Section 13 — Electrical

Power Transformers

IPE Engineering Practice IPE-EP-13-4-1

Document number: IPE-EP-13-4-1 · Section: 13 — Electrical

Table 2 Bil Requirements For Low Voltage Ratings 21Table 2 Bil Requirements For Low Voltage Ratings 21

Table 3 Minimum Fan Cooled Ratings 22Table 3 Minimum Fan Cooled Ratings 22

Table 4 CT Accuracy Class Requirements 22Table 4 CT Accuracy Class Requirements 22

Table 5 Documentation Requirements For Power Transformers per EP 13–4–1 23Table 5 Documentation Requirements For Power Transformers per EP 13–4–1 23

SCOPE

• This Practice including the Power Transformers Data Sheet (EP 13–4–1 DS), covers the requirements for three phase, oil filled power (substation and unit) transformers and pad mounted transformers. Transformers shall conform to this Practice (including compliance to referenced standards and codes), unless written approval from the Owner is obtained for exceptions.
• This Practice is appropriate for attachment to an inquiry or purchase document when accompanied by the referenced IPE Engineering Practices and completed Data Sheets.
• This Practice is appropriate for attachment to an inquiry or purchase document when accompanied by the referenced IPE Engineering Practices and completed Data Sheets.
• Any deviation from this Practice must be approved by the procedure described in EP 1–1–3.
• A revision bar indicates all changes made to this Revision.

2.0 REFERENCES

All applicable sections of the latest standards and codes listed below are a part of this Practice for construction, wiring and testing unless amended herein. It shall be the Manufacturer’s and or suppliers responsibility to be or become knowledgeable to the requirements of these standards and codes. Any changes or alterations to the equipment to make it meet the requirements of the referenced standards and codes shall be at the expense of the Manufacturer and/or the supplier.

STANDARDS AND PUBLICATIONS

STANDARDS AND PUBLICATIONS (Cont.)

DEFINITIONS

• Contractor – Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.
• Inspector – A Inflection Point Engineering, LLC appointed engineer or inspector.
• Manufacturer – The recipient of a direct or indirect purchase order for materials and/or equipment. In this context, a direct order is one issued to a Manufacturer by a Contractor or the Owner. An indirect order is one issued to a Manufacturer by a vendor (recipient of a direct order) for materials, fabricated components, or subassemblies.
• Owner – Inflection Point Engineering, LLC.
• Owner’s Engineer – A Inflection Point Engineering, LLC appointed engineer.
• Purchaser – The party placing a direct purchase order. The Purchaser is the Owner’s designated representative.

4.0 SERVICE CONDITIONS

Transformers shall perform satisfactorily when operated outdoors, either intermittently or continuously, in a corrosive atmosphere likely to be encountered in petroleum and chemical plant installations. Unless otherwise noted on the Transformer Data Sheet, transformers shall be for use in a 104F maximum, –15F minimum ambient at an altitude of 3,300 feet or lower and installed on a level concrete pad.

DESIGN CONSTRUCTION AND MATERIALS

• Temperature Rise

All transformers covered by this Practice shall be designed and nameplated for a 55/65C average winding temperature rise by resistance and suitable for continuous operation with 65C average winding temperature rise by resistance and 80C hottest–spot winding temperature.

• Short Circuit

Transformers covered by this Practice shall be capable of meeting the short circuit requirements of ANSI C57.12.00 and C57.12.90. The design offered shall have been tested and successfully met the ANSI short circuit requirements.

• Basic Impulse Levels

• Power transformers basic impulse level (BIL) shall be in accordance with levels given in ANSI C57.12.00 and ANSI C57.12.10 for transformers through 69 KV. The BIL for insulation classes above 69 KV shall be as specified on the Transformer Data Sheet.
• Pad mounted transformers BIL shall be in accordance with ANSI C57.12.22 and ANSI C57.12.27.
• Acceptable BIL levels for transformers supplied to the Owner shall meet or exceed the values listed in Table 1 and Table 2 (Extracted from the ANSI C57 Standards referenced in 5.3.1 and 5.3.2).
• For all transformer sizes not specified above, the BIL shall be as indicated on the Transformer Data Sheet.
• All transformers with WYE connections will be designed with full line end BIL (insulation) all the way to the neutral bushing.
• Audible Sound Levels

Sound levels shall not exceed the values given in NEMA Standard TR–1 and/or levels required by OSHA.

