Experimental Techniques to Simulate Naturally Polluted High Voltage Transmission Line Insulators

Transcription

1 IEEE Transactions on Dielectrics and Electrical Insulation Vol. 21, No. 5; October Experimental Techniques to Simulate Naturally Polluted High Voltage Transmission Line Insulators O. E. Gouda Cairo University, Faculty of Engineering Electrical power Department, Cairo, Egypt and Adel Z. El Dein Aswan University, Faculty of Energy Engineering, High Voltage Networks Department, Aswan 81528, Egypt ABSTRACT This paper represents experimental techniques to simulate the naturally polluted high voltage insulators, under conditions that simulate the desert environment. Usually, the IEC fog method is used for testing the polluted insulators of high voltage transmission lines, but it does not simulate them under the desert pollution environments. For that reason, in this paper two other suggested techniques are added to the IEC one. The first one is to explain the performance of the polluted insulators under the dew and the second one is to explain their performance under the simultaneous fog and dew. The results of these three tests are compared with each other under different surface polluted layer conductivities. The aim of this paper is to record the leakage current and the warning voltage under different simulation weather conditions that to monitor the insulator strings before the occurrence of the flashover that of course is useful for the efficient maintenance. Also, in this paper, an attempt to simulate the flashover of the insulator in the field condition (actual outdoor condition) is presented. Where, the surface of the insulator is polluted naturally over a relatively long period, while it is permanently under high voltage. Index Terms - Flashover, fog and dew, insulators, leakage current, pollution. 1 INTRODUCTION THE flashover of the high voltage insulators are caused by the combined actions of the pollution and the moisture. That has been known as early as the construction of the outdoor transmission systems. Earlier it was believed that the desert should provide an ideal environment for the power transmission because of the dryness. Later it was discovered that the number of outages attributed to the insulation failure in the desert areas is large. For example in Egypt about 82% failures on 500 and 2 kv systems are caused by the surface contamination [1]. In Saudi Arabia similar outages have been reported occasionally due to sever levels of desert contaminations [2]. During the dry weather condition, pollutants are deposited on insulator surfaces. When the polluted insulator surfaces become moist, some of these pollutants are dissolved that causes the insulator surfaces start to conduct electrically [3-12]. In Egypt several measurements of desert pollution severity were carried out by the High voltage Research Center of the Egyptian Electricity Authority Manuscript received on 3 December 13, in final form 21 April 14, accepted 15 May 14. [3]. By the active program of this center, chemical and grain size characteristics of the pollution resulting from the desert pollution have been studied. The chemical analysis of the contaminant samples, which were taken from the insulators in the Egyptian desert, showed that the soluble salts amounted to 12-% mostly Sulfates Chlorides: CaSo4 9.8%, NaCl 3% and KCL 0.5 % approximately by the weight of deposit [13-14]. In Egypt and some other countries the transmission line insulators are usually exposed to the accumulation of the chemical dust near industrial areas and salt deposits near the cost. They are exposed also to desert pollution and at the same time they are exposed to lack of rain falls and frequent dew in the early morning hours. The performance of the polluted insulators depends mainly on the conductivity of the polluted surface layer or on the equivalent salt deposited density of the polluted surface layer, which are affected by surrounding weather conditions. Experience of the operators in the field of the transmission line maintenance has shown that the ability of the high voltage line insulators to withstand the over voltage differs from one place to another according to the constructed areas. The most important factors affecting, which affect the performance of the insulation, are the heavy pollutions and high humidity or dew in early morning. DOI.19/TDEI

