ARYA INSTITUTE OF ENGINEERING & TECHNOLOGY SEMINAR ON HVDC TRANSMISSION SYSTEM & TECHNOLOGY SUBMITTED TO:- Er. Bharat Bhushan jain Head Of Dept. Dept. Of Electrical Engg. GUDIED BY:- Ms. Shurti Chauhan Assistant Prof. Dept.Of Electrical Engg. SUBMITTED BY:- Virendra Chaturvedi 09EAIEE063 VIII sem, Electrical Engg.

INTRODUCTION What is HVDC? The HVDC technology is used to transmit large amount of power over long distances by overhead transmission lines or submarine cables . It is also used to interconnect separate power systems, where traditional alternating current (AC) connections can not be used.

The first dc link was set up in 1954 in between Swedish main land and the island of Gotland. The use of an HVDC link in an ac system requires converter stations at each end of the line.

LINE DIAGRAM OF HVDC SYSTEM OPERATION GENERATING STATION STEP-UP TXR STEP-DOWN TXR G.S C1 C2 CONVERTR STATION 1 CONVERTER STATION 2 SENDING END RECEIVING END

Why we need HVDC ? Now a days large blocks of power are needed to be transmitted. There arises some technical problems of transmitting power to such a long distance using ac. In the view of the draw backs of ac the HVDC transmission has come into picture.

TYPES OF DC LINKS MONOPOLAR DC LINK More economical. Earth return path; One conductor & BIPOLAR More Reliable. Two Conductors. HOMOPOLAR Two or more Conductors.

Comparison b/w HVDC & EHV-AC system CHARACTERISTICS EHV-AC SYSTEM HVDC SYSTEM 1.) Line Cost. 2.) Skin Effect. 3.) Line losses. 4.) Power Transfer. 5.) Voltage Control. Higher. Present. High. Limited. Difficult. Lower. Absent. Low. No Limit. Easier.

6.)Compensation Required. 7.) Corona & Radio Interference. CHARACTERISTICS EHV-AC SYSTEM HVDC SYSTEM 6.)Compensation Required. 7.) Corona & Radio Interference. 8.) Reliability. Series & shunt Compensation. More. Lesser. No Compensation. Less.

Simple , cheaper & limited. CHARACTERISTICS EHV-AC SYSTEM HVDC SYSTEM 9.) Short-circuit currents. 10.) Control System. 11.) Stability of AC networks. Large. Simple , cheaper & limited. Very Low. Small. Difficult , costlier & fast. Much Higher.

Technical Advantages 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.

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.

LIMITATIONS OF HVDC TRANSMISSION Costly Terminal Equipment. More Maintenance of line conductors. Difficult Voltage Transformation. HVDC Circuit Breakers are not available. Side effect due to Earth current. Block Reactive Power. Presence of Harmonic Distortion.

Comparison between the prices of AC & DC Transmission

Incorporating HVDC into AC systems Two terminal DC link point to point transmission. Back to Back DC link. DC line in Parallel with AC link. Multi-Terminal DC link.

components of an HVDC transmission system

CONVERTER STATION EQUIPMENT Thyristor valves. Converter Transformer. DC Reactor. Harmonics Filtering Equipment. Control Equipment. Reactive power compensation.

HVDC converter arrangements

Converter transformers of one pole at   Talcher, in front of the valve hall. AC harmonic filter area  at Talcher

Typical tower structure and rights of way for alternative transmission system of 2000 MW capacity

PROBLEMS The Design of grounding electrodes for low cost of installation and maintenance Location and screening of electrodes so that ground currents cause negligible electrolytic corrosion of buried and immersed metallic structures.

RECENT ADVANCES GTO’s have come into use. Use of active ac and dc filters. Advanced fully digital control systems using optical fibers.

CONCLUSION Recent studies indicate that HVDC systems are very reliable. The data collected from 31 utilities says that forced unavailability of energy due to the converter station is 1.62% The scheduled unavailability of energy is about 5.39%.

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