Cooper Substation Transformer

7/22/2019 Cooper Substation Transformer

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Service Informatio

ContentsSafety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Product Information. . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Acceptance and Initial Inspection . . . . . . . . . . . . . . . . 3

Handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Installation Location . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Final Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Liquid Level Gauge . . . . . . . . . . . . . . . . . . . . . . . . . .6

Liquid Temperature Gauge . . . . . . . . . . . . . . . . . . . .6

Pressure-Vacuum Gauge . . . . . . . . . . . . . . . . . . . . . .7

Pressure Relief Device . . . . . . . . . . . . . . . . . . . . . . . . 7

Winding Temperature Gauge . . . . . . . . . . . . . . . . . . . 8

Transformer Cooling Fans . . . . . . . . . . . . . . . . . . . . . . 8

High voltage Bushings . . . . . . . . . . . . . . . . . . . . . . . . 9

Low Voltage Bushings . . . . . . . . . . . . . . . . . . . . . . . . 9

De-energized Tap-Changer . . . . . . . . . . . . . . . . . . . 10

Insulating Liquid . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Periodic Maintenance . . . . . . . . . . . . . . . . . . . . . . . . 1

Removing and Replacing Bushings . . . . . . . . . . . . . 1

Removing and Replacing Draw Lead Type Bushings 1

Removing and Replacing Fixed Stud or Spade Type .

Bushings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Cover Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Insulating Liquid Maintenance . . . . . . . . . . . . . . . . . 1

Applicable Standards. . . . . . . . . . . . . . . . . . . . . . . . . 1

R-Temp Fluid-Filled Transformers. . . . . . . . . . . . . . . 1

Envirotemp FR3 Fluid-Filled Transformers. . . . . 1

Spare Parts and Service . . . . . . . . . . . . . . . . . . . . . . 1

SubstationTransformersSubstation Transformer Installation, Operation,and Maintenance Instructions andParts Replacement Information S210-15-10

August 2012 Supersedes 9/99

Figure 1.Open-Type Substation Transformer.

Figure 2.Unit-Type Substation Transformer.


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Substation Transformer Installation, Operation, and Maintenance Instructions and Parts Replacement Information

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The instructions in this manual are not intended as asubstitute for proper training or adequate experience inthe safe operation of the equipment described. Onlycompetent technicians who are famil iar with thisequipment should install, operate, and service it.

A competent technician has these qualifications:

Is thoroughly familiar with these instructions.

Is trained in industry-accepted high and low-voltagesafe operating practices and procedures.

Is trained and authorized to energize, de-energize,clear, and ground power distribution equipment.

Is trained in the care and use of protective equipmentsuch as flash clothing, safety glasses, face shield,hard hat, rubber gloves, clampstick, hotstick, etc.

Following is important safety information. For safeinstallation and operation of this equipment, be sure toread and understand all cautions and warnings.

Safety Instructions

Following are general caution and warning statements thatapply to this equipment. Additional statements, related tospecific tasks and procedures, are located throughout themanual.

Hazard Statement Definitions

This manual may contain these four types of hazardstatements:

DANGER: Indicates an imminentlyhazardous situation which, if not avoided,

will result in death or serious injury.

WARNING: Indicates a potential lyhazardous situation which, if not avoided,

could result in death or serious injury.

CAUTION: Indicates a potentiallyhazardous situation which, if not avoided,

may result in minor or moderate injury.

CAUTION: Indicates a potentially hazardoussituation which, if not avoided, may result inequipment damage only.

SAFETY FOR LIFE!

SAFETY

FOR LIFE

!SAFETY

FOR LIFE

Cooper Power Systems products meet or exceed all applicable industry standards relating to product safety. We activelypromote safe practices in the use and maintenance of our products through our service literature, instructional trainingprograms, and the continuous efforts of all Cooper Power Systems employees involved in product design, manufacture,

marketing, and service.

We strongly urge that you always follow all locally approved safety procedures and safety instructions when workingaround high voltage lines and equipment, and support our Safety For Life mission.

SAFETY INFORMATION

DANGER: Hazardous voltage. Contact withhazardous voltage will cause death or severe

personal injury. Follow all locally approved safetyprocedures when working around high voltage linesand equipment. G103.3

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WARNING: Before instal l ing, operating,maintaining, or testing this equipment, carefully

read and understand the contents of this manual.Improper operation, handling or maintenance can resultin death, severe personal injury, and equipmentdamage. G101.0

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WARNING: This equipment is not intended toprotect human life. Follow all locally approved

procedures and safety practices when installing oroperating this equipment. Failure to comply can resultin death, severe personal injury and equipmentdamage. G102.1

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WARNING:Power distribution and transmissionequipment must be properly selected for the

intended application. It must be installed and servicedby competent personnel who have been trained and

understand proper safety procedures. Theseinstructions are written for such personnel and are not asubstitute for adequate training and experience in safetyprocedures. Failure to properly select, install or maintainpower distribution and transmission equipment canresult in death, severe personal injury, and equipmentdamage. G122.3

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PRODUCT INFORMATION

Introduction

This manual has been prepared to ass ist competenttechnicians in the installation, operation and service ofprimary or secondary unit- or open-type substation trans-formers.