2 20 O. E. Gouda & A. Z. El Dein: Experimental Techniques to Simulate Naturally Polluted High Voltage Transmission Line Insulators In the literature, some static and dynamic models were suggested and developed by making some assumptions and omissions to predict the flashover voltages and to study the performance of polluted insulators [15]. In [16] a historical development of insulator modeling was investigated and also a dynamic arc model was proposed. Where, a scaled shape of a concerned insulator was simulated using the finite element method (FEM) and finally potential distribution on the insulator surface, variation of pollution resistance and flashover voltage were determined and compared with results from other research. The application of least squares support vector machine combined with particle swarm optimization (LS-SVM-PSO) model was described in [17] and used to estimate the critical Flashover Voltage (FOV) on polluted insulators. Where, the effect of the characteristics of the insulator: the diameter, the height, the creepage distance, the form factor and the equivalent salt deposit density on the critical flashover voltage were investigated. The ac flashover performance of the polluted insulators and the flashover process of LXHY3-I6O insulators were investigated at a high altitude site (altitude of 1400 m) in [18]. Where, the solid layer method was used, and evenrising voltage method was adopted. The results of [18] are concluded that the average pollution flashover voltage and the critical flashover distance were decreased with the increase of the pollution. For efficient maintenance of the transmission lines, cleaning of the polluted insulators should be carried out only when the pollution accumulating on insulators surfaces has actually approached a serious level, which can be indicated by recording the leakage current bursts [19-23]. In this paper, three experimental techniques to simulate naturally polluted high voltage transmission line insulators are presented. These three experimental techniques are carried out as follow; the first one is carried out with respect to IEC fog test specifications (test procedure A), the second test is carried out to simulate the dew in early morning (test procedure C), and the third test is carried out to simulate the simultaneous fog and dew (test procedure D). Also, another test is introduced (procedure B) that to simulate the field conditions. In this test the polluted layer is formed while insulators under applied voltage inside the fog chamber, which is completely filled with the fog in a period of 12 hours. 2 EXPERIMENTAL SET-UP 2.1 TESTED INSULATOR SAMPLES In Egypt and some other countries the majority of high voltage transmission lines are insulated using porcelain cap and pin unites of type π- -E4.5, the work published in this paper is the summary of hundreds of tests carried out on some 0 such units. The diameter of this insulator is 3 mm, its total leakage distance is 385 mm, its height is 145 mm and its form factor is FORMATION OF THE POLLUTED LAYER ON THE INSULATOR SURFACE To form the pollution layer on the insulator surface, the solid layer method, which is recommended by IEC, is employed [24-26].The dipping of the tested insulators in the prepared solution at least three times is necessary to cover the insulator surface by uniform pollution layer [14]. In this study the insulators under test are properly cleaned and then are dipped in the solution at least three times separated by 24 hours at least. Then they are suspended vertically and left to dry in the room temperature. According to IEC specifications the composition of the suspension used in forming the pollution layer contains one kg of kieselguhr and g highly dispersed silicon dioxide for 00 ml water. Suitable amount of (NaCL) salt is added to control the resulting pollution layer conductivity. As alternatives to IEC composition lime powder CaO, Ca(OH) 2 with concentration between g/l as standard quantity equivalent to kieselguher is tried as local material [26]. Lime powder is chosen due to its better representation of natural pollution, also it is more stable on the insulator surface, it is much cheaper than kieselguhr and finally it is suitable for holding the moisture in the pollution layer [], [27-31]. An amount of salt (Nacl) should be added to the solution to adjust the solution conductivity. Table 1 shows the chemical elements of the chemical analysis of the lime powder. From the results of table 1, it is seen that the lime powder contains traces of conducting materials, which dissolve in water and increase the conductivity of the polluted layer [28-31]. Table 1. Chemical analysis of the lime. Chemical Percentage Element Ca Si Na Potassium (K) Mg P CO FOG CHAMBER Fog chamber with a suitable size is built for testing a chain of insulators. Its dimensions are 3.5 meter length, 2.5 meter width and 3.5 meter height. It is almost air tight and the relative humidity could be easily raised to 0%. The method of steam fog generation is that used by Karady method [11], [32] and IEC [26]. In this way the fog chamber contains water container and electric heaters that to produce vapor and to control the humidity inside the chamber and hygrometer for measuring the relative humidity. In the fog chamber the wetting inside the fog chamber is uniform, the wetting rate is slow and the washing effect is small. Therefore, the humidity in the fog chamber is controlled by regulating the capacity of the heaters, which is used to boil the water and consequently to control the boiling up humidity, through a resistance. That makes the increase of the relative humidity is rather slow and 0% is reached only after about 15- minutes. The temperature inside the fog chamber during the polluted insulator testing is between o C. The fog chamber is provided with fans to improve a uniform vapor distribution.

