weg transformer

Motors | Automation | Energy | Coatings

POWER TRANSFORMER Manual

WEG TransformadoresBR721

Transforming power into solutionsSUMMARY

1. INTRODUCTION ................................ ................................ ................................ ................................ ....... 5 2. GENERAL INSTRUCTI ONS ................................ ................................ ................................ .................... 5 3. RECEIVING PROCEDU RES ................................ ................................ ................................ .................... 5 3.1. SHIPPING CONDITIONS ................................ ................................ ................................ ..................... 5 3.2. TRANSPORT................................ ................................ ................................ ................................ ........ 5 3.2.1. Nitrogen Cylinder with Automati c Pressurizer ................................ ................................ ................ 6 3.2.2. Impact Recorder ................................ ................................ ................................ ............................. 7 3.3. RECEIVING PLACE................................ ................................ ................................ ............................. 8 3.4. RECEIVING INSPECTION ................................ ................................ ................................ .................. 9 3.5. UNLOADING AND HANDLING ................................ ................................ ................................ ......... 9 3.6. PRESSURE CHECK-UP ................................ ................................ ................................ ....................... 9 3.7. PERMISSIBLE EXPOSURE TIME FOR THE ACTIVE PART ................................ .............................. 9 3.8. ABNORMAL CONDITIONS ................................ ................................ ................................ .............. 10 4. STORAGE ................................ ................................ ................................ ................................ ................ 10 5. INSTALLATION ................................ ................................ ................................ ................................ ...... 11 5.1. GENERAL CONSIDERATIONS ................................ ................................ ................................ ........ 11 5.2. INSTALLATION ON THE PERMANENT BASE ................................ ................................ ............... 11 5.2.1. Installation of a Transformer Fitted with Flat Wheels Running inside Grooved Rails ..................... 12 5.2.2. Installation of a Transformer Fitted with Wheels on I -beam Rails ................................ ................. 13 5.2.3. Installation of a Transformer Fitted with a Skid on a Concrete Base ................................ ............. 15 5.3. ALTITUDE OF INSTALLATION ................................ ................................ ................................ ....... 16 REDUCTION FACTOR K ................................ ................................ ................................ ........................... 17 5.4. TANK GROUNDING................................ ................................ ................................ .......................... 17 5.5. PROTECTIVE AND HANDLING COMPONENTS ................................ ................................ ............ 17 6. TRANSFORMER ASSEM BLY ................................ ................................ ................................ ............... 17 6.1. APPLICATION OF PACKING................................ ................................ ................................ ............ 17 6.2. DETACHABLE RADIATORS ................................ ................................ ................................ ............ 18 6.2.1. Assembly of Radiators ................................ ................................ ................................ .................. 19 6.2.2. Lifting the Radiators ................................ ................................ ................................ ..................... 20 6.2.3. Disassembling the Radiators ................................ ................................ ................................ ........ 21 6.3. OIL EXPANSION TANK ................................ ................................ ................................ .................... 21 6.3.1. Preparation for the Expansion tank Assembly ................................ ................................ ............... 21 6.3.2. Expansion tank fitted with rubber bag ................................ ................................ ........................... 22

1

Transforming power into solutions 6.3.3. Expansion tank fitted with rubber membrane ................................ ................................ ................ 22 6.4. ACCESSORIES ................................ ................................ ................................ ................................ .. 24 6.5. BUSHINGS ................................ ................................ ................................ ................................ ......... 24 6.5.1. DIN Bushings ................................ ................................ ................................ ............................... 24 6.5.2. Condensive Bushings (ABB) ................................ ................................ ................................ ......... 25 7. ACCESSORIES ................................ ................................ ................................ ................................ ........ 26 7.1. OIL LEVEL INDICATOR ................................ ................................ ................................ ................... 26 7.2. OIL THERMOMETER ................................ ................................ ................................ ........................ 27 7.2.1. Fastening and Warnings ................................ ................................ ................................ ............... 27 7.2.2. Maintenance ................................ ................................ ................................ ................................ 27 7.3. THERMAL IMAGE THERMOMETER FOR THE WINDINGS................................ ........................... 29 7.3.1. Adjustment of the Winding Thermometer ................................ ................................ ....................... 30 7.4. MICRO-PROCESSED TEMPERATURE CONTROLLERS ................................ ................................ 33 7.4.1. PT100 ................................ ................................ ................................ ................................ .......... 35 7.5. BUCHHOLZ RELAY ................................ ................................ ................................ .......................... 35 7.6. DEHYDRATING BREATHER ................................ ................................ ................................ ........... 38 7.6.1. Silica Gel ................................ ................................ ................................ ................................ ..... 38 7.7. PRESSURE RELIEF DEVICE ................................ ................................ ................................ ............. 39 7.7.1. Construction Details ................................ ................................ ................................ ..................... 40 7.8. PRESSURE SURGE RELAY ................................ ................................ ................................ .............. 42 7.9. VOLTAGE REGULATOR ................................ ................................ ................................ .................. 43 8. TAP CHANGERS ................................ ................................ ................................ ................................ ..... 43 8.1. MANUALLY ACTUATED ROTATING-TYPE TAP CHANGER (WITHOUT VOLTAGE)................ 43 8.2. LINEAR TAP CHANGER WITHOUT VOLTAGE APPLICATION ................................ .................... 45 8.3. ON-LOAD MOTOR DRIVEN TAP CHANGER ................................ ................................ ................. 46 9. MINERAL INSULATIN G OIL ................................ ................................ ................................ ................ 47 9.1. TRANSFORMER PROVIDED WITH DRY GAS AND A NON VACUUM-RESISTANT EXPANSION TANK................................ ................................ ................................ ................................ ........................ 49 9.2. TRANSFORMER PROVIDED WITH DRY GAS AND A VACUUM-RESISTANT OIL EXPANSION TANK................................ ................................ ................................ ................................ ........................ 51 9.3. TRANSFORMER WITH A LOWERED OIL LEVEL................................ ................................ ........... 52 9.4. GENERAL CONSIDERATIONS ................................ ................................ ................................ ........ 53 9.5. OIL FILTERING ................................ ................................ ................................ ................................ . 55 9.6. OIL DRAINAGE ................................ ................................ ................................ ................................ . 56 10. AIR BLEEDING ................................ ................................ ................................ ................................ ..... 56

2WEG Transformadores Manual 7410.3211 Rev 2 10/2003

Transforming power into solutions 11. CHECKING THE GEN ERAL CONDITION OF PO WER TRANSFORMERS BEF ORE START-UP ................................ ................................ ................................ ................................ ................................ ....... 57 11.1. INSPECTION ESSAYS ON A TRANSFORMER BEFORE START-UP ................................ ............ 63 12. APPLYING POWER ................................ ................................ ................................ .............................. 63 13. MAINTENANCE ................................ ................................ ................................ ................................ .... 64 13.1. EMERGENCY TROUBLESHOOTING ................................ ................................ ............................. 64 ATTACHMENT A WARRANTY CONDITIONS FOR SERIES -MANUFACTURED AND ENGINEERED PRODUCTS ................................ ................................ ................................ ....................... 65 ATTACHMENT B METHOD FOR PRESSURI ZING A TRANSFORMER ................................ .......... 66 ATTACHMENT C VACUUM SERVICE ................................ ................................ ................................ . 68 ATTACHMENT D. COLLECTING SAMPLES OF THE TRANSFORMERS INSULATING L IQUID ................................ ................................ ................................ ................................ ................................ ....... 69 ATTACHMENT E - PERIODIC INSPECTION S EVERY SIX MONTHS A ND EVERY 3 YEARS ........ 73 ATTACHMENT F - RECOMMENDATIONS ................................ ................................ ............................ 76 ASSISTENTES TCNICOS AUTORIZADOS WEG TRA NSFORMADORES ................................ ........ 77


Transforming power into solutions


Transforming power into solutions1. INTRODUCTION This manual is intended to provide the customer with all required in form ation for receiving, installation and maintenanc e of oil-submerged power transformers. Compliance with these instructions will contribute to a good performance and an extende d life of the transformer. All WEG transformers are designed and constructed strictly according to the last available ABNTs standards. Therefore, the contents of this manual remain subject to changes without previous notice. If you wish to get a deeper look into this matter, we recommend you to read the following standards: NBR 7037 Receiving, installation and maintenance proce dures for power transformers submerged in mineral insulating oil. NBR 5416 Procedure for the application of loads to power transformers. It is also very important to have in hands the transformer installation literature that is issued by the local power suppliers of your region, since many of them may be statutory standards. For further explanation, refer to our Technical Assistance department. IMPORT ANT: Please also check the WEG warranty cond itions acco rding to ATTACHMENT A. NOTE: Some of the inf ormation or recommendations contained in this manual may not apply to certain transformers, as they are general guidelines. Therefore, please disregard them whenever they are not applicable to your newly purchased equipment.