• Cooling Classes and Ratings
• Power transformer rating shall be based on self–cooled operation (OA rating).
• All liquid filled power transformers 500 KVA and larger shall have provisions for increasing their continuous KVA rating by the use of cooling fans. Provisions shall include capacity in all current–carrying parts for the higher fan cooled rating, including bushings, current transformers, tap changing components, make–up leads etc. Transformers 10,000 KVA and larger shall be supplied equipped with (FA) fan cooling. Fan–cooled ratings (FA rating) in percent of self cooled ratings shall be not less than the figures shown in Table 3. Transformers less than 10,000 KVA shall be supplied with “FA”, when specified on the Data Sheet.
• Forced cooling shall consist of the maximum number of stages available with one stage of cooling being available on transformers less than 12 MVA and two stages of cooling being available on transformers 12 MVA and larger.
• All transformers shall be supplied having a base OA rating at 55/65oC. 55C rated only transformers are not acceptable.
• Forced Cooling
• Unless specified otherwise on the Data Sheet, cooling equipment will be supplied remotely at 120/208 VAC, single phase or three phase.
• Cooling controls shall be furnished in NEMA 4X stainless steel (or NEMA 7 when specified) enclosures and completely wired for operation. The control enclosure shall be located on the transformer at a height suitable for operation and maintenance by an individual standing at base level.
• Where forced cooling equipment must be shipped detached from the transformer, the necessary wiring harnesses and installation instructions shall be included.
• The Top Oil Temperature Switch shall include an indicator readable from the base level.

• Fans shall be controlled via a manual switch with control positions hand–off–auto. Automatic control shall be via the Top Oil Temperature method.
• Complete cooling system controls shall be provided, including but not limited to; motor controllers, relays, terminal blocks, transformers, fuse/circuit breaker disconnects, alternate source transfer equipment (when specified), etc. All control equipment shall be UL Listed, with contactors, controllers, relays, etc. NEMA–rated.
• Provisions shall be made in the cooling controls for a users remote contact shut off of all cooling equipment. This should be brought out to a terminal block for users connection.
• Cooling fans, guards, brackets, and hardware shall be of corrosion resistant materials.
• All fans shall have OSHA approved guards.
• Transformer radiators provided shall comply, as a minimum, with the following types/construction as required/specified on the associated filled out Data Sheet EP 13–4–1DS:
• Modified network panel radiator type shall be the Manufacturer’s standard design with a minimum panel thickness of 0.049 inches (18 gage).
• Modified network panel radiator shall be a special design with a minimum of 0.049 inches or

0.125 inch thickness metal, as specified on the Data Sheet, and have a center spacing between panels of no less than 4 inches.

• Tube type radiator shall be the Manufacturer’s standard design with tube thickness a minimum of 0.049 inches (18 gage).
• Tube type radiator special design shall be the Manufacturer’s standard design except tube thickness to be a minimum of 0.125 inches.
• Transformer Winding
• All substation and unit transformer windings shall be copper only. Padmounted transformers may have aluminum windings.
• Transformers having WYE connected windings shall have their neutral point brought out to a neutral (X0) bushing. The X0 bushing shall have the same BIL as the line bushing.
• WYE connected windings shall be designed to operate with the neutral solidly grounded or grounded through an external resistance with values from zero (solidly grounded) to that which limits the current to that specified on the Data Sheet.
• Unless specified otherwise, on the Transformer Data Sheet, all oil filled transformers shall be equipped with manual no–load tap changing as follows:
• The tap changer shall be provided on the high voltage winding.
• The tap changer shall have five positions, with two 2–1/2% full capacity taps above the nominal voltage tap and two 2–1/2% full capacity taps below the nominal voltage tap.
• Tap changer mechanism shall be manually operated with transformer de-energized and shall have handles brought out through the tank.
• The tap changer shall be marked, in agreement with the nameplate, to indicate which tap is connected. For a given winding, the number 1, or the letter A shall be assigned to the tap having the greatest number of effective turns.
• The tap changer handle shall have provisions for padlocking, and shall provide visible indication of the tap position without unlocking.
• When load–tap–changing is specified on the Transformer Data Sheet, it shall conform to ANSI C57.12.30 and the specific requirements on the Transformer Data Sheet.

