International Journal of Mechatronics, Electrical and Computer Technology

Transcription

1 Effect of Corona Ring on Potential Distribution and Electric Field on Silicon Insulator in Polluted Condition Rasool Feiz Kerendian 1*, Hasan Keshavarz Ziarani 1, Javad Ebrahimi 2 1 Electrical Eng. Dept., Giasodin Jamshid Kashani Institute for Higher Ed., Abyek, Iran 2 Young Researcher and Elite Club, Borujerd Branch, Islamic Azad University, Borujerd, Iran *Corresponding Author rasool.feiz@yahoo.com Abstract Silicon insulator is one of the insulators that used in many condition and to have acceptable voltage distribution along the insulator, corona ring is used. It is necessary knowing the electrical field intensity distribution and electrical potential on surface of insulator. In this paper at first silicon insulator and its advantages are explained then the cause of using corona ring is described and at end effect of corona ring on potential distribution and electric field in polluted condition is evaluated. To show that the Finite Element Method (FEM) is used in simulation. The results of the simulation showed the probability of breaks in the polluted condition is more than in usual condition. Keywords: Corona ring, FEM, FRP, Silicon insulator 1. Introduction Insulator is one of the important equipment in power network that has effect on the system characteristic such as reliability. One of the insulators that widely uses is silicon rubber. It has good marketing. The silicon insulator has some advantage to compare with other insulator porcelain and glass that are included [1]: 1) Excellent Hydrophobicity 2) Light weigh 3) Good electrical performance 1394

2 4) Small volume 5) Good resistance to ultra violet that caused the silicon insulator has more life that other insulator. Duo to the above tips the best choice for reign with various pollutions is using the silicon coating, because by using the silicon insulator the coast of cleaning and maintenance will reduced. The SIR insulator structure with fibreglass insulator bars FRP is showed in figure 1. As can be seen, FRP core is placed between two metal electrodes. To protect the FRP core from natural stress such as ultra-violent, ozone, and also to create creep distance to reduce length of insulator, the sheds is used. Figure 1: The SIR insulator structure with fibreglass insulator bars FRP Corona phenomena may happen in the air around insulator in high electric field strength. Corona occurs on all types of transmission lines, but it becomes more noticeable at higher voltages (345 kv and higher). That caused acoustic noise, radio interference, energy losses, ozone, and that ozone and ultra violet have effect such as fatigue and premature aging in insulator. In other hand electric field intensity may cause partial discharge this in turn can be broken insulators in terms of mechanical and electrical. Amount of corona is dependent on environmental conditions. So the electric field strength around insulator should be control. To this purpose the corona ring is used. In fact corona ring is used to improve the performance of 1395

3 insulator. The corona rings is used to improved voltage distribution along the insulator [2] [3]. Similar studies on the electric field and potential distribution, such as [4] and [5] has been done.. In this paper effect of pollution on distribution potential and electric field on the surface of silicon rubber insulator as 2D by using stronger software such as MAXWELL is presented. 2. Insulator modeling In figure 2 the insulator and corona ring is showed. It contains 10 sheds. Figure 2: The model of insulator Detailed simulation parameters are given in Table 1. Simulation studies are focused on maximum electrical field intensities distribution and electrical potential. 1396

4 Table 1: Simulation parameters Material relative permitivity Plywood dust 1.5 Silicon rubber 4 FRP 7 Cement dust 8 There are many relative permittivities due to the many kind of pollution and some of them are showed in table 1. In this study only the plywood dust is used as pollution. To shows pollution condition and effect of that on electrical field intensity distribution and electrical potential, a layer of pollution is used on the surface of insulator. 3. Simulation results In this part the simulation result for clean condition, polluted condition and polluted condition with corona ring is presented. This result shows the effect of pollution and corona ring. Plywood dust is used as pollution with relative permittivity that shows in table 1 in pollution condition. a) Without pollution In this part the insulator without pollution and without corona ring is simulated. Figure 3 shows the electrical field intensity distribution and electrical potential on surface of insulator without pollution. 1397

5 A: electrical field intensity B: electrical potential distribution Figure 3: Electrical field intensity and electrical potential of insulator without pollution Electrical field intensity distribution and electrical potential on surface of insulator without pollution and without corona ring is showed in figure 3. The electric field intensity on the surface of insulator has normal value. b) With pollution Figure 4 shows the electrical field intensity distribution and electrical potential on surface of insulator with pollution on the surface of insulator. To shows pollution condition and effect of that on electrical field intensity distribution and electrical potential, a layer of pollution is used on the surface of insulator. The pollution is layer of plywood dust and its relative permittivity is

6 There is other pollution such as cement dust with relative permittivity 8 and water drops, but in this paper only using plywood dust as pollution is presented. A: electrical field intensity B: electrical potential distribution Figure 4: Electrical field intensity and electrical potential of insulator with pollution The electrical field intensity and electrical potential distribution on surface of insulator in the pollution condition shows in figure 4. It is clear from this figure the electric field intensity is increased to compare with clean condition, so the probability of electrical break in polluted condition is more than the condition without pollution. In figure 5 the distribution potential and electric field diagrams on silicon surface in polluted condition and without corona ring are given. 1399

7 A: Electric potential B: Electric field intensity Fig (5): The effect of changes in C parameter on e-field intensity in normal conditions c) With pollution and corona ring Figure 6 shows the electrical field intensity and electrical potential distribution insulator with pollution on the surface of insulator with corona ring. 1400

8 A: electrical field intensity of insulator with B: electrical potential distribution of insulator pollution and corona ring with pollution and corona ring Figure 6: Electrical field intensity and electrical potential of insulator with pollution and corona ring The distribution potential and electric field diagrams on silicon surface in polluted condition and with corona ring are given in

9 A: Electric potential B: Electric field intensity Figure 7: Electrical field intensity and electrical potential diagrams 4. Conclusion This study has presented electrical field and potential distributions silicon rubber insulators. Simulation contain clean and polluted situation. As is clear from the simulation results electrical potential distribution on surface of insulator doesn t have significant. But there is difference between the field distribution in polluted condition by using corona ring and without corona ring. It is clear the probability of electrical break in polluted condition is more than the condition without pollution and by using the corona ring this probability is reduced. So by using the corona ring the electric field strength around insulator can be controlled. 1402

10 References [1] Rohaiza Bte Hamdan, ELECTRIC FIELD STUDY OF SILICON RUBBER INSULATOR USING FINITE ELEMENT METHOD (SLIM) University Teknologi Malaysia, April [2] Sima W., Espino-Cortes F.P., Edward A.C. and Jayaram H.S., Optimization of Corona Ring Design fo Long- Rod Insulators Using FEM Based Computational analysis IEEE International Symposium on Electrical Insulation, Indianapolis, in USA, September 2004 Page(s) : [3] Sima W., Wu K., Yang Q., Sun C., Corona Ring Design of +/-800 kv DC Composite Insulator Based on Computer Analysis, IEEE International Conference on electrical Insulation and Dielectric Phenomena, October 2006, Page(s): [4] Zhao, T., and Comber, G. "Calculation of Electric Field and Potential Distribution along Nonceramic Insulators Considering the Effects of Conductors and Transmission Towers," IEEE Trans. Power Delivery, Vol. 15, No. 1, January 2000, pp [5] Chakravorti, S.; Steinbigler, H. "Boundary Element Studies on Insulator Shape and Electric Field around HV Insulators with or without Pollution," IEEE Trans. Electrical Insulation, Vol. 7, No. 2, April 2000, pp