26 1200 USER-Medium-Voltage Transformers - Rev1 06_10_21.pdf

Vermont Air National Guard Electrical Distribution Project LN Consulting, Inc.

South Burlilngton, Vermont Project No. 19045

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SECTION 26 1200

MEDIUM-VOLTAGE TRANSFORMERS - REV1 06/10/21

PART 1 GENERAL

1.01 SECTION INCLUDES

A. Liquid-filled pad-mounted distribution transformers.

1. Based on Green Mountain Power standards.

B. Liquid-filled submersible distribution transformers

1.02 RELATED REQUIREMENTS

A. Section 26 0529 - Hangers and Supports for Electrical Systems.

1.03 REFERENCE STANDARDS

A. IEEE 386 - IEEE Standard for Separable Insulated Connector Systems for Power Distribution Systems Rated 2.5 kV through 35 kV; 2016.

B. IEEE C57.12.00 - IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers; 2015.

C. IEEE C57.12.01 - IEEE Standard for General Requirements for Dry-Type Distribution and Power Transformers; 2015.

D. IEEE C57.12.28 - IEEE Standard for Pad-Mounted Equipment -- Enclosure Integrity; 2014.

E. IEEE C57.12.90 - IEEE Standard Test Code for Liquid-Immersed Distribution, Power, and

Regulating Transformers; 2015 (Corrigendum 2017).

F. IEEE C57.111 - IEEE Standard Guide for Acceptance of Silicone Insulating Fluid and Its

Maintenance in Transformers; 1995 (Reaffirmed 2009).

G. NEMA 260 - Safety Labels for Padmounted Switchgear and Transformers Sited in Public Areas;

1996 (Reaffirmed 2004).

H. NETA ATS - Acceptance Testing Specifications for Electrical Power Equipment and Systems;

2017.

I. NFPA 70 - National Electrical Code; Most Recent Edition Adopted by Authority Having

Jurisdiction, Including All Applicable Amendments and Supplements.

J. Green Mountain Power Standards.

1.04 SUBMITTALS

A. Shop Drawings: Indicate electrical characteristics and connection requirements, outline dimensions, connection and support points, weight, specified ratings and materials.

B. Product Data: Provide electrical characteristics and connection requirements, standard model design tests, and options.

C. Test Reports: Indicate procedures and results for specified factory and field testing and inspection.

D. Manufacturer's Installation Instructions.

E. Manufacturer's Certificate: Certify that products meet or exceed specified requirements.

F. Manufacturer's Field Reports: Indicate activities on site, final adjustments and overcurrent protective device coordination curves, adverse findings, and recommendations.

G. Project Record Documents: Include copy of manufacturer's certified drawings.

H. Maintenance Data: Include maintenance instructions for cleaning methods; cleaning materials recommended; procedures for sampling and maintaining fluid.

I. Maintenance Materials: Furnish the following for Owner's use in maintenance of project.

1. Extra Fuses: One of each type and size.

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1.05 QUALITY ASSURANCE

A. Conform to requirements of NFPA 70.

B. Manufacturer Qualifications: Company specializing in manufacturing the products specified in this section with minimum three years documented experience and with service facilities within 100 miles (160 km) of Project.

C. Testing Agency Qualifications: Company member of International Electrical Testing Association and specializing in testing products specified in this section with minimum three years documented experience.

D. Products: Listed, classified, and labeled as suitable for the purpose intended.

E. Product Listing Organization Qualifications: An organization recognized by OSHA as a

Nationally Recognized Testing Laboratory (NRTL) and acceptable to authorities having jurisdiction.

PART 2 PRODUCTS

2.01 MANUFACTURERS

A. Cooper Power Systems, a division of Eaton Corporation: www.cooperindustries.com/#sle.

B. Howard Industries.

C. Refer to Green Mountain Power for additional information regarding substitutions.

2.02 LIQUID-FILLED TRANSFORMERS

A. Liquid-Filled Transformers: IEEE C57.12.00, three phase, pad-mounted, self-cooled transformer unit.

B. Cooling and Temperature Rise; IEEE C57.12.00; Class OA. 65 degrees C, self-cooled.

C. Insulating Liquid: Mineral Oil.

2.03 SERVICE CONDITIONS

A. Meet requirements for usual service conditions described in IEEE C57.12.01 and for the specified unusual service conditions.

2.04 RATINGS

A. Capacity: See drawings for kVA.

B. Primary Voltage: Dual Voltage: 2.4/4.16 and 7.2/12.47 kV wye connected.

C. Taps: Standard primary taps.

D. Secondary Voltage: As noted on drawings volts, wye connected.

E. Impedance: 5.75 percent maximum.

F. Basic Impulse Level: 95 kV.

2.05 ACCESSORIES

A. Accessories: IEEE C57.12.00 standard accessories.

B. Tap Changer: Externally-operated type.

C. Primary Terminations: Bushing wells to IEEE 386; provide six for loop feed. Include bushings for insulated loadbreak connectors.

