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Compressed Gas Insulated Transmission Bus Systems CGIT Westboro, Inc. 30 Oak St

Compressed Gas Insulated Transmission Bus Systems CGIT Westboro, Inc. 30 Oak Street Westborough, Massachusetts 01581 USA Tel. (508) 836-4000 Fax (508) 366-6115 CGIT Westboro, Inc. 1 “Compressed Gas Insulated Transmission Bus Systems” CONTENTS INTRODUCTION ____________________________________________________ 3 CGIT DESIGN FOR SF6 TRANSMISSION BUS SYSTEMS ____________________ 4 General Design __________________________________________________ 4 Design Considerations____________________________________________ 4 Description of Components________________________________________ 7 Bus Assemblies_______________________________________________ 7 Tripost Support Insulator________________________________________ 8 Conical Insulators _____________________________________________ 9 Elbows, Tees and Crosses _____________________________________ 10 Particle Traps _______________________________________________ 10 Finger Contacts______________________________________________ 10 SF6 to Air Bushings ___________________________________________ 11 Bus Supports________________________________________________ 11 APPLICATIONS OF SF6 CGIT BUS _____________________________________ 12 Introduction____________________________________________________ 12 Power Plant Optimization ________________________________________ 12 PP8 Power Station ___________________________________________ 13 Line Crossings _________________________________________________ 14 Rowville Project______________________________________________ 14 Penuelas Project_____________________________________________ 15 Underground Transmission_______________________________________ 16 Direct-Buried ________________________________________________ 16 Trenched ___________________________________________________ 16 Long Vertical Shafts_____________________________________________ 17 Balsam Meadows Hydro Electric Station __________________________ 18 Revelstoke Hydro Project ______________________________________ 20 Elevated Installations _________________________________________ 21 Teesside Power Plant _________________________________________ 21 Retrofit of Existing Installations ___________________________________ 23 Consolidated Edison Dunwoodie Station __________________________ 23 Seabrook Nuclear Power Plant Substation. ________________________ 24 Long-Term Extensions___________________________________________ 25 Claireville___________________________________________________ 25 CONCLUSION _______________________________________________ 27 CGIT Westboro, Inc. 2 “Compressed Gas Insulated Transmission Bus Systems” INTRODUCTION Company Background CGIT (Compressed Gas Insulated Transmission) Bus Systems have been in use worldwide since 1970. First developed by High Voltage Power Corporation in cooperation with the Massachusetts Institute of Technology, purchased by the Westinghouse Electric Co. in 1974 and purchased by ABB Power T&D in 1989. In 1999 AZZ incorporated purchased the product line. CGIT Westboro, Inc. remains the world leader in the supply of transmission bus for long distance gas insulated bus applications. Product Background CGIT provides a compact, reliable and economical alternative to conventional cable systems and overhead lines for power transmission. The effective electric and magnetic shielding afforded through the CGIT design allow for minimized right-of-way requirements as well as safer environmental conditions. Standard CGIT systems are suitable for voltages between 115 kV through 1200 kV with current ratings as high as 6000 Amperes. The first commercial CGIT system was installed in 1972. Since then, more than 46 miles (75km) of CGIT have been delivered and installed worldwide. Simple and inexpensive interfaces exist to almost all types of high-voltage equipment including GIS, transformers, oil paper cables, and SF6-air bushings. The CGIT system has been utilized in many unconventional applications in addition to standard transmission paths. The CGIT system can be installed in the following ways: At ground level Elevated above ground on pillars or support structures Below grade in an open or covered trench Directly buried underground Vertically in tunnels, shafts or towers Suspended from existing substation structures The CGIT system provides economic advantages for installation, operation, and maintenance. A pre-designated number of sections, each terminating in plug/socket joints, are pre-established prior to arrival to site. Type HM contact assemblies provide the high current conductor connections that continue the low loss electrical paths of the system. The lower losses within the CGIT circuits equate to lower operating costs. Once installed, maintenance of the system can be reduced to annual SF6 gas moisture and pressure checks, and mechanical assembly checks (i.e. bus exterior, supports, etc.). Since the CGIT system includes no active or switching components that may wear during use, it is never intended that the system be opened for inspection or maintenance. Further advantages of CGIT are: CGIT Westboro, Inc. 3 “Compressed Gas Insulated Transmission Bus Systems” No auxiliary pumping or cooling equipment No fire hazard The safety of dead-front, grounded, construction Long life with high reliability No radio noise