Installation Manual Bushings, IEEE/ANSI Standard

Installation Manual Bushings, IEEE/ANSI Standard Type COTA 150.2050 for Transformers Type COBA for OCB Bushing Replacement E 8322.72 2007

Contents Page 1. Introduction 3 2. Scope 3 3. Construction 3-5 4. Nameplate 5 5. Application 6-9 6. Packaging and Transportation 9 7. Receiving and Initial Inspection 9 8. Cleaning 10 9. Installation 10-17 10. Commissioning 17-18 11. Maintenance 18-19 12. Storage 19 13. After Sales Service 19 14. Draw Lead Adapters 19-20 15. Technical Ordering Data 20-22 Notes 23 2

1. Introduction This manual is protected by copyright. Imparting to any third party and reproduction of any kind without written permission from Trench is strictly prohibited. Trench is not responsible for any damage or failure that would result from improper operation, customer furnished materials or failure to observe the recommendations contained in this manual. This applies even if there is no specific instruction included for the erection or operation of the particular bushing. All information contained in this manual is subject to change without notice and does not represent a commitment on the part of Trench. Based on Trench's experience and industry standard practices the highest level of reliability is achieved when the recommendations regarding handling, operation and maintenance, as outlined in this manual, are followed. 2. Scope The material that is provided in this manual does not cover all possible conditions; any specific questions regarding this manual should be directed to Trench or its authorized service representative. Trench assumes no liability or responsibility for any damage or failure that would result from improper handling, application, installation or use of this product. This manual covers all Trench bushings, Type COTA, that are designed for draw lead or fixed conductor application mounted vertically or horizontally based on the specific capability of the bushing applied on liquid filled transformers and reactors. This manual also covers all Trench bushings, Type COBA, which are designed specifically for replacement of bushings for oil circuit breakers. 3. Construction 3.1 Function The COTA condenser bushings are constructed for transformer applications and meet or exceed all applicable dimensional, electrical and mechanical requirements of the IEEE/ANSI Standard C57.19.00-1995 and IEEE/ANSI Standard C57.19.01 2000. The COBA condenser bushings are constructed for oil circuit breaker (OCB) applications and meet or exceed all applicable dimensional, electrical and mechanical requirements of the IEEE/ANSI Standard C57.19.00-1995 and IEEE/ANSI Standard C57.19.01 2000, Annex A. For typical construction details see cut view section figures 1.1, 1.2 and 1.3. 3.2 Active Part (Condenser) The active part of the bushing is made of an oilimpregnated insulating paper with layers of aluminum foil positioned to ensure radial and axial homogeneity of the electric field. The paper and foil are wound around either a central aluminum tube or a copper conductor. 3.3 Housing The housing is made of a cast aluminum head, outdoor insulator, mounting flange, ground sleeve (COTA 250 and above), epoxy insulator (Fig. 1.1 & 1.3), or fiberglass insulator (Fig.1.2) all held together by the central aluminum tube or the copper conductor. Pretensioned cone spring washers provide mechanical stability over the entire temperature range, ensuring a leak free bushing. The sealing between all joints is accomplished with 0 - Ring gaskets. Each bushing is hermetically sealed and equipped with its own independent oil system, separate from the transformer s oil. 3.4 Head The cast aluminum head serves as an oil expansion tank and is designed as a high voltage electrode. The design of the head allows for horizontal storage, shipping and inclination in service up to 40 from vertical. The oil level can be monitored over the entire temperature range using the oil level indicator in the head. When the design of the head is rectangular this bushing will allow vertical or horizontal mounting without modifying or de-rating the bushing. The oil level indicator on this head will only indicate that the bushing has an adequate level of oil. 3

Fig. 1.1 Typical Design COTA 250 - COTA 1175 Draw Lead Top terminal Draw lead stud Oil level indicator Head housing Insulator Active part Name plate Voltage Tap (COTA 550 and above) Air escape plug (COTA 1050 and above) Mounting flange Grounding sleeve Test tap (COTA 350 and below) Epoxy insulator Fig. 1.2 Typical Design COTA 150 & COTA 200 Fixed Conductor Top terminal Oil level indicator Head housing Insulator Active part Test tap Mounting flange FRP tube Conductor Bottom terminal Fig. 1.3 Typical Design COTA 250 - COTA 1675 Fixed Conductor Top terminal Oil level indicator Head housing Insulator Active part Name plate Voltage Tap (COTA 550 and above) Air escape plug (COTA 1050 and above) Mounting flange Grounding sleeve Test tap (COTA 350 and below) Epoxy insulator Bottom Terminal 4

3.5 Mounting Flange The cast aluminum mounting flange on COTA and COBA 550 and above has two lifting lugs and a voltage tap. COTA 150 350 are equipped with a test tap. On COTA and COBA 250 and above, the porcelain insulator is secured to the mounting flange using special cement and an 0-Ring gasket. 3.6 Inboard End Insulator The inboard end insulator of the COTA 150, 200 and some models of the COTA 250 and 350 are an explosion resistant, void free, fiberglass tube. 4. Nameplate Each COTA and COBA bushing is supplied with a nameplate incorporating the information required by IEEE/ANSI C57.19.00. In addition to these minimum requirements, Trench nameplates include the voltage class and the weight. The weight shown will be pounds. The ANSI L dimension shown on the nameplate will be with and without the removable or Split-Conductor. For the layout of the nameplate information see figure 2. Fig. 2 The inboard end insulator of the COTA and COBA 250 and above are protected by a cone shaped, shatter resistant, vacuum molded, epoxy-resin insulator. The epoxy-resin insulator is designed to be installed during the in-tank drying process of the active part of the transformer and can withstand temperatures up to 130º C. A special aluminum electrode is embedded into the end of the epoxy-resin insulator to control the electrical field strength in this area of the bushing. 3.7 Outdoor Insulator The standard outdoor insulator for COTA and COBA bushings is porcelain. The porcelain is manufactured by the wet process, is homogeneous and free from laminations, cavities or other flaws affecting its mechanical strength or dielectric quality. One-piece porcelain is standard on all COTA and COBA bushings through 900 kv BIL. 1050 kv BIL and above can be provided with one-piece porcelain upon request. No porcelain will be provided with gasket joints between pieces of porcelain. All COTA bushings can be provided with a non-ceramic insulator. These insulators consist of an explosion resistant fiberglass tube with silicone rubber sheds molded over the tube. CAUTION: Special care must be taken when handling COTA bushings with Silicone Rubber Insulators (SRI). Slings must not be placed between the sheds and lifting must follow recommendations in Section 9. 4.1 Key to Nameplate: 1. Technical Ordering Number without accessories, see Annex for details. 2. Voltage Class 3. Maximum Current Rating. (For draw lead bushings this rating is based on the rating of the Split-Conductor ) 4. Maximum Line to Ground Voltage 5. Outline Drawing Number (As originally sold) 6. Lightning Impulse and Dry Test Voltage 7. Inboard end length 8. Percent Maximum Power Factor 9. Capacitance between Test Tap and Conductor (150 350) Capacitance between Voltage Tap and Conductor (550 2150) 10. Capacitance between Voltage Tap and flange (not available on 150 350) 11. Approximate weight including Split-Conductor in pounds. 12. Year of Manufacture 13. Serial Number (Includes accessory codes as originally sold) 5