• Rectangular core and coil designs are not acceptable for transformers rated larger than 10 MVA and/or those with windings rated 69KV and higher.
• For transformers 5,000 KVA and larger, the core to tank grounding strap grounding point shall be externally accessible from outside the tank to allow ground connection removal for testing. The connection shall be made up in a junction box meeting the requirements of paragraph 5.12.3.
• Tanks
• Transformer tanks shall be designed and braced so as to eliminate movement of the bushing terminals due to deformation of the tank over the full range of positive and negative pressures for which the tank is designed.
• The main transformer tank and any attached compartment piping, etc., that is subject to operating pressures shall be designed to withstand, without permanent deformation, pressures 25 percent greater than the maximum operating pressures resulting from the system of liquid preservation used.
• For transformers that will be liquid filled at the job site, tanks shall be designed for vacuum filling (essentially full vacuum) in the field. Auxiliary compartments such as expansion tanks, when not designed for vacuum filling, shall be so designated and isolating valves shall be provided.
• The main cover construction shall be bolted or welded.
• One or more manholes shall be provided in the cover. Manholes shall be located and sized to permit changeout of bushings.
• Tank grounding provisions shall consist of two ground pads, welded on the base or on the tank wall near the base. One ground pad shall be furnished near the neutral bushing.
• Bushings
• All bushings rated 5 KV and higher shall be porcelain. Bushings 600V class and lower can be either porcelain or molded/cast resin (epoxy) material.
• Outdoor transformers with exposed bushings and with nominal voltages greater than 4KV (line to line) shall have these bushings supplied as “extra creep”. When extra creep bushings are not available, the next available higher voltage class bushing shall be supplied.
• Neutral bushings shall be provided on all WYE connected windings, or where provision is made to permit windings to be connected either WYE or Delta.
• Neutral bushing shall have the same insulation/BIL class as the line bushings.
• Neutral bushings shall not be electrically connected to the transformer tank.
• All bushings 15KV class and higher shall be designed to permit power factor testing by the Owner. Suitable weather tight plugs shall be provided to cover the probe test connection point when not in use.
• Bushings must be rated for full current capacity of the transformer including forced cooling. Documented bushing ratings for the application, e.g. outdoors, in a flanged chamber, etc., must be provided at the time of bid. If the application results in a derating of the bushing, this must be identified, and appropriate measures taken to correct the problem.

• Bushing studs/type and pads shall be as specified on the Transformer Data Sheet.
• Liquid Preservation System
• Transformers rated 10,000 KVA (OA) and lower shall be supplied with a sealed tank system, unless specified otherwise. The system shall comply fully with a sealed tank system as described in ANSI C57.
• Transformers greater than 10,000 KVA (OA)
• All transformers greater than 10,000 KVA (OA) shall be supplied with a positive pressure nitrogen gas pressurization system (Inert Air System), unless specified otherwise on the Data Sheet by the Owner. The system shall use standard replaceable cylinders of nitrogen (see ANSI C57).
• Inert air system requirements
• System shall use a three stage pressure reducing scheme.
• Two or more pressure gauges shall be supplied, one for supply cylinder pressure and one for transformer tank pressure.
• Transformer inlet shut off valve shall be provided.
• Transformer tank pressure relief valve shall be supplied.
• Transformer tank purge valve shall be provided.
• Oil collection/sump system with drain shall be provided to prevent oil contamination throughout the inert gas system.
• Provide all fittings and tubing to connect gas cylinder to the regulating device.
• Provide one gas cylinder with fittings to be shipped with the transformer.
• Provide a space heater with thermostat in the regulator cabinet (120/208 VAC heater).
• Enclosures
• The regulator cabinet shall be rated NEMA 4X stainless steel (gasketed) with a window to allow reading of all gauges without opening the cabinet door. The cabinet shall have a hinged door with a handle operated latch. The latch shall have provisions for locking with a padlock. The cabinet shall have a breather and drain.
• Provide a cabinet (rated NEMA 4X) for the nitrogen gas cylinder. The cabinet shall have a hinged door with a handle operated latch. The latch shall have provisions for locking with a padlock. A suitable tank retaining method shall be provided. If gauges are located in this compartment, a window must be provided to allow reading of the gauge. Provide appropriate breathers and drain for the cabinet.
• Alarms: Alarm contacts shall be rated 125 VDC, 5 ampere or higher and shall be wired to a terminal block located in the regulator cabinet. The following alarms shall be provided as a minimum:
• Low cylinder pressure
• High tank pressure
• Low tank pressure
• The following systems may be quoted as an alternate to those specified above if they are more suitable to the application and/or the transformer design recommended.
• Gas/oil sealed system
• Expansion (conservator) tank system
• Coatings