3 IEEE Transactions on Dielectrics and Electrical Insulation Vol. 21, No. 5; October THE HIGH VOLTAGE SOURCE Two testing transformers are used in testing the clean and the polluted insulators, one of the transformers is rated at 40 kv, where its equivalent R/X is 0.15 and its short circuit current equals 7 A just complying with IEC [14, 26]. The second transformer is rated at 250 kv, its equivalent R/X is 0.2 and its short circuit current equals 1.5 A, which is used only for testing the clean insulators. The transformers, which are used in the tests, are fed from 2 V supply through an induction regulator for smooth control of the test accuracy of 1 %. Hollow aluminum conductors of 1.5 cm diameter are used to connect the elements of the circuit in the high voltage side for reducing the corona effects. The flashover voltage, its wave shape and the leakage current are observed and recorded on the chart recorder. The outlines of the test circuit are presented in Figure 1. layer as a function of time, for different amounts of salt/liter. From the results of this figure, it is concluded that the conductivity variation with the time decreases with the increasing of the amount of salt/liter. This may be attributed to the possibility to absorb higher amount of water by the pollution layer as the salt concentration increases. In this paper, the maximum conductivity achieved is taken as the measured quantity. Figure 3 gives a relation between the amounts of salt/liter against the surface layer conductivity, where the minimum and maximum measured values of the polluted surface layer conductivity are plotted gm salt/liter 50 gm salt/liter 0 gm salt/liter Time (Minutes) Figure 2. Surface layer conductivity as a function of time Figure 1. Outlines of the circuit used in testing. 2.5 POLLUTION LAYER CONDUCTIVITY MEASUREMENT The performance of an insulator under normal pollution conditions is usually governed by the surface layer conductivity or equivalent salt deposited density and its distribution on the surface of the insulator. For measuring the pollution layer conductivity, according to IEC, 2 V/mm A.C., 50 Hz of the leakage path, was applied to the insulator under testing while it is highly humid atmosphere [14], [33] inside the fog chamber. The test voltage was applied for the period just enough to measure the leakage current. In this paper the reference layer conductivity is taken to be the conductivity at o C. Each test is repeated several times, each one is separated by 5 minutes from the other test for the same unit and in each test the conductivity was calculated according to the following IEC relation [34]. K I F f ( 1.6 / 1.03 t ) (1) V Where K is conductivity of the surface layer in µs at o C, t is the ambient temperature, I is the leakage current, V is the applied voltage and F f is the form factor. Figure 2 shows the variation of the conductivity of the contaminated insulator Amount of salt (gm/liter) Figure 3. The conductivity of polluted insulator layer versus the amount of salt (gm/liter). 2.6 VARIATION OF FLASHOVER VOLTAGE OF POLLUTED INSULATORS WITH POLLUTION LAYER CONDUCTIVITY The insulator flashover voltages are determined by the multiple-level method [26], with a voltage increment equals 3-5% of the expected flashover voltage. The leakage current pulses, in each test, are recorded on a chart recorder. The recording of the leakage current is carried out while the insulators are subject to applied voltage of 50, 70 and 90% of the flashover voltage. Each test is repeated at least ten times on three specimens of equally contaminated for each voltage level. The tests, of leakage current recording, are carried out at 0% relative humidity. The relation between the average flashover gradient (kv/cm) of the present tests and the

4 22 O. E. Gouda & A. Z. El Dein: Experimental Techniques to Simulate Naturally Polluted High Voltage Transmission Line Insulators conductivity of the insulator surface is given in Figure 4. Also, figure 4 gives the same relation between the flashover gradient and the conductivity of the natural polluted insulators [35] and between the flashover gradient and the conductivity of the artificial contaminated insulators as measured by previous researchers [15]. From figure 4 it is noticed that the sets of results are approximately close. But the flashover gradients of the artificial tests of the present work and the work carried out by other researchers are slightly lower than the flashover gradients of the natural pollution. That may be because the ionizability of (NaCl) that is used in controlling the artificial pollution conductivity almost does not vary in water but that is not the case for composition of natural pollution deposit which contains weaker electrolytes such as CaSo 4 in desert pollution [23]. They differ in solubility and ionizability by several times. These results agree with that mentioned in [35]. This explains why artificially polluted insulators give lower flashover voltage than those of naturally polluted insulators. Monitoring of the leakage current usually gives a good contribution about the possibility of the insulator flashover. Figure 5 gives the relation between the maximum value of the leakage current I m and the surface layer conductivity under different voltage levels. The values of I m, which is considered in this figure, is the mean value of the maximum leakage current that is recorded for more than ten tests at each voltage level, 50%, 70% and 90%, of the flashover voltage. The average leakage current values are calculated from the following relation. I 1 n m I mi n i 1 Where n is the number of tests at each voltage level, i=1, 2, n. The corresponding standard deviation is calculated using the following formula [36] 1 n 2 ( I mi I m50%) 3 n 1 i 1 (2) Flashover gradient (kv/cm) Present tests Ref. [15] Ref. [35] Leakage current (ma) % of FOV 70 % of FOV 90 % of FOV Insulator pollution layer conductivity (µs) Figure 4. Average pollution