2. GENERAL INSTRUCTIONS All those who work in electrical facilities, either in assembly, operation or maintenance work, should be permanently informed and updated about the standards and safety prescriptions ruling their tasks, and should be advised to adhere to them. Their supervi sor should make sure, before the beginning of the work, that everything has been duly checked and he should warn his staff about the hazards involved in each proposed task. We recommend that such services be carried out by qualified personnel only. Fire combat equipment and first aid placards should be available at the work place, always in very visible and accessible places.

3. RECEIVING PROCEDURES 3.1. SHIPPING CONDITIONS All transformers are tested at the factory, before being dispatched, in order t o assure their perfect working condition. Transformers can be transported either fully or partially assembled, considering the application of special components for the safe transport of the equipment until the place of destination, including loading and unloading procedures.

3.2. TRANSPORT Dimensional limits for transport and a few of the transformer features define the conditions for shipments of such equipment, as fo llows:


Transforming power into solutions Fully assembled (Transformers smaller than 3MVA), considering the application o f radiators directly welded to the tank. An Exception is made to the Dehydrating breather and wheels, when available, which are usually packed separately; Partially disassembled, whenever their dimensions exceed the transport limits and, necessarily, whenever radiators are of a detachable type. The transport of power transformers is carr ied out with the use of th e following accessories: Nitrogen cylinder with automatic pressurizer; Impact recorder or impact indicator (without recorder). 3.2.1. Nitrogen C ylinder with Automatic Pressurizer Always when a transformer is to be transported partially disassembled, one the following conditions should be taken in account with regards to the main tank transport: Oil level lowered until 150mm from the lid, with th e chamber above the surface pressurized with nitrogen at a pressure of 0,2kgf/cm2

at 25C, without the use of a nitrogen cylinder and automatic

pressure regulator. Application: In all cases where the main tank weight, including the lowered oil level, is lo wer or equal to 40 tons and/or equal of lower than the voltage class of 145kV; Oil level lowered until 150mm from the lid (FIGURE 1), with the chamber above the surface pressurized with nitrogen and connected to nitrogen cylinder and automatic pressure reg ulator, preset at a pressure of 0,2kgf/cm2

at 25C. Application: Whenever requested by the customer,

limited to a main tank weight of 40 tons, including the already lowered oil level and/or higher than a voltage class of 145kV; Completely empty tank, press urized with super dry nitrogen and connected to nitrogen cylinder and automatic pressure regulator (FIGURE 2), preset at a pressure of 0,2kgf/cm2

, a 25C. Application: In from the lid, is

all cases when the main tank weight, including the already lowered oil level at 150mm

higher than 40 tons, justifying therefore, a complete drainage of the insulating oil (transport without oil), or when the customer requires so. IMPORTANT: A warning label is stickered to the transformers inspection lid in order to warn about the hazards related to the nitrogen contents inside the tank. people


Transforming power into solutionsFIGURE 1

FIGURE 2 AUTOMATIC PRESSURE REGULATOR

3.2.2. Impact Recorder There are two types of impact recorders: Impact Indicator is used in all power transformers that are equal or higher than 30MVA and/or of a voltage class equal or higher than 230kV for the domestic market. When the transformer is to be exported, such impact indicator is used in all power transformers that are equal or higher than 5MVA. Four (4) pieces are used, which are fixed to the tank sidewalls. Three-dimensional Impact Recorder is used only when required by the customer and/or by an insurance Company. This reco rder is fixed to the main transformer lid, by means of fastening screws, the nearest possible to its geometrical center. The recorder is turned on before the transformer is loaded by WEG and should remain turned on until the unit is unloaded. They are intended to indicate whether chocks and vibrations have occurred in th e traver se, longitudinal and vertical directions during the transport, loading and unloading processes. The magnitude of vibration and chock s is recorded in term s of g (Multiples of gr avity acceleration), accord ing to TABLE 1. The ranges of the impact indicator are analyzed after the transformer is unloaded and should be sent back to WEG


Transforming power into solutionstransformadores. If they have proven to be out of the limits, the Technical Assistance Department wi ll take all necessary steps. However, if the recommended acceleration limits have been exceeded, it doesnt meant that damages have occurred to the transformer. If such excess occurs, our technical department should carry out a deeper analysis of the occur rence, defining whether or not an internal assessment or eventually the adoption of another specific action is necessary. It is necessary to take in account that not only the maximum value is imp ortant, but how many times such value has been reached during the transport.

TABLE 1 ACCEPTABLE ACCELERATION VALUES DURING TRANSPORT DIRECTION Longitudinal Traverse TRANSPORT By Truck or By Sea 1,0g 1,0g By Railroad 4,0g 1,0g 3,0g

Vertical 3,0g NOTE: g = Gravity Acceleration (9,81 m/s)

The following procedures should be followed to turn off and remove the impact recorder: Remove the weatherproof protection; Check the box sealing for integrity. If damages are found, please report them immediately to WEG Transformadores; Remove the box lid. In case of rain, do not allow the penetration of any kind of humidity to the inside of the recorder; Turn off the recorder; Mark the point where the transport process has been ended; Turn the recorder on; Close t he box lid; Unload the Transforme r; Remove the box lid; Turn off the recorder; Mark the point where the unloading process has been ended; Remove the impact recorders base from the unit; Replace the lid of the recorder box; Close the box with the supplied seal and send the impact recorder containing the roll of records to the sales department of WEG Transformadores, preferably using the same transporting company for return. IMPORTANT: In case the transport and unloading work is carried out by the same Company, it is not necessary to turn off the recorder and switch its position between one and another operation.

3.3. RECEIVING PLACE Whenever possible, the transformer should be unloaded directly onto its definitive base. When the transformer is to be unloaded on a temporary place, the gr ound should be checked for all safety conditions and strain distribution, and also for proper level and cleanliness. The equipment should never be placed in direct contact with the ground.


Transforming power into solutions3.4. RECEIVING INSPECTION Before unloading, a preliminary inspect ion should be carried out on the transformer in order to identify any damages caused during the transport, checking for its external condition (Distortions, oil leakage and scratches on the painting) and damages and / or missing accessories and components. each box, according the checklist supplied in each box. If there is any part m issing or damaged, please notify WEG Transformadores (Te chnical Assistance department), informing the name and quantity of the missing part and photos or sketches of damaged parts. Check the contents of

3.5. UNLOADING AND HANDLING All the transformer unloading and handling work should be carried out and supervised by specialized people, following all safet y rules and using supporting points indicated on the drawings. The use of any other points will result in severe damages to the transformer. The following should be avoided during the unloading process: The transformer imbalance (Maximum 10); Abrupt movements; Impact against the ground; Side impact.

3.6. PRESSURE CHECK -UP When the pressure inside the cylinder reaches 0,15kgf/cm (15kPa) the truck driver should get in contact with WEG Transformadores Technical Assistance Department.

3.7. PERMISSIBLE EXPOSURE TIME FOR THE ACTIVE PART The transformer is usually shippe d full of dry air or nitrogen gas, under low pressure. Tasks like internal inspection (carried out by authorized people only), bushing installation, internal connection and others, are carried out with the transformers open lid, and as a result the core a nd coils absorb humidity by being exposed to the atmosphere. Therefore, the core and coils exposure t ime should be restricted to the range stated on CHART 1. The transformer tank should not be opened while it is raining, when storms are about to occur or the relative humidity exceeds 80%. Close and seal the inspection window and openings, immediately after the internal tasks have been interrupted or completed. However, not only the work with the open lid, but also the time in which the transformer remains closed and full of air should be counted as exposure time, since the core and coils will absorb humidity during that period too. If the time in which the transformer remains closed with air is less than 4 hours, it should be counted as exposure time . Otherwise, if the time in which the transformer remains cl osed with air is higher than four hours, consider only 4 hours as exposure time. 362kV, the total permissible exposure time is illustrated on CHART 1. when


Transforming power into solutionsCHART 1

3.8. ABNORMAL CONDITIONS Any kind of abnormal condition that might occur during or after transport should immediately reported to the Technical Assistance department of WEG Transformadores. In such case, the transport ing company should: 4. STORAGE For a transformer transported without oil, stora ge with an expansion tank and corresponding pipeline is recommended. Make sure to fill it with insulating oil until the normal level and install the supplied Dehydrating breather with silica gel as soon as it is received, even in case it will not p ut in operation immediately after being received. Regular inspections must be carried out. In case of short storage time intervals (maximum 6 months) the transformer can be stored withou t oil, provided that it remains pressurized with dry gas (between 0,05 and 0,2 kgf/cm). In such a case, a gas pressure inspection should be carried out preferably on a daily basis, in order to detect leakages in due time and to avoid the penetrat ion of humidity. All components and accessories, when received and stored separately, s hould comply with the following: All accessories should be stored in suitable places; Radiators should be stored next to the transformer, and they should not get in contact with the ground; Bushings should be stored, if possible, in sheltered and dry place s; Inform the exact location of the transformer for an eventual inspection; Inform the type of damage caused to the equipment; Abnormal conditions: Accident or pressure drop of nitrogen or dry air.