5. Application 5.1 Bushing Mounting 5.1.1 Bushing for Vertical Mounting Trench COTA bushings that are designed for vertical mounting is very simple to apply. The only consideration is the inclination of mounting from vertical and orientation of the oil level indicator. All COTA and COBA bushings designed for vertical mounting may be inclined up to 40 from vertical. When inclined, the oil level indicator must be orientated facing out, allowing easy viewing of the oil level from the ground. Mounting at inclinations greater than 40 from vertical may be allowed only after consultation with Trench. In most cases of allowed mounting greater than 40 from vertical the oil level indicator will be required to face the ground. In this position the oil level indicator will not provide true oil level indication. Trench will provide special instructions for reading the oil level of the bushing when inclined greater than 40 from vertical. 5.1.2 Bushing for Vertical or Horizontal Mounting Trench COTA bushings that are designed for vertical and horizontal mounting, are very simple to apply. The only items that need to be considered are the location of oil level indication and the orientation of the head. The oil level indicator on these bushings is only an indication of the amount of oil in the bushing, not the actual oil level. The oil level indicator has a red floater behind the glass. In normal operation the red floater will be at the top of indicator, indicating sufficient oil is in the bushing. If the floater is at the bottom of the indicator this indicates a low oil volume. It is important to consider the location of the oil level indicator when applying these bushings on new or re-manufactured transformers. For proper location of the oil level indicator for vertical or horizontal application see figure 3, A and B. It is sometimes desirable to incline vertically mounted bushings. For these applications the following guidelines are offered to maintain proper oil level indication: With the oil level indicator facing down the maximum angle of inclination from vertical is 12º. With the oil level indicator at its highest point (bushing turned 90º) the maximum angle of inclination from vertical is 18º. The heads of these bushings are rectangle and the orientation of the bushing can affect the phase to phase spacing in air. Consideration of this fact must be taken into account when applying these bushings. Contact Trench if you have any questions on the application of these bushings designed for vertical or horizontal mounting. Fig. 3 Proper location of Oil Level Indicator 6

5.2 Current Path Options A key item to consider when applying bushings is the current path options. Trench COTA bushings offer two current path options, draw lead or fixed conductor. 5.2.1 Draw lead 5.2.1.1 Draw lead cable(s) application Current path via the transformer s copper cable(s) to a silver-plated copper cable terminal through multi spring contacts to the copper alloy top terminal. For selection of the appropriate draw lead cable terminal refer to section 5 or contact Trench. Oil Water Particles Oil Strength Oil Condition Mineral <15 PPM Max. 39,630 per gallon Size 59 to 2362 µ inch >70 kv per 0.1 inch The following figure provides recommendations for applying the insulated draw lead conductor to the Trench COTA bushings. Fig. 4.2 When the draw lead cable option is selected, the embedded aluminum end shield allows simple, space saving assembly without additional shields and barriers. For reference, the following table provides typical distances from the centerline of the bushing to the nearest grounded part. Fig. 4.1 5.2.1.2 Draw Lead Cable Loading The following guidelines are offered for selecting and applying flexible, copper draw lead conductor with more than 200 strands with a strand diameter less than.03 inch and the cable insulated with 5 mils of index 105 insulation. R Minimum COTA (mm) (inch) 150 65 2.56 200 75 2.95 250 85 3.35 350 120 4.72 550 145 5.71 650 180 7.09 750 225 8.86 900 270 10.63 1175 300 11.81 The above table is based on the following transformer or reactor oil condition. COTA BIL Rating 150 and 200 250 and 350 550 to 750 900 to 1175 Cross Section mm Max. Load Amps A/mm 70 215 3.10 95 265 3.07 150 385 2.57 285 640 2.25 350 750 2.14 70 200 2.86 95 250 2.63 150 360 2.40 285 600 2.11 350 700 2.00 70 190 2.71 95 235 2.47 150 340 2.27 285 540 1.89 490 815 1.66 95 180 1.89 150 265 1.77 285 430 1.56 450 600 1.33 665 800 1.20 7

