Draft Specification - 48 19 23.50_DRAFT.pdf

SECTION 48 19 23.50

87,000 KVA CLASS II GAS-INSULATED GSU POWER TRANSFORMERS

PART 1 GENERAL

1.1 DESCRIPTION OF WORK

This Section covers the design, manufacturing and factory testing of two three-phase generator step-up (GSU) power transformers rated 87,000 kVA, 230 kV high-voltage, 13.8 kV low-voltage, Class GDAF cooling, for delivery f.o.b. to Detroit Dam power plant. The transformer shipment, hauling, site reassembly, and field testing requirements are as required in SECTION 48 20 00. Throughout this Section, the transformer tank layout is identified by Segments 1 through 4, as defined in IEEE C57.12.10, Figure 1, and indicated on drawing X-XXX.

1.2 GENERAL ARRANGEMENT AND CONNECTED POWERTRAIN

1.2.1 General Arrangement

The transformers specified in this Section will replace two existing banks of single-phase transformers (Banks T1 and T2), presently located at the Detroit Dam power plant. The new three-phase transformers shall be designed and manufactured as required herein for rail mounting across the existing rails embedded in the three single-phase piers such that the transformer assembly spans the three piers.

1.2.2 Connected Powertrain

Each new three-phase transformer shall be sized per the requirements of paragraph, "Ratings and Electrical Characteristics", to transmit the power of one connected hydrogenerator. Generators 1 and 2 are each rated xx,xxx kVA, 0.95 pf. The expected typical loading on each new three-phase transformer may be 87,000 kVA continuous.

1.3 REFERENCED PUBLICATIONS

The publications listed below form a part of this specification to the extent referenced. The publications are referred to within the text by the basic designation only.

AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING (ASNT)

ASNT SNT-TC-1A (2011; Corr Feb 2013) Recommended Practice for Personal Qualification and Certification in Nondestructive Testing

ASME INTERNATIONAL (ASME)

ASME B1.1 (2003; R 2008) Unified Inch Screw Threads (UN and UNR Thread Form)

ASME B1.20.1 (2013) Pipe Threads, General Purpose (Inch)

ASME B16.1 (2010) Gray Iron Pipe Flanges and Flanged Fittings (Classes 25, 125, and 250)

ASME B16.24 (2011) Cast Copper Alloy Pipe Flanges and Flanged Fittings (Classes 150, 300, 600, 900, 1500, and 2500

ASME B18.2.6M (2012) Metric Fasteners for Use in Structural Applications

ASME BPVC SECTION IX (2013) