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Amity University Rajasthan Transmission Line Def. – A transmission line basically consists of 2 or more parallel conductors used to connect a source to a load. What is a transmission line? • Uniform transmission line is one which has its electrical parameters remaining constant along its length of the line. • In which voltage to current ratio does not vary with distance if the line is terminated in its characteristics impedance. • Electrical parameters of lines are R-L-C-G (ResistanceInductance-Capacitance-Conductance). • These parameters are defined per unit length of the conductor and are called Primary constants of the line. Amity University Rajasthan Uses of Transmission lines:- • To transfer the energy or signal from the transmitter to the receiver. • It acts as communication media. • In most cases, transmission lines are metallic conductors. • Few e.g. of Transmission lines are: Parallel wires Twisted pair wires Ribbon type Co-axial cables Micro-strip lines Wave guides Amity University Rajasthan REASONS FOR AC GENERATION AND TRANSMISSION Due to ease of transformation of voltage levels and rough collector cage motors, ALTERNATING CURRENT is universally utilised. Both for GENERATION and LOADS and hence for TRANSMISSION. Generators are at distant places, away from the populated areas i.e. the load centers They are either PIT HEAD THERMAL or HYDEL Turbines drive synchronous generators giving an output at 15-25 kV. To reach the loads at homes/industry at required safe levels, transformers step down voltage. Amity University Rajasthan COMPARISION OF HVAC & HVDC SYSTEMS – CONVENTIONALLY POWER TRANSMISSION IS EFFECTED THROUGH HVAC SYSTEMS ALL OVER THE WORLD. – HVAC TRANSMISSION IS HAVING SEVER LIMITATIONS LIKE LINE LENGTH , UNCONTROLLED POWER FLOW, OVER/LOW VOLTAGES DURING LIGHTLY / OVER LOADED CONDITIONS,STABILITY PROBLEMS,FAULT ISOLATION ETC – CONSIDERING THE DISADVANTAGES OF HVAC SYSTEM AND THE ADVANTAGES OF HVDC TRANSMISSION , POWERGRID HAS CHOOSEN HVDC TRANSMISSION FOR TRANSFERRING 2000 MW . Amity University Rajasthan ADVANTAGES OF HVDC OVER HVAC TRANSMISSION – CONTROLLED POWER – ASYNCHRONOUS OPERATION POSSIBLE BETWEEN REGIONS HAVING DIFFERENT ELECTRICAL PARAMETERS – NO RESTRICTION ON LINE LENGTH AS NO REACTANCE IN DC LINES Amity University Rajasthan Amity University Rajasthan COST: AC vs DC Transmission Line Cost AC Line Cost DC Terminal Cost DC Terminal Cost AC Break Even Distance HVDC IN INDIA Back-to-Back HVDC LINK CONNECTING CAPACITY REGION (MW) Vindyachal North – West 2 x 250 Chandrapur West – South 2 x 500 Vizag – I East – South 500 Sasaram East – North 500 Vizag – II East – South 500 Amity University Rajasthan BASIC PRINCIPLES OF HVDC TRANSMISSION Amity University Rajasthan Amity University Rajasthan Amity University Rajasthan Amity University Rajasthan Amity University Rajasthan USE OF DC Direct current is put to use in common life for driving our portable devices, UPSs, battery systems and vastly in railway. DC AS A MEANS OF TRANSMISSION This has been possible with beginning of High power/ high current capability thyristor. & Fast acting computerized controls Amity University Rajasthan If DC is required to be used for transmission & since our primary source of power is A.C, The following are three basic steps:1. Convert AC into DC (rectifier) 2. Transmit DC 3. Convert DC into AC ( inverter) Amity University Rajasthan Any Query ? Amity University Rajasthan