The values on the previous page are based on a maximum ambient temperature of 40 C, an average 24 hour ambient of 30 C at a frequency of 60 Hz and a maximum rise of the transformer oil of 65 C. Contact your local Trench representative with any questions regarding the above recommendations. 5.2.1.3 Split-conductor Application Current path via Trench s copper Split-Conductor draw lead conductor through multi spring contacts to the copper alloy top terminal. Application of Split-Conductor bushings, COTA 150 through 350, through 2,000 A, for new or re-manufactured transformers require some special consideration at the time the transformer is designed. The split of the Split-Conductor is located 1/2 (12.5 mm) below the gasket surface of the bushing mounting flange. The inside diameter of the mounting flange does not allow enough space to assemble or disassemble the Split-Conductor. For this reason the transformer design must allow the Split-Conductor to be lifted vertically 6 (150 mm). This additional vertical lift capability is not required when these bushings are applied as replacement bushings on existing transformers. When the 3,000 amp Split-Conductor is applied the weight of the conductor as well as the winding leads may make it difficult to allow vertical lift of the conductor. For this reason the location of the split may need to be changed from the location indicated above. Please consult Trench on your specific requirement. It is recommended that when selecting a Split- Conductor application for new or re-manufactured transformers that the Trench holding tool be supplied with the transformer. It will make installation easier and safer for the transformer. Tool Type Part No. 150...350 up to 1,5000 A 804-0001 150...200, 3,000 A 804-0002 250...350, 2,000 A 804-0005 550...750 up to 1,400 A 804-0002 900...1175 up to 1,600 A 804-0004 1300 up to 1,600 A 804-0006 The only other consideration is the design of the mounting flange shipping cover. (All COTA Split- Conductor bushings) The shipping cover will require a supporting bar welded to the center underside of the shipping cover. This supporting bar must have matching threaded holes to allow the inboard section of the Split-Conductor to be secured during transport of the transformer. In addition, some provisions should be considered to lift the shipping cover when the bushing is installed. Split-Conductors when attached to the winding leads can be very heavy. For specific shipping cover design requirements and detailed drawings of the required Split-Conductor contact Trench. When the "Split-Conductor" option is selected additional shields or barriers may be required depending on the applied voltage and/or mounting conditions, see figure 5.1-5.4. 5.2.2 Fixed conductor application Current path via a fixed copper conductor. When the fixed conductor option is selected additional shields or barriers may be required depending on the applied voltage and/or mounting conditions. 5.2.2.1 Terminals and Shields The following figures 5.1-5.4 show some of the many different terminals and shields that are available from Trench for COTA bushings. Fig. 5.1 Two Hole Spade Fig. 5.2 Four Hole Spade 8

Fig. 5.3 Thread Stud 7. Receiving and Initial Inspection As a general rule, every bushing should be unpacked in a dry place (shop). Once unpacked, the bushing should be kept in a dry room and protected from atmospheric influence. Fig. 5.4 Typical Shield & Terminal Before unloading, complete a visual inspection of the crate and note any apparent damage on the bill of lading. After unloading, open the top of the crate, being careful not to damage the porcelain and other bushing parts, and thoroughly inspect each bushing. The following areas should be closely examined: Visual inspection of insulator for chips cracks or other visible damage. Check for extensive oil traces. Small traces of oil on the inboard end are insignificant; they occur during factory tests prior to shipping or after factory testing of the transformer. For additional application information on Trench COTA bushings, contact the nearest Trench factory. 6. Packaging and Transportation Standard shipping crates, from the factory, contain 1, 3 or 4 bushings. CAUTION: When the bushing is placed in the crate the oil level indicator must be facing down and remain in this position whenever the bushing is in a horizontal position. Factory shipping crates are marked with arrows indicating the correct orientation requirement. Each bushing designed for vertical mounting has a special decal on the head as a reminder. Should there be any signs of damage, evidence of rough handling in transit and/or parts shortage, contact the carrier at once. Also notify Trench or its authorized representative. For more information about unloading the bushings, see section 9.1. Unpacking and handling. We recommend not to damage or destroy the original shipping crate(s). They may be re-used for the same purpose when the transformer is delivered to its final destination. If it is desired to perform electrical tests on the bushing before it is installed in the transformer refer to section 10, Commissioning for instructions. PRECAUTION: The bushing must not be tested while still in the shipping crate and the bushing must be in a vertical position away from other structures. Failure to follow these precautions may result in inaccurate reading and test results. 9

8. Cleaning Before mounting the bushing it should be thoroughly cleaned. 8.1 Cleaning medium and accessories The following cleaning medium may be used for wiping oil remaining on the surface of the bushing: Industrial or similar solvents Necessary accessories: Dust and lint-free rags A dust free brush or large paint brush Washing bottle Length of insulated wire or cotton cord Compressed dry air Silk Paper 8.2 Cleaning Procedure The following areas of the bushing must receive a thorough cleaning: The outdoor insulator The inboard insulator and metal ground sleeve if so equipped The interior of the central tube of draw lead bushings The bottom terminal connection surface The inside area of the voltage tap or test tap The gasket surface of the mounting flange The gasket surface of the bolted top terminal on draw lead bushings The oil level indicator sight glass The insulator and metallic parts are to be wiped with the specified rags with the indicated cleanser. Grooves, corners and drillings or any other cavities are to be rinsed with the washing bottle or the recommended brush or paint brush. Remaining residues, possible lint or hairs should be wiped off by a final cleaning. The insulator and the metallic parts should be eventually wiped with a clean silk-paper. A rag soaked with the available cleaning medium should be attached to one end of the wire or cord and the other end drawn through the central tube of the bushing (draw lead bushings only). Pull the rag, one direction only, through the tube several times. The last 10 two passes should be made with dry clean rags. When a compressed air-bottle is available, all grooves, comers, drillings and other cavities should be blown off thoroughly. A visual control should make sure that all residues of oil, cleanser and cleaning accessories have been removed. Including the central tube of draw lead bushings. 9. Installation 9.1 Unpacking and handling Before lifting the bushing out of the shipping crate, remove all supports from above and remove the bolts connecting the mounting flange to the crate. A crane and two textile slings are required for lifting the bushing out of the shipping crate. The following procedure must be followed while lifting the bushing (see figure 6.1): CAUTION: The bushing shall not be subjected to radial rotation in the crate or after removal. The oil level indicator shall always be facing downward. The bushing should be suspended with its head up. The maximum permissible inclination with the head downward is 15º as shown in figure 6.1. Draw Lead bushings may require that the Split- Conductor be installed prior to being installed into the transformer. In this case the bushing should be positioned horizontally outside of the crate, with the oil level indicator facing downward, as shown in figure 6.1. The maximum rotation tolerance is +30º, as shown in Detail A. No additional radial rotation is permitted. The Split-Conductor must be reassembled prior to being installed into the bushing. Once assembled carefully insert the Split-Conductor into the bushing from the bottom following the instruction detailed later in this section. To place the bushing in the vertical position: For COTA 150 and COTA 350 bushings, which are not heavy, this is possible with only one sling. Attach the sling under the uppermost shed around the insulator. As you lift the bushing, hold the lower end with one hand so that the bushing does not touch the ground while it is moving to the vertical position. For putting COTA 550 and above bushings to the vertical position, one crane and one hoist is necessary because the bushings are very heavy.

