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1

The behavior of radiation component of lightning electric versus current time front changes

Izadi M., Kadir M.Z., Gomes Ch.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 11a

308-311

EN

The electromagnetic fields associated with a lightning channel can have an effect on power lines by creating induced voltages on the power networks. The shape of a channel base current especially up to the first value has a great effect on the radiation components of electromagnetic fields, while the electromagnetic fields due to lightning can be evaluated by considering the different field components. This study considers the behavior of the radiation component of the electric field versus current time front changes as the radiation component is a critical component of the electric field. The results show that the radiation component has a greater effect on the total field at far distances from the lighting channel while this effect will be larger for close and intermediate distances from the lightning channel only during the initial time periods. Furthermore, the results illustrate that the current time front has an inverse relationship with the radiation component of an electric field at different distances from the lighting channel.

PL

W artykule przedstawiono analizę wpływu zmian czoła fali prądowej, wyładowania atmosferycznego na poziom emitowanego promieniowania pola elektrycznego i oddziaływanie tego pola na linie energetyczne. Zbadano także zawartość promieniowania pola elektrycznego w całkowitym wytworzonym polu w zależność od odległości od wyładowania.

2

On the Trend of Improvement of Thermal Model for Calculating the TOT and HST

Askari M. T., Kadir M. Z. A. A., Izadi M.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 12a

297-301

EN

As the transformers are one of the expensive equipment of power systems optimum loading is notified by designers, nowadays loading was done base on the IEC and IEEE standards according to the hot spot temperature (HST) as an effective criteria on loading and overloading. To predict HST and TOT, many principal models have been proposed such as classic thermal, alternative thermal and dynamic thermal models. In this paper attempts have been made to introduce reliable and acceptable thermal models, and explain the procedure of calculating the top oil temperature and hot spot temperature as two criteria to evaluate the load ability and the insulation life of transformer. Eventually, different types of thermal models are compared with each other on a 30-MVA oil-natural air-forced transformer.

PL

W artykule zaproponowano sposób tworzenia modelu termicznego transformatora, oraz opisano procedurę obliczania maksymalnej temperatury oleju i uzwojeń. Te dwie wartości zdefiniowano jako parametry określające dopuszczalną obciążalność i żywotność izolacji transformatora. Dokonano porównania różnych modeli termicznych, stworzonych na podstawie 30 MVA transformatora z olejem naturalnym i wymuszonym obiegiem powietrza.

3

Evaluation of lightning return stroke parameters using measured magnetic flux density and pso algorithm

Izadi M., Ab Kadir M. Z., Gomes C., Askari M. T.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 10a

201-204

EN

Return stroke current along lightning channel is reckoned as a fundamental factor for the prediction of electromagnetic fields at observation points, whilst it can be simulated by current models. The most common current model is the engineering model which is more dependent on the height dependent attenuation factor and the return stroke velocity. Yet, the estimation of constant parameters at attenuation factor and return stroke velocity value are complicated. Using measured values and the PSO (particle swarm optimization) optimization method, this paper aimed at determining the values of current velocity along lightning channel and constant parameters in MTLE and MTLL engineering current models and the behaviour of both current models with respect to measured field were processed where the observation point is set at intermediated distance from lightning channel. Moreover, the results were compared with the previous results and were validated with the measured fields. The results illustrated that the MTLL model cannot be as an appropriate current model compared to MTLE current model for the intermediate distance case. Also, the results based on the MTLE model and the initial data determined by PSO algorithm were in good agreement with the measured fields. The proposed method was also capable of setting up appropriate values for unknown parameters in return stroke current models. In addition, the simulated field using the MTLE current model and initial data from PSO algorithm improved the average difference in percent between simulated field and measured field compared to the initial data from previous studies.

PL

W artykule analizuje się prędkość prądu w kanale wyładowania piorunowego. Do tego celu wykorzystuje się dane pomiarowe i algorytm PSO. Metodę tę porównano z klasyczną metodą bazującą na określaniu tłumienia i szybkości uderzenia powrotnego. (Analiza prądu w kanale wyładowania piorunowego na podstawie pomiaru indukcji magnetycznej z wykorzystaniem algorytmu PSO)

4

Analytical Field Expressions due to Inclined Lightning Channel

Izadi M., Ab Kadir M. Z., Gomes Ch., Wan Ahmad W. F.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 11

277-280

EN

In order to have a fast determination of electromagnetic fields peaks associated with inclined lightning channel, the analytical electromagnetic field expressions were proposed, assuming a pulse shaped return stroke current at channel base and by considering the channel angle and the observation point angle effects on the electromagnetic fields. Also, the return stroke velocity effects on the peaks of electromagnetic fields were processed. The results were compared with the perpendicular lightning channel case. The proposed fields' expressions are very useful in determining the peak values of electromagnetic fields, since they are considered as critical parameters in estimation of lightning induced voltage peak on the power line.

PL

Zaproponowano analityczną metodę wyznaczania pola elektromagnetycznego towarzyszącego odchylonemu kanałowi wyładowania. Przyjęto impulsowy kształt uderzeniowego prądu. Przeprowadzono obliczenia dla różnych kątów kanału wyładowania.