Transforming power into solutions The oil can be stored in drums, which should remain in a horizontal position, keeping both lids horizontally aligned and, if possible, protected with canvas and also avoiding their contact with the ground; Transformers fitted with on -load tap changer sh ould follow the same equipment storage guidelines; Transformers fitted with auxiliary circuit panels should remain with their heating resistors turned on, controlled by thermostats adjusted to the recommended temperature of 30C.

5. INSTALLATION 5.1. GEN ERAL CONSIDERATIONS Power transformers, rated for 3000kVA or higher, are usually transported partially disassembled. In such a case, after the transformer has been positioned on its definitive base, additionally to the recommendations of item 5.1 and the standard NBR 7037, it is also important to follow the particular guidelines on item 6, TRANSFORMER ASSEMBLY. For the transformer installation, it is essential to have qualified personnel and proper equipment and tools available. Do not attempt to assembl e transformers on rainy days. Before starting the tra nsformer assembly work, the following steps must be carried out: Visual inspections, particularly with regards to the proper level of the base and the outside of the transformer tank in order to verify any damages occurred during handling; Make sure the nameplate ratings are compatible with the technical specification of the equipment; For reconnectable units, make sure the shipping connection complies with the specification; Check for the units gro unding connections (refer to item 5.4); If the transformer is to be installed in a sheltered facility, the room should be well ventilated so that any heated air can be freely exhausted, being replaced with fresh air. Any obstacles to the airflow inside the room should be avoided. Therefore, all air inlet windows should be located next to the floor and should be properly distributed, preferably bellow the transformer level and should have the same maximum dimensions as the transformer. The exhaustion windows sh ould be located as high as the building allows. The number and size of the exhaust windows will depend on their distance above the transformer, performance and the loading cycle, which should be 15 to 20% higher than that of the inlet windows.

5.2. INSTAL LATION ON THE PERMANENT BASE Before installing the unit on its perm anent base, make sure the following is compli ed with: The permanent installation place should properly finished with regards to its civil construction, making sure that no dust, soil or o ther materials will not fall on the equipment; The unit base should be properly leveled (maximum pitch: 1,5); The base concrete must be properly cured and its foundations must be strong enough to withstand the units weight; For lifting the transformer, a ll used cables should be fastened to the supplied straps, hooks or lugs for this purpose.


Transforming power into solutions5.2.1. Installation of a Transf ormer Fitted with Flat Wheels Running insi de Gr ooved Rails Should be installed in the following sequence: Install all wheels to the transformer, using hy draulic j acks sized for at least 50% of the units weight; Before resting the wheels into the groove, make sure all of them are properly adjusted; Lower the transformer with the help of the hydraulic jacks until it remains resting on the bottom of

the groove. Never allow the transformer to remain inclined like shown on FIGURE 3 (b).

FIGURE 3

(a)

(b)

After fully assem bled, check for: Distortion and cracks at the wheels; Deflection of axles; Fastening of wheels; Level of the installed transformer (Refer to FIGURE 4 and TABLE 2).



TABLE 2 TRANSFORMER HEIGHT [mm] 0 2000 2001 5000 > 5001 5.2.2. Installation of a Transformer Fitted with Wheels on I -beam Rails Should be installed in the following sequence: Install all wheels to the transformer, using h ydraulic jacks sized for at least 50% of the units weight; Before resting the wheels on the rails, make sure all of them are properly adjusted; Lower the transformer with the help of the hydraulic jacks until it remains resting on the rails like shown on FIGURE 5 (a). Never allow the transformer to remain inclined like shown on FIGURE 5 (b). 0 - 1,5 0 - 0,5 0 - 0,08



(a)

(b)


Transforming power into solutionsAfter fully assembled, check for: Distortion and cracks at the wheels; Deflection of axles; Fastening of wheels; Level of the installed transformer (Refer to FIGURE 4 and TABLE 2).

5.2.3. Installation of a Transform er Fitted with a Skid on a Con crete Bas e Should be installed in the following sequence: Before resting the skid, make sure it will be properly adjusted for the concrete base; Lower the transformer with the help of the hydraulic jacks until it remains resting on the concrete like shown on FIGURE 6. Never allow the transformer to remain inclined.

FIGURE 6

After fully assembled, check for: Distortion, cracks or flexion of the skid; Level of the installed transformer (Refer to FIGURE 4 and TABLE 2).


Transforming power into solutions5.3. ALTITUDE OF INSTALLATION Our transformers are designed according to ABNT s standards, and therefore they are suitable for installation until 1000m above the sea level. In case of altitudes being higher than 1000m, the transformer has either a reduced capacity or it will require a more effective cooling system. For the operatio n in higher altitudes, the temperature limits s pecified on TABLE 3 should not be exceeded.

TABLE 3 TEMPERATURE RAISING LIMITS Temperature raising limits [C] Windings Metallic parts Method of resistance variation Not in contact In contact with Transformer type Of the Of the with the solid Natural or the solid Forced oil oil hottest insulation and forced oil insulation or circulation point not adjacent to circulation adjacent to it. with driven it. without oil flow driven oil flow Without Should not reach The temperature expansion tank temperatures should not (B) or without inert 55 60 65 50 higher than the reach, in no gas above the maximum case, any level oil surface specified for the that could hottest point of damage those With expansion (C) 55 60 65 55 the insulation, parts, other tank or with inert either adjacent or parts or adjacent gas above the (D) (D) (D) (D) 65 70 80 65 in contact with it. materials oil surface (A) All insulating materials, according to practical experience and essays, should be suitable for the temperature raising limit to which the transformer is rated. (B) Measure close to the oil surface. (C) Measure next to the upper part of the tank when an expansion tank i s fitted, and close to the oil surface when inert gas is used. (D) When paper insulation is used, it should be thermo -stabilized. Submerged in oil The reduction of rated power for altitudes higher than 1000m is calculated according to the following equation:(A)

H 1000 Pr = Pn 1 k 100 Being: Pr = reduced power, in kVA Pn = rated power, in kVA H = altitude, in m (rounding up always immediately to the next hundred of meters) k = reduction factor, according to TABLE 4


Transforming power into solutionsTABLE 4 REDUCTION OF RATED POWER FOR ALTITUDES HIGHER THAN 1000m Type of cooling (submerg ed in insulating oil) Reduction factor k Natural cooling (ONAN) Forced ventilation (ONAF) Forced circulation of the insulating liquid and with forced ventilation (OFAF) Forced circulation of the insulating liquid and with water cooling (OFWF) 5.4. TANK GROUNDING The tank should be effectively and permanently grounded by means of its supplied grounding connector. A permanent grounding mesh of low resistance is essen tial for a suitable protection. The tank is designed with one or two grounding connectors. The connection between these connectors and the grounding mesh should be made with a bare copper cable of suitable gauge. 0,004 0,005 0,005 0,000

5.5. PROTECTIVE AND HANDLING COMPONENTS Transformers must be protected against overloads, short -circuits and surges. Usually, Fusible switches, circuit breakers, isolating switches, lightning arresters and other devices are used for this purpose. All

such components should be properly sized in order to be coordinated with transformer commissioning and should be tested before connections are made. They should be installed as close as possible to the transformer. The links used on fusible switches should be according to the transformer demand and rated power. The lightning

arrester gr ounding should be made using separate cables from the transformer neutral grounding.

6. TRANSFORMER ASSEMBLY For transformers supplied partially disassembled, it is essential to use quali fied technicians for field reassembly, preferably under supervision of a representative from WEG Transformadores. We recommend the following assembly sequence, with additional attention to the contents of the NBR 7037 standard: Packings; Detachable Radiators; Oil expansion tank; Accessories; Bushings.

6.1. APPLICATION OF PACKING All packings used for temporary closing plates should be replaced with new ones, which are supplied separately. Thoroughly remove all stains and other materials adhered to the surface of flanges and groov es until the surface is free of paint. Clean with a piece of cloth before using the new packings. Care must be taken not to allow particles to fall inside the tank during the commissioning work. To evenly compress a pack ing, tighten the screws one by one, progressing in the numerical sequence shown on FIGURE 7, repeating those procedures a few times.


Transforming power into solutionsWhen assembling particularly bushings, this process must be strictly followed in order to protect the porcelain from crack ing or even breaking. When tighten ing the screws, use wrenches along with a torque meter. Please refer to TABLE 5 for the required torque for each screw.