flashover voltage gradients versus the pollution conductivity. The warning voltage level could be set at 80 or 90% of the flashover voltage of any insulator with a given pollution conductivity. This could be successfully carried out in the laboratory where test conditions are under control; this is not the case in the field. Setting the warning voltage level at 80% of the flashover voltage may be preferred as it is allowed for the slightly lower values in the field conditions. The used monitors can compare the amplitude of leakage current bursts with the preset level. If the number of the counted bursts exceeds a set value, a signal will produce alarm and the washing pattern of insulators should be carried out. 3 LEAKAGE CURRENT ANALYSIS 3.1 ARTIFICIAL LEAKAGE CURRENT IN THE LABORATORY The aim of recording the leakage current under different simulating conditions is to monitor the severity of the pollution layer, which is essential for efficient maintenance of the high voltage transmission line insulators Figure 5. Maximum value of leakage current versus the surface layer conductivity at various voltage levels. When the surface of the polluted insulators absorbs moisture from the humid air in the fog chamber, the insulator surface becomes conducting. With the application of the tested voltage instantaneously on the insulator in case of laboratory artificial testing, the leakage current rises and after certain time it drops to a very small value. In this time, the polluted layer losses its water and becomes dry. After short time the polluted layer on the insulator surface absorbs another amount of water vapor that leads to the formation of the partial arcs which are represented by subsequent pulses. Figure 6 shows samples of these pulses. The number of leakage current pulses versus the conductivity of the insulator surface is given in Figure 7 for different values of test voltage, 50, 70 and 90% of the flashover voltage. From this figure it is noticed that increasing the pollution layer conductivity and increasing the applied voltage lead to the increase of the number of current pulses per minute. A relation between average repetition times versus the surface layer conductivity in a case of IEC tests is given in Figure 8.

5 IEEE Transactions on Dielectrics and Electrical Insulation Vol. 21, No. 5; October (a) Conductivity 25 µs, applied voltage 22 kv, 50 mv/div, 0.5 ms/div. (b) Conductivity 35 µs, applied voltage 22 kv, 50 mv/div, 0.5 ms/div. Figure 6. Pulses of leakage current samples in stages of zero current periods, streamer discharge and glow corona. Number of pulses per minute % of FOV 70 % of FOV 50 % of FOV Figure 7. Surface layer conductivity versus the number of pulses per minute under different voltages. Average repetition time (Sec) % of FOV 70 % of FOV 50 % of FOV Figure 8. Surface layer conductivity versus the average repetition time of leakage current pulses. 3.2 FIELD LEAKAGE CURRENT SIMULATION It is difficult to simulate the natural pollution conditions perfectly in the laboratory. In the field (actual outdoor condition), the insulator surface gets polluted naturally over a long period, while it is permanently under a high voltage, on the occasions when moisture collects on the insulator surface, leakage current pass, dry bands may form depending upon the moisture intensity, air temperature variations and other weather parameters, finally, partial arcs may develop over a long period before complete flashover. On the other hand, in the laboratory the tests usually are carried out in a fog chamber. The rate and amount of moisture in the fog chamber are of course much smaller than those available in nature. Therefore, conditions of the leakage current in the laboratory basically different from what is expected in the field conditions. To simulate the field conditions, as we can as possible, the insulators under testing are hanged inside the fog chamber and the humidity is raised to 0% for 12 hours under voltage (procedure B). The leakage current was then recorded. A comparison between the results given from the two groups of tests: the first test simulates the IEC (procedure A) and the second test simulates the natural conditions IEC (procedure B) is given in Table 2. Table 2. Leakage current of the IEC test procedures A and B. Formation of the dry band Number of pulses per minute under 50, 70 and 90% of the flashover voltage, µs. Average repetition of leakage current pulses, under 50, 70 and 90% of the flashover voltage, µs. IEC test (procedure A) The first pulse forms a dry band in a short time length. 11 pulse/minute, 17 pulse/minute and 28 pulse/minute 7.5, 5 and 3.5 s., Test to simulate the field conditions (procedure B) The dry band formed over a long period 6 pulse/minute, 11 pulse/minute and 13 pulse/minute, 6.5 and 5 s, 4 TESTING OF POLLUTED INSULATORS UNDER SIMULATION OF THE WEATHER CONDITIONS In this type of tests, to simulate the weather conditions in early morning artificial dew on the polluted insulators is formed as follows: The insulators under test are left in a refrigerator of about 4 o C for 24 hours, after that they are hanged inside the testing chamber at the room temperature. This procedure leads to the dew formation on the polluted insulator units under testing [36-40]. This procedure, in this paper, is defined as a procedure C, which is used to simulate the dew formation on the overhead transmission line insulators in the early morning. In other procedure, to simulate the simultaneous fog and dew, the insulators under test are left in a refrigerator of about 4 o C for 24 hours, and then the insulators are left for ten minutes in the fog chamber of a relative humidity equals 0% before testing. This procedure, in this paper, is known as procedure D. The flashover voltage versus the polluted insulator surface conductivity in case of testing by the above two procedures C and D beside the results that obtained from the IEC test (procedure A) is given in Table 3.