The transformer assembly including tank, radiators, throats, and terminal chambers shall be cleaned to the bare metal and sealed with a moisture resistant, long–life coating. The coating shall consist of rust inhibiting primer, Manufacturer’s standard intermediate coating and two finish coats of light gray catalyzed epoxy. The total coating thickness shall be a minimum of 5 mils. If the Manufacturer’s paint system is different, request that complete details of the system be provided to the Owner for review and approval. The details shall include specific justification of the paint system for use in a petro–chemical environment.

• Hardware
• All hardware (except bushing connection hardware) including bolts, fasteners, caps, plugs, etc., shall be Series 300 stainless steel.
• All external wiring shall be run in rigid galvanized steel (RGS) conduit with compatible fittings. Flexible cable and/or U.L. listed flexible liquid tight conduit can be used between the device (e.g. meters, fans, etc.) and the conduit. RGS conduit runs must be maximized as much as is practical.
• All junction boxes shall be gasketed water tight cast metal or NEMA 4X stainless steel.
• All enclosures and devices shall be appropriate for the area classification in which the transformer will be located.
• All main auxiliary cabinets shall be rated NEMA 4X stainless steel and be equipped with breather and drain and, unless specified otherwise, space heaters and thermostat.
• All external aluminum components, parts, shall be rated copper free.
• Current Transformers (CT)

When current transformers are specified on the Transformer Data Sheet, they shall be in accordance with the following:

• The CT shall be in full compliance with ANSI/IEEE C57.13.
• The CT shall be mounted in the transformer tank and all mounting and wiring shall conform to ANSI Standards. Adequate clearance shall be allowed from CT terminals and all metal parts.
• The accuracy class for relaying and metering shall not be less than that listed in Table 4, unless specified otherwise on the Transformer Data Sheet.
• All CTs shall be multi–ratio with five (5) leads.
• All secondary CT leads shall be run in rigid galvanized steel conduit. CT leads shall be routed into the main auxiliary cabinet and terminated on shorting type terminal blocks.
• Fault Pressure Relay (FPR)
• When specified, FPR shall be rate–of–rise pressure type (such as Qualitrol 900–1) for sealed tank transformers, and Buchholz relays of the 2–float type for conservator type transformers. Qualitrol 900–1 relays shall be mounted on a tank shut off valve (if oil activated) provided specifically for the relay (mounting on the transformer main drain valve is not acceptable).

• The system provided shall be complete with all required auxiliary relays and a reset push– button. The 900–1 trip relay shall operate an auxiliary relay located in the transformer auxiliary cabinet. This relay shall seal itself in electrically, target and have a reset push button. The auxiliary relay shall have two N.O. and two N.C. contacts wired to terminal blocks for the Owner’s use. The auxiliary relay contacts shall be rated no less than 125 VDC, 10 ampere. The Owner’s control voltage is 125 VDC, unless specified otherwise on the Data Sheet.
• Terminals and Terminations (Line and Load)
• The type of termination and arrangement shall be as specified on the Transformer Data Sheet and/or attached drawings.
• The neutral bushing shall be located as indicated on the Transformer Data Sheet.
• Cable termination compartments, if specified, shall be for cables entering from below, and shall be designed to avoid kinking the cable during installation/removal (construction shall allow the cable to be moved/swing out laterally not pushed down).
• When flexible connectors (terminations) are specified to connect the transformer bushings to bus duct, or other devices, power cable is not an acceptable “flexible connector.”
• If double primary cable entrances are specified for the purpose of extending the primary feeder, or providing a second fully rated feeder, removable links inside the junction box or switch enclosure shall permit isolating the extended (additional) section of the feeder. If a junction box without switch is specified, removable links shall also be provided to isolate the transformer while using the extended feeder.
• Full height air terminal chambers, when specified, shall be of sufficient size and rigidity to allow training and supporting of cables, mounting of potheads or stress cones, and mounting of station class lightning arrestors. If bus work is required it shall be insulated copper bus bars with tin plated joints and supported with porcelain insulators of the same ratings as the line bushings. Space heaters (120/208 volt) with thermostat shall be provided, unless specified otherwise.
• All terminal chambers will be provided with a separate copper ground bus. The bus shall be 1/4” x 2” x 8” long and located on the transformer tank near the base.
• All padmounted transformers, unless specified otherwise, shall be of the compartmental–type, having separate high and low voltage compartments. The compartments shall be separated by a metal barrier. The high and low voltage compartments shall have hinged doors with padlockable door handle having three point latching.
• All padmounted transformers shall be of the live front design (ANSI C57.12.22). Bushings shall have pad type (blade) terminals suitable for the cables/bus duct specified, but as a minimum shall provide a two hole pad on the HV bushing and a six hole pad on the LV bushing.
• When high voltage metal enclosed switches (or other type) are to be used as high side disconnect devices on the transformer, they shall be supplied by the transformer Manufacturer or others as identified on the Data Sheet.
• Metal enclosed switchgear (switches) (MEI) shall be in compliance with EP 13–25–1 and a filled out Owner–approved EP13–25–1DS. Acceptable switch Manufacturer’s shall be as specified by the Owner.

