1ZSC ABJ en. Gas insulated wall bushing, type GGFL Technical guide

Transcription

1 1ZSC ABJ en Gas insulated wall bushing, type GGFL Technical guide

2 Original instruction The information provided in this document is intended to be general and does not cover all possible applications. Any specific application not covered should be referred directly to ABB or its authorized representative. ABB makes no warranty or representation and assumes no liability of the accuracy of the information in this document or for the use of such information. All information in this document is subject to change without notice. This document must not be copied without our written permission, and the contents thereof must not be imparted to a third party nor be used for any unauthorized purpose. Contravention will be prosecuted.

3 Content Design...5 Shed form...7 Transportation and storage...7 Long term storage...7 General specifications...7 Testing...8 Standards...8 Routine testing...8 Type tests...8 Test tap...8 Dimensions and data...9 Electrical data...10 Dielectric losses...11 Connection details...12 Outer terminal...12 End-shields...13 Insulation gas...14 Shipping...14 Gas monitoring...15 Mechanical loading...17 Seismic tests...17 Short-time current...18 Ordering particulars...19

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5 Design The GGFL type wall bushing is an SF6 gas-insulated bushing intended for use in HVDC valve halls. It can also be used in AC applications. Having no oil and no condenser core gives a lightweight, yet rigid, design. The bushing was first introduced in Sylmar Converter station in Southern California It experienced and performed well during the 1994 Northridge earthquake. Later, seismic requirements were enhanced and the design improved even further by introducing a flexible bellow. The bellow stabilizes the conductor and is primarily used on larger bushings above 400 kv DC. The design is suitable for horizontal (wall bushing) as well as vertical mounting (roof bushing) and any intermediate angle. The bushing consists of an aluminum intermediate flange fitted with two composite insulators. The insulators consist of a glass fiber reinforced epoxy tube fitted with silicone rubber sheds for excellent electrical properties, also in rain and pollution conditions. The flanges of the insulators, which connect to the intermediate flange and to the cover of each high voltage end, are made of aluminum and are fastened with screws and nuts and provided with O-ring seals. The current is carried from the outdoor outer terminal through the cover via a firmly attached multiple contact or welded to a tubular aluminum conductor. There is a corresponding arrangement at the indoor end to carry the current to the indoor outer terminal. Terminal Outdoor corona shield Cover Silicone rubber sheds Outdoor insulator Intermediate flange Fastening plane Indoor insulator Drain holes Indoor corona shield Cover Terminal Density guards Flexible bellow Rating plate Rupture disc unit Corona shield with support, only on GGFL 400 and 420, 1ZSC AAH and -AAL M12 for grounding Fig. 1. Example no. 1 of GGFL bushing design. 1ZSC ABJ en Technical guide GGFL 5

6 Several different studs are available for the air side connections and may be selected to properly interface to the relevant current clamp. The standard color of the composite insulator is ANSI 70 light gray. The bushing, being of a non-condenser core type, does not demand a capacitive test tap. For applications where online voltage divider is requested, a capacitive test tap can be provided by introducing an isolated floating shield in the wall flange. Compared to other designs with conventional condenser cores, this design gives a bushing easy to handle due to its relatively low weight. The reduced number of different materials also gives an electrically stable solution. The main gas sealing interfaces are obtained from known and proven designs from gas-insulated substations. Outer terminal Cover Intermediate flange Gas valve Insulator Bursting disc Rating plate Fig. 2. Example no. 2 of GGFL bushing design. Fig. 3. Example no. 3 of GGFL bushing design, with measuring tap. 6 Technical guide GGFL 1ZSC ABJ en

