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S. A. Soman

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Research Interests

Power System Analysis: Power System Economics, Computation, Modeling and Optimization

Power System Protection : Current and Voltage Transformers, Wide Area Measurement Systems, System Protection

Courses Offered

  • EE659 A First Course in Optimization
  • EE114 Power Engineering I
  • EE710 Large Sparse Matrix Computations
  • EE655 Computer Aided Power System Analysis
  • EE651 Digital Protection of Power Systems
  • EE334 Power Systems
  • EE326 Power Systems Lab
  • EE636 Matrix Computations
  • EN642 Power Generation and Systems Planning
  • EN304 Electrical Energy Systems

Academic Background

  • B.E. in Electrical Engineering from Maulana Azad College of Technology Bhopal in 1989
  • M.E. in Electrical Engineering from Indian Institute of Science Bangalore in 1992
  • PhD in Electrical Engineering from Indian Institute of Science Bangalore in 1996

Work Experience

  • As a faculty from 1996 onwards in IIT Bombay

Contact Information

Department of Electrical Engineering
IIT Bombay, Powai
Mumbai 400 076, India
Email : soman[AT]ee.iitb.ac.in
Phone (Internal(O)) : (0091 22) - 2576 7435
Phone (Internal(R)) : 8435
Office room no: 224
Fax: (0091 22) - 25723707

Books Written

  • S A Soman, S A Khaparde and Shubha Pandit, Computational Methods for Large Sparse Power Systems Analysis: An Object Oriented Approach, Kluwer Academic Publishers (now with Springer Verlag) 2001.

