A SEMINAR ON

“HVDC TRANSMISSION”

SUBMITTEDBY

Utkarsh J. Jambhule(BE12FO3FO25)

UNDER THE SUPERVISION OF

Dr. Archana G. Thosar (H.O.D)

INTRODUCTION:

With the increasing of requirement of electrical power supply the facilities have to be increased in that transmission plays an important role.

Here HVDC (high voltage direct current) transmission plays major role in power transmission.

First HVDC transmission linked between gotland and mainland in sweden in 1954.

The HVDC transmission has many advantages over HVAC transmission.

HVDC MEANS…..

HVDC stands for High Voltage Direct Current and is today a well-proven technology all over the world.

Two AC systems having different frequencies can be linked up together by means of HVDC link.

HVDC technology is used to transmit electricity over long distances.

WHY DC TRANSMISSION ?

Losses are less in DC transmission while comparing to AC transmission.

Only two conductors are required for DC with positive and negative polarities.

DC overhead lines or cables are less expensive.

DC lines are useful for long distances above500km.

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Comparison of HVAC and HVDC

Conventionally power transmission is affected through HVAC systems all over the world.

HVAC transmission is having several limitations like, line length , uncontrolled power flow, over/low voltages during lightly / over loaded conditions, stability problems, fault isolation etc…

But HVDC have low transmission losses and it requires only two conductors.

Comparison between the prices of AC & DC

Transmission

Wind Power

AC Transmission

Line

Converter Station

Inverter Station AC

Transmission Line

DistributionLine

HVDC Transmission Line

HVDC transmission system

1. Converters

2. Smoothing reactors

3. Harmonic filters

4. Reactive power source

5. Electrodes

6. Dc lines

7. Ac circuit breakers

Homopolar link

Monopolar link

Bipolar link

HVDC Transmission can be broadly classified into:-

It uses one conductor.

The return path is provided by ground or water.

Use of this system is due to cost considerations.

A metallic return may be used where earth resistivity is too high

Each terminal has two converters of equal rated voltage,

connected in series on DC side.

The junctions between converters is grounded.

If one pole is isolated due to fault, the other pole can operate

with ground and carry half the rated load ( or more using

overload capabilities of its converter line.)

It has two conductors each having same polarity, usually negative.

Since the corona effect in DC transmission lines is less for

negative polarity, homopolar link is usually operated with negative

polarity.

The return path for such a system is through ground.

Back to Back Transmission.

Point to point Overhead lineTransmission.

Point to point Underground Cable Transmission.

Point to point Sub marine Transmission.

The losses which occurs in the systems are comparatively low at all the stages (i.e.) at generation , transmission & distribution level.

The losses at transmission level can be highly reduced by HVDC transmission.

Advantages of HVDC

Technical

AdvantagesEconomic

Advantages

Lesser Corona Loss and Radio interference.

The voltage regulation problem is much lessserious for DC, since only the IR drop isinvolved. For the same reason steady statestability is no longer a major problem.

No skin and proximity and Ferranti effect

Asynchronous operation possible betweenregions having different electrical parameters.

DC lines and cables are cheaper than AC linesor cables.

The towers of the DC lines are narrower,simpler and cheaper compared to the towers ofthe AC lines.

Line losses in a DC line are lower than thelosses in an AC lines.

The disadvantages of HVDC are in conversion,switching, control, availability and maintenance.

There is nothing like DC transformer which canchange the voltage level in a simple way. Voltagetransformation has to be provided on the AC sides ofthe system.

The required converter stations are expensive and havelimited overload capacity.

Rihand-delhi and chandrapur-padghe were the first long distance hvdc projects in India.

In 1990 ,rihand-delhi (singrauli) thermal power complex with a combined power generation of Several thousand MW was put in to service. it covers over a distance of 814 km.

The 1500 MW transmission chandrapur-padghe was put in to service. it covers over distance of 736 km.

APPLICATIONS OF HVDC TRANSMISSION IN INDIA:

Conclusion Recent studies indicate that HVDC systems are very

reliable.

Very large investments Eg. In China and India shows thatHigh Voltage Direct Current will very important in thefuture, especially in big and new-industries countries.

1.C.L.wadhwa ‘electrical power systems'-third edition

2. I.J.nagrath and d.p.khotari 'power system engineering

3. S.S. vadhera 'power system analysis and stability

4. Soni gupta bhatnagar 'power system engineering

5. K.R.padiyar ‘hvdc power transmission systems'

BIBLIOGRAPHY: