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)