iosr-JEEE   Volume-7 ~ Issue-6

Abstract: Time Domain Reflectometry is a technique used for fault location and partial discharge analysis in underground electric distribution cables. The technique is based on the analysis of the propagation of short electric pulses. In underground cables, semiconductor layer properties and degradation cause perturbations in the signal wave shape. These perturbations complicate the interpretation of reflectograms and, as a consequence, fault location. This work presents a circuit model of distributed elements that includes the electrical resistance of the semiconductor layers. The results of computer simulations using the proposed model are compared with measurements in new and aged XLPE cables. This comparison shows that the proposed model can represent the phenomena satisfactorily.

Keywords : Underground cables, Simulation of Time Domain Reflectometry, Attenuation spectrum.

[1] V. DUBICKAS, H. EDIN and R. PAPAZYAN, "Cables Diagnostics with On-Voltage Time Domain Reflectometry," Royal Institute of Technology, 2006.
[2] D. k. CHENG, "Field and Wave Electromagnetics," Second Edition, Addison-Wesley Publishing Company, Boston, pp. 370 - 428, 1989.
[3] F. T. ULABY, E. MICHIELSSEN and U. RAVAIOLI, "Fundamentals of Applied Electromagnetics," Sixth Edition, Pearson, University of Michigan, pp. 67 - 131, 1994.
[4] P. WAGENAARS, P.A.A.F Wouters, P.C.J.M. Van Der Wielen and E.F. Steennis, "Estimation of Transmission Line Parameters for Single-core XLPE Cables," International Conference on CMD, pp. 1132 – 1135, Beijing, 2008.
[5] M. E. KOWALSKI, "A Simple and Efficient Computational Approach to Chafed Cable Time-Domain Reflectometry Signature Prediction," Stinger Ghaffarian Technologies (SGT), Inc. NASA Ames Research Center, 2008.
[6] V. DUBICKAS, "Development of On-line Diagnostic Methods for Medium Voltage XLPE Power Cables" Doctoral Thesis, Stockholm, Sweden 2009.
[7] R. PALUDO, "Refletometria no Domínio do Tempo: Análise das Camadas Semicondutoras de Cabos Isolados," Dissertation of Master, Curitiba 2009.
[8] R. PAPAZYAN and R. ERIKSSON, "Calibration for Time Domain Propagation Constant Measurements on Power Cables," IEEE Transactions on Instrumentation and Measurement, vol. 52, pp. 415 – 418, 2003.
[9] R. HEINRICH, S. BONISCH, D. POMMERENKE, R. JOBAVA and W. KALKNER, "Broadband Measurement of the Conductivity and the Permittivity of Semiconducting Materials in High Voltage XLPE Cables," Eighth International Conference on (IEE Conf. Publ. No. 473), pp. 212 – 217, 2000.
[10] G. MUGALA, R. ERIKSSON and P. Petersson, "Comparing Two Measurements Techniques for High Frequency Characterization of Power Cable Semi conducting and Insulating Materials," IEEE Trans. on Dielectrics and Electrical Insulation, vol. 13, pp. 712 – 716, 2006.

Abstract: In this study, a new boost converter with an active snubber cell is proposed. The active snubber cell provides main switch to turn on with zero voltage transition (ZVT) and to turn off with zero current transition (ZCT). The proposed converter incorporating this snubber cell can operate with soft switching at high frequencies. Also, in this converter all semiconductor devices operate with soft switching. There is no additional voltage stress across the main and auxiliary components. The converter has a simple structure, minimum number of components and ease of control as well. The Fuzzy Logic (FL) controller with two inputs maintains the load voltage by detecting the voltage variations through d-q transformation technique is connected in feedback of these converters. The presented theoretical analysis is measured in simulation results by 2.3kW and 100 kHz boost converter. Here output voltage up to 400v is given Also, the overall efficiency of the new converter has reached a value of 97.8% at nominal output power.