7 Shed form The standard shed form for GGFL bushings is the anti-fog type with alternating long and short sheds. The specific creepage distance, and thus the total creepage for a given flashover distance may be tailored by altering the shed profile. This is fairly easy using the extrusion method to apply silicone sheds in a helical form. ABB GGFL bushings are usually provided with one of the standard profiles giving a creepage to flashover ratio in the range of 3.3 to 3.6. Some outdoor applications have been provided with a profile exceeding ratio R R8 30 The specific creepage distance have ranged from 23 mm/ kv DC in the Sylmar reference installation to about mm/kv DC for some of the coastal installations. In general, silicone rubber performs better than porcelain, and the need to apply silicone grease, as has been the case for many DC installations with porcelain, is not required with silicone rubber sheds. For special customer demands regarding creepage distance, other shed forms may be used Fig. 4. Example of shed form. Transportation and storage The bushing must be protected from penetrating water if stored outdoors. This means that it must not be stored in areas where it can be predicted that the ground will become wet and muddy during heavy rain. Shelter the bushing from rain and snow with a tarpaulin or roofing. The bushing is supplied with the gas volume filled with nitrogen gas (N 2 ) at a pressure of 25 kpa. This pressure should be maintained during shipping and storage. General specifications Application: Wall bushing Classification: SF 6 gas insulated bushing Ambient temperature: +60 C to -30 C, for use in valve halls or equivalent environments, other temperatures can be evaluated on request. Altitude of site: < 1000 m. Bushings for other altitudes can be provided on request. Type of insulating media: SF 6 gas at 5.7 bar absolute pressure at 20 C Markings: Conforming to IEC/IEEE The bushings are normally delivered from ABB in boxes with the bushing supported by blocks and fiber boards. The boxed are marked with Top end. This information can be important and shows how the bushing is oriented inside the box. Care must be taken when storing the bushings so that the silicone rubber sheds are not damaged. For instance, rodents, insects or birds can destroy the sheds. The largest bushings are delivered with shipping supports to secure the conductor during transport and storage. The supports must be removed, see the installation and maintenance for each GGFL type for further instructions. Long term storage Bushings for long term storage (>1 year) should be kept indoors with controlled temperature and low humidity. 1ZSC ABJ en Technical guide GGFL 7

8 Testing All manufactured parts are individually pressure tested during manufacturing. Pressure testing of each individual bushing is carried out at 900 kpa (9 bar) overpressure and tightness test is carried out at 600 kpa (6 bar) overpressure according to IEC and IEC/IEEE The bushing is protected from overpressures by a bursting disc installed on the intermediate flange or at the end cover depending on the design. Test tap The GGFL bushings provided with capacitive test taps have designs that comply with the standard ANSI/IEEE C Type A Normally grounded tap. The test tap is positioned on the intermediate flange. For bushings without measuring tap, the capacitance of the bushing may be measured between the wall flange and the high voltage end. Standards The GGFL bushing is designed and tested according to IEC 60137, IEC/IEEE , and IEEE C For applications that call for different specifications, please contact ABB. Routine testing The bushing is routine tested according to applicable standards IEC 60137, IEEE C and IEC/IEEE for DC applications. The tests include measurement of partial discharge quantity, tan δ, capacitance, dry power frequency withstand, and if applicable DC voltage withstand, polarity reversal test and insulation of test tap. Visual inspection and tightness/pressure tests of gas insulated bushings are performed and an individual routine test report is issued with each bushing. Fig. 5. Test tap. Type tests Complete type tests have been performed and reports are available on request. 8 Technical guide GGFL 1ZSC ABJ en

9 Dimensions and data The design of the GGFL type wall bushing is highly flexible, and parameters can be selected within a wide range. Tables 1 and 2 are given as examples of applications previously installed. Bushing Catalog number Dimension drawing Mass with Cantilever Total Creepage Test tap Bellow SF 6 gas (kg) test load Nx1 min length (m) distance (mm) A-side/B-side GGFL 450 1ZSC AAA 1ZSC AAA ,2 3600/3600 No No GGFL 450 1ZSC AAB 1ZSC AAB ,9 3600/3600 No No GGFL 450 1ZSC AAC 1ZSC AAC ,6 4507/3600 No No GGFL 530 1ZSC AAA 1ZSC AAA ,0 5215/5215 No No GGFL 378 1ZSC AAB 1ZSC AAB ,7 7693/5215 No No GGFL 325 1ZSC AAC 1ZSC AAC ,2 7693/3445 No No GGFL 530 1ZSC AAD 1ZSC AAD ,0 8932/5215 No No GGFL 650 1ZSC AAE 1ZSC AAE ,2 6985/5746 No No GGFL 650 1ZSC AAF 1ZSC AAF ,3 5746/5746 No No GGFL 550 1ZSC AAG 1ZSC AAG ,8 5215/5215 No No GGFL 857 1ZSC AAA 1ZSC AAA , /10348 Yes No GGFL 787 1ZSC AAB 1ZSC AAB ,0 7516/7516 Yes No GGFL 782 1ZSC AAC 1ZSC AAC , /7516 No No GGFL 1050/420/3150 1ZSC AAA 1ZSC AAA , /10650 No No GGFL 1050/420/3150 LC 1ZSC AAB 1ZSC AAB , /13250 No No GGFL 1460 LF E , /14400 Yes Yes GGFL 1300 LF L ,4 9280/5850 Yes Yes GGFL 1425 LF P , /15900 Yes Yes GGFL 1425 LF R , /15900 Yes Yes GGFL 400 1ZSC AAA 1ZSC AAA , /13500 No Yes GGFL 600 1ZSC AAA 1ZSC AAA , /17100 No Yes GGFL 800 1ZSC AAA 1ZSC AAB , /11430 No Yes Table 1. Mechanical data and dimensions. 1ZSC ABJ en Technical guide GGFL 9

