ABSTRACT

WELCOME

GAS INSULATED TRANSMISSION LINE Presented by ANAND KRISHNAN.M EEE-S5 ROLL NO-10

CONTENTSINTRODUCTIONEXECUTIVE SUMMARYHYBRID GILADVANTAGES AND DISADVANTAGES OF GILAPPLICATIONSCONCLUSIONREFERENCES

INTRODUCTION Gas insulated transmission lines are composed of pipes that houses conductors in highly insulating sulphur hexafluoride gas. Hence the name gas insulated transmission line (GIL). They can be used either as an over head system or as an underground system according to our needs. Most commonly, they are used as an underground system. They are mainly used in tunnels.Low operating loss is one of main features.

EXECUTIVE SUMMARY WHY GAS INSULATED TRANSMISSION LINE Gas insulated transmission lines have been using for the last 30 yearsThe gas insulated transmission line was firstly invented in 1974 in Germany. Starting in 1996 with basic studies on prototype a 2nd generation of GIL has been developed using N2/SF6 gases.The use of GIL would make it feasible to construct the large capacity transmission link.

CROSS SECTION OF GIL

How to reduce the cost of GIL ?

Standardization of components. Introduction to nitrogen. Gil uses mixture of 80% nitrogen and 20% sulphur hexafluoride, it both cost effective and environmentally acceptable.

Advantages of replacing SF6-N2 MIXTURE INSTEAD OF SF6

Less harm to the atmosphere. Reduced cost for the GIL Useful for long distance power transmission. Insulating property is improved.

SPECIFICATIONS OF GIL

Table 3.1 specifications PARAMETER SPECIFICATI0NS Rated voltage 245 to 550KV Max. operation g voltage287.5KV Lighting impulse withstand voltage 1050KV AC withstand voltage 460KV Rated current 6300A Rated short time withstand current 50KA 2 Sec Rated gas pressure 0.3MPa Min. gas pressure 0.29MPa

INSTALLATION ABOVEGROUND INSTALLATIONGIL installation aboveground is a trouble-free option, even for extreme environmental conditions. GIL are unaffected by high ambient temperatures, intensive solar radiation or severe atmospheric pollution (such as dust, sand or Moisture) . Particularly high transmission power can be achieved with aboveground installation.

Fig 5.1 above ground installation

TUNNEL INSTALLATION

Tunnels made up of prefabricated structural elements are another quick and easy method of gil installation.

With this method of installation the land above the tunnel can be fully restored to agricultural use. Only a negligible amount of heat is dissipated to the soil from the gil.

The system stays accessible for easy inspection and high transmission capacity is ensured.

HYBRID GILFor long distance power transmission lines with higher capacity and reliability we are using hybrid gil instead of GIL. It is because of over population and increased power demand. It has large capacity .the hybrid GIL has a structure between that of GIL and XLPE cables.In hybrid gil there are three sub conductors Based on our H-GIL insulation design has a required dimensions. current capacity of 6400 to 7500 a is feasible with a diameter roughly equal o that of GILS presently in use(500mm) and an allowable sub conductors temperature of 900c.if the allowable temperature can be increased to 1100c through new materials, the current capacity will increase by about 20%.

CROSS SECTION OF H-GIL

The proposed H-GIL basic structure in which conventional GIL central conductors divided into 3 sub conductors. which are each individually covered with a solid dielectric such as polyethylene, and insulated with high pressure SF6 gas. Since the internal sub conductors have small diameters, they can be made flexible.

CLASSIFICATION OF H-GIL

Sub conductor diameter Solid dielectric covering diameter Type 1 0.15d 0.3d Type 2 0.15d 0.25d Type 3 0.15d 0.2d Type 4 0.2d 0.3d Type 5 0.2d 0.25d Type 6 0.25d 0.3d

ADVANTAGES OF GAS INSULATED TRANSMISSION LINESHigh current carrying capacity compared with overhead transmission lines and XLPE cables..It needs limited working space.High efficiency.It is safe.No danger of fire.Higher current carrying capacity.Low capacitive loss. Since it is an enclosed type long distance transmission line, the chance of leakage current is less.The chance of fault occurrence is less. Good appearanceMaintenance cost is low.High power ratings.

DISADVANTAGES OF GAS INSULATED TRANSMISSION LINES SF6 Gas is harmful, Since most of the sulphur products are harmful to the atmosphereA large amount of cost.It in less flexible than cables. So it cannot be used for long distance power transmission.Difficult to install the GIL composed of large bore aluminium pipes in a gently curved long tunnel.The length of each GIL section is limited for the purpose of transportation through trucks.

APPLICATIONSWithin tunnels.Ideal for environment that are sensitive to electro-magnetic fields.If the space available is less.Suitable for metropolitan area where high energy ratings.Well suited for high power transmission.

CONCLUSIONWe can conclude that GILs are one of the best transmission systems in the world. They have been operating safely, reliably in all parts of the world for more than 20 years. In order to improve the performance of GIL we are using SF6 - N2 mixture instead of SF6 or H-GIL. Researches are going on in this topic to improve the efficiency of transmission system.

REFERENCES[1]JORGE RIEDI "Gas insulated transmission lines" IEEE POWER ENGINEERING 2012www.findarticles.comwww.cgit-westboro.com

THANKS

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LIST OF FIGURES

FIGURE NAME PAGE

NO. NO.

4.1 CROSS SECTION OF GIL

5.1 ABOVE GROUND INSTALLATION

5.2 TUNNEL INSTALLATION

5.3 VERTICAL INSTALLATION

5.4 DIRECT BURIED INSTALLATIOM

7.1 CROSSSECTION OF H-GIL

ABSTRACT

LIST OF TABLES

TABLE TITLE PAGE NO. NO.

3.1 SPECIFICATIONS

6.7 CLASSIFICATION OF HGIL

ABBREVATIONS

GIL - Gas Insulated Transmission Lines

H-GIL-Hybrid Gas Insulated Transmission Lines

N2 - Nitrogen

SF6 - Sulphur Hexafluoride

Standardization of components. A modular design for tailor made installations compromising four different elements- straight, angle, disconnect and compensator units the system.

Optimization of pipeline laying techniques. Use of automated and computerized welding equipment to maximize the length of the pipe section transported to reduce the number of joints.

Introduction to nitrogen. Gil uses mixture of 80% nitrogen and 20% sulphur hexafluoride, it both cost effective and environmentally acceptable.

SF6 Gas is harmful, Since most of the sulphur products are harmful to the atmosphere

A large amount of cost.

It in less flexible than cables. So it cannot be used for long distance power transmission.

Difficult to install the GIL composed of large bore aluminium pipes in a gently curved long tunnel.

The length of each GIL section is limited for the purpose of transportation through trucks.