Keywords: Soft switching, zero current transition, zero voltage transition, DC-DC converter, Fuzzy Logic Controller

[1] G. Hua, C. S. Leu, Y. Jiang, and F. C. Lee, "Novel Zero-Voltage-Transition PWM Converters," IEEE Trans. on Power Electron., vol. 9, pp. 213-219, Mar. 1994.
[2] G. Hua, E. X. Yang, Y. Jiang, and F. C. Lee, "Novel Zero-Current-Transition PWM Converters," IEEE Trans. on Power Electron., vol. 9, pp. 601-606, Nov. 1994.
[3] H. Mao, F. C. Lee, X. Zhou, H. Dai, M. Cosan, and D. Boroyevich, "Improved Zero-Current-Transition Converters for High-Power Applications," IEEE Trans. on Ind. Applicat. , vol. 33, pp. 1220-1232, Sept./Oct. 1997.
[4] J. G. Cho, J. W. Baek, G. H. Rim and I. Kang, "Novel Zero-Voltage-Transition PWM Multiphase Converters," IEEE Trans. on Power Electron., vol. 13, pp. 152-159, Jan. 1998.
[5] C. J. Tseng and C. L. Chen, "Novel ZVT-PWM Converters with Active Snubbers," IEEE Trans. on Power Electron., vol. 13, pp. 861-869, Sept. 1998.
[6] V. Grigore and J. Kyyra, "A New Zero-Voltage-Transition PWM Buck Converter," in Proc. 9th Mediterranean Electrotechnical Conf. (MELECON′98) , Tel Aviv, Israel, vol. 2, 1998, pp. 1241-1245.
[7] J. M. P. Menegaz, M. A. Co., D. S. L. Simonetti, and L. F. Vieira, "Improving the operation of ZVT DC-DC Converters," in Proc. 30th Power Electron. Spec. Conf. (PESC′99) , Charleston, vol.1, 1999, pp. 293-297.
[8] K.M., Smith, and K.M., Smedley, "Properties and Synthesis of Passive Lossless Soft-Switching PWM Converters", IEEE Trans. on Power Electron., vol.14, pp. 890-899, Sept. 1999.
[9] C. M. de O. Stein, and H. L. Hey, "A True ZCZVT Commutation Cell for PWM Converters," IEEE Trans. on Power Electron., vol. 15, pp. 185-193, Jan. 2000.
[10] D. Y. Lee, B. K. Lee, S. B. Yoo, and D.S. Hyun, "An Improved Full-Bridge Zero-Voltage-Transition PWM DC/DC Converter with Zero-Voltage / Zero-Current Switching of the Auxiliary Switches," IEEE Trans. on Ind. Applicat., vol. 36, pp. 558-566, Mar. / Apr. 2000.

Abstract: This work concentrates on improving the system stability and increase the stability margin by well know FACT device STATCOM in nine bus system. The STATCOM generally used for power quality improvement as well as enhancement of stability. The enhancement of stability shows the capability of STATCOM during disturbance.

Keywords: Nine Bus system, Power Swing, Load Angle, STATCOM, PASCAD

[1] Beaulieu G., Bollen, M.H.J, Malgarotti S. and Ball R., Power quality indices and objectives. Ongoing activities in CIGRE WG36-07.Power Engineering Society Summer Meeting, 2002. IEEE, Volume:2, 21-25 July 2002, Pages: 789 – 794 vol.-2.

[2] M.H.J. Bollen, Understanding Power Quality Problems: Voltage Sags and Interruptions. New York, IEEE Press, 1999.

[3] M.H.J. Bollen, L.D.Zhang, Different methods for classification of three-phase unbalanced voltage dips due to faults. Electric Power Systems Research, Volume 66, Issue 1 2003, pages 59-69.

[4] P.M. Anderson and A.A. Fouad, "Power System Control and Stability", the IOWA state university press AMES IOWA USA, volume I, first edition 1977, chapter 2, page 37-38.

[5] Mehrdad Ahmad, Mostafa Alinezhad, "Comparison of SVC and STATCOM in Static Voltage Stability Margin Enhancement", Proceedings of World Academy of Science, Engineering and Technology, Vol. 38, Feb. 2009.

[6] Y.H. Song and A.T. Johns, "Flexible ac transmission systems (FACTS)", The Institute of Electrical Engineers, London, 1999.

[7] N.G. Hingorani and L. Gyugyi, "Understanding FACTS: concepts and technology of flexible ac transmission systems", IEEE Press,NY, 1999.

[8] K. R. Padiyar and A. L. Devi, "Control and simulation of static condenser," in Proc. 9th Annu. Applied Power Electronics Conf. Expo., Feb. 13-17, 1994.

[9] P. Rao, M.L. Crow and Z. Yang, "STATCOM Control for Power System Voltage Control Applications", IEEE Transactions on Power Delivery, Vol. 16, pp. 18-23, 2000.

[10] M.F. McGranaghan, D.R.Mueller, M.J.Samotyj, Voltage sags in industrial systems, IEEE Trans. Industry Applications, Vol.29, no.2, March/April 1993, pp.397 – 403.