power system engineering lecture 27

8/3/2019 Power System Engineering Lecture 27

1/12

Review of Last Class

Introduction HVDC Advantages

Disadvantages: Cost, Harmonics, Reactive power, Point to

point access, Overload conditions

Types of HVDC links

Monopolar

Bipolar

Homopolar

Components of HVDC System


2/12

Introduction

First HVDC Commercial System (1954): 100 kV, 20 MW,

Mainland of Sweden to island of Gotland, Monopolar, Cable system.

Mercury arc technology

1972 onwards all the HVDC system use thyristor valves

The Biggest HVDC System: 300 kV, 6300 MW,ITAIPU Brazil.

Highest rating of device: 5 kV, 3 kA (now 10 kV, 4kA)

In India:

Sileru-Barsoor 200 kV 400 MW 196 km 1989

Rihand-Delhi 500 kV 1500 MW 814 km 1990

Talcher-Kolar 500 kV 2000 MW 1397 km 2003


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Types of HVDC links

Monopolar link

Only one energized conductor normally of negative polarity Earth or sea water used as return path

In the case of fault complete shutdown of the system


4/12

Types of HVDC links

Bipolar link

Two conductors with polarities (+ve and -ve) represented as

Neutral points (junction between convertors) are grounded Normal operation no current through the earth

If there is fault on one conductor other conductor can be used

with half of the rating


5/12

Structure of HVDC System

Homopolar link

Two or more conductor with same polarity (generally -ve) Operates earth as return

If there is fault on one conductor other conductor can be used

with half of the rating


6/12

Components in HVDC Transmission

Convertors

Convertor

transformer

Smoothing reactor

AC (Harmonic) filter Overhead lines

Reactive power

source

Earth electrode

DC Filters

Circuit Breakers


7/12

Basics of Convertor

http://www.cdeep.iitb.ac.in/nptel/Electrical%20Engineering/Power%20System%20Operation%20and%20Control/Course_home_L18a.html

http://en.wikipedia.org/wiki/Silicon-controlled_rectifier

ThyristorTerms used in Convertor analysis
http://www.cdeep.iitb.ac.in/nptel/Electrical%20Engineering/Power%20System%20Operation%20and%20Control/Course_home_L18a.htmlhttp://en.wikipedia.org/wiki/Silicon-controlled_rectifierhttp://en.wikipedia.org/wiki/Silicon-controlled_rectifierhttp://en.wikipedia.org/wiki/Silicon-controlled_rectifierhttp://en.wikipedia.org/wiki/Silicon-controlled_rectifierhttp://www.cdeep.iitb.ac.in/nptel/Electrical%20Engineering/Power%20System%20Operation%20and%20Control/Course_home_L18a.htmlhttp://en.wikipedia.org/wiki/File:SCR.JPG


8/12

Convertor Operation5&6| 6&1 | 1&2 | 2&3 | 3&4 | 4&5 | 5&6 | 6&1 |

http://www.cdeep.iitb.ac.in/nptel/Electrical%20Engineering/Power%20System%20Operation%20and%20Control/Course_home_L18a.htmlhttp://www.cdeep.iitb.ac.in/nptel/Electrical%20Engineering/Power%20System%20Operation%20and%20Control/Course_home_L18a.html


9/12

Current and Voltage in Convertors



10/12

Effect of Firing Angle on Voltage Output

= 0 = 30 = 90 = 150



11/12

Convertor Operation



12/12

Convertor Analysis

power system engineering lecture 27

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