Substation transformers are designed for installation onthree-phase systems. All units are constructed for in-dooror outdoor mounting on a concrete pad with high and lowvoltage cables entering operating compartments throughenclosed sidewal l mounted bushings (unit-typetransformers) or through cover or sidewall mountedbushings (open-type transformers).

Although every effort has been made to anticipate normalinstallation, operation and servicing problems, theseinstructions do not cover all possible variations inequipment or application conditions. All possibleinstallation, operation or service contingencies are notdiscussed. If additional information is required, contact a

factory representative.It is important that personnel using these instructions befully acquainted with industry accepted high and lowvoltage safe operating practices and procedures. Theseinstructions are not intended as a substitute for propertraining or adequate experience in the safe operation ofthe equipment described.

Read This Manual FirstRead and understand the contents of this manual andfollow all locally approved procedures and safety practicesbefore installing or operating this equipment.

Additional InformationThese instructions cannot cover all details or variations inthe equipment, procedures, or process described, nor toprovide directions for meeting every possible contingencyduring installation, operation, or maintenance. Foradditional information, contact your Cooper PowerSystems representative.

Acceptance and Initial Inspection

It is important that a thorough inspection of thetransformer be madebeforeit is unloaded from the carrier.

1.Ensure that all parts listed on the bill of lading arepresent.

2.Before unloading the tr ansforme r, make aninspection to detect any signs of damage ormishandling. Locate any accessory parts that mayhave been shipped separately.

3. If any damage is detected or shortages are noticed,write a brief description on the freight bill. Normally,the transformer is sh ipped FOB point ofmanufacture, and it is the customer's responsibilityto file a claim against the carrier. If the transformerwas shipped FOB destination, notify your factory

representative. He or she will, with the inspectorreport, take the necessary steps to file a claiagainst the carrier.

Handling

For unloading, lifting hooks are provided near the top

the transformer tank. Cable pull angles should not be ov30 from vertical. Otherwise, spreaders should be used hold the lifting cables apart to avoid any bending of thstructure or lifting hooks.

If the transformer cannot be lifted by crane, it may bskidded or moved with rollers. When jacking a transform

to insert rollers underneath it, insure that at least two jackare used and that two adjacent corners are raisesimultaneously and evenly to avoid warping the basJacks may be placed only at the corners of thtransformer base.

Do not place jacks under cooler assemblies, valves, osheet metal parts. When using rollers, use as many anecessary to distribute the weight uniformly. To puattach pulling eyes to the holes in the base at either end the transformer.

Do not attach pulling lines to moldings or other sheemetal parts of the transformer.

StorageWhenever possible, the transformer should be stored at ipermanent location.

The insulating liquid should be at its proper level and thgas space pressurized to approximately two psig. Thenshould be tightly sealed so that no moisture or air caenter the tank. Periodic inspection should determine ththe pressure gauge does not remain at zero, and propliquid level is maintained at all times.

The transformer should not be stored in the presence corrosive gases (e.g., chlorine). Exterior surfaces of thtransformer should be maintained against rust an

corrosion.Before placing a transformer into service after aex-tended storage time, check fans, alarm and contrcircuits, and the dielectric strength of the insulating liquid

Quality Standards

ISO 9001 certified quality management system

WARNING:Do not attempt to lift the transformeby placing a continuous loop of cable or chain

around the unit or lifting lugs. Improper handling canresult in death, severe personal injury and equipmendamage.

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Installation Location

The transformer should be located on a concrete pad ofsufficient strength to support the weight of the unit. Thepad must be level. The location of the transformer,whether indoor or outdoor, should provide for adequateaccessibility, ventilation and ease of inspection. Thetransformer should be at least 24 inches from anyobstruction. Location in areas of corrosive chemicalsshould be avoided.

These substation transformers are bui lt to operate ataltitudes up to 3300 feet at 30 C average and 40 Cmaximum ambient, unless otherwise specified. Beforeoperating a standard transformer at higher altitudes,contact your factory representative.

Adequate vent ilat ion must be prov ided. For indoorinstallations, room air inlets should be located at floor level;the air outlets should be located as high as the room will

permit. The number and size of the air inlets dependsupon the rating of the transformer. In general, about 20square feet each of inlet and outlet area should beprovided for each 1000 kVA of transformer capacity. If theventilation system is adjustable, it should be lockedpermanently open to avoid overheating of the transformerin case of operator error.