List of Publications

International Journals

  1. P. Murali and S. A. Soman, Pq chart: a real-time situational awareness tool for transmission lines, IET Generation, Transmission & Distribution, vol. 14, no. 26, pp. 6603–6612, 2021.
  2. P. Gupta and S. A. Soman, Calibrating CVTs of a Substation From Local PMU Data: An SVD Approach,IEEE Transactions on Power Systems, vol. 36, no. 4, pp. 3362-3371, July 2021.
  3. H. Goklani, G. Gajjar, and S. Soman, Instrument transformer calibration and robust estimation of transmission line parameters using pmu measurements, IEEE Transactions on Power Systems, vol. 36, no. 3, pp. 1761–1770, 2020.
  4. Akhil Raja and Soman S.A., A Graph Theoretic Approach to Accelerate Natural Cutset Prediction During an Out-of-Step Condition, Elsevier International Journal of Electrical Power and Energy Systems, Available online 03 July 2020.
  5. Mehta R.P., Rao M.S.S. and Soman S.A., A cost-causal marginal participation method using min-max fairness for transmission services cost allocation, Sādhanā, Indian Academy of Sciences , Published online: 18 July 2020.
  6. Minal Chougule and Soman S.A., Real-time data-assisted replay attack detection in wide-area protection system, IET Special Issue on Next Generation of Synchrophasor-based Power System Monitoring, Operation and Control , Volume 14, Issue 19, 02 October 2020, p. 4021 4032.
  7. A. Nadkarni and S. A. Soman, Real-time spatio-temporal trend and level (t&l) filtering scheme for early detection of voltage instability, IET Generation, Transmission & Distribution, vol. 13, no. 8, pp. 1255–1265, 2019.
  8. A. Raj, G. Gajjar, and S. A. Soman, Controlled islanding of transmission system using synchrophasor measurements, IET Generation, Transmission & Distribution, vol. 13, no. 10, pp. 1942–1951, 2019.
  9. K. V. Khandeparkar, S. A. Soman and G. Gajjar, Detection and Correction of Systematic Errors in Instrument Transformers Along With Line Parameter Estimation Using PMU Data, IEEE Transactions on Power Systems, vol. 32, no. 4, pp. 3089-3098, July 2017.
  10. Kalyan Dasgupta and Shreevardhan Soman, Estimation of Zero Sequence Parameters of Mutually Coupled Transmission Lines from Synchrophasor Measurements , IET Generation, Transmission & Distribution , Jun. 2017.
  11. Y. K. Bichpuriya, S. Soman, and A. Subramanyam, Combining forecasts in short term load forecasting: empirical analysis and identification of robust forecaster, Sādhanā, Indian Academy of Sciences , vol. 41, no. 10, pp. 1123–1133, 2016.
  12. Swati Lavand and S. A. Soman, Predictive Analytic to Supervise Zone 1 of Distance Relay using Synchrophasors, IEEE Transaction on Power Delivery , 2016.
  13. M.S.S. Rao and S.A. Soman, Marginal Pricing of Transmission Services Using Min-Max Fairness Policy, , IEEE Transactions on Power Systems , vol. 30, no. 2, pp. 573-584, Mar. 2015.
  14. Kalyan Dasgupta, A. M.Kulkarni, and S. A. Soman, Studying Electromechanical Wave Propagation and Transport Delays in Power Systems, IJEEPS , 2013.
  15. Kalyan Dasgupta, A. M. Kulkarni , and S. A. Soman, On the wave propagation of disturbances in homogeneous electromechanical systems, Journal of vibration and acoustics , 2013.
  16. Gopal Gajjar and S. A. Soman, Power System Oscillation Modes Identifications: Guidelines for applying TLS-ESPRIT Method, IJEEPS , 2013.
  17. P.V. Navalkar and S.A. Soman, Secure Remote Backup Protection of Transmission Lines Using Synchrophasors, IEEE Transactions on Power Delivery , vol. 26, no. 1, pp. 87-96, 2011.
  18. M. S. S. Rao, S. A. Soman, P. Chitkara, R. K. Gajbhiye, N. Hemachandra, B. L. Menezes, Min-Max Fair Power Flow Tracing for Transmission System Usage Cost Allocation: A Large System Perspective, IEEE Transactions on Power Systems Volume 25, Issue 3, August 2010, Page(s):1457-1468
  19. S. Dambhare, S. A. Soman, M. Chandorkar, Current Differential Protection of Transmission Line using the Moving Window Averaging Technique, IEEE Transactions on Power Delivery Volume 25, Issue 2, April 2010 Page(s):610-620
