261219 Pad mounted Liquid Filled Medium Voltage Transformers.pdf

11-01-22

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SECTION 26 12 19

PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS

PART 1 - GENERAL

1.1 DESCRIPTION

A. This section specifies the furnishing, installation, connection, and testing of the pad-mounted, liquid-filled, medium-voltage transformers, indicated as transformers in this section.

1.2 RELATED WORK

A. Section 09 06 00, SCHEDULE FOR FINISHES: Finishes for electrical equipment.

B. Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS:

Requirements that apply to all sections of Division 26.

C. Section 26 05 73, OVERCURRENT PROTECTIVE DEVICE COORDINATION STUDY:

Short circuit and coordination study, and requirements for a coordinated electrical system.

1.3 QUALITY ASSURANCE

A. Quality Assurance shall be in accordance with Paragraph, QUALIFICATIONS

(PRODUCTS AND SERVICES) in Section 26 05 11, REQUIREMENTS FOR

ELECTRICAL INSTALLATIONS.

1.4 FACTORY TESTS

A. Factory Tests shall be required.

B. Factory Tests shall be in accordance with Paragraph, MANUFACTURED

PRODUCTS in Section 26 05 11, REQUIREMENTS FOR ELECTRICAL

INSTALLATIONS, and the following requirement:

1. Transformers shall be thoroughly tested at the factory to ensure that there are no electrical or mechanical defects. Tests shall be conducted as per IEEE Standards. Factory tests shall be certified.

The following tests shall be performed:

a. Perform insulation-resistance tests, winding-to-winding and each winding-to-ground.

b. Perform turns-ratio tests at all tap positions.

1.5 SUBMITTALS

A. Submit in accordance with Paragraph, SUBMITTALS in Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS, and the following requirements:

1. Shop Drawings:

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a. Submit sufficient information to demonstrate compliance with drawings and specifications.

b. Include electrical ratings, nameplate data, impedance, outline drawing with dimensions and front, top, and side views, weight, mounting details, decibel rating, termination information, temperature rise, no-load and full-load losses, regulation, overcurrent protection, connection diagrams, and accessories.

c. Complete nameplate data, including manufacturer’s name and catalog number.

2. Manuals:

a. When submitting the shop drawings, submit companion copies of complete maintenance and operating manuals, including technical data sheets, wiring diagrams, and information for ordering replacement parts.

1) Identify terminals on wiring diagrams to facilitate installation, maintenance, and operation.

2) Indicate on wiring diagrams the internal wiring for each piece of equipment and interconnections between the pieces of equipment.

3) Approvals will be based on complete submissions of manuals, together with shop drawings.

b. If changes have been made to the maintenance and operating manuals originally submitted, submit updated maintenance and operating manuals two weeks prior to the final inspection.

1) Update the manual to include any information necessitated by shop drawing approval.

2) Show all terminal identification.

3) Include information for testing, repair, troubleshooting, assembly, disassembly, and recommended maintenance intervals.

4) Provide a replacement parts list with current prices. Include a list of recommended spare parts, tools, and instruments for testing and maintenance purposes.

B. Certifications:

1. Submit the following certifications.

a. Certification by the manufacturer that the transformers conform to the requirements of the drawings and specifications.

b. Certification by the Contractor that the transformers have been properly installed, connected, and tested.

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1.6 APPLICABLE PUBLICATIONS

A. Publications listed below (including amendments, addenda, revisions, supplements, and errata) form a part of this specification to the extent referenced. Publications are referenced in the text by designation only.