Connections

Connections must be made without placing undue stresson the bushing terminals. Conductors should be securelyfastened in place and supported properly, with allowancefor expansion and contraction. Make sure that the tapconnection is proper for the required voltage. Changes in

tap connections must be done ONLY with the transformerhigh voltage and low voltage circuits completely"DE-ENERGIZED". Safely verify that there is no voltagepresent at the terminals.

Transformers equipped with an internal terminal board arenormally shipped with the higher voltage connected,unless otherwise specified by the customer.

A secure and effective low resistance ground is essentialfor protection. The transformer must be grounded

permanently by connecting a heavy ground cable to theground pad located at the bottom of the tank. If thetransformer is designed for operation in a solidly groundedneutral system, the neutral connection should be solidlyand permanently grounded with minimum resistance.

Lightning arresters are recommended for every trans-former installation. Arresters of proper rating should belocated as close as possible to the transformer termina-

tions.When alarm contacts or controls are supplied with thetransformer accessories, a connection box may beprovided to facilitate termination of the customer's cableor conduit.

Final Inspection

The final inspection can be done in three major steps:Electrical, Internal and External.

Electrical inspection should determine that:

1.All external connections have been made proper ly(phasing of connections to terminal bushings, etc.).

2.All connections are tight and secure.

3.All accessory contact circuits are operational.

4.Current transformer circuits, if supplied, havesecondaries either shorted or connected through theirload.

5.Tap changer is operative and properly positioned.

6.The correct transformer ratio exists for units furnishedwith internal terminal board.

7.There is no grounding of windings that are not intendedto be grounded. A 1000-volt megger test isrecommended.

8.There is continuity in all windings.

9.The dielectric strength of the insulating liquid is 30 kVminimum when new. (Refer to section for "TestingInsulating Liquid" in this manual.)

10.The neutral and ground connections have beenproperly made.

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INSTALLATION

WARNING: Do not change connections on atransformer that is energized. Ground all circuits

before making any transformer connection. Failure toobserve precautions when making connections canresult in exposure to high voltages, which can causedeath, severe personal injury or damage to theequipment.

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WARNING: Do not make any connections,except as authorized by the nameplate orschematic. Improper connections can result in severepersonal injury and damage to the equipment.

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WARNING: Improper grounding may result inpersonal injury or damage to the equipment.!

WARNING:Do not tamper with interlocks, alarmor control circuits. Doing so can produce unsafe

conditions for operators or result in damage to the

equipment.

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If an internal inspection is required, assure that:

1.There is no evidence of moisture.

2.All available bolted connections are tight.

3.There has been no shifting of any parts or any otherdamage.

The external inspection should determine that:

1.All scratches have been painted.

2.The bushings are clean.

3.The accessories are operative.

4.There are no tools, or other objects, left on top of thetransformer or inside any enclosure.

5.The liquid level is correct.

6.The transformer holds positive pressure.

7.The manhole covers are tightly bolted.

8.All protective covers are closed and bolted tight.

9.The mechanical pressure relief device is reset.

CAUTION:Whenever it is necessary to open aliquid-filled transformer, insure that the liquid

temperature is higher than the outside air temperature.Otherwise, internal moisture condensation may occur,which could lead to failure of the transformer.

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CAUTION: Before breaking the seal of anyhandhole, manhole or bushing hole, bleed

internal pressure to zero. Seals should not be brokenin the presence of fog, rain or snow, or if there is anyevidence of condensation on the transformer tank. Ifeven a very slight amount of such moisture enters thetransformer tank, it can decrease the dielectric strengthof the cooling liquid to dangerously low levels, whichcan result in damage to the equipment.

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CAUTION: Only authorized personnel shouldbe permitted on top of the transformer and every

precaution should be taken to avoid dropping objectsinto the transformer. Workers should not have anythingin their pockets (such as pens, pencils, coins, etc.) andtheir clothing should not have loose metal buttons,

badges, buckles, etc. Wristwatches should also beremoved. When dropped into the transformer tank,such objects can cause equipment malfunction anddamage.

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6

Liquid Level Gauge

A liquid level indicator is provided to aid in the systematicinspection of the transformer under load. It consists of afloat-arm inside the tank, an indicating pointer and amagnetic coupling between the two across a liquid-tightseparation.

The gauge may be furnished with SPDT (Single PoleDouble Throw) alarm contacts to give a remoteannunciation of low liquid level. For contact wiring andterminal points, see the accessory connection diagramfurnished with the transformer.

