VA 26 22 00-2010 LOW-VOLTAGE TRANSFORMERS.pdf

1、09-10 26 22 00 - 1 SECTION 26 22 00 LOW-VOLTAGE TRANSFORMERS SPEC WRITER NOTE: Delete between /_/ if not applicable to project. Also delete any other item or paragraph not applicable to the selection and renumber the paragraphs. PART 1 GENERAL 1.1 DESCRIPTION This section specifies the furnishing, i

2、nstallation, and connection of dry-type general-purpose transformers. 1.2 RELATED WORK /A. Section 13 05 41, SEISMIC RESTRAINT REQUIREMENTS FOR NON-STRUCTURAL COMPONENTS: Requirements for seismic restraint of nonstructural components./ B. Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS:

3、General electrical requirements and items common to more than one section of Division 26. C. Section 26 05 21, LOW-VOLTAGE ELECTRICAL POWER CONDUCTORS AND CABLES (600 VOLTS AND BELOW): Cables and wiring. D. Section 26 05 26, GROUNDING AND BONDING FOR ELECTRICAL SYSTEMS: Requirements for personnel sa

4、fety and to provide a low impedance path for possible ground fault currents. E. Section 26 05 33, RACEWAY AND BOXES FOR ELECTRICAL SYSTEMS: Conduits and outlet boxes. 1.3 QUALITY ASSURANCE Refer to Paragraph, QUALIFICATIONS, in Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS. 1.4 SUBMITT

5、ALS A. In accordance with Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS, submit the following: B. Shop Drawings: 1. Clearly present sufficient information to determine compliance with drawings and specifications. 2. Include electrical ratings, impedance, dimensions, weight, mounting de

6、tails, decibel rating, terminations, temperature rise, no load and full load losses, and connection diagrams. 3. Complete nameplate data, including manufacturers name and catalog number. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-09-10 26 22 00

7、- 2 C. Manuals: 1. When submitting the shop drawings, submit companion copies of complete maintenance and operating manuals, including technical data sheets and wiring diagrams. 2. If changes have been made to the maintenance and operating manuals originally submitted, then submit four copies of the

8、 updated maintenance and operating manuals to the /Resident Engineer/ /COTR/ two weeks prior to final inspection. D. Certifications: Two weeks prior to the final inspection, submit four copies of the following to the /Resident Engineer/ /COTR/: 1. Certification by the manufacturer that the materials

9、 conform to the requirements of the drawings and specifications. 2. Certification by the contractor that the equipment has been properly installed and tested. 1.4 APPLICABLE PUBLICATIONS A. Publications listed below (including amendments, addenda, revisions, supplements, and errata) form a part of t

10、his specification to the extent referenced. Publications are referenced in the text by designation only. B. National Fire Protection Association (NFPA): 70-08 National Electrical Code (NEC) C. National Electrical Manufacturers Association (NEMA): ST20-92 Dry-Type Transformers for General Application

11、s TP1-02 . Guide for Determining Energy Efficiency for Distribution Transformers TR1-00 . Transformers, Regulators, and Reactors PART 2 - PRODUCTS 2.1 GENERAL PURPOSE DRY-TYPE TRANSFORMERS A. Unless otherwise specified, dry-type transformers shall be in accordance with NEMA, NEC, and as shown on the

12、 drawings. Transformers shall be UL-listed and labeled. B. Dry-type transformers shall have the following features: 1. Transformers shall be self-cooled by natural convection, isolating windings, indoor dry-type. Autotransformers will not be accepted. 2. Rating and winding connections shall be as sh

13、own on the drawings. 3. Transformers shall have copper windings. 4. Ratings shown on the drawings are for continuous duty without the use of cooling fans. 5. Insulation systems: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-09-10 26 22 00 - 3 a. Tr

14、ansformers 30 kVA and larger: UL rated 220 C system with an average maximum rise by resistance of 150 C in a maximum ambient of 40 C. b. Transformers below 30 kVA: Same as for 30 kVA and larger or UL rated 185 C system with an average maximum rise by resistance of 115 C in a maximum ambient of 40 C.

15、 6. Core and coil assemblies: a. Rigidly braced to withstand the stresses caused by short-circuit currents and rough handling during shipment. b. Cores shall be grain-oriented, non-aging, and silicon steel. c. Coils shall be continuous windings without splices except for taps. d. Coil loss and core

16、loss shall be minimized for efficient operation. e. Primary and secondary tap connections shall be brazed or pressure type. f. Coil windings shall have end filters or tie-downs for maximum strength. 7. Certified sound levels determined in accordance with NEMA, shall not exceed the following: Transfo

17、rmer Rating Sound Level Rating 0 - 9 KVA 40 dB 10 - 50 KVA 45 dB 51 - 150 KVA 50 dB 151 - 300 KVA 55 dB 301 - 500 KVA 60 dB SPEC WRITER NOTE: If a specific impedance is required to limit fault currents, verify that the transformer impedance is shown on the drawings. 8. If not shown on drawings, nomi