  20. S. Dambhare, S. A. Soman, M. Chandorkar, Adaptive Current Differential Protection Schemes for Transmission Line Protection, IEEE Transactions on Power Delivery Volume 24, Issue 4, Oct 2009 Page(s):1832-1841
  21. D. Dua, S. Dambhare, R. K. Gajbhiye, S. A. Soman, Optimal Multistage Scheduling of PMU Placement: An ILP Approach , IEEE Transactions on Power Delivery Volume 23, Issue 4, October 2008 Page(s)1812-1820
  22. R K Gajbhiye, B. Gopi, P. Kulkarni, S. A. Soman, Computationally Efficient Methodology for Analysis of Faulted Power Systems With Series Compensated Transmission Lines: A Phase Coordinated Approach , IEEE Transactions on Power Delivery Volume 23, No 2, April 2008 Page(s):873 - 880
  23. R. K. Gajbhiye, ,D. Naik, S. Dambhare, S. A. Soman, An Expert System Approach for Multi-Year Short-Term Transmission System Expansion Planning: An Indian Experience , IEEE Transactions on Power Systems Volume 23, Issue 1, Feb 2008 Page(s):226-237
  24. R. K. Gajbhiye, A. De, S. A. Soman, Computation of Optimal Break Point Set of Relays—An Integer Linear Programming Approach , IEEE Transactions on Power Delivery Volume 22, No 4, Oct 2007 Page(s):2087-2098
  25. A. Abhyankar, S. A. Soman, S. A. Khaparade, Min-Max Fairness Criteria for Transmission Fixed Cost Allocation , IEEE Transactions on Power Systems Volume 22, Issue 4, Nov 2007 Page(s):2094 - 2104
  26. A. Abhyankar, S. A. Soman, S. A. Khaparade, Optimization Approach for Real Power Tracing: An Application toTransmission Fixed Cost Allocation , IEEE Transactions on Power Systems Volume 21, Issue 3, Aug 2006 Page(s):1350-1361.
  27. Abhyankar A. R.; Khaparde; Soman S. A.; Pentayya P., A Transmission pricing mechanism based on power tracing for central transmission utility in India, International Journal of Emerging Electric Power Systems, Volume 2. Issue 1, Article 1033, 2005.
  28. Agalgoankar A. P.; Kulkarni S. V.; Khaparde S. A.; Soman S. A., Placement and penetration of distributed generation under standard market design, International Journal of Emerging Electric Power Systems Volume 1, Issue 1, Article 1004, 2004.
  29. Soman, S.A.; Nguyen, T.B.; Pai, M.A.; Vaidyanathan, R., Analysis of angle stability problems: a transmission protection systems perspective, IEEE Transactions on Power Delivery, Volume 19, Issue 3, July 2004 Page(s):1024-1033.
  30. Gajjar, G.R.; Khaparde, S.A.; Nagaraju, P.; Soman, S.A., Application of actor-critic learning algorithm for optimal bidding problem of a Genco, IEEE Transactions on Power Systems, Volume 18, Issue 1, Feb. 2003 Page(s):11 - 18.
  31. Pandit, S.; Soman, S.A.; Khaparde, S.A., Design of generic direct sparse linear system solver in C++ for power system analysis, IEEE Transactions on Power Systems, Volume 16, Issue 4, Nov. 2001 Page(s):647 - 652.
  32. Pandit, S.; Soman, S.A.; Khaparde, S.A., Object-oriented network topology processor [power system automation], IEEE Computer Applications in Power, Volume 14, Issue 2, April 2001 Page(s):42 - 46.
  33. Pandit, S.; Soman, S.A.; Khaparde, S.A., Object-oriented design for power system applications, IEEE Computer Applications in Power, Volume 13, Issue 4, Oct. 2000 Page(s):43 - 47.
  34. Pandian, A.; Parthasarathy, K.; Soman, S.A., Towards faster Givens rotations based power system state estimator, IEEE Transactions on Power Systems, Volume 14, Issue 3, Aug. 1999 Page(s):837 - 843.
  35. A. Pandian, S. A. Soman, K. Parthasarathy, Variable pivot column oriented givens rotations based power system state estimator, International Journal of Electrical Power & Energy Systems, Volume 20, Issue 3, March 1998, Page(s) 183-189.
  36. A. Pandian, K. Parthasarathy, D. Thukaram and S. A. Soman, A numerically stable decomposition based power system state estimation algorithm, International Journal of Electrical Power & Energy Systems, Volume 20, Issue 1, January 1998, Page(s) 17-23.
  37. Soman, S.A.; Parthasarathy, K.; Thukaram, D., Curtailed number and reduced controller movement optimization algorithms for real time voltage/reactive power control, IEEE Transactions on Power Systems, Volume 9, Issue 4, Nov. 1994 Page(s):2035 - 2041.

Papers in conference proceedings

  1. M. Chougule, G. Gajjar, and S. Soman, Pmu supervised secure backup protection of distance relays, IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe), 2019, pp. 1–5.
  2. P. Dutta, A. Nadkarni, G. Gajjar, and S. Soman, Voltage unbalance quantification and mitigation using a pmu-based combined transmission and distribution system linear state estimator, IEEE Milan PowerTech 2019, pp. 1–6.
  3. H. Goklani, G. Gajjar, and S. Soman, Quantification of minimum unbalance required for accurate estimation of sequence parameters of transmission line using pmu data, IEEE Power & Energy Society General Meeting (PESGM) , 2019, pp. 1–5.
  4. P. Murali, G. Gajjar, and S. Soman, Sensitivity vectors and contingency ranking using linearised ac load flow, IEEE Innovative Smart Grid Technologies Asia (ISGT Asia), 2019, pp. 491–496.
  5. H. Goklani, G. Gajjar, and S. Soman, Simultaneous three-phase line parameter estimation and instrument transformer calibration using pmu data, 2020 21st National Power Systems Conference (NPSC)IEEE, 2020, pp. 1–5.
  6. S. Lokhande, S. Soman, and N. Hiremath, Quick learn approach for load forecasting during covid 19 lockdown, 2020 21st National Power Systems Conference (NPSC), IEEE, 2020, pp. 1–6.
  7. G. R. Gajjar and S. Soman, Analysis of sustained oscillations in power systems observed through wide measurements, IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC), 2017, pp. 1–6.
  8. G. R. Gajjar, P. V. Navalkar, and S. Soman, Considerations on measurement locations for wams based linear state estimation of power systems, 7th International Conference on Power Systems (ICPS), IEEE, 2017, pp. 671–676.
  9. S. Pai and S. Soman, Forecasting global horizontal solar irradiance: a case study based on indian geography, 7th International Conference on Power Systems (ICPS), IEEE, 2017, pp. 247–252.
  10. G. R. Gajjar, R. Gajbhiye, M. Chougule, and S. Soman, Codit: commissioning diagnostic tool for wams based linear state estimation of power systems, 20th National Power Systems Conference (NPSC), IEEE, 2018, pp. 1–6.
  11. H. Goklani, G. Gajjar, and S. Soman, Phase segregated soft calibration of instrument transformers using synchronised phasor measurements, 2018 Power Systems Computation Conference (PSCC), IEEE, 2018, pp. 1–7.
  12. S. A. Lavand and S. Soman, Local supervision of distance relay using rodrick prescott filter, 2018 Power Systems Computation Conference (PSCC), IEEE, 2018, pp. 1–7.
  13. A. Nadkarni and S. Soman, Applications of trend-filtering to bulk pmu time-series data for wide-area operator awareness, Power Systems Computation Conference (PSCC), IEEE, 2018, pp. 1–7.
  14. M. D. Chougule, G. Gajjar, and S. Soman, Pincs: A power system integrated cybernetwork simulator for wams, 2018 20th National Power Systems Conference (NPSC), IEEE, 2018, pp. 1–6.
  15. Y. K. Bichpuriya, S. Soman, and A. Subramanyam, Robust probability density forecasts of yearly peak load using non-parametric model, IEEE Power and Energy Society General Meeting (PESGM), 2016, pp. 1–5.
  16. K. Salunkhe, G. Gajjar, A. Kulkarni, and S. Soman, A combined model and measurement based scheme for assessment of poorly damped power swings,
    IEEE Annual India Conference (INDICON). IEEE\\, 2016, pp. 1–6.
  17. G. R. Gajjar and S. Soman, Simulation of power systems for wams applications, IEEE 6th International Conference on Power Systems (ICPS). IEEE, 2016, pp. 1–6.
  18. S. A. Lavand, G. R. Gajjar, S. A. Soman and R. Gajbhiye, Mining spatial frequency time series data for event detection in power systems, 13th International Conference on Development in Power System Protection, Edinburgh, Scotland, UK, Mar. 2016, pp. 1-6, doi: 10.1049/cp.2016.0083.
  19. R. Mehta and S. Soman, Efficient cost allocation for transmission system, IEEE International Conference on Power System Technology (POWERCON) IEEE, 2016, pp. 1–6.
  20. Y. K. Bichpuriya and S. Soman, Application of probability density forecast of demand in short term portfolio optimization, IEEE International Conference on Power System Technology (POWERCON), IEEE, 2016, pp. 1–6.
  21. K. Khandeparkar, S. A. Soman, K. Ramamritham, R. Gupta, A. M. Kulkarni, and G. R. Gajjar, Timely query processing in Smart Electric Grids: Algorithms and Performance in E-Energy, International Conference on Future Energy Systems, Banglore, Jul. 2015.