Liquid Temperature Gauge

The temperature gauge is furnished to indicate the topliquid temperature in the tank in degrees Centigrade. Thetemperature-sensitive element is mounted in a leak-proofwell, permitting removal of the thermometer withoutlowering the oil level. The device is furnished with anadditional red pointer to show the highest temperatureattained since the last reset. To reset the maximumindicator, turn the knob in the center of the dial.

The thermometer can be furn ished with two SPDTcontacts for a high temperature alarm, for energizing a fancircuit or for a low temperature alarm. For wiring andcontact settings, refer to the schematic furnished with thetransformer.

ACCESSORIES

Figure 3.

Liquid Level Gauge.Figure 4.Liquid Temperature Gauge.


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Pressure-Vacuum Gauge

The pressure-vacuum gauge indicates whether the gasspace in the tank is under positive or negative pressure.

The pressure wil l vary depending on the transformertemperature. If the transformer is de-energized oroperating under light load in low ambients, the pressuremay be negative.

Note: If the indicator reads zero and does not changeunder any load condition, the transformer shouldbe checked for a possible leak in the seal.

If sufficient air has been absorbed by the liquid duringshipment or storage, the transformer may operate

indefinitely in the vacuum range, depending upon theloading conditions. This, in itself, is not cause for concern,provided the pressure vacuum gauge does not remain onzero for any length of time an indication of a leak.

The unit may be equipped with pressure vacuum switcheswith two SPDT contacts for remote alarm on positive andnegative pressure. For wiring and contact ratings, refer tothe schematic furnished with the trans-former.

When required, the pressure gauge is furnished with apressure regulator that will automatically regulate the tankpressure between 7.0 psig positive and 3.0 psig negative.

The pressure regulator is fitted with a valve and fitting totake gas samples.

Pressure Relief Device

Al l su bstati on tra ns formers are fur ni sh ed wi th mechanical pressure relief valve (PRV) or pressure rel

device (PRD). The cover-mounted PRD consists of a seresetting, spring-loaded diaphragm and a mechanicoperation indicator. Should the tank pressure increaabove that for which the device is set, the gas pressuwill lift the diaphragm and let the gas escape quickImmediately after the pressure returns to normal, tdiaphragm will reset and reseal the transformer. mechanical indicator will protrude vertically. This must reset manually to indicate subsequent operations.

Contacts are optional. For wiring information, refer to tschematic furnished with the transformer.

Figure 6.Pressure Relief Device.

Figure 5.Pressure-Vacuum Gauge.


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Winding Temperature Gauge

Transformers may be furnished with a winding temperaturegauge as optional equipment. A temperature sensitivestem is mounted in a leakproof well, permitting removal ofboth the instrument and stem without lowering the liquidlevel. The well is heated by both the surrounding liquid anda heater element which is energized from a currenttransformer mounted inside the tank to simulate the hotspot winding temperature gradient. The combination of thetwo temperatures is indicated on the gauge. An additionalred pointer is furnished to show the highest temperatureattained since the last reset. The maximum indicator isresettable by means of a pushbutton through the bottomof the dial bezel.

The gauge has three separate SPDT switches for fancontrol and alarm circuits. For wiring the contact settings,refer to the schematic furnished with the transformer.

The equipment is calibrated to indicate the hottest spot ofthe transformer windings. All contacts are factory set tooperate at the temperatures shown in the connectiondiagram.

If readjustment of the contacts is desired, consult thefactory for detailed instruction.

Transformer Cooling Fans

In order to increase the transformer load withoutoverheating the windings, a set of fans can be furnished asan optional item. Fan control consists of a contact oneither the liquid temperature gauge or the windingtemperature gauge (when furnished), and "Manual-Auto"control switch.

For continuous run, the switch is turned to the "Manual"position. In the "Auto" position, the fans are controlled bythe contacts on the temperature gauge. For contact andtemperature settings, refer to the schematic furnished withthe transformer.

Refer to wiring schematic for control equipment supplied.

WARNING: Fan guards are furnished andinstalled for your protection. Do not remove fan

guards or probe into the fan with long objects. Doingso can result in severe personal injury and equipmentdamage.

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Figure 7.Winding Temperature Gauge.

Figure 8.Transformer Cooling Fan.


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High Voltage Bushings

High voltage leads for ratings 2.4 kV and up are normally

brought through the tank end wall using a porcelainbushing. To prevent excessive mechanical loading of thebushing, only flexible connections should be made to thebushing terminal. The bushing should never be used as astructural member to support other current-carrying parts.

Care must be taken in handling the bushing to avoidcracking the porcelain or damaging its surface.

Should it become necessary to replace a bushing or itsgasket, proceed as follows:

1.Vent the tank to the atmosphere until pressure is zero.

2.Lower the liquid level to a point below the bushinglevel.