Fig. 6.1 The basic procedure with crane and hoist is as follows (see figure 6.2): Attach one end of each sling to each of the two lifting lugs on the mounting flange. Attach the free ends to the bottom of the hoist. Attach the hoist to the crane hook. Adjust the hoist to ensure that the crane's boom will be long enough to let down the bushing to the vertical position. Attach two guide slings around the outdoor insulator between the head and the uppermost shed. Attach two more long slings to the crane hook. Draw the free ends of the slings through the guide slings and then attach them to the lifting lugs on the mounting flange using shackles. Adjust the suspension equipment to ensure that the bushing will remain in the horizontal position with the oil level indicator facing downward during lifting. If the bushing is inclined during lifting, the head must be in the highest position. Lift the bushing high enough to ensure that it will not touch the ground when it is moving to the vertical position. Actuate the hoist until the bushing is positioned vertically. Check the oil level as described in section 11.1 "checking the oil level". If the bushing is to be installed vertically (no inclination), no further adjustments are necessary. It can be moved to the transformer for installation. If the bushing is to be installed at an inclination ( 40º), the following considerations must be done. If the oil level indication over the entire operating temperature range is desired, the oil level indicator must face to the side. Other installation positions with the oil level indicator facing down are acceptable under certain conditions. Such installations may allow only minimum oil level monitoring. Installation positions in which the oil level indicator faces up are never permitted. To install the bushing at an inclination ( 40º) with the oil level indicator facing to the side, the following procedures must be followed (see figure 6.3): 11

Fig. 6.2 For bushings COTA 150 through COTA 350, the inclination can be adjusted by hand because the bushings are not heavy. It is not necessary to change the slings after lifting. For bushings COTA 550 and above the following points must be followed: Position the bushing vertically in a frame or in a cavity with its mounting flange resting on a soft surface. Remove the shackle connection, which were positioned downward if the bushing is inclined. Remove both slings connecting the bushing to the hoist. A single sling through both lifting lugs and around the body of the mounting flange will be used to attach the bushing to the hoist. Now lift the bushing carefully. Set the desired inclination by adjusting the hoist. The bushing can now be moved to the transformer for installation. Bushings designed for horizontal mounting require the following installation procedures. Bushing must be in a vertical position for a minimum 4 hours then gradually tilted to the horizontal position before mounting in the transformer. Care should be taken with the sight glass location. There are two considerations to be made when positioning horizontally mounted bushings on the transformer. First is to maintain the functionality of the oil level indicator. Second is the ability to visually see the oil level indicator from the ground. Take these considerations into account before applying slings. When these bushings are mounted horizontally on the transformer sidewall the oil level indicator should be positioned so that the indicator is located at the highest point on the side of the bushing head. 12

Fig. 6.3 When these bushings are mounting vertically on the transformer cover the oil level indicator should be orientated so that the indicator can be viewed from the ground. Attach the sling between the two lowest sheds of the outdoor insulator. As you lift the bushing, hold the inboard end with one hand to balance the bushing. Now install the bushing into the transformer. Be careful not to drag or bang the inboard end on the mounting flange while it is moved into the transformer sidewall. 9.2 Bolting to the transformer The following instructions are only valid when the gasket between the bushing and the transformermounting flange is a 0-Ring. For flat gaskets, the instructions are valid if the mounting flange is equipped with a mechanical gasket stop. For all other arrangements, the torque requirement depends on the type of gasket system used. Trench takes no responsibility for damage caused by over torque in other arrangements. The transformer and bushing mounting flange should be clean and free of foreign material with the gasket in place before the bushing is set. After the bushing has been set in place on the mounting flange install all the washers and bolts until finger tight. Then tighten the bolts a fraction of a turn at a time, working progressively in a crisscross (star) pattern until all bolts are uniformly tight. Typical Torque Values Bolt Size Foot pounds Newton meters 1/2 13 threads 35 47 5/8 11 threads 65 88 3/4 10 threads 100 135 1 8 threads 260 352 1 1/8 8 threads 260 352 Trench recommends washers when bolting the bushing to the transformer. 13

9.3 External electrical connections External connections to the bushing must be sufficiently slack or flexible to avoid putting a mechanical strain on the bushing parts. Terminal connectors should be of ample size to minimize bushing overheating during possible overloads. Ridged buss connection to bushings is not recommended in areas of seismic concern and because of transformer tank flexing during vacuum filling operations. 9.4 Connection to transformer 9.4.1 Top terminal assembly The typical top end of a COTA draw lead bushing is shown in figure 7. If the bushing is applied with draw lead cable(s) or a Split-Conductor the top terminal has to be removed. If the bushing is equipped with a Split- Conductor and is replacing a bottom connected bushing there is no need to remove the top terminal. To remove the top terminal the procedure is as follows: Remove the four fixing screws. The terminal can be pulled off axially using a force of approximately 44 lb. (200 N). The bolts, cone spring washers and the 0-Ring gasket must be stored in a safe place. If lifting off the top terminal is difficult, use two of the bolts removed and thread them into the two threaded holes as shown in figure 7. By tightening the bolts into these holes the top terminal will become lose and further removal by hand will be possible. Fig. 7 CAUTION: Do not attempt to rotate the top terminal. The top terminal itself is not threaded to the draw lead cable terminal or the top of the Split-Conductor. For the procedure to reassemble the top terminal after draw lead cable or Split-Conductor installation, see sections 9.4.2. 9.4.2 Draw lead cable connection COTA draw lead bushings are designed with a hollow tube through which the flexible draw lead cable(s) can be pulled. The cable is considered a component of the transformer and is not supplied as part of the bushing. For new transformers there are two ways to connect a draw lead cable terminal to the transformer cable, crimping or brazing. Trench makes no endorsement on which method used. It is entirely up to the transformer manufacturer and their customer. However, brazing the cable to the terminal requires special care to avoid effecting the silver-plating that provides the high current interface between the draw lead cable terminal and the multiple spring contacts in the bolted top terminal. CAUTION: When brazing, the temperature at the current interface should not exceed 650º C. The selection of the draw lead cable terminal for the specific connection method and size cable is covered by the technical ordering data in section 5. CAUTION: Once the draw lead cable terminal has been attached and before it is installed in the bushing it must be protected from damage to the contact surface. If it becomes damaged it will have to be replaced After mounting the bushing on the transformer, secure the draw lead cable terminal with the retaining pin and locking device. The retaining pin must pass through the corresponding hole in the central tube of the bushing. Install the 0-Ring and place the top terminal over the draw lead cable terminal. Fasten the top terminal to the head with the four screws and cone spring washers provided (torque = 15 ft. lb. /20 Nm). 14