FIGURE 7

TABLE 5 RATED M6 M8 M10 M12 M16 M20 M24 CROSS SECTION mm 20,1 36,6 58,0 84,3 157,0 245,0 353,0 STEEL 5,6 kgf.m 0,6 1,5 3,0 5,0 12,5 24,5 42,0 N.m 5,9 14,7 29,5 49,3 123,2 241,6 414,1 kgf.m 0,9 2,3 4,6 8,0 20,0 39,0 67,0 8,8 N.m 8,8 22,7 45,3 78,9 197,2 384,5 660,6 kgf.m 0,2 0,4 0,8 1,5 3,8 7,3 12,0 BRASS N.m 1,97 3,9 7,9 14,8 37,5 71,9 118,3

6.2. DETACHABLE RADIATORS The radiators are detached for transport purposes and, to avoid the penetration of impurities, humidity and other contaminants, their flanges are covered with lids, which shoul d be removed upon commissioning. They are packed in stacks on a wooden pallet and tied with straps (FIGURE 8 (a)) or in a wooden crate (FIGURE 8 (b)) when they are exported. To handle this set of radiators, it necessary to use a lift truck wooden pallet. When a transformer is fitted with a forced ventilation system (The radiators plus a set of fans fixed on their lower part), those fans are detached from the radiators for transport purposes. Therefore, after the radiators are re-installed, the corresponding fans are fixed and their supplied power supply cables are connected. or straps all around the



(a)

(b)

The oil passage from the radiators to the tank is through the connection flanges (FIGURE 9 (1)) welded to the tank. The radiators are fixed to the connection flanges (1) by means of the radiator flanges (4), including in a few cases a butt erfly valve (2), which allows for a disassembly without having to drain the oil from the units tank. Those valves, available on the upper and lower pipes, are actuated by means of levers (3). The radiator is fitted with an upper plug (9) in order to fill -in with oil and to purge air from the upper header pipe, and a lower plug (8) for oil drainage. To make it easier to lift the radiator, two lifting lugs are available (10 and 11), one welded to the lower header pipe and another to the upper header pipe.

6.2.1. Assembly of Radiators Wash the inside of the radiator with clean and preferably heated (Maximum 50 if there is any indication of humidity penetration. All packings used for the temporary closing plates should be replaced separately (item 6.1). Install the new packings into the radiator butterfly valve grooves. If you find it difficult to apply them, apply four spots of silicone glue and then press the packing into the groove using your hands. with the new ones suppliedo

C) mineral insulating oil



Where: 1. 2. 3. 4. 5. 6. 7. Connection flange to the tank Type-type intercepting valve Lever Radiator flange Header pipe Anti-vibration support Elements 8. 9. 10. 11. 12. 13. 14. Lower plug Upper plug Lower lifting lug Upper lifting lug Bottom of the header pipe Tank Fittings

6.2.2. Lifting the Radiators When lifting radiators individually, care must be taken in order to avoid collisions and consequent smashing. Therefore, separate each one from its crating by fastening a steel cable to the l ifting lugs (item 10 and 11 of FIGURE 9), according to FIGURE 10.

FIGURE 10


Transforming power into solutions6.2.3. Disassembling the Radiators The following procedure should be adopted in order to disassemble the radiators in case it beco mes necessary in the future: Close the corresponding Butterfly valves (FIGURE 9, item 2). Drain the insulating liquid from the radiators through the lower plugs (FIGURE 9, item 8). To make the drainage easier, op en the upper plug too (FIGURE 9, i tem 9). Detach the radiators and fit their corresponding fittings and blind flanges for both the radiators and their intercepting valves. Store them according to FIGURE 8 ( a).

6.3. OIL EXPANSION TANK The oil expansion tank is an accessory designed to compens ate variations of oil volume as a result of temperature and humidity variations. It has a cylindrical shape, with its axis arranged in a horizontal position and it is in stalled high enough to assure a minimum allowable level for all insulating parts, in a condition of minimum oil level. It is made of st eel plates and it is capable of full vacuum mechanical resistance. It is fixed by means of a structural profile steelwork. It has flanged pipes for t he connection of the Dehydrating bre ather and gas relay p ipelines, for the connections of the oil level indicator, and valves for oil filling and drainage. The expansion tank is usually packed separately from the main tank and without oil. All of its pipeline ends are covered with flanges.

6.3.1. Preparation f or the Expansion tank Assembly Make sure the inside of the expansion tank is clean and dry. If necessary, wash with clean and preferab ly heated o il (Maximum 50C). If the expansion tank is fitted with an insulating oil expansion tank system (Membrane / its integrity and proper operation. Install the expansion tank (Lifting it by its proper points) and its eventually existing corresponding support brackets. bag), check for

NOTES: a) In case of transformers shipped with or without oil, but with a vacuum -resistant expansion tank, fit the interconnection pipeline between the expansion tank and the transformer lid, including the gas relay and correspo nding valves. b) In case of tra nsformers shipped without oil and a non - vacuum-resistant expansion tank, fi t the pipeline, but do not fit the gas relay and corresponding valves. The end of the pipeline connected to the transformer lid can be used for vacuum application.

21

Transforming power into solutionsFIGURE 11 OIL EXPANSION TANK FITTED WITH RUBBER BAG

Where: 1. 2. 3. 4. 5. 6. 7. Body Lid Relay pipeline Rubber bag Support Base 1FF Valve 8. 9. 10. 11. 12. 13. Drier pipeline OLI connection Level indicator Float adjustment Stiffener Bag connection

6.3.2. Expansion tank fitted with rubber bag The rubber bag used on oil expansion tanks of our transformers is an optional accessory. It is designed to prevent the insulating liquid from getting in contact with the atmosphere, thus preserving it from humidity and oxidation. The connection of the bag with the atmosphere is made by means of the D ehydrating breather (containing silica gel) that keeps the air always dry on its inside, thus allowing the bag to become full or empty with volume variations of the insulating liquid. The existing air between the rubber bag and its surroundings should be bled-off upon field installation, during the oil filling. Pre pared oil is filled into the tank until th e rubber bag becomes empty. Except otherwise stated, the temperature should remain between 5 and 35o

C, and the air relative

humidity between 45 and 85% during the essays. Therefore, make sure there will be no unexpected fresh airflow in order to avoid any variation of temperature and relative humidity, which could jeopardize the results. It should withstand the air tightness testing with introduction of dry air at a pressure of 0,1kgf/cm . No leakage should be verified during the testing.2

6.3.3. Expansion tank fitted with rubber membrane Exceptionally, the expansion tank is used with a rubber membrane. The vacuum and over -pressure resistant tank, made of steel plates, consists of two halves, lower and upper (FIGURE 12), both flanged in the middle where the rubber membrane is installed. The rubber membrane is fastened to the lower flange by means of two flat packings, which are supported by the middle r ing and fastening elements as shown on FIGURE 13. The upper part is installed after the membrane is installed in the lower part. It is fastened by the very same screws clamping the membra ne and is trimmed with a c ircular rubber string.



FIGURE 13

Where: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Oil level indicator Membrane Membrane bleeding va lve Inspectio n lid Lifting lug Dehydrating breather Equalization Support Relay Pipeline Flat packing Drainage valve Expansion tank lower part Expansion tank upper part Fastening of the upper and lower assembly 15. Membrane fixing middle flange 16. Circular packing


Transforming power into solutions6.4. ACCESSORIES When the Gas Relay (Buchholz) is detached from the transformer (packed in a separa te box) for transport purpose, it is necessary to fit its pipeline. O Oil level indicator (OLI) and in a few cases, the Expansion Tank Oil Level Indicator (ETOLI), is fixed to the expansion tank lid. These accessories must be connected to the transformer s auxiliary terminal box, upon field installation, by means of the supplied distribution cables. These cables are already sized for their proper lengths and each one of them is fitted with identification rings and a threaded water proof end on each end. Aft er completing this stage, test these circuits by means of a buzzer or multi -range meter. To install the Dehydrating breather (shipped in a separate packing), proceed as follows: Remove the plug located at the end of the dehydrating breather air pipeline i nterconnecting the oil expansion tank to the side of the transformer where the dehydrating breather will be installed (it is not necessary to drain the oil from the tank); Remove the upper lid from the dehydrating breather and fill it with silica gel; Re-install the lid onto the dehydrating breather; Seal the corresponding pipes threads; Connect the dehydrating breather to its corresponding pipe with its sight glass turned to toward the inspection position; After fixing it, remove the lower glass part from the air dehydrator a nd fill it will the same

transformer oil until reaching the existing red indication; Carefully reinstall the glass part into the air dehydrator; Make sure it will be perfectly fastened, in order to prevent the penetrat ion of humidity into the transformer.

6.5. BUSHINGS Bushings are devices designed to pass winding leads to the outside of the transformer. They consist basically on the following: Insulating body: vitrified porcelain; Passing lead: electrolytic copper or brass; Termina l: Brass or bronze; Sealing: rubber and hydraulic cardboard; The shape and dimensions of the bushings used on power transfers vary according to the operating voltage and current. DIN bushings and ABB -condensive bushings are currently used.