3.Remove the nuts and washers used to clamp theflange of the bushing.

4.Pull the bushing outward as far as necessary to replacethe gasket and/or to unfasten the cable connection atbushing inner end.

Only in rare circumstances will there be insufficient slack inthe cable leads to facilitate bushing replacement throughthe wall. The alternative means of gaining access to theconnections is through the manhole.

When reinstalling the bushing, install a new gasket in thgasket recess on the underside of the flange to insure ththe gasket is properly seated in the groove. A flat washand lock washer should be placed between the mountinnut and the flange. After the nuts are finger tight, each onshould be tightened to a torque of 605 inch pound

After completion, pressure test the transformer.

When condenser-type bushings are used, supplementaleaflets forming a part of the complete instruction book wbe provided.

Low Voltage Bushings

Low voltage leads for ratings in the 1.2 kV Class anormally brought through the tank wall using an indobushing. This is a cast resin or porcelain bushing.

The low vo ltage bushing should not be used as

structural member. As a rule, only flexible connectionshould be made to any bushing. Avoid rigid connectiobetween the bushing and other bus supports to eliminathermal expansion forces to the bushing.

If a bushing is damaged and leaking transformer coolancontact your factory representative for proper repaprocedures.

Figure 9.High Voltage Bushing.

Figure 10.Low Voltage Bushings.


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10 11

De-energized Tap-Changer

The tap-changer provides a means of changing thevoltage ratio of a de-energized transformer withoutbreaking the transformer seal. It is operated by means of arotatable handle located on the side of the transformer.

The tap-changer is normally provided with five or sevenpositions, as indicated on the tap-changer dial plate andtransformer instruction nameplate.

Insulating Liquid

The insulating liquid in substation transformers is eitherconventional transformer oi l , R-Temp fluid orEnvirotemp FR3 fluid. When makeup liquid isrequired, use only approved fluid of the same type that isin the transformer. It is important to check the proper liquidlevel in the transformer at all times by periodically

observing the liquid level gauge. In addition, the dielectricstrength of the insulating liquid must be maintained at ahigh value.

It is recommended that a sample be taken of the liquidand tested within one week after energization, andannually thereafter.

WARNING: Do not operate the tap-changerwhile the transformer is energized. Doing so can

result in severe personal injury and equipment damage.

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Figure 11.De-energized Tap-Changer..

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Periodic Inspection

1.External: Periodically check the condition of the paintand finish, especially when the transformer is exposedto inclement atmospheric conditions. If weatheringtakes place, clean the tank thoroughly, wipe off any

insulating liquid that might have been spilled on thesurface and repaint with a factory approved paint.Occasionally, inspect and tighten all bolted joints andcheck for leaks.

2.Regularly inspect all gauges. The liquid level mustremain normal, considering the temperature effect.Refill when samples have been taken. Prolongedperiods of zero pressure could indicate a gas leak andshould be checked out. The liquid temperature shouldnot rise higher than the design value on the nameplate,plus ambient temperature.

3.Liquid samples should be taken periodically andanalyzed as indicated under "Sampling". It isrecommended that you keep a log of the test values todetermine when reconditioning or replenishing serviceis required.

Removing and Replacing Bushings

Bushing construction falls into two general categories:"draw lead" type as represented by Figure 12 and bottomconnected types with a fixed center stud or internal spadeas represented by Figure 13.

The method for removing bushings will differ dependingupon the type of construction. The two methods are dealtwith separately in the written material that follows.

Before any work commences, standard safety precautionsmust be observed.

Additional precautions include the following:

Lock in the open position disconnect switches in thesupply lines to and from the transformer.

If the transformer is under vacuum or pressure, bringthe tank to ambient pressure.

If the bushing to be removed is below the liquid level,lower the level sufficiently to prevent fluid loss.

To protect from the atmosphere and contaminants,store in clean, dry, sealed containers any removedliquid that will be returned to the trans-former.

Removing and Replacing DrawLead Type Bushings

Removing

1.Unscrew and remove the top terminal cap, exposin

the threaded stud end of the draw lead cable. In somcases, the threaded stud will be held by a pin thmust also be removed.

2.Fasten a pull wire, cord or rod to the stud in order guide the lead through the bushings bore and preveit from falling into the opening when the bushing removed. (In some cases, the lead will be of sufficiethickness to be self-supporting; if so, this part of tprocedure can be omitted).

3.Remove the bushing mounting clamp nuts at the tato release the mounting clamp plate and free thbushing for removal.

4.Remove the bushing, guiding the draw lead conductand terminal stud through the base of the bushing.

MAINTENANCE

WARNING: Before working with bushings,make sure that the transformer is de-energized

and that all circuits to and from the transformer aregrounded in order to discharge any stored energy andprevent accidental re-energization. Failure to do so mayresult in death, severe personal injury and equipmentdamage.

