high voltage dc

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Presentation Outline

Introduction.

History of HVDC.

HVDC goes global.

India adopts HVDC.

Main Components of HVDC System Types of HVDC System

Advantages of HVDC

Disadvantages of HVDC.

Applications of HVDC

References

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Introduction

WHAT IS HVDC ?

In a HVDC (High voltage D.C.) transmission system, electricity is takenfrom an AC power network, converted to DC in a converter station and

transmitted to the receiving point by a transmission line (overhead) orcable(underground).

It is then converted back to AC in another converter station andinjected into the receiving AC network.

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Introduction

HVDC is famous for

(i) Power transfer over long distances from point to point

(ii) Underwater (sea) transmission

(iii) Interconnection of two AC systems with two different

frequencies

(iv) Better power system stability as a parallel link with

existing AC system

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HVDC System4

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HVDC goes Global

Currently there are some more than 100 of HVDC systemsacross the whole world ,out of which 6 are in India.

Some of them are as follows:

-Between Sweden & Denmark.

-Between south & north islands of New Zealand.

-Between Italy & Sardinia.

-Between Los Angeles & Oregon.

-Between north African deserts & central Europe.

-Between UK & western Europe. Proposal of a.c transmission across the English channel was

abandoned and get replaced by HVDC system

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HVDC In INDIA

In India presently 6 HVDC systems are in operation. India- Pioneer developer of HVDC since 1990 with the first

HVDC set up of 1000MW 814Km Rihand-Dadri line between

U.P & Rajasthan.

2000MW 1440Km Talcher-Kolar link is biggest so far connectingfour states-orissa,andhra pradesh,tamilnadu and karnataka.

In march 2000,Power-grid(largest power transmission utility of

India) awarded a new long distance HVDC transmission project

to SIEMENS,Germany. More greater plans are cooking to add 1lakh MW of power by

2014 in which HVDC will play vital role to transmit these powers

to all corners of India.

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Main Components of HVDC System

Converter Transformers Steps up AC voltage and provides isolation

Series Converters

Converts AC to DC or DC to AC

Smoothing Reactor

Reduce harmonics and transients on DC side

AC Filter and DC Filter

Reduce harmonics Shunt Capacitors

Reactive power generation

Control System

Performance control

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Types of HVDC System

Back to Back Converters

Monopolar Configuration

Bipolar Configuration

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Advantages of HVDC

Advantages of HVDC can be classified as:

Advantages of dc

transmission

TechnicalAdvantages

EconomicAdvantages

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TechnicalAdvantages

Reactive power requirement

System stability

Short Circuit Current

Independent Control of ac system Fast change of energy flow

Lesser Corona Loss and Radio interference

Greater Reliability.

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No limits in transmitted distance

Direction of power flow can be changed

very quickly

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Economic Advantages

Cost of transmission lines of HVDC is much lower ascompared to HVAC due to the following factors. Reduced number of conductors

Reduced size of conductor for the same power transmission

Reduced size of transmission towers and the space requiredfor them

But the cost of converters for controlling voltages ismuch higher as compared to transformers and other

switchgear equipments in HVAC. Therefore the overall investment cost in an HVDC

system is lower if the distance of transmission isabove 500 to 800 km

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Economic advantages

DC lines and cables are cheaper than ac lines or

cables.

The towers of the dc lines are narrower, simpler

and cheaper compared to the towers of the ac

lines.Line losses in a dc line are lower than the losses

in an ac lines.

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DC

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high voltage dc

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