D. Primary Switching: Internal liquid-immersed gang-operated load break switch. Provide two, for primary selective switching.

E. Primary Overcurrent Protection: Internally-mounted, liquid-immersed, expulsion fuses.

1. Provide fuses for both 4160 volt and 12470 volt operation. Install 4160 volt fusing for initial operation.

F. Secondary Terminations: Spade lugs.

G. Other Accessories: Dual voltage tap changing switch 4160/12470 volts.

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2.06 FABRICATION

A. Conform to the requirements of IEEE C57.12.28.

2.07 FACTORY FINISHING

A. Clean surfaces before applying paint.

B. Apply corrosion-resisting primer to all surfaces.

C. Apply finish coat of baked enamel paint to 2 mils (0.5 mm) thick.

D. Finish Color: Manufacturers standards Munsell Green, or as directed by Owner..

2.08 SOURCE QUALITY CONTROL

A. Provide factory tests to IEEE C57.12.90 and IEEE C57.12.00. Include the routine tests as defined in the standards and the following other tests:

1. Impedance voltage and load loss.

2. Dielectric tests.

3. Audible sound level.

4. Short circuit capability.

5. Temperature rise.

B. Test insulating liquid samples in accordance with IEEE C57.111.

2.09 SUBMERSIBLE TRANSFORMERS

A. Submersible transformers shall meet the other relevant sections of this specification as well as what is listed under the submersible transformer section of this specification.

B. SCOPE

1. Single-phase submersible transformers for use on the 12470 GrdY/7200 Volt 60 Hertz,.

underground distribution system and appropriate for 3 phase banking. The transformers are intended for installation below ground in vaults and for operation on a primary loop or radial system. The transformers shall be suitable for continuous submersion. The transformers will be connected phase-to-neutral in both single-phase or three-phase applications. The low voltage windings will be connected closed delta or closed Y.

C. STANDARDS

1. All material and equipment furnished under these specifications shall conform to the latest applicable approved standards of the IEEE, ANSI, and NEMA, except as otherwise specified herein.

D. RATINGS

1. All ratings shall be for 60 Hertz alternating current, oil immersed, self-cooled transformers capable of continuous operation at rated kVA without exceeding either a 55 degree C average temperature rise or a 70 degree C hot spot temperature rise.

2. The electrical characteristics of the completely assembled high and low voltage terminals shall be 7200/12470Y, and 120/240 (4 low-voltage bushings).

3. The basic impulse level (BIL) shall be 95 kV.

E. RADIAL FEED

1. Transformers will be suitable for radial feed.

F. CONSTRUCTION

1. Construction of the units shall be such that they can be lifted and lowered into place in a suitably designed and constructed enclosure having a minimum diameter of 36 inches. To allow for cabling space and proper airflow for cooling, the transformers covered by this standard shall not have overall diameters in excess of 30 inches for sizes 100 kVA and smaller, in excess of 33 inches for 167 kVA or 38 inches for 250kva and larger.

2. The transformer tank, cover, and all external appurtenances shall be of corrosion-resistant 304L stainless steel. This includes welds, plugs (may be brass), nameplates, etc.

3. A protective (paint) coating of semi-gloss sky gray similar in color to ANSI Standard no. 70 shall be applied that is at least 3 mils thick.

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4. Welds shall be smooth and shall not cut workers hand or gloves. The tank and cover shall be capable of withstanding a full vacuum.

5. Tank Cover

a. The tank cover shall be welded to the tank. No handhole shall be installed in the cover.

b. The threads between the oil fill plug and the boss on the tank shall be sealed with a liquid pipe thread compound. Teflon tape is undesirable as it leaves shreds floating in the oil. Suggested products are Rectorseal, liquid Teflon, or similar sealants. If a fill plug is not provided, a 1/4-inch NPT boss with a brass plug shall be provided for the purpose of pressure testing.

G. Tank Ground

1. The tank grounding connection shall be per ANSI C57.12.20, Section 6.5.4 except:

a. The connection shall consist of a stainless steel boss or pad and shall be equipped with a solder less tinned copper-alloy connector that will accommodate #8 solid through #2 AWG stranded copper wire. The clamping eye bolt threads shall be

3/8-16NC.

b. The tapped hole in the boss or pad and the stud of the connector shall be 1/2inch-13NC,Class 2 fit. The tapped hole shall be coated with an oxide-inhibiting compound before installation of the connector.

c. This connection shall be plainly labeled “G”.

d. Extra tank ground bosses shall be protected with oxide-inhibiting compound and a plastic flanged cup pressed into the threads (aluminum cups are not acceptable).

2. Base bars of 401 Stainless Steel shall be provided on the transformer tank to protect the bottom of the tank while in transit and when installed in the underground enclosure.

Minimum bar height is 1.00 inch.

3. The lifting provisions shall be permanently attached and arranged on the tank to provide a distributive balanced lift in a vertical direction for the completely assembled transformer.