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Figure 12.Draw Lead Type Bushing.


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12

Replacing

Replacement draw lead type bushings can be installed byfollowing the removal procedure in reverse order. Clampbolts should be tightened as specified in Table 1.

The gasket under the bushing mounting flange and thetop gasket should be new or in good condition to ensure apositive seal. The gasket mating surfaces must be clean

and smooth.

The threaded stud is keyed to the inside of the bushing toprevent rotation while the terminal cap is being tightened.It is important to have the threaded stud correctly seated.

This can be accompl ished by pull ing the stud up andturning it until it is aligned and seated.

Removing and Replacing FixedStud or Spade Type Bushings

Removing

1.Remove inspection cover (manhole) nearest tobushing, only after all precautions outlined under

"Removing and Replacing Bushings" have been taken.

2.To remove the inspection cover:

a.Thoroughly clean the cover. Remove all dirt, greaseand moisture.

b.Release and remove cover bolts.

c.Remove the cover. Lift vertically to prevent damageto bolt or cover gaskets.

3.Unbolt the connectionsusually flexible strapsfrom thebottom end of the bushing stud.

4.Remove the bushing mounting clamp nuts at the tank

to release the mounting clamp plate and free thebushing for removal.

5.Remove the bushing.

Replacing

Replacement bushings can be installed by following theremoval procedure in reverse order. Clamp bolts should betightened as specified in Table 1.

The gasket under the bushing mounting flange should benew or in good condition, and the gasket mating surfacesmust be clean and smooth.

After installing and connecting the new bushing, replacethe inspection opening cover, making certain the gasket isin good condition and the gasket mating surfaces areclean and smooth.

Return to the transformer any liquid removed and checkfor the correct level.

A brief pressure test of the transformer at 5 psig to confirmthe integrity of the seals around all openings above theliquid level is recommended. A solution of soap and waterwill give indication of a leak by the presence of bubbles.

Bushing Clamps

4-Hole Aluminum Cast Bushing Clamps 70-80 in.-lbs.

Molded Tri-Clamp Bushing 40-60 in.-lbs.

All other 3 & 4 hole Bushing Clamps 40-60 in.-lbs.

2-hole Bushing Clamps 55-65 in.-lbs.

TABLE 1Torque Values

Internal Spade Bushings

1/2" Steel (Grade 8) 50 ft.-lbs.

3/8" Steel (Grade 8) 50 ft.-lbs.

Internal Stud Bushings

3/8"-16 Brass Nuts 16 ft.-lbs.

5/8"-11 Aluminum Nuts 60 ft.-lbs.

5/8"-11 Brass Nuts 75 ft.-lbs.

1"-14 Brass Nuts 121 ft.-lbs.

Bushing Lead Block, Steel Hardware 110 ft.-lbs.

Figure 13.Fixed Stud and Spade Type Bushings.


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Cover Removal

(For Envirotemp FR3 fluid-filled units, see InsulatingLiquid Maintenance Section before continuing.)

Transformers that have been system connected should bede-energized, grounded, and disconnected before beingopened for inspection.

Substation transformers may have either bolt-on or weld-in-place main tank covers. Access to the interior of atransformer with a bolt-on main tank cover withouthandholes requires removal of the entire cover. Access tothe interior of the welded-in-place main tank cover designis typically through manhole or handholes.

To Remove a Bolt-On Main Tank Cover

1.Thoroughly clean the cover. Remove all dirt, greaseand moisture.

2.Relieve internal tank pressure by manually operatingthe pressure relief valve.

3.Remove the hardware (3/8 inch nuts using a 9/16socket) which attaches the cover to the tank.

4.Gently pry the cover upward, making sure that thecover gasket does not come in contact with thetransformer insulating liquid. Lift vertically to preventdamage to cover, bolts, and tank gasket.

5.Remove the gasket sections from the tank flange,noting the location and orientation (up/down) of eachpiece.

To Reinstall the Bolt-On Main Tank Cover

1.Return the gasket sections to their original positioand orientation.

2.Reinstall the cover, using 25 ft-lbs. torque to tighten tcover hardware. After installing all the nuts, re-torqeach nut to insure the proper torque is achieved.

3.Remove the pressure relief valve and pressurize thheadspace to insure that there are no leaks. Thpressure should not exceed 7 psig. The establishepressure should be maintained for at least four houto insure that all the seals are proper.

To Remove a Bolted-On Manhole orHandhole Cover

1.Thoroughly clean the cover. Remove all dirt, greaand moisture.

2.Relieve internal tank pressure by manually operatinthe pressure relief valve.