When the bushing is installed on the transformer, the optional (Standard on COTA 1050 and above) air escaping screw (7.4 ft. lb./10 Nm) located on the top terminal can be used for the air release while oil filling the transformer. This option is recommended when bushings are installed on transformers with conservator type oil preservation systems. 9.4.3 Split-Conductor connection When the applied current exceeds the rating of draw lead cable(s), the COTA bushing can be supplied with Trench's "Split-Conductor". The Split-Conductor is an accessory supplied by Trench as part of the bushing. The Split-Conductor can be removed from the bushing for connection to the transformer winding lead or installed in the bushing and connected to the winding leads after the bushing has been installed in the transformer If the Split-Conductor has been shipped separately from the bushing and the bushing is to be installed with the Split-Conductor in place the following must be done: Installing the Split-Conductor is done with the bushing in a horizontal position with the oil level indicator facing down. First remove the top terminal. Carefully slide the top of the Split-Conductor into the bottom of the bushing until the upper end extends beyond the central tube. Care should be taken not to scratch the Split- Conductor or the central tube of the bushing during installation. Next install the retaining pin with locking device and re-install the top terminal. The locking pin rests on the top of the central tube, not through the hole used for draw lead. This allows the Split-Conductor to rotate for easy alignment inside the transformer. Then install the bushing in the transformer and make the connection to the bottom of the bushings in the same manner as a COTA bushing with a fixed conductor. The other method is to separate the Split-Conductor at the joint, take the lower end with the bottom terminal and make the connection to the transformer active part winding lead. Then re-connect the upper part of the Split-Conductor as shown in figure 7.0 when ready to install the bushing. Use only the screws and washers provided with the Split-Conductor. CAUTION: Once the lower end of the Split- Conductor has been attached to the winding lead and before it is installed in the bushing the split joint must be protected from damage to the contact surface. If it becomes damaged it will have to be replaced. 9.5 Split-Conductor installation The Split-Conductor joint is designed to be located 1/2 (12.5 mm) below the gasket surface of the bushing mounting flange. (For 3,000 amp Split- Conductors the split may have a different location. Refer to the outline drawing of the bushing to confirm location.) Because of the limited space of the mounting flange inside diameter on bushings through 69 kv it is necessary to lift this joint above the gasket surface of the mounting flange and hold the conductor in this position during assembly of the Split-Conductor. Trench has designed a tool for holding the conductor in place. If not available a hardened steel rod, 1/4 (6 mm) in diameter, 12 (300 mm) long can be used. If a rod is used, extra care must be taken to avoid dropping any hardware into the transformer tank. Installation steps: Prepare the bushing for installation by removing the top terminal and retaining pin with locking device, then place a cord or wire through the central tube of the bushing. Locate the upper part of the Split-Conductor, which should be located in the crate with the bushing or it may have been installed in the bushing during transport. At the top end of the upper part of the Split-Conductor you will find a 5/16-18 UNC tapped hole. Install an eye bolt into the hole for attachment of the cord or wire from the bushing. CAUTION: Care must be taken to protect the contact surfaces at both ends of upper part of the Split-Conductor. If it becomes damaged it will have to be replaced Remove the hardware from the bushing flange shipping cover and lift the cover 6 (150 mm). The lower end of the Split-Conductor will be attached to the underside of the shipping cover. The lower end of the Split-Conductor will weigh between 5.7 and 7.5 kg (12.5 and 16.5 lb.) and will be connected to the transformer winding lead, adding additional weight. 15

Fig. 8 Split Conductor Assembly With the shipping cover lifted install the Trench holding tool (or steel rod) using the small through hole located 1/2 (12.5 mm) below the joint of the Split- Conductor. With the lower end of the Split-Conductor supported remove the hardware that attaches the shipping cover to the Split-Conductor. This will be the same hardware that will be used to assemble the upper part of the Split-Conductor. An 8 mm or 5/16 Allen wrench can be used to remove the cap screws. CAUTION: if the steel rod is used care must be taken not to drop any hardware into the transformer tank. Assemble the upper part of the Split-Conductor using the hardware used the secure the shipping cover. Torque the cap screws to 17 ft. lb. (23 Nm). Attach the cord or wire, which exits the lower end of the bushing, to the lifting eye previously installed to the top of the Split-Conductor. CAUTION: When handling the bushing in a horizontal position make sure that the oil level indicator is always facing down to prevent the gas in the head from entering the condenser part of the bushing. 16

Begin to install the bushing over the Split-Conductor while pulling on the cord or wire. As the bushing is being lowered over the Split-Conductor align the oil level indicator to the desired final position. As the bushing lower end approaches the Trench holding tool (or steel rod) remove the holding tool (or steel rod). At this point the full weight of the Split- Conductor, between 11.2 and 17.5 kg (24.6 and 38.5 lb.), will be supported by the cord or wire. The Split-Conductor must not be allowed to drop into the transformer tank. Continue lowering the bushing, while pulling on the cord or wire until the bushing rests on the mounting flange. With the Split-Conductor still supported by the cord or wire install the retaining pin with locking device through to small hole near the top of the Split-Conductor. Secure the bushing to the mounting flange and install the top terminal to the head using the four screws and washers provided. Torque to 15 ft. lb. (20 Nm). CAUTION: For Split-Conductor applications, the retaining pin does not pass through the corresponding hole in the central tube of the bushing. The retaining pin with locking device will rest on top of the central tube, supporting the Split- Conductor during service. After the bushing has been installed in the transformer, the optional air escape plug (7.4 ft. lb./10 Nm) located on the top terminal can be used for air release while filling the transformer. If the Split-Conductor is delivered installed in the bushing and it is to be removed, the following should be done: With the bushing in a horizontal position with the oil level indicator facing down, remove the top terminal. With the top terminal removed, remove the retaining pin and carefully pull the Split-Conductor from the bottom of the bushing. Caution must be used in removing the Split-Conductor, as it can be heavy and as long as the bushing. Care must also be taken not to scratch the Split-Conductor or the central tube of the bushing. 9.6 Fixed conductor installation Bottom connected bushings with a fixed conductor are designed for highest current ratings. They carry the current through the center conductor that is not removable. It is not necessary to remove the top terminal on such bushings. The connection to the winding leads depends on the design of the transformer. 10. Commissioning 10.1 General check The following procedures must be completed before placing the bushing under voltage: Check the oil level (see section 11.1, "Checking the oil level"). Wait at least 24 hours after the bushing has been placed in the vertical position before applying voltage. Power factor and bushing capacitance measurements can be made for comparison with subsequent field measurements. 10.2 Test tap Bushings for insulation class of 69 kv and lower are provided with a test tap. The test tap shown in figure 9.0 is located just above the mounting flange and provides measuring power factor and capacitance of the bushing. In order to connect to the test tap, remove the threaded cap and connect the lead of the power factor with the measuring equipment. After the measurement has been completed, re-assembling the sealing cap (torque = 15 ft. lb./20 Nm). This will ground the test tap for proper operation of the bushing. CAUTION: There is a high voltage output if the test tap is not grounded. Always keep it grounded with either an over-measuring circuit, sealing cap or grounding link. The test tap can withstand a power frequency voltage test of 2 kv. Many bushing users measure the power factor and the capacitance of the bushing as a field test. For more information on this practice, refer to section 11, "Maintenance". 17