interference No appreciable external magnetic fields Very low dielectric losses CGIT DESIGN FOR SF6 TRANSMISSION BUS SYSTEMS General Design The CGIT bus system is intended for 3-phase, 50 Hz or 60 Hz operation, and is made in fully assembled and factory tested straight modules of up to 18 meters (59 feet) in length. Changes in direction are accomplished with elbows, which are pre-assembled in the factory and high voltage tested prior to shipping. Each single-phase unit of the CGIT consists of a grounded aluminum enclosure tube containing a concentric tubular aluminum alloy conductor arranged in a coaxial configuration. The conductor is supported using the well-proven and reliable CGIT epoxy insulators. For added reliability particle traps are mounted at each support insulator location. Particle traps were pioneered by CGIT Westboro, Inc., and has been an integral part of the CGIT product since the first installation in 1972. Design Considerations The design of the CGIT system is based on the following criteria: Maximum System Voltage Rated Lightning impulse Withstand Voltage (BIL) Rated Switching Impulse Withstand Voltage (SIL) Power Frequency Withstand Voltage Table 1 shows the CGIT characteristics for the various voltage classes offered. The critical dielectric design parameter for compressed gas insulated transmission lines is usually the lightning impulse requirements (BIL). Another factor influencing the dimensions of the coaxial system is the ampacity rating. For a high ampacity system the current requirements determine the size of the conductor. Thus, the design of a gas insulated transmission line is an optimization of the dielectric, ampacity and material costs. CGIT Westboro, Inc. 4 “Compressed Gas Insulated Transmission Bus Systems” CGIT Westboro, Inc. 5 “Compressed Gas Insulated Transmission Bus Systems” CGIT Systems Characteristics by Voltage Class CGIT Voltage Class 145 kV 242kV 362 kV 550 kV 800 kV Rated Voltage kV 121/145/169 242/300 362 420/550 800 One Minute Power Frequency Withstand Voltage kV 215/310/365 425/460 500 680/740 960 Lightning Impulse Withstand Voltage kV 550/650/750 900/1050 1050/1300 1425/1550 2100 Switching Surge Insulation Level kV N/A 720/750 850/950 1050/1175 1425 Open Air Current Rating Amps 2500 3000 3500 4500 5000 Open Air Power Loss per Single- phase Meter at Rated Current Watts 117 150 170 232 261 Short Circuit Current kA 63 80 100 100 100 Capacitance per Single-phase Meter Pico- Farads 59.5 52.6 53.1 54.2 45.1 Surge Impedance Ohms 56 63.4 62.8 61.5 73.9 Inductance per Single-phase Meter Micro- Henrie s 0.187 0.211 0.210 0.205 0.247 Enclosure Inside Diameter mm 226.1 292.1 362.0 495.3 609.6 Conductor Outside Diameter mm 88.9 101.6 127 177.8 177.8 Nominal SF6 Gas Filling Density per Single-phase Meter kg/m3 30.76 30.76/33.0 30.76/3.0 30.76 30.76 Factory Test: 60 Hz 1 – minute withstand voltage kV 215/310/365 425/460 500 680/740 960 Field Test: 60 Hz 1 – minute withstand voltage kV 172/248/292 340/368 400 544/592 768 Table 1 CGIT System Dimensions Maximum System System dimensions and minimum clearance - inches Voltage KV A B C D E F G H J K 72.5 2.0 0.5 0.25 6.50 9.0 12 24 32 40 8.25 145/172 3.5 0.6 0.30 9.50 13.5 15 36 48 50 9.50 242/300 4.0 0.5 0.30 12.10 16.0 18 36 48 60 12.50 362 5.0 0.5 0.25 14.75 19.0 22 36 48 72 14.00 420 6.0 0.5 0.25 18.50 24.0 26 36 52 84 18.00 550 7.0 0.5 0.25 20.00 25.5 28 36 52 90 18.00 800 7.0 0.5 0.25 24.50 29.5 32 42 60 104 21.00 1200 8.0 0.5 0.38 30.00 35.0 40 48 66 122 24.00 System dimensions and minimum clearance - millimeters A B C D E F G H J K 72.5 51 12.7 6.4 165 229 305 610 813 1016 210 145/172 89 15.2 7.6 241 343 368 914 1219 1270 241 242/300 102 12.7 7.6 307 406 457 914 1219 1524 318 362 127 12.7 6.4 375 483 559 914 1219 1829 356 420 152 12.7 6.4 470 610 660 914 1321 2134 457 550 178 12.7 6.4 508 648 711 914 1321 2286 457 800 178 12.7 6.4 622 749 813 1067 1524 2642 533 1200 203 12.7 9.5 762 889 1016 1219 1676 3099 610 CGIT Westboro, Inc. 6 “Compressed Gas Insulated Transmission Bus Systems” Description of Components The CGIT Westboro Inc. bus system consists of four major elements: Conductor Enclosure Support insulators Conductor contacts A detailed description of the system and key components follows. Bus Assemblies The basic CGIT bus system consists of three parallel isolated phases of coaxial transmission line. Each phase of the transmission line consists of a grounded 6063-T6 aluminum alloy tube, which encloses a concentric tubular 6101-T64 aluminum alloy conductor. The inner conductor is supported within the outer enclosure by solid dielectric insulators. The interior of the bus is filled with SF6 to provide electrical insulation between the inner conductor and the outer enclosure. The various components of the bus assembly including straight sections, elbows, tees and crosses are factory assembled in shipping units up to 60 feet (18 meters) long. Depending upon the physical requirements of a particular installation, the bus sections may also be factory assembled to switches, breakers or other active station components. The sections are shipped filled with dry nitrogen at 5 psig (35 kPag) to keep the interior of the bus clean and dry. In the field, center conductors are joined together using plug-in contacts. The outer enclosure is either butt welded with an internal backup ring or uploads/Ingenierie_Lourd/ cgit-application-guide.pdf