• The transformer tank shall have appropriate flange and/or throat as required to match up to the high side disconnect MEI device.
• Connection of the MEI switch copper bus load conductors to the transformer high side bushings shall be via flexible copper connectors (with tin plated joints). Insulated power cable shall not be used as the connector and is not considered an acceptable “flexible connector”.
• Coordination of the switch, connection and connector supply shall be as indicated on the Data Sheet EP 13–4–1DS.
• Accessories

Each transformer shall be equipped with all standard ANSI accessories and shall include, but not be limited to the following:

• Substation and unit transformers
• Dial type thermometer for indicating top liquid temperature. The device shall have two hands, one showing oil temperature at time of reading, and the second showing the maximum temperature reached since last resetting. The thermometer shall also have sealed contacts suitable for outdoor application to control cooling devices and alarm per paragraph 5.6 of this practice. Contacts shall be suitable for control requirements and 125 VDC alarm circuit.
• Pressure–vacuum gauge and a pressure vacuum bleeder valve mounted on the transformer tank and piped to the gas space above the oil.
• Liquid level indicator.
• Silica gel breather for transformers with conservator oil–preservation systems.
• Globe valve to serve as a drain valve, bottom filter connection, and liquid sampling valve. Include plugs/caps and chains.
• Globe valve for the top filter press connection and vacuum pump connection. Include plugs/ caps and chains.
• Radiator valves (top and bottom), when detachable radiators are supplied.
• A mechanical pressure relief device, located on the tank cover, complete with a mechanical target (visible from ground level) and an electrical alarm contact. Alarm contact shall be wired down to the auxiliary equipment cabinet and terminate on a terminal block (contact rated for 125 VDC, 5 ampere).
• Two tank ground pads drilled and tapped for ground connection (typical 2/0 AWG copper wire with compression lug). Pads shall be located on diagonally opposite corners of the tank base.
• Winding temperature (hot spot) CT, controls and indicator on all transformers 5000 KVA and larger.
• Padmounted transformers
• Filling plug and filler press connections.
• Drain valve with sampler.
• Ground pad in HV and LV compartment.
• Pressure relief device (self sealing with operation indicator).
• Dial type thermometer.
• Magnetic liquid level gauge.
• Pressure vacuum gauge.
• Captive Transformer

• This is a substation power transformer which supplies a single utilization device, usually a large motor. The transformer may be located in a remote substation or close to the device it supplies.
• When used with large motors, the transformer design shall be suitable for across–the–line starting of the motor and must be able to withstand the mechanical and thermal duty imposed by the magnitude of the motor starting currents and the permissible number of starts and intervals between starts.
• Transformers Supplying Non–sinusoidal Load Currents
• When transformers are identified as supplying non–sinusoidal load currents, such as those associated with adjustable frequency motor drives, the transformer capability shall be defined as outlined in C57.110.
• The transformer Manufacturer shall obtain required line and load characteristics (to include harmonics) and determine the optimum design and size transformer required to safely provide full load demand with a suitable design margin. The Owner shall review all calculations, and agree on design margin prior to approval for purchase.
• Lightning Arresters

When lightning arresters are specified on the Transformer Data Sheet they shall comply with the following:

