1.LIGHTNING ARRESTER MODELING USING ATP -EMTP BYNEHA KARDAM M.TECH (POWER SYSTEM)(11/PPS/010)1

2. INTRODUCTION Metal Oxide Surge Arrester has been in service since 1976. They protect major electrical equipment from damage bylimiting overvoltage and dissipating the associated energy Metal Oxide surge Arrester should be highly reliable inmost application because the metal oxide surge arrester areless fail than silicon carbide arrester as a result of moistureingress and contamination. Experience has shown that most failures of silicon carbidearrester occur because gap spark over.2 3. These failures have been reduced using Metal oxide surgearrester, by moisture ingress or contamination, to a levellow enough to permit repetitive spark over at or nearnormal operating voltage. Gaps are not required in metal oxide surge arrester. The elimination of gaps results in an increased probabilityof failure of metal oxide surge arrester on systemovervoltage lower than normally required to cause thespark over of gapped arresters. metal oxide surge arresters might be more vulnerable tohigh energy lightning surge than silicon carbide arresters.3 4. THE ADVANTAGE OF METAL OXIDE SURGEARRESTER IN COMPARISON WITH SILICONCARBIDE GAPPED ARRESTER Simplicity of design, which improves overall qualityand decreases moisture ingress. Easier to maintenance especially to clear arc. Increased energy absorption capability.4 5. DISADVANTAGE OF METAL OXIDESURGE ARRESTER Voltage is continually resident across the metal oxide andproduces a current of about one milli ampere. While thislow-magnitude current is not detrimental. Higher currents, resulting from excursions of the normalpower frequency voltage or from temporary over voltagessuch as from faults or ferroresonance, produce heating inthe metal oxide. If the temporary overvoltage are sufficiently large inmagnitude are long in duration, temperatures may increasesufficiently so that thermal runaway and failure occur5 6. Operating analysis of metal oxide surge arrester, IEEEand Pinceti model, using ATP-EMTP is done. The lightning arrester models base on the Ohio BrassPVR 221617 21kV and Precise PAZ-P09-1 9 kV 10kAclass 1 by applying standard impulse current wave(8/20 sec) is being used. The models can predict the operation of the metaloxide surge arrester in the system within 10% errors.6 7. IEEE MODEL The model recommended by IEEE W.G 3.4.11 . In this model the non-linear V-I characteristic isobtained. For slow surges the filter impedance is extremely lowand A0 and A1 are practically connected in parallel7 8. On the contrary, during fast surges, the impedance ofthe filter becomes significant, and causes a currentdistribution between the two branches. For precision sake, the current through the branch A0rises when the front duration decreases. A0 resistance is greater than A1 resistance for anygiven current, the faster the current surge, the higherthe residual voltage.8 9. The comparison of the calculated peak values with themeasured values shows that the frequency dependentmodel gives accurate results for discharge currentswith times to crest between about 0.5 s and 45 s. The main problem of this model is how to identify itsparameters. The W.G.3.4.11 suggests an iterativeprocedure where corrections on different elements arenecessary until a satisfactory behavior is obtained. The starting values can be obtained through formulasthat take into account both the electrical data (residualvoltages), and the physical parameters (overall height,block diameter, columns number)9 10. The inductance L1 and the resistance R1 of the model comprise the filter between the two non-linear resistances. The formulas for these two parameters are L1 = 15 d/n H R1 = 65 d/n and for , L0 = 0.2 d/n H R0 = 100 d/n C = 100 n/d pF10 11. PENCETI MODEL The operating principle is quite similar to that of the IEEE frequency-dependent model.11 12. PINCETI MODEL The model here presented derives from the standard model, with some minor differences. By comparing the frequency dependent model and pinceti model, it can noted that :- The capacitance is eliminated, since its effects on model behavior is negligible. The two resistances in parallel with the inductances are replaced by one resistance R (about 1 M) between the input terminals, with the only scope to avoid numerical troubles.12 13. STATIC CHARACTERSTICS OF THE NON LINEAR ELEMENT These curve derives from the curves proposed by IEEE W.G.3.4.11, and are referred to the peak value of the residual voltage measured during a discharge test with a 10 kA lightning current impulse.13 14. To define the inductances, the following equations can be used :- L1 = [(V r1/T2 V r8/20) V r8/20 ] * Vn H L0= 1/12 [ (V r1/T2 V r8/T2 )V r8/20]* Vn H14 15. DATA USING IN THE MODEL (PRECISE PAZ-P09-1-9KV 10KA CLASS 1) IEEE Model15 16. Pinceti Model16 17. DATA USING IN THE MODEL (OHIO BRASS PVR 221617) IEEE Model17 18. Pinceti Model18 19. MODELING RESULTS OF PRECISE PAZ P09-1 Modeling results and errors in each model prepareWith manufactures data sheets.19 20. Percent error of each model prepare withmanufactures data sheets.20 21. IEEE model has errors higher than Pinceti model in the high current testing more than 10 kA with standard wave front (8/20 s.) When testing with the steep wave front, Pinceti model has errors higher than IEEE model. for the switching impulse testing, the percentage errors are equal.21 22. MODELING RESULTS OF OHIO BRASS PVR 221617 Modeling results and errors in each model preparewith manufactures data sheets.22 23. Percent error of each model prepare with manufactures data sheets.23 24. IEEE model has errors higher than Pinceti model both for the standard wave front (8/20 s.) testing and switching impulse testing. When testing with the steep wave front, Pinceti model has errors higher than IEEE model.24 25. CONCLUSION The percentage errors from the modeling result can bedescribes as follows : 1. At standard wave front percentage errors of IEEE modelis higher than Pinceti model. 2.At steep wave front percentage errors of IEEE model isless than Pinceti model. 3. At switching overvoltage condition percentage errors ofIEEE model is nearly the same as Pinceti model.25 26. Both models can predict the operation of the metal oxide surge arrester in the system. There is less than 5% errors for standard wave front (8/20 s.) at 5-20 kA . less than 10% errors for standard wave front (8/20 s.) at others. less than 10% errors for steep wave front and less than 14% for switching impulse testing.26 27. REFERENCE IEEE Working Group 3.4.11 Application of Surge Protective Devices SubcommitteeSurge Protective Devices committee, Modeling of Metal Oxide Surge Arrester,IEEE Transaction on Power Delivery, Vol.7, No.1, pp 302-309, January 1992. P. Pinceti , M. Giannttoni, A simplified model for zinc oxide surge arrester, IEEETransaction on Power Delivery, Vol. 14, No.2, pp 393-398, April 1999. E.C. Sakshaug, J.J. Bruke, J.S. Kresge, Metal Oxide Arrester on Distributionsystem Fundamental Considerations, IEEE Transaction on Power Delivery, Vol.4,No. 4, pp 2076-2089, October 1989. Ikmo Kim, Toshihisa Funabashi, Haruo Sasaki, Toyohisa Hagiwara, MisaoKobayashi, A study of ZnO Arrester Model for Steep Front wave, IEEETransaction on Power Delivery, Vol.11, No. 2, pp 834841 April 1996. Andrew R. Hileman ,Insulation Coordination for Power systems,MarcelDekker,Inc., New York Basel ,1999.27 28. THANK YOU28