6 24 O. E. Gouda & A. Z. El Dein: Experimental Techniques to Simulate Naturally Polluted High Voltage Transmission Line Insulators In the method of testing the polluted insulator by procedure D, the amount of water absorbed by the layer of the polluted insulator under test is more than that in both two methods A and C. For this reason the flashover voltage is lower in test procedure D than that in test procedures A and C for the same measured conductivity. That is because the increasing of water absorption by the polluted layer of the tested insulator increases the solvability and ionizability by several times compared with methods A and C. For the same reason the flashover voltage of polluted insulators in case of testing by procedure A is lower than that obtained from using procedure C for polluted insulators testing. Table 3. Average flashover voltage versus surface layer conductivity for different test procedures. Test Procedure Conductivity Average Flashover Voltage IEC Test Procedure (A) Simulating Dew only Test Procedure (C) Simulating Dew and Fog Test Procedure (D) 15 µs 18 kv µs 13 kv 30 µs 11 kv 15 µs kv µs 15 kv 30 µs 12 kv 15 µs 12 kv µs 9 kv 30 µs 6 kv 5 CONCLUSION The following are the main conclusions that can be obtained from the tests that are carried out in the present study: i) The flashover voltages in the artificial tests are lower than the flashover voltages in the field conditions, see Figure 4. Setting the warning voltage level at 80% of the flashover voltage may be preferred as it is allowed for the slightly lower values in the field conditions. Recording the leakage current under different simulating condition is considered as a monitor for the severity of the pollution layer, which is useful for efficient maintenance of high voltage transmission line insulators. ii) An innovative method to simulate the dew formation on polluted insulators is described in this study. This method gives a laboratory simulation method of desert pollution. iii) For monitoring and recording the polluted insulators at sever conditions, two testing procedures are suggested for simulating the conditions in nature. One is to simulate the dew in early morning and the other is to simulate simultaneous fog and dew. REFERENCES [1] H.M. Zarzoura, Investigation on E.H.V Insulator String under Desert Environment, Ph.D., Thesis, Ain Shams University, Egypt, [2] A.EI-Suleiman and M.I. Qureshi Effect of contamination on the leakage current of inland desert, IEEE Trans. Electr. Insul. Vol. 19, No. 4, pp , [3] M.A. El.-Koshairy and F.A. Rizk. Performance of EHV transmission line insulators under desert pollution condition, Cigre, pp. No , [4] E. Nasser, The behavior of insulator, with unevenly distributed pollution layer, ETZ-A, Vol. 84, No. 11, 1963 (in German). [5] E. Nasser, Contamination Flashover of outdoor insulation, ETZ-A- BD, 93, H-6, [6] K. B. 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7 IEEE Transactions on Dielectrics and Electrical Insulation Vol. 21, No. 5; October [28] O.E. Gouda and A. El-Morshedy, Recording of Leakage Currents on Polluted Insulators, Report No. 4 on Pollution Flashover of High Voltage Insulators, FRCU 814, Cairo University Faculty of Engineering, Cairo, Egypt, pp , [29] O.E. Gouda, Factors affecting the conductivities of polluted layers of H. V T.L. insulators 7 th Int l. Sympos. High Voltage Eng. (ISH), Technichs Universitate Dersden, Paper 44.08, pp , [30] O.E. Gouda and M. B. Eteiba, Discharges of leakage currents on the polluted insulators of H.V.T.L. insulators, XIII Int l. Conf. Gas Discharge and their Applications, Glasgow, UK, pp , 00. [31] O. E. Gouda and G. M. Amer, Factors affecting the leakage current bursts of high voltage polluted insulators, 39 th Int l. Universities Power Engineering Conference UPEC, pp , 04. [32] G. Karady, The effect of fog parameters on the testing