grounding systems, overhead distribution lines, lightning protection.

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

Protection Systems Against Lightning-Originated Overvoltages in Resonant Grounded Power Distribution Systems

Description:
A joint research project between AES Sul, the Federal University of Itajubá and the University of Bologna aims at defining the required protections against lightning-originated overvoltages in a reso... see morenant grounded distribution system in order to achieve the adequate lightning performance level with minimum cost. The paper aims at illustrating the effectiveness of the presence of a surge arrester or spark gap and their protective zone by means of simulations obtained with a computer code for the calculation of lightning induced voltages that takes also into account the steady-state voltage. The results of a statistical analysis for a single multiconductor line are eventually presented and discussed.

Authors: A. Borghetti, F. Napolitano, C.A. Nucci, M.L.B. Martinez, G.P. Lopes, J.I.L. Uchoa

2012 International Conference on Lightning Protection (ICLP), Vienna, Austria

Tag(s): Lightning protection, power distribution networks, induced overvoltages.