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Amity University Rajasthan Slide 2 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. 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. 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 (Resistance- Inductance-Capacitance-Conductance). Electrical parameters of lines are R-L-C-G (Resistance- Inductance-Capacitance-Conductance). These parameters are defined per unit length of the conductor and are called Primary constants of the line. These parameters are defined per unit length of the conductor and are called Primary constants of the line. Amity University Rajasthan Slide 3 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 Slide 4 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. REASONS FOR AC GENERATION AND TRANSMISSION Amity University Rajasthan Slide 5 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. COMPARISION OF HVAC & HVDC SYSTEMS Amity University Rajasthan Slide 6 CONTROLLED POWER ASYNCHRONOUS OPERATION POSSIBLE BETWEEN REGIONS HAVING DIFFERENT ELECTRICAL PARAMETERS NO RESTRICTION ON LINE LENGTH AS NO REACTANCE IN DC LINES ADVANTAGES OF HVDC OVER HVAC TRANSMISSION Amity University Rajasthan Slide 7 Slide 8 COST: AC vs DC Transmission Terminal Cost AC Terminal Cost DC Line Cost DC Line Cost AC Break Even Distance Slide 9 HVDC IN INDIA Back-to-Back HVDC LINKCONNECTING REGION CAPACITY (MW) VindyachalNorth West2 x 250 ChandrapurWest South2 x 500 Vizag IEast South500 SasaramEast North500 Vizag IIEast South500 Amity University Rajasthan Slide 10 BASIC PRINCIPLES OF HVDC TRANSMISSION Slide 11 Amity University Rajasthan Slide 12 Slide 13 Slide 14 Slide 15 Slide 16 Direct current is put to use in common life for driving our portable devices, UPSs, battery systems and vastly in railway. USE OF DC 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 Slide 17 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. 1.Convert AC into DC (rectifier) 2. 2.Transmit DC 3. 3.Convert DC into AC ( inverter) Amity University Rajasthan Slide 18 Any Query ?