  22. M. J. Punjabi, P. G. Awate, R. Gajbhiye, S. A. Soman, and K. V Prasad , Short term portfolio optimization for load serving entity considering multiple exchanges and ramping constraints, IEEE PES Innovative Smart Grid Technologies Conference (ISGT), Washington DC, Dec. 2014.
  23. Y.K. Bichpuriya, S.A.Soman, and A. Subramanyam, Robust probability density forecast of yearly peak load, International Conference on Robust Statistics (ICORS), Halle, Germany, Dec. 2014.
  24. Y. K. Bichpuriya, S.A. Soman, and A. Subramanyam, On optimal combination of probability density forecasts using Kullback-Leibler divergence criterion, International Conference on Robust Statistics (ICORS), Halle, Germany, Dec. 2014.
  25. Y.K. Bichpuriya, S. A. Soman, and A. Subramanyam, Non-parametric probability density forecast of an hourly peak load during a month, Power Systems Computation Conference (PSCC), Wroclaw, Dec. 2014.
  26. K. A. Salunkhe, Gopal Gajjar, S. A. Soman, and A. M. Kulkarni, Implementation and applications of a Wide Area Frequency Measurement System synchronized using Network Time Protocol, IEEE PES General Meeting, National Harbour MD USA, Dec. 2014.
  27. M. J. Punjabi, P. G. Awate, R. Gajbhiye, S. A. Soman, and K. V. Prasad, From forecasting to scheduling in short term power procurement using stochastic optimization, EEE PES Innovative Smart Grid Technologies Conference Europe, Istanbul, Dec. 2014.
  28. Gopal Gajjar, A. M. Kulkarni, and S. A. Soman, Interaction of capacitor bank inrush current limiting reactor and medium voltage vacuum circuit breakers, International Conference on Power Systems Transients, Dec. 2013.
  29. Kalyan Dasgupta and S.A.Soman, Line parameter estimation using phasor measurements by the total least squares approach, IEEE PES General Meeting, Dec. 2013.
  30. Dasgupta Kalyan, Kulkarni A. M, and Soman S. A., “Studying Electromechanical Wave Propagation and Transport Delays in Power Systems”, National Power System Conference, Dec. 2012.
  31. Gopal Gajjar and S.A. Soman, Power System Oscillation Modes Identifications From Wide Area Frequency Measurement System, Powercon 2012, Dec. 2012.
  32. Yogesh Bichpuriya, R.S.S Fernandes, and S. A. Soman, Identification of Anomalous Load Profile for Short Term Load Forecasting, Powercon 2012, Dec. 2012.
  33. Gopal Gajjar and S.A. Soman, Power System Oscillation Modes Identifications: Guidelines for applying TLS-ESPRIT Method, 17th National Power System Conference (NPSC), Dec. 2012.
  34. Yogesh K. Bichpuriya, Swaroop A. Upadhyaya , and S. A. Soman, Optimal location of spare transformers at distribution substations for reliability improvement, IET Conference on Reliability of Transmission and Distribution Networks (RTDN 2011), pp.1-5, Dec. 2011.
  35. Yogesh K. Bichpuriya, Prashant V. Navalkar, and S. A. Soman, Benchmarking of reliability indices for electricity distribution utilities: Approach and discussion, IET Conference on Reliability of Transmission and Distribution Networks (RTDN 2011), pp.1-6, Dec. 2011.
  36. R.S.S. Fernandes , Y.K. Bichpuriya, M.S.S. Rao, and S.A. Soman, Day ahead load forecasting models for holidays in Indian context, International Conference on Power and Energy Systems (ICPS), Dec. 2011.
  37. Gopal Gajjar and S.A. Soman, A proposal for distributed architecture for synchronized phasor measurement unit, International Conference on Power and Energy Systems (ICPS), pp.1-7,22-24, Dec. 2011 .
  38. Yogesh Bichpuriya and S. A. Soman, Electric Power Exchanges: A Review National Power System Conference, Dec. 2010.
  39. Yogesh Bichpuriya, M.S.S Rao , and S.A. Soman, Combination approaches for short term load forecasting, IPEC 2010 Conference Proceedings, pp.818-823, Dec. 2010.
  40. R. K. Gajbhiye and S. A. Soman, Facilitating Emission Trading within Power Exchange EEM10, 7th International Conference on the European Energy Markets EEM10, Jun. 2010.
  41. Yogesh Bichpuriya, S.A. Soman, and P.R. Apte, Design and testing of heuristic for market splitting in electric power exchange, TENCON 2009 IEEE Region 10 Conference , pp.1-5, Dec. 2009.
  42. Rajeev Gajbhiyee, S. A. Soman, New Bid Structures for Power Exchange with Modelling in Integer Linear Programming, 6th International Conference on the European Energy Market, 2009.
  43. Sanjay Dambhare; Nandkishore Kinhekar; S. A. Soman; M. C. Chandorkar, ATP-EMTP Analysis of Series Compensated Lines for Distance Protection Schemes, International Conference on Power System Protection, Bangalore, India, February 20-21, 2007
