San Jose City College PE Building &Wellness Center
San Jose, CA
10890002
SECTION 26 12 00
MEDIUM-VOLTAGE TRANSFORMERS
PART 1 - GENERAL
1.1 SUMMARY
A. Work included:
1. Liquid Filled Transformers
2. Dry-Type Transformers
1.2
1.3
1.4
RELATED SECTIONS
A. Contents of Division 26, Electrical and Division 01, General Requirements apply to this Section.
REFERENCES AND STANDARDS
A. References and Standards per Section 26 00 00, Electrical Basic Requirements and Division 01,
General Requirements.
SUBMITTALS
1.5
1.6
A. Submittals as required by Section 26 00 00, Electrical Basic Requirements and Division 01, General
Requirements.
QUALITY ASSURANCE
A. Quality assurance as required by Section 26 00 00, Electrical Basic Requirements and Division 01,
General Requirements.
B. In addition, meet the following:
1. Provide factory tests to applicable IEEE standards. Include the routine tests as defined in the standards and the following other tests: a. Impedance voltage and load loss. b. Dielectric tests. c. Audible sound level. d. Short circuit capability. e. Temperature rise.
2. Test insulating liquid samples in accordance with IEEE standards.
3. Make completed transformer available for inspection at manufacturer's factory prior to packaging for shipment. Notify Owner's Representative or Engineer at least 7 days before inspection is scheduled to be conducted.
4. Allow witnessing of factory inspections and tests at manufacturer's test facility. Notify Owner's
Representative or Engineer at least 7 days before inspections and tests are scheduled.
WARRANTY
A. Warranty of materials and workmanship as required by Section 26 00 00, Electrical Basic
Requirements and Division 01, General Requirements.
PART 2 - PRODUCTS
2.1 MANUFACTURERS
A. Eaton Electrical
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San Jose City College PE Building &Wellness Center
San Jose, CA
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10890002
B. General Electric
C. Square D
D. Cooper, or ABB
E. Or equal.
LIQUID-FILLED TRANSFORMERS
A. Provide compartmental type, self cooled, tamperproof and weatherproof with pad mounting provisions. Comply within the latest applicable standards of NEMA and ANSI. Provide transformer with no exposed screws, bolts or other fastening devices which are externally removable.
B. Voltage: Unless otherwise indicated on Drawings, transformers are 3 phase delta primary and 3 phase wye secondary.
C. Taps: Standard NEMA, ANSI 3 phase primary taps: 10 percent range of tap voltage adjustment for transformers smaller than 30KVA and 15 percent range tap voltage adjustment for 30KVA and larger.
D. Rating: Unless otherwise indicated on Drawings, provide transformer ratings continuous, with an average temperature rise, by resistance, not to exceed 65C in a 30C ambient with 100 percent of rated nameplate load connected to the secondary.
E. Sealed tank construction of sufficient strength to withstand a pressure of 7 PSI without permanent distortion. Provide welded cover with the fastening tamperproof. Provide exterior cooling panels, lifting eyes, jacking pads, and welded cover.
F. Core and coil assembly core type with aluminum windings. Where wye primary.wye secondary is scheduled or required provide triplex or 5-legged core design. Transformer coils or continuous wire wound construction. Provide each coil layer with end fillers or tie-downs to provide maximum mechanical strength. Braze tap terminations directly to bus stubs or lugs firmly mounted. Materials incorporated must have at least a minimum of 1 year of proven field usage. Accelerated laboratory test not acceptable.
G. Tap changing mechanism for deenergized operation only and externally operable with two 2.5 percent full capacity taps above and two 2.5 percent full capacity taps below normal rated primary voltage.
H. High and low voltage compartments to be located side-by-side separated by a steel barrier. Provide full height air filled terminal compartments with individual doors. Provide high voltage door fastenings which are not accessible until the low voltage door has been opened. Provide the low voltage door with a three point latching mechanism with vault type handle provisions for a single padlock. Provide doors with lift off type stainless steel hinges and door stops. Provide removable front sills and ANSI tank grounding provisions in each compartment.
I. Dead front construction with load break gang operated immersed switch with switch hand located in the high voltage compartment for operating with distribution hot stick. Provide 2-position on-off for radial feed unless loop feed is indicated on Drawings. If loop is indicated provide 4-position switch.