Fig. 9 COTA 150 COTA 350 Test tap Fig. 10 COTA 550 and above Voltage Tap Sealing cap Sealing cap Oil plug 10.3 Voltage tap Bushings for insulation class of 115 kv and higher are provided with a voltage tap. The voltage tap shown in figure 10.0 is located just above the mounting flange and can be used for connecting voltage measuring equipment (e.g. a bushing potential device) or for measuring the power factor and capacitance of the bushing. In order to connect the tap outlet, remove the sealing cap and connect the measuring equipment. If a bushing potential device is connected, remove the oil plug and fill the cavity with clean, dry transformer oil. To permit oil expansion, allow a 5/8" (16 mm) clearance between the seal and the surface of the oil. Then replace the plug and gasket with a torque of 7.4 ft. lb. (1O Nm). Under these conditions, the voltage tap will withstand a 20 kv power frequency voltage test. It is not necessary to fill the cavity with oil for power factors or capacitance measurement devices below 10 kv. After the measurement has been completed, re-assemble of the sealing cap (torque = 30 ft. lb./40 Nm) This will ground the voltage tap for proper operation of the bushing. CAUTION: There is a high voltage output if the voltage tap is not grounded. Always keep it grounded with either an over-measuring circuit, sealing cap or grounding link. As mentioned in section 11.1 many bushing users measure the power factor and the capacitance of the bushing as a field test. For more information on this practice, refer to Section 11, "Maintenance". 18 11. Maintenance Under normal operating conditions Trench type COTA bushings require no maintenance. As a guideline the following routine checks can be performed. 11.1 Checking the oil level Trench COTA bushings covered by this instruction manual have prismatic glass oil level indicators. As long as oil is visible within the view of the prismatic glass oil level is within acceptable limits. This rule is valid for all acceptable mounting positions up to a 40º inclination from vertical. CAUTION: If the oil level is at the bottom of the oil level indicator, it indicates a low oil level. The bushing must be taken out of operation immediately. No voltage may be applied to a bushing under such conditions due to the danger of explosion. Check the bushing for leaks and contact Trench. 11.2 PF and capacitance measurement Field measurements of power factor and capacitance can differ from measurements made under the controlled conditions in the factory. The bushing power factor and capacitance should be measured at the time of commissioning and these values should be used as a base to compare future measurements. Please contact Trench should: The power factor doubles from the original commissioning value. The capacitance increases to 110 % of the original commissioning value.

CAUTION: These measurements may only be performed when the bushing is not in operation. Removing or replacing these caps under voltage is strictly prohibited: Dangerous high voltage! The test or voltage tap sealing cap must be screwed on tightly during operation with the following torque values: Test tap sealing cap: 15 ft. lb. /20 Nm Voltage tap sealing cap: 30 lb. /40 Nm. 11.3 C2 Measurements 69 kv Class and below. Trench has conducted extensive investigations into the phenomenon of erratic C2 and PF field measurement on new Trench bushings, 69 kv and below. From the results of this investigation Trench has determined, without exception, that when the C1 and PF are as indicated on the nameplate that the bushing is in good working condition and fit for a lifetime of trouble free service. 11.4 C2 Measurements 115 kv Class and above. Erratic field measurements of the C2 capacitance on bushings 115 kv and above have been reported to Trench. In these cases one or more of the following situations existed, that when corrected, brought the measured values back in line with the nameplate value. The bushing was not vertical with the inboard end resting within the shipping crate. The leads connected to the test equipment were long and not calibrated for the length. The test voltage was below 1 kv. The bushing was tested near a steel reinforced concrete column or concrete floor. The voltage tap compartment was contaminated with moisture. 11.5 Units with Oil Sampling Valve Contact Trench prior to taking an oil sample. 12. Storage Storage practices for COTA bushings depend on where stored and for how long. It is always preferable to store the bushing horizontally in its original factory shipping crate, regardless of storage duration. If the original factory shipping crate is not available the bushing must be stored upright in a suitable support frame. The preferred storage location is indoors, however, if indoor storage is not available, the bushing may be stored outdoors for short periods of time. If stored outdoors, it is highly recommended to enclose the inboard end of the bushing in protective plastic to prevent contamination of this side of the bushing. COTA and COBA bushing inboard ends are susceptible to UV de-coloration when stored outdoors unprotected. Extensive testing has shown that prolonged exposure, more than 10 years, can damage this component of the bushing. Shorter periods of exposure will not effect the functionality of the bushing but may change its appearance. Should this occur treat the insulator with ethanol and a Scotch-Brite pad to restore the original appearance. 13. After Sales Service Should any malfunction occur with a COTA or COBA bushing, inform Trench or its authorized representative. Include with your report complete identification of the bushing, including serial number, type designation and nature of malfunction. This report must be in writing. 14. Draw Lead Adapters When selecting Trench COTA bushings as replacements for other brands of draw lead bushings it will be necessary to apply a Trench draw lead adapter. For most applications a thread-on type adapter can be applied. 14.1 Instructions The following instructions are offered for use when applying the thread-on adapter: Before beginning the installation refer to the preceding instruction in this manual pertaining to the new COTA bushing. 14.2 Measuring Before removing the old draw lead bushing it is recommended that the amount of slack in the draw lead cable be measured. This is accomplished by pulling up the draw lead terminal by hand to determine the amount of slack that may exist. Note that in many cases there may not be any slack. Take note of the approximate slack or lack of slack that is present, this information will be used when the new Trench COTA bushing is installed. 19