6.5.1. DIN Bush ings This item refers to the handling and periodic inspection of porcelain bushings of 15, 25 and 36,2kV insulation levels and current levels of 630 to 3150A. The bushing appearance and suitable dimensions should be found out on the supplied drawing. These bushings are usually shipped attached to the main equipment.

24

Transforming power into solutionsWhen bushings are shipped separately from the main equipment, they are packed in wooden cases, which should be stored and placed in a sheltered place, in order to prevent the penetration of impurities into them. When installing bushings on the main equipment, the following instructions must be strictly followed: When undoing the packing, make a visual inspection for any damages; Make sure the bushing part that is going to be fitted inside the main equipment (particularly the porcelain) and the porcelain surface that will be in contact with the packing at the bushing s fixing part should be thoroughly cleaned with a dry cloth; The bushing fixing nuts should be tightened in a balanced and diagonal sequence (item 6.1). water or any other

When connecting the input cable to the bushing terminal, the following instructions should be fo llowed: The outside terminal should be screwed to the conducting rod, making sure that it will not remain loose; Make sure that the terminal face that is going to be in contact with other materials will not be damaged; When installing the input cable, make sure not t o apply too much of a strain to the bushing end.

All bushing that are in operation should be inspected on a monthly basis: Make sure there is no overheating due to a loose terminal or loose parts in contact with the input cable. The inspection should be carried out with the main equipment power turned off. If loose parts are found, they should be retighten ed; Make sure there is no dirt accumulated on the bushing porcelain. If any dirt is found, it should be thoroughly removed while the main equipment power is turned off; Check the porcelain for any damages; Make sure there is no oil l eakage.

6.5.2. Condens ive Bushings (ABB) Their main insulation feature consists of a paper core impregnated with oil having condensive layers for the electric field control, being wound directly on the central metallic tube. The space between the insulating core and the porc elain cover is filled with transformer oil. The oil expansion chamber located on the HV bushing head is waterproof sealed, a sight glass is also located on the head, which allows for contro lling the oil level on the bu shing inside. All condensive bushings are adapted with a measuring outlet, which is used for checking dielectric loss and capacitance with a grounded flange. These bushings are packed in wooden cases in order to prevent possible physical damages. Smaller types can be manually unpacked while larger types need to be removed with the help of a crane, ropes, cables and hoists. The FIGURE 14 shows all types of condensive bushings and their applications.



IMPORTANT: The condensive bushing types used on WEG transformers are: GOB, GOE, GOH e WTXF. The type of installation and maintenance guide applied to this transformer is attached to this manual.

7. ACCESSORIES Other accessories are required for a perfect operation of the transformer. IMPORTANT: The location of these accessories is indicated on the dimensional drawing.

7.1. OIL LEVEL INDICATOR The insulating oil of the transformer expands or contracts according to the room temperature variation and the variation of load supplied by the tra nsformer. As a result, the oil level will either increase or decrease, which will be shown by the oil level indicator ( FIGURE 15). When the alarm is actuated by the level indicator micro -switch, one of the following problems must be occurring: Lea kage of insulating oil from the transformer or any abnormal condition with the l evel indicator itself. The oil level indicator has a cast aluminum housing, being that the level indications is made by a pointer moving by means of two permanent magnets, whi ch are coupled to a float. The float moves according to the oil level, which transmits an accurate indication to the pointer due to the great sensitivity of the magnets. The display of the magnetic level indicators features three indications, i.e.: MIN, 25 C and MAX.


Transforming power into solutionsWarnings: The micro-switch should not be forced by a constant movement of the float while the level indicator is stored or during transport; Do not bend the rod nor its stroke limiter; Do not put any weight over the float.

FIGURE 15

7.2. OIL THERMOMETER The oil thermometer is used to indicate the oil temp erature. There are two types available: A solid -rod thermometer (FIGURE 16), which used in middle voltage transformers, and a capillary thermometer (FIGURE 17) which is used on power transformers. It consists of a bulb, a capillary and a display. The bulb is dipped into the hottest part of the oil right bellow the lid. The display consists of a box, a sight glass with a scale, a micro -switch, two range pointer s moving only by external action, and one indicating pointer for maximum temperature. The temperature needle drives the latter only when the needle rises; otherwise it remains standstill, thus allowing for the maximum temperature reached in a given period. As the bulb temperature varies, the inside liquid (mercury) expands or contracts, transmitting the temperature variation to the thermometer display internal mechanism, and at the same time the indicating pointer is actuated and, depending on the reached temperature, the protecting system will start the alarm, tripping off and carrying out the automatic control of the cooling device for the oil -submerged transformer. ,

7.2.1. Fastening and Warnings The thermometer should be properly fastened in order to prevent any leakage. The capillary should not be excessively bent or stretched. The display is a waterproof housing and therefore, its lid cannot be removed.

7.2.2. Maintenance The temperature indication should be checked as follows: The thermometer b ulb must be placed together with another thermometer of proven effectiveness in a vessel containing liquid at an even temperature.


Transforming power into solutionsThen, it will be possible to compare both thermometer readings. If there is a temperature variation higher than 5C between t he two values, we recommend changing the transformers thermometer. To check the adjustment of the contacts with the temperature, the following procedure should be followed: dip the thermometers bulb into a vessel containing liquid and slowly ra ise the temperature, checking for the value indicated by the display pointer and the actuation of the micro -switch. The micro=switch is adjusted at the factory, and therefore, no further adjustment is required.

TABLE 6 TEMPERATURE RANGES FOR CONTACT ACTU ATION 1 contact 2 contacts 3 contacts 4 contacts 85C 85/95 85/95/105C 85/90/95/105C

After a periodic inspection of the thermometer, return (t urn to the counter -clockwise direction) the maximum temperature -indicating pointer until it st ops against the main pointer, by means of external control.

FIGURE 16



7.3. THERMAL IMAGE THERMOMETER FOR THE WINDINGS Thermal image is the te chnique used to measure the transformer winding temperature. It is called thermal image because it reproduces the winding temperature in an indirect manner. The temperature of the winding, which is the hottest part of a transformer, is the oil temperature temperature excess of the winding ( t) in comparison with the oil. The winding thermal image thermometer (FIGURE 18) consists of a heating resistance and a single or double temperature sensor, both housed and installed into a protective socket s ubmerged in an oil chamber. The assembly is installed in the transformer lid, equalizing with the top -of-oil temperature, indicating therefore the temperature at the hottest part of the winding and, depending on pre -defined adjustments, it actuates contact s for the control of devices and for alarm triggering and / or turning off the transformer by means of circuit breakers. The heating resistance (Maximum current of 2,5A) is supplied by a current transformer associated to the secondary winding of t he main transformer. plus the

TABLE 7 TEMPERATURE ADJUSTME NT Vf1 Vf2 Alarm Turn-off 85C 90C 95C 105C



7.3.1. Adjustm ent of the Winding T hermometer This procedure is intended to o ffer instructions for the adjustment of RECORD and AKM winding thermometers. Required tools: Screw driver; Multi-tester or bridge for resistance measurement.

After carrying out the temperature -raising essay at the transformer, and through this essay, th e variable resistor should be adjusted and at the same time, the current flowing through the heating coil should be adjusted. As a result, the temperature inside the bag is the maximum winding temperature. Finding out the current at the heating element: B y using the winding -oil temperature increase from the heating-up essay or, if the design values are not available, see CHART 2. By using the top -of-oil temperature (from the heating -up essay or design), you can pick one curve or and approximation to it. By using the winding -oil temperature increase , it is possible to find out the current value ( I) at the heating element. Finding out the current I 1:

I1 =

In 5 IpI n = rated current referred to the transformer highest power rate (Last ven tilation stage). I p = Primary current of the CT.

Where:



Finding out the adjustment resistance in Ohms (R): RECORD: is found by means of the f ollowing relationship:

R=-

2 I I1 I

AKM: The valu e for I can be f ound out through CHART 2 and its gradient. . Calculate and find the value for R through CHART 3.

I I1

Adjustment : RECORD : The adjustment is carried out on the variable resistor of 1,0 installed at the term inal box. The r esistance is measured until the previously calculated value of the adjustment resistance, by using a bridge (preferably) or a m ulti-tester. Fix the resistor part when the R -value has been reached. AKM: The adjustment is carried out by setting the value of the internal variable resistor and the external variable resistor. The equivalent resistance of both variable resistors should be equal to the R -value, found on CHART 2.

IMPORTANT: If the thermometer shows any abnormal condition, either on a periodic ins pection or with the transformer in operation, please report it immediately to WEG Transformadores. Temperature added value above the oil temperature, compared to the heating current Bulb dipped in a bag full of oil. Oil bath stirred by a propel ler, room temperature = 25C T = t(I).