18、nal impedance shall be as permitted by NEMA. 9. Single phase transformers rated 15 kVA through 25 kVA shall have two 5% full capacity taps below normal rated primary voltage. All transformers rated 30 kVA and larger shall have two 2.5% full capacity taps above, and four 2.5% full capacity taps below

19、 normal rated primary voltage. 10. Core assemblies shall be grounded to their enclosures with adequate flexible ground straps. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-09-10 26 22 00 - 4 11. Enclosures: a. Comprised of not less than code gauge

20、 steel. b. Outdoor enclosures shall be NEMA 3R. c. Temperature rise at hottest spot shall conform to NEMA Standards, and shall not bake and peel off the enclosure paint after the transformer has been placed in service. d. Ventilation openings shall prevent accidental access to live components. e. Th

21、e enclosure at the factory shall be thoroughly cleaned and painted with manufacturers prime coat and standard finish. 12. Standard NEMA features and accessories, including ground pad, lifting provisions, and nameplate with the wiring diagram and sound level indicated on it. 13. Dimensions and config

22、urations shall conform to the spaces designated for their installations. 14. Transformers shall meet the minimum energy efficiency values per NEMA TP1 as listed below: kVA Rating Output efficiency (%) 15 97 30 97.5 45 97.7 75 98 112.5 98.2 150 98.3 225 98.5 300 98.6 500 98.7 750 98.8 SPEC WRITER NOT

23、E: Use nonlinear transformers whenever significant harmonic-producing loads, such as switching power supplies, are present. /2.2 NONLINEAR TRANSFORMERS A. Shall be as specified in Paragraph 2.1, with additional features as specified below. B. Transformers shall be designed to withstand the overheati

24、ng effects caused by harmonics resulting from non-linear (non-sinusoidal) loads. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-09-10 26 22 00 - 5 C. Neutral rating shall be 200% of rated secondary phase current. D. Minimum efficiency designed to su

25、pply circuits with a harmonic profile equal to or less than a K factor of 13, without exceeding specified temperature rise. Transformers with K factor of 13 shall be provided, if K factor is not shown on contract drawings. Table below applies to K-13 transformers only. Harmonic K-13 (%) Fundamental

26、100 3rd 70 5th 42 7th 5 9th 3 11th 3 13th 1 15th 0.7 17th 0.6 /2.3 ENERGY SAVING HARMONIC CANCELLATION TRANSFORMERS A. Shall be as specified in Paragraph 2.1, with additional features as specified below. B. The 3rd, 9th, and other zero sequence currents shall be treated via flux cancellation in the

27、secondary windings. C. Each winding shall be independently single-shielded with a full-width copper electrostatic shield. D. Provide two sets of normally-open dry contacts: 170 C and 200 C. E. Neutral rating shall be 200% of rated secondary phase current./ /2.4 BUCK-BOOST TRANSFORMERS SPEC WRITER NO

28、TE: Design must assure that all buck-boost transformers are continuously loaded. Shall be as specified in Paragraph 2.1, with additional features as specified below. 1. Self-cooled, indoor, dry-type, and suitable for connection as auto transformers to provide the percentages of voltage buck or boost

29、 as shown on the drawings. 2. Continuous duty. 3. Insulation system to be 220 C. 4. Sound levels shall not exceed 36 dB. 5. Core assemblies grounded to enclosure. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-09-10 26 22 00 - 6 6. Enclosures cleane

30、d and painted at the factory with primer and manufacturers standard finish. 7. Vibration isolators./ PART 3 - EXECUTION 3.1 INSTALLATION A. Installation of transformers shall be in accordance with the NEC, as recommended by the equipment manufacturer and as shown on the drawings. SPEC WRITER NOTE: C

31、oordinate with mechanical to assure proper ventilation of transformer spaces. Ceiling/wall-mounted transformers shall be mounted in accordance with manufacturers recommendations. B. Install transformers with manufacturers recommended clearance from wall and adjacent equipment for air circulation. Mi

32、nimum clearance shall be 6 in 150 mm. C. Install transformers on vibration pads designed to suppress transformer noise and vibrations. D. Use flexible metal conduit to enclose the conductors from the transformer to the raceway systems. 3.2 ACCEPTANCE CHECKS AND TESTS Perform tests in accordance with

33、 the manufacturers recommendations. Include the following visual and mechanical inspections. 1. Compare equipment nameplate data with specifications and approved shop drawings. 2. Inspect physical and mechanical condition. 3. Inspect all field-installed bolted electrical connections, using the calib

34、rated torque-wrench method to verify tightness of accessible bolted electrical connections. 4. Perform specific inspections and mechanical tests as recommended by manufacturer. 5. Verify correct equipment grounding. 6. Verify proper secondary phase-to-phase and phase-to-neutral voltage after energiz

35、ation and prior to connection to loads. 3.3 FOLLOW-UP VERIFICATION Upon completion of acceptance checks, settings, and tests, the contractor shall demonstrate that the transformers are in good operating condition and properly performing the intended function. - - - E N D - - - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-