  44. Devesh Dua, S. A. Soman, A Comparative Study of Power Swing Detection Methods, International Conference on Power System Protection, Bangalore, India, February 20-21, 2007
  45. Sharvari Bendarkar, R. K. Gajbhiye, S. A. Soman, Optimal Reconfiguration to Improve Voltage Profile of Distribution System using Network Simplex Method, International Conference on Power Systems, Bangalore, India, December 12-14, 2007
  46. Rao, M.S.S., Soman, S.A., Menezes, B.L., Pradeep Chawande, Dipti, P., Ghanshyam, T., An expert system approach to short-term load forecasting for Reliance Energy Limited, Mumbai , IEEE Power India Conference, 2006 10-12 April 2006 Page(s):6
  47. Abhyankar, A.R., Soman, S.A., Khaparde, S.A., Tractability of bilateral transactions considering multiplicity of solution space in real power tracing , IEEE Power India Conference, 10-12 April 2006 Page(s):8.
  48. Gajbhiye, R.K., Kulkarni, P., Soman, S.A., Analysis of Faulted Power Systems in Three Phase Coordinates-A Generic Approach, The 7th International Power Engineering Conference, 2005. IPEC 2005. 29-02 Nov. 2005 Page(s):1 - 6.
  49. Abhyankar, A.R., Soman, S.A., Khaparde, S.A., Allocation of Fixed Transmission Costs by Tracing Compliant Postage Stamp Method , The 7th International Power Engineering Conference, 2005 IPEC 2005, 29-02 Nov. 2005 Page(s):1 - 6.
  50. Chawande, P., Soman, S.A., Apte, P.R., Pandit, S., Experimental Evaluation of Current Transformer Performance under Saturation, The 7th International Power Engineering Conference, 2005 IPEC 2005. 29-02 Nov. 2005 Page(s):1 - 5.
  51. Abhyankar, A.R., Soman, S.A., Khaparde, S.A., New Paradigm of Tracing Algorithms: Application to Fair Loss Allocation in Indian System , International Conference on Future Power Systems, 2005, 16-18 Nov. 2005 Page(s):1 - 6.
  52. Gajbhiye, R.K., De, A., Helwade, R., Soman, S.A., A Simple and Efficient Approach to Determination of Minimum Set of Break Point Relays for Transmission Protection System Coordination, International Conference on Future Power Systems, 2005 16-18 Nov. 2005 Page(s):1-5.
  53. A. R. Abhyankar, S. A. Khaparde, and S. A. Soman, Loss modeling and tractability of bilateral transactions in real power tracing, 13th National Power Systems Conference (NPSC), IIT Madras , pp.370-375, Dec. 2004.
  54. Rajani Vaidyanathan, S. A. Soman, Distance Relay Coordination Considering Power Swings, CRIS International Conference on Power Systems and Communications Infrastructures for the future, Beijing, Sep. 2002.
  55. Shubha Pandit, S. A. Soman, S A Khaparde, Object oriented set theoretic implementation of minimum degree algorithm, 14th Power Systems Computations Conference, Sevilla, Spain, Jun. 2002.
  56. Sarika Khushalani, S. A. Khaparde, S. A. Soman, Congestion management in the emerging energy market structures, International conference on bulk power transmission systems integration in developing countries, CIGRE regional meeting, New Delhi, pp.16-24, Nov. 2001.
  57. G. R. Gajjar, S. A. Khaparde, and S. A. Soman, Modified Model of Negotiations in Market Games Under Deregulated Environment, 11th National Power Systems Conference, IISc Bangalore, pp.222-228, Dec. 2000.
  58. Shubha Pandit, S. A. Soman, and S. A. Khaparde , Design Of Network Topology Processor by Graph Theoretic Abstraction, 11th National Power System Conference, IISc Bangalore, pp.89-94, Dec. 2000.
  59. Pandit, S., Soman, S.A., Khaparde, S.A., Pandian, A., An OOP based real time reactive power control algorithm for large power systems, IEEE Power Engineering Society Winter Meeting, 2000 Volume 2, 23-27 Jan. 2000 Page(s):1174 - 1179 vol.2 Papers in conference proceedings.

Patents

  1. S. A. Soman, P. Apte, P. V. Chawande;Device and method for mitigating magnetic core saturation in a current transformer, Patent No. IN20080059213, Published 23rd October 2009.
  2. S. A. Soman, P. Navalkar; A system and method for detecting and locating a fault and controlling the tripping of a backup relay in a power transmission network using phasor measurement units, Patent No. IN20100111713, Published 10th August 2012.
  3. S. A. Soman, S. Lavand; Method for reliable power swing detection and event detection, Patent No. IN201721002019A, Published 13th December 2019.
faculty/soman.txt · Last modified: 2021/09/06 05:08 (external edit)