14.3 Inspection After removing old draw lead bushing inspect the draw lead cable insulation for any signs of burning or over heating. If there are indications of burning or over heating you should note this condition, as it may be an indication of severe overload or of an inadequately sized draw lead conductor. If this condition exists, consider replacing the insulation with a high temperature, class F, insulation material. 14.4 Installation With the existing threaded draw lead terminal held away from the bushing opening on the transformer cover, install the lock nut supplied with the adapter. The lock nut must be threaded all the way onto the old threaded draw lead terminal. Thread the female end of the draw lead adapter onto the existing threaded draw lead terminal until it is tight. Then tighten the lock nut against the adapter using wrenches on the flats of the lock nut and adapter. With the draw lead adapter installed you can now install the new Trench COTA bushing following the instructions in this manual. Before installing the retaining pin in the Trench draw lead terminal again determine the amount of slack in the draw lead cable. It should be the same as when checked before the old bushing was removed. If there is more than 2 inches (50 mm) of additional slack or if it takes a large amount of force to pull the terminal to the top of the bushing during the last few inches, it is recommended to stop and contact Trench. Applying too much force in pulling up the draw lead cable may damage the transformer. CAUTION: The above instructions do not cover all possible conditions that can arise when replacing old draw lead bushings. Trench assumes no responsibility for any damage or failure, which would result from conditions not known to Trench or by materials not furnished as part of the Trench bushing. 14.5 Other adapter types There may be some instances that a Trench thread-on adapter can not be applied. In those cases an adapter will be provided by Trench, which will require cutting off the old draw lead terminal. If this type of adapter is required Trench will provide detailed instructions to perform the installation. 15. Technical Ordering Data Trench has developed a technical ordering data system that is user friendly. It is designed to allow you to build your own bushing from a selection of standard accessories and options that meet your specific application requirement. The technical ordering data system is made from three components, the bushing Type, the bushing Style number and the bushing Options. At the end of this section are Code tables that list the available options. 1. Type Code COTA, which stands for Condenser Oil Transformer bushing designed according to ANSI Standards. COBA, which stands for Condenser Oil Breaker bushing designed according to ANSI Standards. The type is always at the beginning of the technical ordering data. 2. Style Number The style number is made up seven sets of numbers and/or letters that will provide specific information about the specific bushing. COTA - - - - Set 1 2 3 4 5 6 7 The first set of numbers states the BIL (Basic Insulation Level) of the bushing. The table for Code 1 lists the standard BIL available. The next set of 1 letter and 3 numbers, state the maximum through current rating of the bushing. The letter designates the current path option, F for fixed conductor or H for draw lead. The numbers designates the maximum through current for the bushing X100. (Example 015 = 1,500 amperes) A listing of available ratings is listed in the table for Code 2. The next set of numbers designates the CT pocket length. The CT pocket is the space, just below the mounting flange of the bushing, provided by the last grounded foil layer of the bushing s active apart. The table for Code 3 lists the available CT pocket lengths by style. 20

The next letter designates the mounting flange configuration. The IEEE/ANSI Standards dictate the mounting flange arrangements for most bushings, however, there are a number of exceptions that must be considered when applying bushings as replacements. The table for Code 4 will provide specific letter code designations for each available mounting flange configuration by bushing style. The next letter designates the outdoor insulator material and color. There are 3 options available for the outdoor insulator and are listed in the table for Code 5. The next number designates the outdoor insulator s creep distance in accordance with the four contamination levels as described in the IEEE Guide for Application of Power Apparatus Bushings, C57.19.100. The table for Code 6 list the 4 options. The last set of numbers is the Trench factory code designation that determines a specific bushing s compatibility with other bushings within the same rating. 3. Options The last sets of letters are the Option Codes. The option codes are the accessories that are added to a basic bushing to suit the specific requirement or application. These option codes will appear on the bushing nameplate as part of the serial number and will appear on the bushing outline drawing. The specific outline drawing number will appear on the bushing nameplate. There are presently 4 sets of options available for Trench bushings. CODE 1, Basic Insulation Levels CODE DESCRIPTION 150 25 kv, 150 kv BIL 200 34.5 kv, 200 kv BIL 250 46 kv, 250 kv BIL 350 69 kv, 350 kv BIL 550 115 kv, 550 kv BIL 650 138 kv, 650 kv BIL 750 161 kv, 750 kv BIL 900 230 kv, 900 kv BIL 1050 345 kv, 1050 kv BIL 1175 345 kv, 1175 kv BIL 1300 345 kv, 1300 kv BIL 1550 500 kv, 1550 kv BIL 1675 500 kv, 1675 kv BIL 1800 500 or 765 kv, 1800 kv BIL 2050 756 kv, 2050 kv BIL CODE 2, Maximum Current Ratings CODE DESCRIPTION H014 1,400 A, 250.1175 H015 1,500 A, 150 200 H016 1,600 A, 900 1300 H020 2,000 A, 250 350 H030 3,000 A, 150 200 F020 2,000 A, 150 2050 F023 2,350 A, 200 F027 2,700 A, 150 F030 3,000 A, 150 2050 F050 5,000 A, 150 900 F075 7,500 A, 150 200 F100 10,000 A, 150 F125 12,500 A, 150 CODE 3, CT Pocket Length CODE DESCRIPTION 10 10 CT Pocket (Special) 16 16.5 CT Pocket (Special) 21 21 CT Pocket (Std. 150 350) 23 23 CT Pocket (Std. 550.2050) 26 26.75 CT Pocket (Special) 27 27 CT Pocket (Special) CODE 4, Mounting Flange Configuration CODE kv Class Amps Flange A 25 1,500 7¼ 4 HOLE A 34.5 1,500 7¼ 4 HOLE B 25 3,000 7¼ 4 HOLE B 34.5 3,000 7¼ 4 HOLE C 25 3,000 8¼ 4 HOLE C 34.5 3,000 8¼ 4 HOLE D 25 3,000 9¼ 6 HOLE D 34.5 3,000 9¼ 6 HOLE A 35.5 5,000 14 ¼ 9 HOLE A 46 2,000 8¼ 4 HOLE A 46 3,000 9¼ 6 HOLE A 69 2,000 9¼ 6 HOLE A 69 3,000 10 ¼ 6 HOLE E 69 3,000 10.88 6 HOLE A 115 3,000 13¼ 6 HOLE A 115 3,000 13¼ 6 HOLE A 138 3,000 14¼ 6 HOLE A 138 3,000 14¼ 6 HOLE A 161 3,000 15¾ 8 HOLE A 230 5,000 21 12 HOLE A 345 3,000 21 12 HOLE A 500 3,000 25 12 HOLE F 500 3,000 31 16 HOLE A 765 2,000 35 16 HOLE 21