3.Remove the hardware (3/8 inch nuts using a 9/1

socket) which attaches the cover to the tank.

4.Gently pry the cover upward, making sure that thcover gasket does not come in contact with thtransformer insulating liquid. Lift vertically to prevedamage to cover, bolts, and tank gasket.

5.Remove the gasket sections from the manhole flangnoting the location and orientation (up/down) of eacpiece.

To Reinstall the Bolt-On Manhole orHandhole Cover

1.Return the gasket sections to their original positio

and orientation.2.Reinstall the manhole/handhole cover, using 25 ft-lb

torque to tighten the hardware. After installing all tnuts, re-torque each nut to insure the proper torqueachieved.

3.Remove the pressure relief valve and pressurize thheadspace to insure that there are no leaks. Thpressure should not exceed 7 psig. The establishepressure should be maintained for at least four houto insure that all the seals are proper.

4.Reinstall the access cover using 25 ft-lbs. torque tighten the access cover hardware.

WARNING: Before the tank cover, manholecover or handhole cover is removed, the

transformer tank must be vented to zero pressure byactivating the pressure relief valve. Failure to do somay result in severe personal injury, death or propertydamage.

!

CAUTION: If the main tank cover, manholecover, handhole cover or access cover must

be removed for internal inspection or service of thetransformer, precautions must be taken to preventdirt or moisture from entering the opened unit.Contamination of the insulating fluid will prevent thetransformer from operating properly and may causeserious damage to the transformer.

!

WARNING: Trans fo rmers must never beopened or serviced while system is connected,

ungrounded or energized. Tampering with the coversor cover seals of a transformer that has not beende-energized, grounded and disconnected may result insevere personal injury, death or property damage.

!

WARNING: If the need arises to open a weldedtank unit by cutting welds, purge all gas space

with nitrogen and keep nitrogen flowing during cuttingoperations. Failure to do so may cause gases toexplode in the tank.

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14

Insulating Liquid Maintenance

Sampling Insulating Liquid

Note: A sample of the liquid should be taken when theunit is warmer than the surrounding air to avoidcondensation of moisture on the liquid. Liquidsamples must be drawn from the sampling valvelocated at the bottom of the transformer tank.

Containers used for sampling liquid should be clean anddry large mouth glass bottles.

Do not permit the fluid to splash into the receivingcontainer. Splashing can introduce air and moisture intothe fluid. Rinse the bottle three times with the liquid beingsampled. Make sure the l iquid being sampled isrepresentative of the liquid in the unit.

Test samples should be taken only after the liquid hassettled for some time eight hours for a barrel, up toseveral days for a large transformer. Cold insulating liquidis much slower in settling. Liquid samples from thetransformer should be taken from the sampling valve at

the bottom of the tank.

When sampling, a metal or non rubber hose must be usedbecause oil leaches the sulfur found in rubber. Thepresence of sulfur can prove harmful to transformercomponents.

When drawing samples from the bottom of thetransformer or large tank, sufficient liquid must first bedrawn off to ensure that the sample will be from thebottom of the tank, and not the liquid stored in thesampling pipe.

Testing Insulating Liquid

For testing the dielectric strength of insulating liquids,follow the procedure specified by the American Society for

Testing Materials in ASTM D-877, "Standard Method forTesting Electrical Insulating Oils."

If, at any time, the dielectric strength of the liquid dropsbelow 26 kV, it should be filtered until it tests at 26 kV orbetter.

Filtering Insulating LiquidTransformer oil, R-Temp fluid or Envirotemp FR3 fluidcan be filtered by means of a filter press. The filter press iseffective for removing all types of foreign matter, includingfinely divided carbon and small amounts of moisture. Thepurifier equipment consists of a specifically proportionedfilter press, a positive volume gear pump, driving motor,combined drip pan and mixing tank, necessary piping,valves, strainer, gauges and a drying oven.

Filtration should be continued until the dielectric test of theinsulating liquid is 26 kV or better.

Applicable Standards

1.ANSI C57.91 (Latest Issue), "Guide for LoadingMineral Oil Immersed Transformers."

2.ANSI C57.93, (Latest Issue) "Guide for Installationand Maintenance of Liquid Immersed Power

Transformers."

3.ANSIC57.106 (Latest Issue), "Guide for Acceptanceand Maintenance of Insulating Oil in Equipment."

4.ASTM Specification #D 877, "The Standard Method ofTesting Electrical Insulating Oils."

5.ANSIC57.121 (Latest issue), Guide for Acceptanceand Maintenance of Less Flammable HydrocarbonFluid in Transformers.