B. American Society for Testing and Materials (ASTM):

D3487-16................Standard Specification for Mineral Insulating

Oil Used in Electrical Apparatus

C. Institute of Electrical and Electronic Engineers (IEEE):

386-16..................Separable Insulated Connector Systems for Power

Distribution Systems Above 600 V

592-18..................Insulation Shields on Medium-Voltage (15 kV -

35 kV) Cable Joints and Separable Connectors

C2-17...................National Electrical Safety Code

C37.42-16...............Specifications for High-Voltage (>1000 V) Fuses and Accessories

C57.12.00-21............Liquid-Immersed Distribution, Power and

Regulating Transformers

C57.12.10-17............Liquid-Immersed Power Transformers

C57.12.28-14............Pad-Mounted Equipment - Enclosure Integrity

C57.12.34-15............Pad-Mounted, Compartmental-Type, Self-Cooled, Three-Phase Distribution Transformers, 5 MVA and Smaller; High Voltage, 34.5 kV Nominal

System Voltage and Below; Low Voltage, 15kV

Nominal System Voltage and Below

C57.12.90-21............Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers

C62.11-20...............Metal-Oxide Surge Arresters for AC Power

Circuits

D. International Code Council (ICC):

IBC-21..................International Building Code

E. National Electrical Manufacturers Association (NEMA):

TR 1-13(R2019)..........Transformers, Regulators, and Reactors

F. National Fire Protection Association (NFPA):

70-23...................National Electrical Code (NEC)

G. Underwriters Laboratories Inc. (UL):

467-13..................Grounding and Bonding Equipment

H. United States Department of Energy (DOE):

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10 CFR Part 431.........Energy Efficiency Program for Certain

Commercial and Industrial Equipment

PART 2 - PRODUCTS

2.1 GENERAL REQUIREMENTS

A. Transformers shall be in accordance with ASTM, IEEE, NFPA, UL, as shown on the drawings, and as specified herein. Each transformer shall be assembled as an integral unit by a single manufacturer.

B. Transformers shall be complete, outdoor type, continuous duty, integral assembly, grounded, tamper-resistant, and with liquid-immersed windings.

C. Ratings shall not be less than shown on the drawings.

D. Completely fabricate transformers at the factory so that only the external cable connections are required at the project site.

E. Thoroughly clean, phosphatize, and finish all the metal surfaces at the factory with a rust-resistant primer and dark green enamel finish coat, except where a different color is specified in Section 09 06 00, SCHEDULE FOR FINISHES. All surfaces of the transformer that will be in contact with the concrete pad shall be treated with corrosion-resistant compounds and epoxy resin or a rubberized sealing compound.

F. Transformer shall be manufactured by Cooper Power Systems or approved equal by ABB or Schneider Electric.

2.2 COMPARTMENTS

A. Construction:

1. Enclosures shall be weatherproof and in accordance with IEEE

C57.12.28.

2. The medium- and low-voltage compartments shall be separated with a steel barrier that extends the full height and depth of the compartments.

3. The compartments shall be constructed of sheet steel (gauge to meet

ANSI requirements) with bracing and with reinforcing gussets using jig welds to assure rectangular rigidity.

4. All bolts, nuts, and washers shall be cadmium-plated steel.

5. Sufficient space shall be provided for equipment, cabling, and terminations within the compartments.

6. Affix transformer nameplate permanently within the low-voltage compartment. Voltage and kVA rating, connection configuration, 26 12 19 - 5 impedance, date of manufacture, and serial number shall be shown on the nameplate.

B. Doors:

1. Provide a separate door for each compartment with provisions for a single padlock to secure all doors. Provide each compartment door with open-position doorstops and corrosion-resistant tamperproof hinges welded in place. The medium-voltage compartment door shall be mechanically prevented from opening unless the low-voltage compartment door is open.

2. The secondary compartment door shall have a one-piece steel handle and incorporate three-point locking mechanisms.

2.3 BIL RATING

A. 15 kV class equipment shall have a minimum 95 kV BIL rating.

2.4 TRANSFORMER FUSE ASSEMBLY

A. Not Used

2.5 PRIMARY CONNECTIONS

A. Primary connections shall be 600 A deadbreak wells and inserts for cable sizes shown on the drawings.

B. Surge Arresters: Distribution class, one for each primary phase, complying with IEEE C62.11, supported from tank wall.

2.6 MEDIUM-VOLTAGE SWITCH

A. Not Used.

2.7 MEDIUM-VOLTAGE TERMINATIONS

A. Terminate the medium-voltage cables in the primary compartment with 600

A deadbreak pre-molded rubber elbow connectors, suitable for submersible applications. Elbow connectors shall have a semi-conductive shield material covering the housing. The separable connector system shall include the loadbreak elbow, the bushing insert, and the bushing well. Separable connectors shall comply with the requirements of IEEE

386, and shall be interchangeable between suppliers. Allow sufficient slack in medium-voltage cable, ground, and drain wires to permit elbow connectors to be moved to their respective parking stands.