• They shall be station class zinc/metal oxide arresters, with porcelain bushings, mounted with brackets on the tank or in the terminal chamber next to the high voltage bushings.
• Arresters shall have extra creep porcelain bushings to coordinate/complement with the line bushings on outdoor installations.
• Shall include all mounting brackets, hardware and ground wiring from the arrester ground connection location to the transformer tank grounding pad. Ground conductor shall be 2/0 AWG copper wire or larger as required.
• Provisions (ground pad) for terminating crimp lug connectors shall be provided on the tank for the grounding conductor of the arresters. The ground pad shall be located as close to the arresters as possible and shall not be mounted on radiators or handhole covers.
• Nameplates
• Transformer: The transformer nameplate shall be made of stainless steel. Nameplate information shall include the information required per ANSI C57.12.
• Current Transformers: Stainless steel nameplates shall be provided for each CT. The information shall include:
• Location
• Polarity, referenced to end of bushing
• Ratio, tap ratios
• Accuracy class
• Requirements of ANSI C57.13 para 6.8.
• Transformer Handling Provisions
• Lifting Facilities
• Suitable means (lugs) shall be provided for lifting the complete transformer.
• Suitable lifting eyes shall be provided for lifting the cover.
• Suitable means shall be provided for lifting the coil and core assembly from the tank.

• Moving Facilities for Each Transformer: The transformer base construction shall permit rolling (or sliding) in the directions of both centerlines of the transformer and provisions shall be made for pulling the transformer in these directions.
• Jacking Facilities
• Jacking facilities shall be located near the extreme ends of the junction of the base segments.
• The jack ports or lugs shall be so designed that the lifting members of the jack can be inserted.
• Dimensions and clearances for jacking provisions shall be as shown in ANSI Standards.
• Liquid Filling at the Job Site

If liquid filling of any part of the transformer is required at job site, the transformer Manufacturer shall furnish the liquid, job site supervision, and furnish or make available a suitable filter press and vacuum pump. The transformer Manufacturer shall also test the transformer oil after job site filling with test to include those items identified in paragraph 5.23.2. The oil testing shall be included in the field service cost.

• Transformer Oil
• Transformer shall be supplied complete with all necessary oil. If the oil, either all or a portion, is to be shipped outside of the transformer tank the method of containing and shipping must be identified and approved by the Owner. The manufacturer shall supply a MSDS (material safety Data Sheet) to the Owner before the shipment of the oil and transformer.
• All transformer oil supplied will be tested for insulating quality and presence of PCB’s at the transformer Manufacturer’s facility prior to shipment. The Owner will accept testing of the oil in the transformer after filling or batch testing of the oil prior to filling. A certified report shall be provided for all oil supplied and will include, as a minimum, the following tests:
• Acidity
• Color (ASTM)
• Dielectric Breakdown Voltage
• Interfacial Tension
• Power Factor
• PCB Content
• Field testing of transformer oil by the Manufacturer shall include those tests identified in paragraph 5.23.2.
• Control Wiring
• Control wire shall be stranded #14 AWG or larger size copper conductors with 600 volt SIS, XHHW or XHHW2 insulation.
• Compression type terminal lugs with insulated sleeves and spade or ring tongue type lugs (ring tongue type only on all current transformer circuits) shall be used.
• Terminal blocks shall be suitable for terminating spade and ring tongue type lugs. Blocks shall be rated 20 ampere 600 volts or higher as required. All spare spaces shall have screws inserted.

• Each internal interconnection wire shall be identified at each end with a plastic sleeve or shrink tubing sleeve type wire identification system. The sleeve shall be stamped with the complete destination address at each end. Tape type wire marks are not acceptable. Tabular wiring diagrams and wire number systems are not acceptable. It is preferred that wiring diagrams as well as wire marks, device and terminal strip identification shall use a destination address identification system. The wire identification system used shall be approved by the Owner.
• Transformers 2500 KVA and smaller shall have a ground bus/stud available in the control cabinet for attachment of the Owner’s control ground wire (8 to 12 AWG wire) and equipment ground wire.
• Transformers larger than 2500 KVA shall have a copper ground bus located in the bottom front of the main control cabinet. The ground bus shall be a copper bar, minimum size 1/4 inch thick, 1 inch wide and 6 inches long, with the bar mounted on stand–offs at least 1/2 inches high.