10 Electrical data Typical rated order specific values for installed bushings are shown in the table below. These ratings are in many cases not the limit for each specific bushing and other combinations may be provided. Bushing Catalog number Rated voltage (kv DC/kV AC) Rated current (A DC/A AC) Lightning impulse (kv) Switching impulse Dry/ wet (kv) 2h DC (kv) Polarity reversal (kv) Dry power Capacitance frequency C/C 1 /C 2 (pf) (kv) GGFL 450 1ZSC AAA 175/ /Not tested Not Not /N.A/N.A tested tested GGFL 450 1ZSC AAB 175/ / Not tested Not Not /N.A/N.A tested tested GGFL 450 1ZSC AAC 175/ / Not tested Not Not /N.A/N.A tested tested GGFL 530 1ZSC AAA 210/ / Not /N.A/N.A tested GGFL 378 1ZSC AAB 210/ /Not tested 276 Not /N.A/N.A tested GGFL 325 1ZSC AAC 210/ /Not tested 219 Not /N.A/N.A tested GGFL 530 1ZSC AAD 210/ /Not tested /N.A/N.A GGFL 650 1ZSC AAE 210/ /Not tested /N.A/N.A GGFL 650 1ZSC AAF 210/ / (Wet) 100/N.A/N.A GGFL 550 1ZSC AAG 210/ / (Wet) 145/N.A/N.A GGFL 857 1ZSC AAA 320/ /Not tested 552 Not /80/240 tested GGFL 787 1ZSC AAB 320/ /Not tested /70/220 GGFL 782 1ZSC AAC 320/ /Not tested 450 Not /N.A/N.A tested GGFL 1ZSC AAA 320/ / Not tested /N.A/N.A 1050/420/3150 GGFL 1ZSC AAB 320/ / /N.A/N.A 1050/420/3150 LC GGFL 1460 LF E 515/ / /140/230 GGFL 1300 LF L 500/ / /155/230 GGFL 1425 LF P 515/ / /155/230 GGFL 1425 LF R 500/ / /155/390 GGFL 400 1ZSC AAA 400/ / /N.A/N.A GGFL 600 1ZSC AAA 600/ / /N.A/N.A GGFL 800 1ZSC AAA 800/ / /N.A/N.A Table 2. Electrical data. 10 Technical guide GGFL 1ZSC ABJ en

11 Dielectric losses Due to the low dielectric loss of SF 6, in theory close to zero loss for ideal pure gas, the bushing has an extremely low dissipation factor (tan δ). For DC voltages this is of less concern, but for alternating voltages the bushing displays extremely low dielectric losses. This feature of the GGFL bushing has given an application in the ABB HVDC Light projects, connecting the phase reactor to the HVDC valve. Due to the switching of bipolar transistors in HVDC Light, a large amount of harmonics at high frequency are produced. Any other types of bushing with solid or liquid insulation easily overheat in this position, due to dielectric loss. The GGFL can handle these harmonics due to both the low capacitance as well as the inherent low loss properties of the gas. 1ZSC ABJ en Technical guide GGFL 11

12 Connection details Outer terminal The outer terminal is available in any design requested. Typically, an aluminum terminal stud with stud length 140 mm and diameter 60 mm is specified for currents up to and including 2500 A. Current demands over 2500 A have a terminal switch stud length of 140 mm and diameter of 80/130mm, made of copper. The outer terminal contact force is achieved with six M10 screws. The contact area is protected by an O-ring gasket assembly. Terminal Terminal Torque 40 Nm Conical spring washer Large washer O-ring Torque 40 Nm Washer O-ring Fig. 6. Left: terminal GGFL 400, 600 and 800. Right: terminal GGFL Technical guide GGFL 1ZSC ABJ en