B. Ground metallic cable shield with a cable shield grounding adapter, consisting of a solderless connector enclosed in watertight rubber housing covering the entire assembly, bleeder wire, and ground braid.

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2.8 LOW-VOLTAGE EQUIPMENT

A. Mount the low-voltage bushings, and hot stick in the low-voltage compartment.

B. The low-voltage leads shall be brought out of the tank by epoxy pressure tight bushings, and shall be standard arrangement.

C. Tin-plate the low-voltage neutral terminal and isolate from the transformer tank. Provide a removable ground strap sized in accordance with the NEC and connect between the secondary neutral and ground pad.

2.9 TRANSFORMERS

A. Transformer ratings shall be as shown on drawings. kVA ratings shown on the drawings are for continuous duty without the use of cooling fans.

B. Temperature rises shall not exceed the NEMA TR 1 of 65˚ C (149˚ F) by resistance.

C. Transformer insulating material shall be less flammable, dielectric, and UL listed as complying with NFPA 70 requirements for fire point of not less than 300˚ C (600˚ F) when tested according to ASTM D 92.

Liquid shall be biodegradable and nontoxic and non-bioaccumulating. It shall be Factory Mutual approved and UL Classified, Envirotemp FR3 fluid or equal.

D. Transformer impedance shall be as shown on the drawings.

E. Sound levels shall conform to NEMA TR 1 standards.

F. Primary and Secondary Windings for Three-Phase Transformers:

1. Primary windings shall be delta-connected.

2. Secondary windings shall be wye-connected Provide isolated neutral bushings for secondary wye-connected transformers.

3. Secondary leads shall be brought out through pressure-tight epoxy bushings.

G. Primary windings shall have four 2-1/2% full-capacity voltage taps; two taps above and two taps below rated voltage.

H. Core and Coil Assemblies:

1. Cores shall be grain-oriented, non-aging, silicon steel to minimize losses.

2. Core and coil assemblies shall be rigidly braced to withstand the stresses caused by rough handling during shipment, and stresses caused by any possible short-circuit currents.

3. Coils shall be continuous-winding type without splices except for taps. Material shall be copper.

4. Coil and core losses shall be optimum for efficient operation.

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5. Primary, secondary, and tap connections shall be brazed or pressure type.

6. Provide end fillers or tie-downs for coil windings.

I. The transformer tank, cover, and radiator gauge thickness shall not be less than that required by ANSI.

J. Accessories:

1. Provide standard NEMA features, accessories, and the following:

a. No-load tap changer. Provide warning sign.

b. Lifting, pulling, and jacking facilities.

c. Globe-type valve for oil filtering and draining, including sampling device.

d. Pressure relief valve.

e. Liquid level gauge and filling plug.

f. A grounding pad in the medium- and low-voltage compartments.

g. A diagrammatic nameplate.

h. Dial-type liquid thermometer with a maximum reading pointer and an external reset.

i. Hot stick. Securely fasten hot stick within low-voltage compartment.

2. The accessories shall be made accessible within the compartments without disassembling trims and covers.

K. Transformers shall meet the energy conservation standards for transformers per the United States Department of Energy 10 CFR Part

431.

PART 3 - EXECUTION

3.1 INSTALLATION

A. Not Used

3.2 ACCEPTANCE CHECKS AND TESTS

A. Perform manufacturer’s required field tests in accordance with the manufacturer's recommendations.

3.3 SPARE PARTS

A. Deliver the following spare parts for the project to the Resident

Engineer:

1. Six insulated protective caps.

2. One spare set of medium-voltage fuses for each size and type of fuse used in the project.

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3.5 INSTRUCTION

A. The Contractor shall instruct maintenance personnel, for not less than one 2-hour period, on the maintenance and operation of the equipment on the date requested by the Resident Engineer.

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