R-Temp Fluid-Filled Transformers

Periodic maintenance tests for R-Temp fluid-filledtransformers should be performed on essentially the sameschedule as would be used for conventional mineral oil-filled transformers of similar application. The same type ofsampl ing techn iques shou ld be used. Bas icrecommended tests for R-Temp fluid-filled transformersare dielectric strength, moisture content, and flash and firepoint.

Dielectric Strength

Although the transformer should operate satisfactorily witha fluid dielectric strength of 22 kV, an R-Temp fluiddielectric strength below 25 kV is an indication ofexcessive contamination. In this case, the R-Temp fluidshould be replaced or filtered to remove the moisture orparticulate contamination.

The dielectric strength of R-Temp fluid should be tested inaccordance with ASTM D 877.

WARNING: Do not lower fluid in tank to a levelbelow the top of the core clamp. Insufficient

fluid risks unit failure, which could result in severepersonal injury or death to exposed personnel.

!

CAUTION: When fi ltering any insulatingfluid, the filtering equipment must be free of

contaminants and other l iquids. The presenceof other liquids may alter the physical and electricalcharacteristics of the fluid.

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S210-15-10

1

!SAFETY

FOR LIFE

Flash and Fire Points

Relatively small percentages (2-3%) of transformer oil orcontaminants may substantially reduce the flash and firepoint of R-Temp fluid. If it is suspected that the fluid mayhave been exposed to contamination, the flash and firepoint should be measured in accordance with ASTMD-92. A fire point lower than 300 C probably indicates

some contamination by lower fire point material. If flash orfire points fall below the minimum values required,retrofilling may be required.

Drain and Refill

If it is necessary to drain and refill the transformer, specialcare should be taken to avoid the entrapment of gasbubbles in the system. Sufficient time should be allowedbetween refilling and energization of the transformer to besure that any gas bubbles created during the processhave dissipated.

Contact your Cooper Power Systems representative foradditional handling guidelines.

Envirotemp FR3 Fluid-FilledTransformers

Periodic maintenance should be performed on the sameschedule as would be used for units of similar applicationfilled with transformer oil. The same type of samplingtechniques should be used (ASTM-D923). Basicrecommended tests for Envirotemp FR3 fluid aredielectric strength, moisture content and flash and firepoints.

Acceptance values should meet or exceed those shown inIEC 61203, "Guide for Maintenance of Transformer Estersin Equipment".

If the transformer cover or manhole must be removed finternal service, exposure time to ambient air should bminimal. Avoid exposure times greater than 24 hourImmediately after service is completed, replace the covor manhole. Then, purge and recharge the headspacwith dry nitrogen.

The procedure for recharging the headspace with nitrog

should include the following steps:1.Fill headspace with dry nitrogen to a pressure of 2

psig.

2.Vent headspace to atmospheric pressure.

3.Refill headspace with nitrogen to 2-3 psig.

4.Verify that the unit is hermetically sealed.

If the manhole cover or non-flapper style Bay-O-Net fusare removed for more than 24 hours, any oxygen absorbpacket(s) should be replaced.

Transformer Oil Contamination

Envirotemp FR3 fluid is fully miscible with oil. Thereno known detrimental performance impact wheEnvirotemp FR3 fluid is mixed with mineral oConversely, except for some reduction in flash and fpoints, the same is true for oil mixed in with EnvirotempFR3 fluid. More than 7% mineral oil in EnvirotempFR3 fluid is required to drop the fire point to belo300 C. To maintain its exceptional environmentclassification, contamination of Envirotemp FR3dielectric coolant by any other fluids should be avoided.

Contact your Cooper Power Systems representative fadditional handling guidelines.

Spare Parts and Service

We suggest that you keep one spare set of gaskets for tmanhole and any gasket-type bushings used. Othrenewal parts may be ordered through your local factorepresentative. When ordering parts or requesting servicprovide a complete description of the part or the probleand the complete transformer serial number as listed the nameplate.

CAUTION: When the insu lat ing f lu idtemperature is less than 10 C (14 F), no-load

tap changers and energized loadbreak switches shouldnot be operated and the Bay-O-Net fuses shouldnot be used to make or break a load. (Operationsat lower temperatures may be possible provided itis certified by the switching device manufacturer forloadbreak operation in Envirotemp FR3 fluid atlower temperatures.)

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2300 Badger DriveWaukesha, WI 53188

2012 Cooper Industries. All Rights Reserved.Cooper Power Systems and R-Temp are valuable trademarks of CooperIndustries, in the U.S. and other countries. You are not permitted to usethe Cooper Trademarks without the prior written consent of CooperIndustries.Envirotemp and FR3 are licensed trademarks of Cargill, Incorporated.ANSIis a registered trademark of the American National StandardsInstitute.

One Cooper | www.cooperpower.com | Online

S2101510 August 2012

!SAFETY

FOR LIFE

Cooper Substation Transformer

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