5.25 Storage

Any items requiring special storage at the job site shall be appropriately labeled as such, easily unpacked (accessible) and accompanied with appropriate storage and installation instructions.

TESTING

• General

A report of transformer tests shall be submitted for each transformer. The tests shall be performed in accordance with the ANSI Standard Test Code C57.12.90. The following changes and/or requirements for testing in addition to those in ANSI C57.12.90 shall apply:

• The three–wattmeter method shall be used for core (no–load) loss testing.
• Impedance–loss and impedance–voltage tests shall be performed using the three–wattmeter method.
• Total losses shall not exceed guaranteed values by +4% for each transformer in an order when no loss penalty is in effect. Total loss values that exceed +4% of guarantee shall result in the Owner not accepting the transformer.
• When a loss penalty is specified, as indicated on the data sheet, the total losses shall not exceed the quoted guaranteed values for each transformer in an order. The values for the loss penalty, load test point for losses, and the maximum acceptable losses allowable (the point beyond which the Owner will not accept the equipment) shall be established by the Owner after the bid and made available to the bidder prior to award of an order.
• The base load test point for loss penalty evaluation will generally be at the 75% of full load OA rating, or as specified on the Data Sheet.
• There shall be no allowance above the quoted total loss chosen by the Owner as the penalty base OA evaluation point (+0% above quoted losses at Owner selected percent of OA rating).
• The loss penalty cost shall be for each KW and fraction of KW above the quoted guaranteed total loss value above the Owner’s base load point for assessment (paragraph

6.1.4.1 of this Practice).

• All test equipment must be within current calibration to the test equipment Manufacturer’s accuracy limits, with calibration traceable (unbroken chain) to NBS. The transformer vendor must follow NBS Technical Note 1204 (NBSTN 1204), or equivalent procedure to calibrate and align test components in his test system to provide a system based verification for the entire loss test system. The transformer Manufacturer must state the level of his measurement system error based on NBSTN 1204 method/technique.
• Temperature correction for no load losses shall be given at both actual test ambient temperature (15–25C), and at a calculated value to ANSI standards levels. It is important that tests be performed on “cold” units with a relatively stable temperature gradient throughout the tank, core and coil at an ambient temperature of 15–25C.
• It is important that resistance tests and load loss tests be done as quickly as possible before appreciable heating occurs. However, during resistance testing time must be allowed for the inductive effect to subside (up to 60 seconds depending on the forcing voltage available in the resistance test equipment).
• When witness testing is specified, the Owner shall witness the complete test as specified on the Data Sheets and contract documents.
• Routine Test
• ANSI C57.12 Routine Test.
• Resistance measurements of all windings on the rated voltage tap of each transformer and at the tap extremes of one transformer only of a given rating on an order.
• Ratio tests on the rated voltage connections and on all tap connections.
• Phase–relation and polarity tests on the rated voltage connections.
• No load losses and exciting current at rated voltage and frequency on the rated voltage connection.
• Impedance voltage and load losses at rated current on the rated voltage connections on each transformer, and on the extremes of one unit only of a given rating on an order.
• Applied and induced potential tests.
• Regulation and efficiency at rated load and voltage.
• Insulation resistance tests (high voltage to ground, low voltage to ground, high voltage to low voltage, core to tank).
• Dissipation factor test of windings and bushings.
• Measurement of total losses 25, 50, 75, 100% of full load and at a specified percent of full load rating as part of a loss guarantee, if applicable.
• Leak Test (on all liquid filled transformers).
• Oil Test per Section 5.23.2 of this Practice.
• Special Tests, When Specified Only
• Temperature Tests

• Temperature test or tests, when specified, shall be made on one unit only of an order covering one or more transformers of a given rating, provided that test data is not available from records of temperature tests on a duplicate or essentially duplicate transformer.
• Governed by the stipulation of paragraph 6.3.1.1 above, transformers supplied with auxiliary cooling equipment to provide more than one KVA rating, temperature tests shall be made at 55C–OA, 65C–FA, and 65C–FOA.
• When temperature tests are required on each transformer on an order, such tests will be specified on the Transformer Data Sheets.
• Short–Circuit tests when specified on the Transformer Data Sheet shall be performed in accordance with ANSI C57.12.00 and C57.12.90.
• Additional tests and test requirements will be specified on the Transformer Data Sheet.