T [C]

I [A]



7.4. MICRO -PROCESSED TEMPERATURE CONTROLLERS The micro-processed temperature controllers have been designed to take the place, with the

advantages of the micro -processed technology, of the traditional oil and winding thermometers used on power transformers and reactors. This equipment receives a resistance signal from a sensor, usually a PT100 (FIGURE 22), and calculates it (by means of fitted -in transducer (FIGURE 20)) into an equivalent temperature amount, which can be seen on the temperature monitor (F IGURE 21) with a digital front p anel. It is capable to perform several functions of control and contact actuat ion, being that by means of the front keyboard it is possible to configure parameters and read all measured and preset values (refer to the manufacturer manual). IMPORTANT: Refer to the manufacturers manual of the temperature monitor, attached to this ma nual. The models of temperature monitors being currently used are described as follows: MT1, manufactured by Tree Tech (FIGURE 21), a controller usually referred to as temperature monitor; it has an input for the transfo rmers oil temperature sensor and o ne input for a current transformer (CT); this sensor is usually a PT100 (FIGURE 22), but it can be made of Cu10 or another material and the CT is used to compensate the winding temperature, i.e., among other functions, it is capable to provide the oil and winding temperature readings; MT2, is designed to indicate the temperature of two windings only and is not fitted with an input for oil temperature sensor. Therefore, it should be used together with the MT1 when a temperature indication of further winding s is required; Trafo-guard (manufactured by AKM) , is a little more complete micro -processed controller, but much more expensive; by means of a digital keyboard, it is possible to select the scope in which the operator wishes to check and preset the values for relay actuation; this controller is fitted with an input for a PT100 -type temperature sensor dipped on the top of the oil and another on the bottom of the transformer, in order to get an average temperature; it has inputs for three CTs in


Transforming power into solutionsorder to in dicate three winding temperatures and another input for an oil level indicator. As

outputs, it has four relays for the indication of oil temperature, being four for each winding temperature and two for the indication of oil level, all of them with startin g timer; it has also analog outputs for the indication of four temperatures and serial communication interface RS 232, which allows for printing the data of for the connection to a PC. The micro-processed controllers are necessary when the customer requir es digital temperature indication on the transformer because regular thermometers ar e analog.

FIGURE 20

FIGURE 21

FIGURE 22


Transforming power into solutions7.4.1. PT100 The PT100 is constructed with a platinum sensor that allows for the temperature measurement from 25C to + 850C. When temperature v ariation exists, its ohmic resistance changes (CHART 4), thus allowing for the calculation of this resistance amount into a temperature amount by means of a temperature transducer. It is necessary to inspect on a periodic basis the contacts and physical c onditions of the bulb and wiring of the PT100.

CHART 4

7.5. BUCHHOLZ RELAY The Gas Relay ( FIGURE 23) is designed to protect equipments submerged in insulating liquid, by means of supervision of the oil abse nce or abnormal flow, and abnormal gassing caused by the equipment. The gas relay is usually fitted on transformers provided with an expansion tank for the insulating liquid. This type of relay is capable to accurately detect, for example, the following pr oblems: Leakage of insulating liquid, short circuit inside the equipment causing a great displacement of insulating liquid, inside gassing due to intermittent or continuous failures occurring inside the equipment. The gas relay is usually installed betwe en the main tank and the oil expansion tank of the transformer. The relay housing is made of cast iron, having two flanged openings and two sight glasses showing a graduated scale of gas volume. There are two inside floats, being that the upper float is fo rced to move downwards (this also happens in case of oil leakage). On the other hand, in case an excessive gassing causes an oil ci rculation through the relay, the lower float reacts, even before the gas reaches the relay. In both cases, the floats make contacts when they are displaced.


Transforming power into solutionsThe gas relay has a device for the inside float testing and locking. To check for proper operation of the relay contacts, when it is installed in the transformer, proceed as follows: Alarm: Connect an Ohmmeter to terminal s + C - D. It should indicate an open circuit. Remove the testing device plug and introduce it upside down into the device, lowering it as much as possible in all of its length. The Ohmmeter should indicate a closed circuit. Shutdown Connect an Ohmmeter to terminals + A - B. It should indicate an open circuit. Remove the testing device plug and introduce it upside down into the device, lowering it as much as possible in all of its length. The Ohmmeter should indicate a closed circuit. Before supplying po wer to the transformer, the following items should be checked (FIGURE 24): Remove the lid of the relay -testing device. Remove the float -locking pin from the inside of the testing device. Both floats should be free to move. Replace the cover of the relay -testing device. Purge the air from the relay by means of the 1/8 air valve located on the relay lid. Check the relay for possible leakage that might have occurred during the installation on the transformer a nd fix it. Check the relay for proper fitting wi th regards to the oil float direction, which arrow should be pointing towards the transformers oil expansion tank. If the alarm sounds without turning off the transformer, it is necessary to turn it off immediately and then test the gas removed from the inside of the relay. In this case, the origin of the failure can be assessed accor ding to the gas testing result, i.e.: Combustible gas (contents of acetylene): In this case there must be a failure to be repaired on the electrical part; Non-combustible gas (without acetylene) : in this case, it means there is pure air. The transformer can be turned on again without danger after the air is bled out from the relay. When the alarm sounds repeatedly, it indicates that air is penetrat ing into the transformer. Tur n it off and repair the failure. No gassing (the gas level inside the relay is getting lower and an amount of air is being drawn through the open valve), in this case, the oil level is too low, possibly due to a leakage. Top up with oil until the control l evel and carry out the air tightness essay. The transformer is turned off without a previous alarm. In this case, the transformer must have been thermally overloaded. Turn it on again after a considerable time interval for cooling. The failure can be foun d at the short-circuit contact in the protection relay system. The alarm sounds and the transformer is shutdown immediately before or after the alarm sounds. In this case, one of the above mentioned failures must be the cause. Make the gas testing and pro ceed as described above.



FIGURE 24

ATTENTION! Float locking device for transport purpose and testing of contacts : After installing the relay, remove the insert used to l ock the floats. Operation: To test the contacts, press the internal part with the lid pin. The contacts should actuate automatically. If everything is properly working, close the device again in order to prevent any leakage. Now the relay is ready to be p ut in operation. NOTE: The insert is used for transport purpo ses only.


Transforming power into solutions7.6. DEHYDRATING BREATHER For the purpose of keeping high dielectric rates of the insulating liquid, the transformers are equipped with dehydrating breathers (FIGURE 25), w hich due to their capability to absorb humidity dehydrate the aspired air flowing to the transformer. The Dehydrating breather consists of a metallic vessel, which contains the dehydrating agent (silica gel) and one oil chamber, located in front of the vessel (con taining the agent), thus isolating it from the atmosphere. The dehydrating breather is located at the end of the passage pipe. While the transformer is in normal operation, the oil becomes hot and expands, expelling the air from the expansion tank t hrough the dehydrating breather. If the transformer experiences a load decrease o r lowering of the room temperature, it will also lower the oil temperature, which in turn causes a volume reduction. As a result, an airdrop occurs inside the expansion tank a nd this air will pass first through the oil cup where solid contaminants are entrapped. Thereafter, the air flows through the silica gel crystals, which retain the humidity and finally, the fully clean and dry air is allowed into the expansion tank. The time interval for changing the silica gel varies according to the size of the equipment, load variation and the room temperature. If the color of the silica gel becomes light pink, it means it should be changed or re dried. When a silica gel change is to be made, it is necessary to remove first the wet silica gel and replace it with dry silica gel. The wet silica gel should be properly dehydrated and stored for a future re -use. The wet silica gel should be dried until it becomes blue again, which means it can be re -used. This reconditioned silica gel should be stored in a waterproof container in order to protect it from contaminants and humidity. The oil used in the dryer cup should be changed always when too much of impurity contents ca n be seen (use the same oil f rom the transformer). Make sure the air breathing pipe end remains always dipped in the oil inside t he dryer cup, the oil level should be adjusted to the red mark.

FIGURE 25

7.6.1. Silica Gel The dehydrating agent, called sili ca gel, is vitreous and hard, chemically almost neutral and highly hygroscopic. It is silicon, impregnated with cobalt chloride, and when it is in a fully active condition, it has a crystalline sky bluish appearance.


Transforming power into solutionsWhen it becomes saturated with water, its color changes to li ght pink, indicating that it must be changed. It can have an extended life by means of a drying process that can be applied repeated times, which allows for its re -use. The hydroscopic feature of the silica gel can be restor ed by means of heating in an oven at a temperature of 80 to 100 C, thus evaporating the contents of water. To speed up the drying process, it is recommended to revolve it constantly until it recovers its original color. Any contact with oil or with slightest trac es of oil should be avoided at all costs in order to keep its blue color, otherwise it can become brownish and even black and cannot be recovered. After the regeneration, the silica gel must immediately put into a dry and waterproof closed container.