CODE 5, Outdoor Insulator CODE G B C CODE DESCRIPTION #70 Gray Porcelain Brown Porcelain #70 Gray Silicone Rubber CODE 6, Minimum Insulator Creep Distance DESCRIPTION 1 28mm/kV* (optional) 2 35mm/kV* (optional) 3 44mm/kV* (standard) 4 54mm/kV* (optional) OPTION CODE 8, Top Terminal Plating CODE A T N DESCRIPTION Silver Plated Tin Plated No Plating OPTION CODE 9, Draw Lead Terminal when Ordering Code 10 = R, Crimp Type CODE DESCRIPTION CABLE SIZE mm_ H ID = 0.433" 1/0 50 J ID = 0.500" 2/0 70 K ID = 0.625" 4/0 95 L ID = 0.720" 300 KCMIL 150 N ID = 0.830" 400 KCMIL 185 O ID = 0.925" 535 KCMIL 395 Z Special Specify OPTION CODE 9, Draw Lead Terminal when Ordering code 10 = W, Braze Type CODE M P Z CODE X K L Z DESCRIPTION 0.315" Pilot Hole Spade Special Size OPTION CODE 9, Bottom Terminal when Ordering Code 10 = T, threads DESCRIPTION 1 1/2" - 12 UNF Threads 2" - 12 UNF Threads 3" - 12 UNF Threads Special Threads OPTION CODE 9, Bottom Terminal when Ordering Code 10 = P, Plate (Breaker) CODE DESCRIPTION D IEEE/ANSI FIG. 3.4 E IEEE/ANSI FIG. 3.5 F IEEE/ANSI FIG, 3.6 Z Special Plate OPTION CODE 9, Bottom Terminal when Ordering Code 10 = S, Spade CODE Y X Z OPTION CODE 10 CODE P R S T W Z DESCRIPTION 2 Hole Spade 4 Hole Spade Special Spade DESCRIPTION Bottom Terminal is a Plate Crimp Type Draw Lead Terminal Bottom Terminal is a Spade Bottom Terminal is a Threaded Stud Braze Type Draw Lead Terminal Special OPTION CODE 11 & 12 (For future use) Code Z indicates something special is required. If a specific requirement is not covered by the above codes the letter Z can be used in the option code. The required special option or accessory must be fully detailed and be reviewed by Trench before an order is accepted. If a Z option code does not appear in a specific option code table there can not be a special requirement for the option or accessory. If a bushing is ordered with or without a draw lead terminal, option codes 9 and 10 will not appear on the outline drawing. The draw lead terminal option codes will appear on the order acknowledgment if ordered with the bushing. If a bushing is ordered with a draw lead adapter then codes 9 and 10 will be Z. The Z will not appear on the outline drawing for that bushing. A special paint color on the bushing head would appear as a Z in ordering code 11 and then be assigned a specific option code for the color. 22

Notes 23

Trench Facilities The Trench Group is your partner of choice for electrical power transmission and distribution solutions today; and for the development of your new technology solutions of tomorrow. Trench Austria GmbH Paschinger Strasse 49 Postfach 13 A-4060 Linz-Leonding Austria Phone: 43-732-6793-0 Fax: 43-732-671341 Trench Brasil Ltda Via Expressa de Contagem, 2685 Contagem, Minas Gerais CEP 32370-485 Brazil Phone: 55-31-3391-5959 Fax: 55-31-3391-1828 Trench China MWB (Shanghai) Co., Ltd. No. 3658, Jiancheng Road Minhang, Shanghai Peoples Republic of China 200245 Phone: 86-21-54720088 Fax: 86-21-54723118 Trench Fushun Dong Er Dao, Shuncheng District Fushun, Liaoning Province Peoples Republic of China 113126 Phone: 86-413-7644009/7644007 Fax: 86-413-7641423 Trench Limited Bushing Division 432 Monarch Avenue Ajax, Ontario Canada L1S 2G7 Phone: 905-426-2665 Fax: 905-426-2671 Trench Limited Coil Product Division 71 Maybrook Drive Scarborough, Ontario Canada M1V 4B6 Phone: 416-298-8108 Fax: 416-298-2209 Trench Limited Instrument Transformer Division 390 Midwest Road Scarborough, Ontario Canada M1P 3B5 Phone: 416-751-8570 Fax: 416-751-6952 Trench Limited Power Line Carrier Division 815 Middlefield Road, Unit 6A Scarborough, Ontario Canada M1V 1R9 Phone: 416-291-8544 Fax: 416-291-5581 Trench France S.A. 16, Rue du Général Cassagnou B.P. 70 F-68 302 St. Louis, Cedex France Phone: 33-3 89-70-2323 Fax: 33-3 89-67-2663 Trench Germany GmbH Nürnberger Strasse 199 D-96050 Bamberg Germany Phone: 49-951-1803-0 Fax: 49-951-1803-224 Trench Switzerland AG Lehenmattstrasse 353 CH-4052 Basel Switzerland Phone: 41-61-315-51-11 Fax: 41-61-315-59-00 Trench (UK) Limited South Drive Hebburn Tyne & Wear NE 31 1 UW Phone: 44-191-483-4711 Fax: 44-191-430-0633 www.trenchgroup.com Bulletin E8322.72 Subject to change without notice (07.2007) Printed in Canada.