DRAWING AND DATA REQUIREMENTS

All drawings provided for this equipment shall show equipment as specified and ordered. Typical drawings are not acceptable unless they are revised to show only the equipment being furnished. Drawings shall be supplied in the quantities shown on the Transformer Data Sheet.

• Information To Be Supplied With Quotation
• Winding types, materials and bracing.
• Core design, materials, type, and weight.
• Full–load noise levels in decibels.
• Load tap changer description (when specified).
• Number of days of field service allowed (when specified) and cost per day.
• Specific listing of any exceptions to those requirements specified.
• Equipment or features included but not necessarily specified.
• Loss guarantees as follows: No Load Loss Watts at 100% of Rated Voltage: Total Loss Watts at 75oC and 25, 50, 75, 100, and 125% Base KVA at Rated Voltage.
• Regulation guarantees from loading as follows: 100% Power Factor at 75 C and Base KVA; 80% Power Factor at 75oC and Base KVA to zero load with the primary impressed voltage maintained constant.
• Estimated weight Lb (Kg):
• Core and coil
• Tanks and fittings
• Total assembled transformer including liquid
• Volume of liquid, in gallons.
• Impedance at rated tap and self–cooled rating (percent).
• Verification of bushing ratings for application (see 5.9.7).
• Structural drawings showing plan view and all elevations.

• Details on shipping including requirements for disassembly of any items, travel restrictions, and costs for field assembly management support by the transformer Manufacturer.
• Information To Be Submitted for Approval By the Owner After Receipt of Order
• Complete structural drawings showing:
• Plan and all elevations with complete dimensions of:
• High voltage termination method.
• Low voltage termination method (flanged throat, conduit stub–ups to terminal chambers or other specified termination method, conduit opening for neutral connection).
• Location of all accessories.
• Total weight of transformer with and without oil.
• Anchor bolt locations.
• Ground pad locations.
• List of parts requiring field installation.
• Wiring Diagrams containing
• Complete elementary control diagrams and interconnecting wiring diagrams of the forced cooling equipment.
• Wiring diagrams of all devices with switches or electrical connections.
• Terminal blocks shall be clearly marked for all customer connections.
• Current transformer connections.
• Drawing indicating the catalog number, quantity, horsepower, location, and mounting provisions for future forced cooling equipment or forced cooling equipment if supplied.
• Nameplate Data Drawing (paragraph 5.20)
• Data covering forced cooling fans, lightning arresters, current transformers and other accessories, including load tap changer, when specified.
• Complete data for current transformers supplied including saturation curves, winding/lead/weld resistance, connection resistance, ratio, accuracy, and Manufacturer.
• Certified Information To Be Supplied
• All information requested in sections 6.0, 7.1, and 7.2 of this Practice.
• Installation, Operating and Maintenance Manuals.
• Parts Listing and Recommended Spare Parts.
• Test Reports for testing required in section 6.0 of this Practice, the Data Sheets, and other testing required as part of the contract.

SPARE PARTS

A complete spare parts recommendation based on the total purchase order is required within 60 days after the Manufacturer (Supplier) receives the purchase order. Spare parts recommendations shall include:

• A complete spare parts list, including parts location diagrams or drawings.
• Lists of priced spare parts as recommended by the Manufacturer to be on hand during start–up and the first year’s operation.

• Delivery dates and normally stocked items.

SHIPPING

• Transformers shall be shipped with oil when possible and with a positive nitrogen pressure. Pressure and temperature shall be recorded on a tag attached to the pressure–vacuum gauge at the time of shipment.
• All transformers shall be equipped with recording impact meters.
• Parts and accessories, such as cooling radiators, bushings, lightning arresters, neutral grounding resistors, etc., which require disassembly from the transformer for shipment, shall be prepared by the Manufacturer in a manner to exclude moisture and damage when handled by commercial carrier systems.

10.0 TABLES

TABLE 1

TRANSFORMER BIL REQUIRED FOR THE VOLTAGE CLASS INDICATED REGARDLESS OF WINDING LOCATION

TABLE 2

BIL REQUIREMENTS FOR LOW VOLTAGE RATINGS

TABLE 3

MINIMUM FAN COOLED RATINGS

TABLE 4

CT ACCURACY CLASS REQUIREMENTS

TABLE 5 DOCUMENTATION REQUIREMENTS FOR POWER TRANSFORMERS PER EP 13–4–1

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