Provide dry well canister mounted current limiting fuses externally replaceable with distribution hot stick. Size fuses to manufacturer's recommendation to final design load. Provide Series NX Arc-
Strangler fuses. Provide distribution class lightning arrester mounted in the high voltage compartment.
J. Secondary Terminals: Low voltage bushings, 6 hole spade, molded epoxy with blade type spade terminals for NEMA standard hole spacing arranged for vertical take-off. Provide low voltage neutral with insulated busing grounded to the transformer tank by removable grounding strap. Wye-wye connected transformers are provided with the high and low voltage neutrals internally tied with a removable link for testing.
K. Accessories:
1. 1-inch drain valve/sampling device
2. Dial type thermometer
3. Magnetic liquid level gauge
4. Pressure/vacuum gauge
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San Jose City College PE Building &Wellness Center
San Jose, CA
2.3
10890002
5. Pressure relief valve
6. 1000KVA and larger provide sudden pressure relay
L. Degrease, clean, phosphatize, prime and finish enclosures with a gray, baked enamel. Visibly ground the core of the transformer to this enclosure by means of a flexible ground strap.
M. Mount transformer core and coil on vibration mounting pads designed to suppress transmission of
120 cycle frequencies and harmonics thereof. Arrange and select pads in consideration of core and coil weight. Provide additional noise suppressing mountings external to transformers where transformers are located in mechanical spaces.
N. Maximum sound levels from no load to rated load:
1. 45dB through 150KVA.
2. 50dB through 300KVA.
DRY-TYPE TRANSFORMERS
A. Dry-Type Transformers: IEEE C57.12.55; three phase, pad-mounted, self-cooled transformer unit with solid-cast windings.
B. Cooling and Temperature Rise: ANSI C57.12.01; Class AA. 220 degree C insulation class with 150 degree C rise over 40 degree C ambient.
PART 3 - EXECUTION
3.1 EXAMINATION
3.2
A. Verify that support pads are ready to receive products.
B. Verify that field measurements are as shown on shop drawings.
INSTALLATION
A. Provide transformers with working pad of 2500 to 3000 PSI concrete. Size pads to extend 6-inches on each side from the transformers most prominent dimension. Refer to structural detail 7/S4.02 for more information. Provide 3/4-inch by 10 foot ground rod at each corner thermally bonded to a No. 2 bare copper ground conductor, bonded to transformer, and concrete reinforcement.
3.3
B. Mount transformers no closer to combustible materials than allowed by applicable codes. Mount transformers away from structure as recommended by manufacturer and power utility to allow for adequate ventilation.
C. Provide 8-inch round by 24-inch (above and below grade) concrete and steel bollards where subject to vehicular traffic.
D. Provide oil enclosure consisting of fire resistant dikes, curbed areas, or basin or trenches filled with coarse crushed stone. Provide requirements of applicable codes unless specifically noted otherwise on Drawings.
E. Transformers grouped together or grouped with other electrical equipment are to have finishes matching in color and type.
F. Install plumb and level.
FIELD QUALITY CONTROL
A. Inspect and test in accordance with NETA ATS, except Section 4.
B. Perform inspections and tests listed in NETA ATS, Section 7.2. In addition to the basic requirements of Section 7.2, include the following:
1. Dry-Type Transformers: a. Perform turns ratio tests at tap positions. b. Verification that as-left tap connections are as specified. c. Perform excitation-current tests on each phase. d. Measure the resistance of each winding at each tap connection. e. Overpotential test on high- and low-voltage windings-to-ground.
2. Liquid-Filled Transformers:
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San Jose City College PE Building &Wellness Center
San Jose, CA
10890002 a. Calculate the polarization index. b. Perform excitation-current tests in accordance with test equipment manufacturer's published data. c. Measure insulating liquid's specific gravity, water content, and dissipation factor or power factor.
C. Check for damage and tight connections prior to energizing transformers.
D. Measure primary and secondary voltages and make appropriate tap adjustments so that secondary voltage is above and within 2 percent of rated voltage.
E. Examine and remedy excessively noisy transformer to achieve an acceptable noise level or replace with a new unit with an acceptable sound level.
END OF SECTION
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