M. Shigihara

Analysis of the disruptive effect model for the prediction of the breakdown characteristics of distribution insulators under non-standard lightning impulses

One of the most commonly used methods for predicting the strength of insulation subjected to lightning impulses of non-standard waveshapes is the Disruptive Effect Model, for which there are different procedures for the estimation of the parameters required for its application. This paper aims at analyzing the main methods for the determination of such parameters. The investigation is based on the comparison of the measured and calculated volt-time characteristics of a 15 kV pin-type porcelain insulator considering two short tail impulse waveshapes (1.2 /4 μs and 1.2 /10 μs), as well as the standard 1.2 /50 μs impulse voltage waveshape. The results relative to the positive and negative polarities of the three voltage waveshapes are presented and discussed.

Evaluation of the performance of different methods for estimating the parameters of the disruptive effect model — Application to 15 kV insulators

This paper presents an evaluation of the performance of different methods for estimating the parameters required for the application of the Disruptive Effect Model to the analysis of the breakdown characteristics of 15 kV distribution insulators subjected to lightning impulses. The tests involved the application of both the standard (1.2/50 μs) and non-standard lightning impulse voltage waveshapes (1.2/4 1.2/10 3/10 μs) and 7.5/30 μs)of positive and negative polarities. The obtained Vxt characteristics are compared with those predicted by the Disruptive Effect Model using the most common procedures for estimating the parameters necessary for its application, including a novel method which is presented in the paper. An analysis of the results relevant to the various procedures shows that the parameters obtained according to the proposed method lead to a better agreement between theoretical and experimental results.

A proposal for the prediction of the volt-time curves of MV insulators based on the Disruptive Effect Model

This paper presents a novel method to estimate the parameters of the Disruptive Effect Model for the prediction of the volt-time curves of medium voltage (MV) insulators. Two non-standard impulse voltage waveshapes, of both polarities, were adopted in the tests, namely 1.2 / 10 μs and 7.5 / 30 μs. The measured volt-time characteristics of a 15 kV class pin-type insulator were compared with those predicted by four different procedures related to the Disruptive Effect Model: Darveniza and Vlastos; Hileman; Ancajima et al., and the one proposed in this paper. The results show that the methods by Darveniza and Vlastos and by Hileman do not predict insulator breakdown for the lower peak voltage levels of the 1.2/10 μs waveshape of both polarities. On the other hand, a relative good agreement is found between theoretical and experimental results for the calculations performed using the method proposed in this paper and the one by Ancajima et al.

Capacity of carrying lightning currents in LPS copper cables and connectors experimental verifications

This paper presents the results of a series of tests on patches of bare copper cable, usually used in LPS to check their ability to conduct lightning currents.

Risk analysis associated to lightning in oil refinery construction sites

This work presents a study on plant and workers protection against direct lightning in oil refineries construction sites. Since these sites have large and free open air areas, workers are exposed to direct lightning strokes. This study analyzes each structure calculating the risks based on recommendations of the standard IEC 62305-2/2006 [1]. Moreover, it defines both the structure protection volumes using the rolling sphere method, and the protection systems against lightning for each structure using natural components or not.

Experimental verifications of direct lightning protection in flammable liquid storage tanks: Cases of carbon-steel and aluminum geodesic domes

This paper presents experimental and theoretical results of laboratory tests concerning the simulations of continuing current effects from typical cloud-ground lightning. The tests were carried out from High Power Laboratory of Institute of Energy and Environment of University of Sao Paulo. Carbon-steel and aluminum plates from the cover of geodesic domes of a typical tank were used in the tests. Results of the tests are presented considering several conditions, as well as their theoretical results, which were compared with those values presented in the main references dealing with related subjects, such as plates used in aircraft.

Volt-time curves of 24 kV porcelain insulators under non-standard impulse waveshapes

This paper presents an application of novel method in order to assess the characteristic of volt-time curves based on Disruptive Effect Model. The tests were performed on a pin-type, porcelain insulator of 24 kV class. Besides the standard 1.2/50 μs impulse voltage waveshape, four non-standard impulse waveshapes, of both polarities, were adopted in the tests, namely 1.2/4 ms, 1.2/10 ms, 3/10 μs, and 7.5/30 μs. The volt-time characteristics obtained from the tests were compared with those predicted by three different procedures related to the Disruptive Effect Model. The results show that the methods by Darveniza and Vlastos and by Hileman do not predict insulator breakdown for the lower peak voltage levels in some cases. On the other hand, a good agreement was found between theoretical and experimental results for the calculations performed using the method proposed by the authors.

Effects of lightning in oil plants construction sites — Step and touch voltage simulation and tests in work footwear

This paper presents a study on the effects caused by indirect lightning on oil refinery construction site workers. We made some tests on work footwear, commonly used by workers in these refineries, and some simulations for a specific site for the evaluation of step and touch voltages.

Continuity tests in reinforced concrete columns for natural LPS

In the present paper, we show results concerning measurements as well as several computer simulations in relation to the implementation of standards I EC 62305 [2] [3] [4] [5] and the Brazilian NBR 5419 [1] with regard specifically to the use of structure natural components, such as vertical and horizontal columns, used as a means of current flow in the incidence of a lightning discharge.