13 End-shields End-shields are necessary for corona-free operation at voltages exceeding approximately 200 kv DC or 170 kv AC rms phase-to-ground (300 kv system). The end shields are attached to existing screws at both ends of the bushing. For retrofitting, the bushing can be made to fit existing building and yard hardware. Bushing Dimension drawing Corona shield outdoor Corona shield indoor GGFL 450 1ZSC AAA No corona shields are needed No corona shields are needed GGFL 450 1ZSC AAB No corona shields are needed No corona shields are needed GGFL 450 1ZSC AAC No corona shields are needed No corona shields are needed GGFL 530 1ZSC AAA 1ZSC AAB 1ZSC AAB GGFL 378 1ZSC AAB 1ZSC AAB 1ZSC AAB GGFL 325 1ZSC AAC 1ZSC AAB 1ZSC AAB GGFL 530 1ZSC AAD 1ZSC AAB 1ZSC AAB GGFL 650 1ZSC AAE 1ZSC AAB 1ZSC AAB GGFL 650 1ZSC AAF 1ZSC AAB 1ZSC AAB GGFL 550 1ZSC AAG 1ZSC AAB 1ZSC AAB GGFL 857 1ZSC AAA 1ZSC AAA 1ZSC AAA GGFL 787 1ZSC AAB 1ZSC AAA 1ZSC AAA GGFL 782 1ZSC AAC 1ZSC AAA 1ZSC AAA GGFL 1050/420/3150 1ZSC AAA 1ZSC AAR 1ZSC AAR GGFL 1050/420/3150 LC 1ZSC AAB 1ZSC AAR 1ZSC AAR GGFL ZSC AAM Required, usually provided by customer. Coordinated with bus-work. GGFL ZSC AAM Required, usually provided by customer. Coordinated with bus-work. GGFL ZSC AAM Required, usually provided by customer. Coordinated with bus-work GGFL ZSC AAM Required, usually provided by customer. Coordinated with bus-work. GGFL 400 1ZSC AAA 1ZSC AAG 1ZSC AAH GGFL 600 1ZSC AAA 1ZSC AAK 1ZSC AAK GGFL 800 1ZSC AAB 1ZSC AAJ 1ZSC AAB Table 3. End shields. 1ZSC ABJ en Technical guide GGFL 13

14 Insulation gas The main insulation consists of pure compressed SF 6 gas (sulfur hexafluoride). A N 2 + SF 6 mixture is used in extremely cold climates (below -30 C). The two purposes of the compressed gas are to cool the tubular conductor and to provide insulation from ground. Its capacity for doing so depends on the density of the gas. The bushing is normally filled with gas at a pressure of 570 kpa (5.7 bar) absolute at 20 C. The filling is made through a gas connection valve on the intermediate flange. This valve can be connected through tubing to ground level to enable emergency topping up during service. The pressure gauge, if used, is intended to give a locally visible check of the internal pressure of the bushing, roughly indicating whether the bushing has the correct gas density or not. The SF 6 gas density monitor may be set to give signals at a number of different levels, either for warning or to trip at low gas density. The quality of the SF 6 gas should comply with standards IEC and 60796b Specifications and acceptance of new sulfur hexafluoride. Gas and gas handling equipment are not included in the delivery from ABB. We refer to suppliers like Dilo and Svenska Transforfilter AB (Malmqvist) for purchase of gas handling equipment and gas. Shipping The bushing is shipped at a slight overpressure of 0.25 bar, with nitrogen gas. After installation and prior to operation a vacuum must be drawn so that air and humidity are removed and after that SF 6 gas is added to the operating pressure (570 kpa abs. at 20 C). 14 Technical guide GGFL 1ZSC ABJ en

15 Gas monitoring Since the late 1990 s, each gas insulated bushing for HVDC projects has been supplied with two independent threestage density switches. The devices are sometimes called density monitors, pressure monitors etc., but should more correctly be labeled density switches. The function is to activate one of three independent switching contacts, each one for a different density level of the insulating gas. The first is activated at a pressure of 530 kpa (5.3 bar) abs. at 20 C to indicate low gas density. The second signal level is activated at 520 kpa (5.2 bar) abs. at 20 C to indicate very low gas density. The third level gives an alarm at 500 kpa (5 bar) abs. at 20 C, which is the dimensioning density of the bushing. At gas densities below 500 kpa the type test levels for dielectric strength do not apply. The ability of the bushing to conduct current declines progressively with falling gas density. Fig. 7. Density guard. The devices only activate the internal switches, and it is up to the user to connect and interpret the position of the switches in their alarm and monitoring system. Furthermore, alarm settings, trip settings etc. are often requested, but the devices themselves do not differentiate between alarms and trips, it is up to the user to decode, and perhaps at the third level, corresponding to the lowest density-pressure setting, the user may wish to trip or block the energized equipment for investigation. Once again, sometimes the three levels are referred to as alarm level 1 and alarm level 2 and the third level considered a trip level. Switch number D3 D2 D1 P/T = nominal Ground Terminal block number Fig. 8. Circuit diagram example. 1ZSC ABJ en Technical guide GGFL 15