TABLE 8 SILIC A GEL FEATURES Blue shade Purple shade Light shade (or pink) 7.7. PRESSURE RELIEF DEVICE The pressure relief devices are installed in transformers submerged in insulating liquid in order to protect them against possible distortion or rupture of the tank in case of internal failure as a result of too high pressure. They can be classified in two basic types: a) Membrane-type ( FIGURE 26), or also known as an explosion pipe (steel pipe) through which the pressure relief will occur upon the rupture of the phenolite membrane. Whenever the transformer is submitted to vacuum, this membrane should be isolated fro m the tank and, when handled, every care must be taken not to damage it. A temporary protective membrane is usually used for transport purposes, which should be removed before the transformer is put in operation. Make sure the membrane is in a good conditi on; Dry silica gel Silica gel with approx. 20% of absorbed humidity Silica gel with 100% of absorbed humidity (Saturated).

FIGURE 26

b)

Valve-type ( FIGURE 27), is a valve fitted with a spring, extremely sensitive and quick (operates in less than two millesimals of a second) provided with an instantaneous actuation strength magnification system, also referred to as VAP. It closes automatically after the operation, thus


Transforming power into solutionspreventing the entry of any external agent into the transformer. It does not need to be isolated from the tank when the tank is submitted to vacuum.

FIGURE 27 VAP IMG

FIGURE 28 VAP COMEM

7.7.1. Construction Details The aluminum flange (FIGURE 29) (1) is fastened to the tank by means of screws and is sealed by means of the pack ing (2); the stainless steel disc (3) is pressed by two springs (6 and 7) and is sealed by the packings (4 and 5). When the pressure actuating on the disc area (3) limited by the packing (4) reaches the operating pressure value determined by the springs, the di sc moves upward a small amount, which makes the pressure to actuate over a larger area defined by the packing (5) and results therefore in a higher force, which causes the full and instantaneous opening of the valve. After the pressure has been reduced to the springs make the disc (3) return to its normal closed position. A mechanical indicator (8) is moved upward by the disc (3) and the indicator pin (8) of a bright color, which clearly indicates that valve has been actuated, is kept in the Alarm position by means of an O-ring (9), and can be manually rearmed by pushing it downward against the disc. A weatherproof alarm switch (10) can be supplied upon order, which is actuated by the valve disc (3) and can be manually rearmed by means of a lever (11). normal values,


Transforming power into solutionsA small orifice for bleeding the air between the packings (4 and 5) prevents the valve from abnormal operations due to eventual imperfect sealing between the packing and the disc or due to the presence of particles on the packings. The valve is usually rated for an operation pressure of 0,7kgf/cm 10% and is supplied with ni trilic rubber packings.

FIGURE 29 VAP IMG

FIGURE 30 VAP COMEM


Transforming power into solutionsTABLE 9 IMG MODELS TYPE ALARM CONTACT VP 02 VP 02/1 VP 02/2 VP 02/1 VP 02/2 Circuit Range Without contact 01-contact (Alarm) 02-contacts (Alarm and turn -off) The device is started when the tank internal pressure exceeds 0,7 2 0,07kg/cm . Normally open 4A/220Vca and 0,6A/110Vcc 7A/127Vca and 0,78A/127Vcc

When the VAP 02/1 and VAP 02/2 contacts are made, one of the following problems must be occurring: Internal damage : It is necessary to carry out an analysis of the gas contents i n the oil, measure the oil dielectric strength and the transformers insulation resistance. Damage to the sealed switch : If the alarm contact is started without starting the VAP, it is most likely that the abnormal condition is the sealed switch itself. Th erefor e, it should be inspected.

7.8. PRESSURE SURGE RELAY The pressure surge relay (FIGURE 31) is a protective accessory for sealed -type transformers. Usually, the pressure surge relay is installed above the maximum level of the insulating liquid, with in the space between the top of the insulating liquid and the transformers lid. Nevertheless, it is also acceptable to fit it horizontally over the transform ers lid. The relay is designed to actuate when failures occur in the transformer, which result i n an abnormal internal pressure, and its actuation occurs only by sudden pressure changes (pressure gradients above 0,2atm/s) regardless the transformers normal operational pressure. On the other hand, the relay does not actuate upon slower pressure chang es, which are typical in a normal operation of the transformer, an also during system disturbances (lightning, maneuver over voltage or short -circuit), unless such disturbance should cause any damage to the transformer. When a transformer is transported f illed with insulating liquid or vacuum is applied in the field, it is important to make sure that insulating liquid will not penetrate into the pressure -equalizing orifice or into the relay. Usually, the flange to which the relay is to be installed is supp lied with a sealing flange only. This accessory is supplied separately and should be fitted after the transformer is installed and its tank is filled with insulating liquid.

FIGURE 31


Transforming power into solutions7.9. VOLTAGE REGULATOR The voltage regula tor is designed the control the voltage amount on the transformers secondary winding, providing its adjustment in case an unexpected voltage supply drop or increase occurs on the primary winding. It works interlocked with the start of a motor, which does the under -load tap changeover. The manufacturers of voltage regulators used on WEGs transformers are: Tre Tech for RT1 and RT2, and MR for VC 100 -BU. IMPORTANT: The instruction manual from the manufacturer of the voltage regulator used in this transform er is attached to this manual.

8. TAP CHANGERS 8.1. MANUALLY ACTUATED ROTATING -TYPE TAP CHANGER (WITHOUT VOLTAGE) The rotating-type tap changer allows for changing the voltage relationship of a transformer provided the is no power supply connected, b y means of adding of removing fiel d turns without having to open the transformer. The rotating tap changer (FIGURE 32) consists of fixed copper pins between two panels of insulating material. The handle along with the moving contact has one or more brazed wedges, according to the current they are to withstand. These wedges are positioned by means of strong steel springs, thus assuring a high pressure between the wedge and the pins. The design will determine the type of external operating mechanism for the t ap changer, required for each case. The tap changer and the operating mechanism are usually shipped fully assembled and with their contacts adjusted at their rated voltage position.

FIGURE 32 ROTATING -TYPE TAP CHANGER


Transforming power into solutionsFIGURE 33 ASSEMBLY OF A ROTATING -TYPE TAP CHANGER

FIGURE 34 TAP CHANGER ACTUATION


Transforming power into solutions2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Actuating flange Bronze bushing 0-Ring 0-Ring O-Ring Countersink head screw Fix disc Moving disc Tap changer handle Hex socket cylindrical head screw Handle axle 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Cross head Heavy-duty elastic pin Heavy-duty elastic pin Bushing Handle cover Hexagonal head screw Locking nut Locker screw Locker Plate

NOTE: The rotat ing-type tap changer and its operating mechanism do no required maintenance. Nevertheless, if maintenance becomes necessary, please get in contact with WEGs Technical Assistance Department.

8.2. LINEAR TAP CHANGER WITHOUT VOLTAGE APPLICATION The linear ta p changers without v oltage ap plication allow for changing the voltage relationship of a turned-off transformer by means of adding or removing field turns without having to open the transformer. This type of tap changer consists of two rules, one conta ining the brushes (copper plates) and the other one containing the gear in order to change the position and the fixed brass pins for the connection to the cables and to the brushes. Every stroke corresponds to one position. However, it is recommended that upon brushes be stroked until the end in order to clean their contacts. each tap change, the

FIGURE 35 CAPT LINEAR TAP CHANGER

45

Transforming power into solutionsFIGURE 36 SQUARIO LINEAR TAP CHANGER

8.3. ON-LOAD MOTOR DRIVEN TAP CHANGER The on-load tap changer is designed to make the required tap changeover in an on -load condition. The changeover maneuver is carried out by a system consisting of motor, reducing gear, contactor and electric contro l system (contactors, switches, etc). The control signal (either manual or automatic) is sent to the contactors, which in turn start the motor. The motor in turn, along with the reducing gear, performs the required rotation in order to changeover the tap. The on-load tap changers used on WEGs transformers are manufactured by MR do Brasil and ABB.

FIGURE 37 ON-LOAD TAP CHANGERS

(a) MR do Brasil

(b) ABB


Transforming power into solutionsIMPORTANT: The technical manual of the On -load tap changer used in this transformer is attached to this manual.