They shall be designed to provide a safety factor of 5.

4. Automatic pressure relief device designed to re-seal after operating.

5. A means of manually venting the tank.

H. TRANSFORMER TAPS

1. No transformer taps are required.

I. CONNECTORS AND TERMINALS

1. Primary Bushing

a. Transformers shall come equipped with two high voltage bushing wells (H1 and H2), and corresponding load break inserts for dead front application. The bushing wells shall be welded to the transformer cover, 200-amp rated, separable, and rated for primary switching per IEEE 386. Gasketed bushing wells are not acceptable. The bushing well shall have a cover or cap to prevent the entrance of moisture or dirt during shipping or storage. The cap shall be secured in a manner that prevents its loss during shipment or temporary storage.

b. The bushings shall conform to IEEE C57.12.23.

c. The load-break bushing inserts shall be Cooper Power Systems (Catalog No.

2604797B01M) or Elastimold (Catalog No. 1601A4).

d. One parking stand shall be welded in Segment 3 as shown in the latest IEEE

C57.12.23.

2. Secondary Terminals or Leads

a. Low voltage bushings shall be cover mounted.

b. The low voltage terminal shall be copper allow NEMA 4 hole pads mounted on threaded studs.

c. The low voltage terminals shall accommodate eitehr aluminum or copper conductors.

3. Ground connections shall be suitably sized for the short-circuit rating of the transformer as defined in the latest IEEE C57.12.00

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J. FUSING

1. Transformer H1 bushing leads shall be provided with Cooper Power Systems Bay-O-Net, dual sensing, load break, cover-mounted, externally removable links in series with underoil, internally mounted 15 kV partial range current limiting fuses (CLF).

2. The partial range current limiting fuses shall be placed in series with the Bay-O-Net fuse holder and be mounted internally under oil. Partial range current limiting fuses shall have a nominal voltage rating of 15 kV.

3. The Bay-O-Net fuse sizes shall per Table 4 of Cooper Power Systems publication 240-98.

The backup CLF shall be coordinated with the Bay-O-Net fuse, per Table 4 of Cooper Power Systems publication 240-98, and size to melt only on internal transformer faults.

4. The Bay-O-Net fuse and fuse holder mush be interchangable with RTE brand components.

5. The Bay-O-Net fuse housing operating mechanism shall be interlocked with teh primary switch to prevent fuse from being removed or inserted while the transformer is energized.

6. The backup CLF shall be RTE type ELSP, or equal. It shall be located on the source side of the Bay-O-Net fuse.

K. TRANSFORMER OIL

1. Transformers shall be insulated with new (unused) mineral oil. The oil shall meet the requirements of ANSI C57.12.00, Article 6.6.1 (1), ANSI C57.106 and ASTM 3487 Type II.

The transformer nameplate shall indicate that the PCB content of said transformer is less than 1 PPM or at time of manufacture gas chromatographic analysis certified non-detectable PCB. The oil shall be inhibited mineral oil containing 0.2 % by weight

DBPC.

L. NOISE

1. Transformer sound levels shall not exceed the values specified in the latest revision of

NEMA Publication TR 1-0.11.

M. PAINT FINISH – NONE REQUIRED

N. NAMEPLATES

1. A stainless steel diagrammatic nameplate shall be affixed to the tank cover (or any

2. nameplate extension bracket) using stainless steel fasteners. The nameplate shall state all information per ANSI C57.12.00, nameplate A, except the nameplate shall include the following:

a. A manufacturer’s serial number barcode shall be etched into the nameplate using a character size of 128A. The barcode shall be a maximum ½” high and 2½” wide. The manufacturer’s identification characters shall not be included in the barcode.

b. The date (month/year) of manufacture. Serial numbers that include a date code will not suffice.

c. The statement “Contains less than one ppm PCB at time of manufacture.” Separate “NON PCB” stickers, labels, or extra nameplates will not suffice.

d. The gallons of oil.

e. The weight of the transformer for all sizes including 25 kVA.

f. The manufacturer and catalog number for the primary fuses and fuse holder.

g. Items i., iii., iv., and v., above, may be either on the nameplate or a separate stainless steel nameplate. Stenciling or other labels will not be acceptable.

PART 3 EXECUTION

3.01 EXAMINATION

A. Verify that support pads provided under Section 03 3000 are ready to receive products.

B. Verify that field measurements are as indicated on shop drawings.

3.02 INSTALLATION

A. Install plumb and level.

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B. Install safety labels to NEMA 260.

3.03 FIELD QUALITY CONTROL

A. See Section 01 4000 - Quality Requirements, for additional requirements.

B. Inspect and test in accordance with NETA ATS, except Section 4.

C. Perform inspections and tests listed in NETA ATS, Section 7.2.

3.04 ADJUSTING

A. Adjust primary taps so that secondary voltage is above and within 2 percent of rated voltage.

END OF SECTION