International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 02 | Feb-2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 517 Transient Protection for two terminals HVDC System P V N Mohan Krishna 1 , A.Hemanth kumar Raju 2 , M.E.C.Vidya Sagar 3 1,2,3 Dept. of Electrical and Electronics Engineering, SRKR Engg college, A.P, India ----------------------------------------------------------------------------***----------------------------------------------------------------------------- Abstract - The relation between the parameters of dc transmission line and the variation of transient energy has been analyzed under various fault conditions in this paper. According to that, a new transient energy protective scheme is proposed. It is developed based on the distributed parameter line model in which the transient energy distribution over the line can be obtained from the voltage and current measurements at both terminals and the fault can be recognized from the calculated value simply. The test system is modelled based on the CIGRE benchmark and considered the distributed parameters of the dc transmission line. Comprehensive test studies show that the performance of transient energy protection scheme is encouraging. It can not only identify internal fault and external faults correctly and quickly, but can also respond to the high ground resistance fault. Finally, two main factors, including fault resistance and transmission distance, that affect the performance of the protection are also discussed. Index Terms—HVDC, test and result, transient Key Words: Transient Energy, HVDC 1. INTRODUCTION RECENTLY, the number of high-voltage direct current(HVDC) systems is increasing rapidly throughout the world, due to their advantages of long distance and large capacity power transmission, asynchronous interconnections, and their ability to prevent inadvertent loop flows in an interconnected ac system [1]–[3]. These definite technical and environmental advantages make HVDC transmission systems more attractive than high- voltage alternating current (HVAC)systems in power system projects. Over the last two decades, HVDC transmission systems developed more rapidly than HVAC transmission systems around the world. The traditional protection system for the HVDC transmission line often uses the voltage and its change rate to detect the ground fault in the dc line [4]. But it is affected easily by fault impedance. With the rapid advance of microelectronics technology and microcomputer protections, travelling- wave theory has been implemented and adopted in HVDC transmission lines successfully [5]. However, travelling- wave-based methods still have problems that limit their application, such as lacking mathematical tools to represent travelling wave, being easily influenced by noise, and so on [6], [7]. Recently, based on the characteristics of low-frequency differential transient energy at the two ends of the dc line, a new protection scheme for UHVDC lines is proposed . However, this paper does not take into account the distributed parameters of the transmission line. Infact, the typical characteristic of modern HVDC transmission systems is the long distance; thus, the effect of the distributed parameters cannot be ignored and may cause the mal operation of relay protection .A novel transient energy principle is proposed in this paper. Based on the steady-state transmission-line equations, the distributed parameters of the dc line have been taken into account. The increments of transient energy in the dc line are utilized to identify internal fault and external fault. With PSCAD/EMTDC, the test system is modelled considering the distributed parameters. Comprehensive test studies show that the proposed principle is simple, reliable, and practical. It can provide correct responses under various fault conditions including high ground resistance faults. Finally, the two main factors that affect performance of the protection are also discussed: fault resistance and transmission distance. And the relationships between the two factors and the sensitivity of transient energy protection have been deduced. This paper is organized as follows. In Section II, the protection principle used in this paper is given. The test system is given in Section III. Test results are given in Section IV, followed by the conclusions in Section V. 1.1 TRANSIENT ENERGY PROTECTION PRINCIPLE FOR TWO TERMINAL HVDC SYSTEM. Fig -1: Diagram of the HVDC transmission system. Before Fig.1 shows a main structure diagram of the typical HVDC transmission system. The dc transmission-line protection devices are installed at the two ends of the line M and N.   ,   and   ,   are dc currents and dc voltages at M and N, respectively. The positive directions of the aforementioned electrical vectors are defined in the diagram. The transient energy of the measuring point from   to   is   ∫   ሺሻ       ∫   ሺሻ     (1)