9. MINERAL INSULATING OIL Mineral insulating oil is used in order to per form two important functions on power transformers: Cooling and internal electric insulation. The oil cooling is performed by means of the radiators fins which make the heat exchange with the atmosphere upon a cycle that starts when the hot oil (oil surfa ce) flows upward and then downward through the fins, becoming cooled upon a nearer contact with the atmosphere, returning to the bottom of the tank and so forth. The insulation of the transformers active part is highly essential, since the components are to each other and are subject to electric arches and could impair their perfect operation. There are two types of mineral insulating oil: Naphtenic (Type A) and Paraffinic (Type B). a) Naphte nic: It is naphtenic -based insulating oil without inhib iting contents, import ed in an innatura condition, which is submitted to a careful dehydrating process in order to make it comply with the contents of CNP 06/85 Act and the Technical Regulation No. CNP 18/85. This product is supplied either in epoxy -coated drums or in bulk shipments. This oil features such a high performance that it can meet the most stringent international standards for this type of product, and therefore it can be recommended without any rest rictions for high voltage transformers and circuit breakers using mineral insulating oil. Furthermore, the largest transformer manufacturers approve this oil type. b) Paraffinic : This type of oil is supplied either in drums or in bulk shipments in an in -natura condition. It is a paraffin -based oil wh ich, upon a proper dehydrating and physical and chemical treatment (contact with clay), can be used on transformers. As it is a product that requires a pre-treatment in order to be used as insulating oil, the distributor does not guarantee its performance. The CNP 09/88 Act and the Technical Regulation No. CNP 06/79 refers to the application of paraffinic insulating oil on voltage transformers up to 145 kV. very close



TABLE 10 FEATURES OF THE A -TYPE MINERAL INSULATING OIL (FOR MAXIMUM VO LTAGE OF AN EQUIPMENT RATED FOR MORE THAN 145kV) Features (A) (B) (C) at 20 C o at 40 C o at 100 C (B) (B) ( B) (B) (G) (B) (D)o

Essay method NBR 7148 NBR 10441 NBR 11341 NBR 11349 ASTM D 974 NBR 6234 ASTM D 1500 NBR 5755 NBR 5779 NBR 10505 NBR 11343 NBR 5778 NBR 6869o

Unit mm /s C C mgKOH/g mN/m mg/kg o C kVo o 2

Density, 20/4 oC Kinematical viscos ity Flash point Flow point Neutralization rate o Interfacial voltage at 25 C Color ASTM Water contents Chlorides and sulfates Corro sive sulphur Aniline point o Refraction rate at 20 C Dielectr ic strength

(B) (B) (D) at 100 C at 90 Co

Guaranteed figures Minimum Maxim um 0,861 0,900 25,0 11,0 3,0 140 -39 0,03 40 1,0 35 Absent Absent 63 84 1,485 1,500 30 0,50 -

Dielectric loss rates (D)(E)(G) or Dissipation factor Contents of oxidation inhibitor DBPC/DBP Carbon percentage Stability to oxidation: (F) . Neutralization rate . S ludge o . Dissipation factor, at 90 C(IEC247)

ASTM D 924 % IEC 247 ASTM D 2668 ASTM D 2140 IEC 74 % mass % mgKOH/g %mass %

0,40

0,08 To be noted 0,4 0,10 20

(A) Before starting an inspection, the supplier should provide the inspector with a certificate containing all the features of the supplied products and as stated on this table. (B) These essays should be carried out by the supplier, witnessed by an inspector, on a sample removed from the drums or tanks as well as further essays if necessary. (C) The kinematical viscosity essay should be c arried out at two temperatures between the mentioned ones. (D) The Water contents and Dielectric strength essays do not apply to products carried on vessels or tanker trucks or when they are stored in tanks in which water a bsorption could occur. In such a case, a proper physical treatment should be carried out so that the values specified on the current technical regulation can be restored. o (E) This specification requires that the insulating oil should comply with the power factor limit at 100 C by mea ns o of the ASTM D 924 method, or with the dissipation factor at 90 C by the IEC 247 method. This specification does not require that the insulating oil should comply with the measured limits by means of both methods. o (F) The dissipation factor essay at 90 C, of an oxidized oil by means of the IEC 74 method is carried out according to IEC 247 method and after the preparation of this oil, which is made according to item 10.4.1 of the essay method IEC 10A (Central Office) 56. (G) These items do not apply to re fining plants, which however, should deliver their products in such condi tions that, upon a conventional absorption treatment with clay, carried out by the distributors, it can meet the specified values. Note: The contents of this table are according to CNP 06/85 Act and the corresponding technical regulation, CNP 18/85.


Transforming power into solutionsTABLE 11 MINERAL INSULATING OIL FEATURES - TYPE B (FOR A MAXIMUM EQUIPMENT VOLTAGE EQUAL OR LOWER THAN 145kV) Features (A) Density 20/4 C Kinematical viscosityo

Essay method (B) (C) at 20 C o at 40 C o at 100 Co

Unit mm /so o 2

NBR 7148 NBR 10441 NBR 11341 NBR 11349 ASTM D 974 NBR 6234 ASTM D 1500 NBR 5755 NBR 10505 ASTM D 1552 NBR 11343 NBR 6869 IEC 156 NBR 5778 ASTM D 924 IEC 247 ASTM D 924 AST D 2668 ASTM D 2140 IEC 74

Flash point (B) Flow point (B) Neutralization rate (B) o Interfacial voltage at 25 C Color ASTM Water cont ents ( B) (D) Corrosive sulphur Total sulphur Aniline point (B) Dielectric stre ngtho

C C mgKOH/g mN/m mg/kg % mass o C kV %

(B) (D)

Refraction rate at 20 C o Dielectric loss factor a 100 C o (B) (E) (G) u a 90 C o Dissipation factor a 25 C Contents of oxidation inhibitor DBPC/DBP Contents of aromatic carbons Stability to oxidation: (F) . Neutralization rate . sludge o . Dissipation factor at 90 C (IEC 247)

Guaranteed figure s Minimum Maximum 0,860 25,0 12,0 3,0 140 -12 0,03 40 1,0 35 Absent 0,30 85 91 30 42 1,469 1,478 0,50 0,40 0,05 Non-detectable

% mgKOH/g % mass %

7,0 -

0,40 0,10 20

(A) Before starting an inspection, the supplier should provide the inspector with a certificate con taining all the features of the supplied product s and as stated on this table. (B) These essays should be carried out by the supplier, witnessed by an inspector, on a sample removed from the drums or tanks as well as further essays if necessary. (C) The kinematical viscosity essay should be carried out at two temperatures between the mentioned ones. (D) The Water contents and Dielectric strength essays do not apply to products carried on vessels or tanker trucks or when they are stored in tanks in which water absorption could occur. In such a case, a proper physical treatment should be carried out so that the values specified on the current technical regulation can be restored. o (E) This specification requires that the insulating o il should comply with the power factor limit at 100 C by means o of the ASTM D 924 method, or with the dissipation factor at 90 C by the IEC 247 method. This specification does not require that the insulating oil should comply with the measured limits by means of both methods. o (F) The dissipation factor essay at 90 C, of an oxidized oil by means of the IEC 74 method is carried out according to IEC 247 method and after the preparation of this oil, which is made according to item 10.4.1 of the essay method IEC 10A (Central Office ) 56. (G) These items do not apply to refining plants, which however, should deliver their products in such con ditions that, upon a conventional absorption treatment with clay, carried out by the distributors, it can meet the specified values. Note: The contents of t his table are according to CNP 09/88 Act and the corresponding techni cal regulation, CNP st 06/79, and its revision No. 2 of November 1 , 1988. 9.1. TRANSFORMER PROVIDED WITH DRY GAS AND A NON VACUUM -RESISTANT EXPANSION TANK a) After the vacuum p rocess (according to Attachment C), fill the transformer with oil through the lower valve under vacuum (Thermo -vacuum System) until approx. 150mmHg or 0,2kgf/cm above the lid;


Transforming power into solutionsb) Interrupt the vacuum between the oil level and the transformers lid with dry meter indicates a zero reading; c) d) e) f) Remove the vacuum pump hose; Fit the valves and gas relay to the pipeline and open the fitted -in valves; Open plug-B or install the dehydrating breather without silica gel; Proceed with the oil filling, no preferably through the transformers upper valve, until the expansion tank level that will be compatible with the oil temperature (detectable by the oil level indicator); g) h) Close plug-B; Check the oil expansion tank system for proper operation (Rubber bag applicable; i) Inject nitrogen into the bag until its internal pressure reaches 0,05kgf/cm . Do not allow the nitrogen pressure to exceed 0,05kgf/cm2 2

gas until the vacuum

or membrane), if

so that the bag can slowly accommodate itself and keep

its original shape and allow the oi l to flow to the upper part of the expansion tank within approximately 40 minutes. Make sure the pointer of the magneti c indicator will start to move to the minimum level; j) Start the bags pressuring process by applying no more than 0,05kgf/cm2

and wait u ntil the bag2

accommodates itself, which can be seen by the indication of positive pressure on the v acuum meter. Attention: Repeat this process until the pressure inside the bag reaches 0,1kgf/cm within

approximately 40 minutes. Wait until the pressure s tabilizes before finalizing the pressurizing procedure.



FIGURE 38 - TRANSFORMER PROVIDED WITH DRY GAS AND A NON VACUUM -RESISTANT OIL EXPANSION TANK

9.2. TRANSFORMER PROVIDED WITH DRY GAS AND A VACUUM -RESISTANT OIL EXPANSION TANK a) After the vacuum process (according to attachment C), fill the transformer with oil under vacuum (Thermo-vacuum System) through one of

weg transformer

Documents

expansion tank assembly

altitude of installation

oil expansion tank

tank grounding

assembly of radiators

transforming power

detachable radiators

transformer assem bly