16 It is important to remember that each of the three contacts is merely switching at each respective level, and whether each step is regarded as alarm or trip is defined by the user and should be adapted by the owner to the local procedures at each station. The units do not provide an active signal, and referring to items such as alarm or trip signals from the density monitor may lead to erroneous conclusions. The user is to connect a voltage control signal to a connection block for each switching step. The interpretation of the switch position is then made by checking which of the contacts is carrying the voltage, indicating if the gas density is above or below the pre-set level of engagement for switch action. The recommendation from ABB is to not operate the bushings at levels below the third stage, since the bushings are type and routine tested with a level three condition of the insulating gas. This implies the insulating characteristics of the bushings are guaranteed down to the lowest level of the density switch. The third stage may thus in practice be regarded as a trip level but this is decided and programmed into the user's alarm system. When dealing with gas insulation it is preferred to deal with the concept of density. The insulating properties of SF6 are dependent on the density, the number of molecules in the enclosed space, and not directly the pressure, which could be compared to how active the molecules are. This is the background to the devices being labeled as density switches, but for simplicity the pressure of the gas at a temperature of 20 C is commonly used. This can be seen in the descriptions below where a pressure level is related to a temperature. If dealing with density only, the temperature reference could be removed. Thus, the nominal filling condition the density giving a pressure of 570 kpa absolute at 20 C is the correct interpretation. The same density gives a higher pressure at higher temperatures, and a lower at lower temperatures. All references to pressure in the following description are referred to at 20 C. 16 Technical guide GGFL 1ZSC ABJ en

17 Mechanical loading The cantilever operational and test loads are given in the table below. The force is applied at the center of the outer terminal of the bushing. For extraordinary requirements which include earthquakes, extreme environmental conditions and heavy equipment, consult the supplier. The tests are performed in accordance with IEC and IEEE C Seismic tests The GGFL1300 designed for severe seismic requirements for southern California has been verified by a full-scale shake table test. This test is used as a reference for similar bushings. Bushing Dimension drawing Max. cantilever operating load Max. cantilever test load GGFL 450 1ZSC AAA GGFL 450 1ZSC AAB GGFL 450 1ZSC AAC GGFL 530 1ZSC AAA GGFL 378 1ZSC AAB GGFL 325 1ZSC AAC GGFL 530 1ZSC AAD GGFL 650 1ZSC AAE GGFL 650 1ZSC AAF GGFL 550 1ZSC AAG GGFL 857 1ZSC AAA GGFL 787 1ZSC AAB GGFL 782 1ZSC AAC GGFL 1050/420/3150 1ZSC AAA GGFL 1050/420/3150 LC 1ZSC AAB GGFL GGFL GGFL GGFL GGFL 400 1ZSC AAA GGFL 600 1ZSC AAA GGFL 800 1ZSC AAB Table 4. Mechanical loading. 1ZSC ABJ en Technical guide GGFL 17

18 Short-time current The rated thermal short-time current (Ith) is calculated according to IEC The rated dynamic current (Id) is 2.5 times the 1 second short-time current. Bushing Catalog number Rated current Short-time current I th ka, rms, 1s Dynamic current Id ka, peak GGFL 450 1ZSC AAA GGFL 450 1ZSC AAB GGFL 450 1ZSC AAC GGFL 530 1ZSC AAA GGFL 378 1ZSC AAB GGFL 325 1ZSC AAC GGFL 530 1ZSC AAD GGFL 650 1ZSC AAE GGFL 650 1ZSC AAF GGFL 550 1ZSC AAG GGFL 857 1ZSC AAA GGFL 787 1ZSC AAB GGFL 782 1ZSC AAC GGFL 1050/420/3150 1ZSC AAA GGFL 1050/420/3150 LC 1ZSC AAB GGFL GGFL GGFL GGFL GGFL 400 1ZSC AAA GGFL 600 1ZSC AAA GGFL 800 1ZSC AAB Table 5. Short-time current. 18 Technical guide GGFL 1ZSC ABJ en

19 Ordering particulars When ordering, please state: Type and catalog number for bushing. Catalog number for outer terminal. Additional accessories or modifications. Test required, in addition to the normal routine tests. Ordering example: Bushing: GGFL1050/420/3150 1ZSC AAA Outer terminal: Cu/Ag, D = 80 mm 1ZSC AAC 1ZSC ABJ en Technical guide GGFL 19

20 Contact us ABB AB Components SE Ludvika, Sweden Phone: Fax: Copyright 2015 ABB., All rights reserved. 1ZSC ABJ en,