Traveling Wave Differential Relaying Presented by Jinqian Yu

Table of Contents 1. IntroductionIntroduction 2. Line model for traveling wavesLine model for traveling waves 3. Traveling waves’ propagation & measurementTraveling waves’ propagation & measurement 4. Differential algorithm based on traveling wavesDifferential algorithm based on traveling waves 5. Feasibility of implementationFeasibility of implementation

Introduction Basic idea The occurrence of a fault can trigger a series of traveling waves which contain the earliest available evidence to a relay that the fault has taken place. It is possible to design a differential relay scheme based on traveling waves. Advantages Ultra-high speed Less susceptible by system transient phenomenon

Line model for traveling waves Distributed parameter model → Solution (lossless line) Where v is surge velocity z is surge impedance

Traveling waves propagation & measurement k is reflection coefficients, such that The reflection coefficient at fault location is -1

Measurement Sending end → Receiving end → F and f denote forward wave and backward wave respectively

Differential algorithm based on traveling waves →

Derive the Bergeron’s equations In a healthy line, it takes time T= d/v that a forward wave from terminal S travel to terminal R where the wave is regarded as backward wave. Use these equations and take t = t – T in equations in last slide, we get the Bergeron’s equation:

Feasibility issues Though Bergeron’s equations always hold if there is no internal fault between two terminals of a line and this differential relaying scheme seems foolproof, some problems still remain unsolved. 1.The relay has to rely on a narrow window of available data to make a decision. 2.It is difficult to recognize and capture the data carried by wavefront as it travels at such a high speed. 3.Data acquisition system must be high bandwidth to obtain the high-frequency content of traveling waves.

Conclusion Differential relaying based only traveling waves is just one of those relatively new scheme using traveling waves. In theory, it has demonstrated the possibility of ultra-high speed for a relay. However, some technical issues need to be solved before implementation. Traveling wave differential relaying is still an interesting technique and worth our attention.

Reference [1] Tagaki, T., Baba, J.I., Uemura, K. and Sakaguchi, T. Fault protection based on traveling wave theory, Part 1–Theory. Electrical Engineering in Japan, Vol. 98, No. 1, [2] Tagaki, T., Baba, J.I., Uemura, K. and Sakaguchi, T. Fault protection based on traveling wave theory, Part 2–Sensitivity analysis and laboratory test, IEEE paper No. A 78, pp , [3] Dommel, H.W. and Michels, J.M., High speed relaying using traveling waves transient analysis, IEEE paper No. A78, pp , [4] Bewley, L.V., Traveling Waves on Transmission Systems, John Wiley & Sons, Inc. New York, [5] Chamia, M. and Liberman, S. Ultra high speed relay for EHV/UHV transmission lines – development, design and application, IEEE Trans, on PAS, vol. PAS-97, No. 6, pp , [6] Mansour, M.M and Swift, G.W., A multi-microprocessor based traveling wave relay – Theory and realization, IEEE Trans. Vol. PWRD-1, No. 1, [7] Bollen, M.H.J. and Kerston, W.F.J., Traveling-wave-based protection: directional, differential or distance? Proc 10th Power Systems Computation Conf., 1990.

[8] Bollen, M.H.J. Traveling-wave-based protection of double-circuit lines. IEE Proceedings-C, Vol. 140, No. 1, [9] Arun G. Phadke, James S. Thorp. Computer relaying for power systems, John Wiley & Sons, Inc, New York, pp , [10] Zecun Zhou. High voltage technology, China electric power press, pp

Thank you! Q&A