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SAMEER GUPTASAMEER GUPTA
Transmission Line Transmission Line
DefDef. – . – A transmission line basically consists of 2 or more A transmission line basically consists of 2 or more parallel conductors used to connect a source to a load.parallel conductors used to connect a source to a load.
What is a transmission line?What is a transmission line?•Uniform transmission line is one which has its electrical Uniform transmission line is one which has its electrical parameters remaining constant along its length of the line.parameters remaining constant along its length of the line.•In which voltage to current ratio does not vary with distance if In which voltage to current ratio does not vary with distance if the line is terminated in its characteristics impedance.the line is terminated in its characteristics impedance.•Electrical parameters of lines are R-L-C-G (Resistance-Electrical parameters of lines are R-L-C-G (Resistance-Inductance-Capacitance-Conductance).Inductance-Capacitance-Conductance).•These parameters are defined per unit length of the conductor These parameters are defined per unit length of the conductor and are called Primary constants of the line.and are called Primary constants of the line.
Uses of Transmission linesUses of Transmission lines:-:-
•To transfer the energy or signal or power 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 wiresTwisted pair wiresRibbon typeCo-axial cablesMicro-strip linesWave guides
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 TRANSMISSIONREASONS FOR AC GENERATION AND TRANSMISSION
– 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 FROM ER TO SR
COMPARISION OF HVAC & HVDC SYSTEMS
ADVANTAGES OF HVDC OVER HVAC ADVANTAGES OF HVDC OVER HVAC
TRANSMISSIONTRANSMISSION
COST: AC vs DC Transmission
Terminal Cost AC
Terminal Cost DC
Line Cost DC
Line Cost AC
Break Even Distance
HVDC IN INDIABack-to-Back
HVDC LINK CONNECTING REGION
CAPACITY (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
BASIC PRINCIPLES
OF
HVDC TRANSMISSION
Direct current is put to use in common life for driving our portable devices, UPSs, battery systems and vastly in railway locomotives.
USE OF DC
DC AS A MEANS OF TRANSMISSIONDC AS A MEANS OF TRANSMISSION
This has been possible with beginning of
High power/ high current capability thyristor.
&
Fast acting computerized controls
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)