of artificially contaminated insulators in a fog chamber, IEEE Trans. Power App. Syst., Vol. 94, pp [33] IEC Publication No. 507, Artificial pollution tests on high voltage insulators to be used on A.C. system, [34] M.T. Gencglu and M. Cebeci, The pollution flashover on high voltage insulators, Electr. Power Syst. Research, Vol. 78, pp , 08. [35] H. Pei-Zohng and X. Cheng-Dong, Tests and investigations on naturally polluted insulators and their application to insulation design for polluted areas, Cigre Report 33-07, Paris, [36] J. Li, S. Caixin, W. Sima, Q. Yang and J. Hu, Contamination level prediction of insulators based on the characteristics of leakage current, IEEE Trans. Power Delivery, Vol. 25, No. 1, pp ,. [37] O. E. Gouda and A. Z. El Dein, Simulation of overhead transmission line insulators under desert environments, IET Generation, Transm. Distribution, Vol. 7, No. 1, pp. 9 13, 13. [38] M. Zhirh and O.E. Gouda, Artificial testing of contaminated H.V. outdoor insulators, th Int l. Sympos. H.V. Eng. (ISH), Montreal, Canada, pp , [39] Z. Chenlong, Z. Zhicheng, G. Song, M. W. Liming and G. Zhicheng, Analysis of characteristic of natural pollution test and artificial simulation method, IEEE Conf. Electr. Insul. Dielectr. Phenomena (CEIDP), pp , 12. [40] M.M. Khalifa and A. El-Morshedy, A study of wet flashover characteristics of polluted insulators, IEEE Conf. Cables and Overhead Lines for 2 kv and Above, No. 176, Ossama E. Gouda was born in He received the B.Sc. degree in electrical engineering from Cairo University, Egypt in He finished the M.Sc. and Ph.D. degrees in the field of High Voltage, from Cairo University, Egypt, in 1979 and 1982, From 1988 to 1993, he was Associate Professor, Department of Electrical Engineering, and Cairo University. In 1988 he was with the Department of Electrical Engineering, Kema Institute, Arnhem, Netherland, where he was a Research Fellow. Since 1993, he has been a Professor of Electrical Engineering Department, Cairo University. Currently, he is the head of High Voltage Group of Electrical Engineering Department Cairo University. He published more than 1 papers and he was supervisor for about 60 M.Sc. and Ph.D. degrees students. His fields of interest include high-voltage phenomena, protection of power system and electromagnetic transients. He is a regular reviewer for IEEE Transactions on Power Delivery, Electric Power Components and Systems, and IET Generation, Transmission & Distribution. Adel Zein El Dein Mohamed was born in Egypt in He received the B.Sc. and M.Sc. degrees in electric engineering from the Faculty of Energy Engineering, Aswan, Egypt, in 1995 and 00, respectively, and the Ph.D. degree in electric engineering from Kazan State Technical University, Kazan, Russia, in 05. From 1997 to 02 he worked as a teaching assistant at the Faculty of Energy Engineering, Aswan, Egypt. From 02 to 05 he was with Kazan Energy Institute, Kazan, Russia and with Kazan State Technical University, Kazan, Russia where he received his Doctor of Engineering Degree. From 05 to 11, he had been a staff member at the Department of High Voltage Networks, Faculty of Energy Engineering, Aswan University, Aswan, Egypt. Since 11, he is an Associate Professor, Department of High Voltage Networks, Faculty of Energy Engineering, Aswan University, Aswan, Egypt. In 14, he joined the department of High Voltage Engineering (Hikita Lab), Kyushu Institute of Technology (KIT), Japan, as a researcher. His fields of interest include calculation of electric and magnetic fields and their effects, comparison of numerical techniques in electromagnetics, design of microstrip antennas and filters, and the calculation of specific absorption rate (SAR) in the human body. He is a regular reviewer for IEEE Transactions on Power Delivery, Electric Power System Research, and IET Generation, Transmission & Distribution.