HVDC LIGHT:- NEW TECHNOLOGY FOR A BETTER ENVIRONMENT By, NAGASHREE K [1DA06EE024]

CONTENTS INTRODUCTION HVDC Light Technology HVDC Light Basic Principle HVDC Light Characteristics HVDC Light Cable REASONS BEHIND A CHOICE OF HVDC DIFFERENCE B/W HVDC LIGHT AND CLASSICAL HVDC ADVANTAGES HVDC LIGHT APPLICATION CONCLUSION

INTRODUCTION HVDC Light is a unique and proven power transmission, specially designed to transmit power underground and underwater and is It is friendly to the environment. It offers numerous environmental benefits, including “invisible” power lines, neutral electromagnetic fields, oil- free cables and compact converter stations. The potential of the technology to meet special requirements in centralized low and medium power grids. Its preference over other transmission systems, AC in particular, and its application for better quality of power delivery.

HVDC Technology HVDC Light technology is well suited to meet the demands of competitive power market for transmission up to 330MW and for DC voltage in the ± 150kV range. It consists of two AC to DC converter stations and a pair of underground cables interconnecting each converter station. The AC to DC converters employs the latest in power semiconductor technology, the IGBT and is based on Voltage Source Converters which has characteristics well suited to meet the demands from the new markets.

HVDC Light Basic Principle Conventional HVDC Converter technology is Based on the use of Line commuted convertrs. The key part of the HVDC Light converter consists of An IGBT valve bridge. 1. No special converter transformers are necessary b/w the valve bridge and AC grid. 2. A small shunt AC filter is placed on the AC side of reactor. On DC side there is a DC capacitor that serves as a DC filter too

Main Circuit Diagram

HVDC Light Basic Characteristics Independent control of active and reactive power Feeding of power into passive networks ( i.e. network without any generation) Power quality control Modular compact design, factory pre-tested Short delivery times Reloadable/Leasable Unmanned operation Robust against grid alterations

HVDC Light Cable Marine Cable Terrestrial Cable

Magnetic fields are eliminated since HVDC Light® cables are laid in pairs with DC currents in opposite directions. Risk of oil spill, as in paper-oil-insulated cables, is eliminated. The cable insulation is PE based and not dangerous. The cable metals can be reused.

HVDC Light Cable development

THE REASONS BEHIND A CHOICE OF HVDC INSTEAD OF AC Lower investment cost in transmission and terminal station. Unlike AC cables, which generally have a technical limit of around 100km due to reactive power and losses, DC-cables have no technical limit to distance. An optimized HVDC transmission line has lower losses than AC lines for the same power capacity. When considering the cost of installing an HVDC Light underground transmission it is important to consider the total life cost benefits and not just the initial up front capital

Difference b/w HVDC Light and classical HVDC Power range: Classical HVDC is most cost effective in high power range, above approx some 250 MW. HVDC Light , comes in unit sizes ranging from a few tens of MW up to presently 550 MW. Independence of AC n/w: HVDC light does not rely on the AC network’s ability to keep the voltage and frequency stable. HVDC Light can feed load into a passive network. Modular: HVDC Light is based on a modular concept with a number of standardized sizes for the converter stations. Most of the equipment is installed in enclosures at the factory. Conventional HVDC is always tailor made to suit a specific application.

4. Active and reactive power control: Classic HVDC terminals can provide limited control of reactive power by means of switching of filters and shunt banks. The HVDC Light control makes it possible to create any phase angle or amplitude, which can be done almost instantly. 5. LOW POWER OPERATION AND POWER REVERSAL: The HVDC light converter can operate at very low power, The power reversal is obtained by changing the direction of the DC current and not by changing the DC voltage.

Advantages of HVDC light Reduced environmental impact, an underground cable has no visual impact on the landscape. Faster and easier issue of permits using DC underground cables. Underground cables rarely meet with public opposition and often receive political support. HVDC Light® cables have extruded polymer insulation. Their strength and flexibility make the HVDC Light® cables well suited for severe installation conditions both underground as a land cable and as a submarine cable

Cond… Shore grid strengthening:- A further possible use for HVDC Light in offshore wind farm applications The grid is sometimes rather weak (radial structure) along the coastline. An HVDC Light can then be assigned the task of strengthening the Points of Common Connections The width of the corridor to install the underground cable can be as narrow as 4 meters, which will give greater flexibility with the selection of a transmission route. As there is no need to maintain wide distances between groups of cables, DC cables can be ploughed direct in the ground or laid together in narrow trenches.

HVDC Light Applications Underground power links Connecting wind farms Powering islands and remote loads Interconnecting networks City center in feed Oil and gas offshore platforms Multiterminal HVDC Light grid

Conclusions The conclusion was that the HVDC Light fulfilled the technical requirements and that there is a great potential to further exploit the controllability of the converters. HVDC Light is the ultimate tool to enhance performance and interaction with the complex environment. The advantages include its modularity, standardized design leading to short delivery times, and compact stations and cables reducing environment impacts .

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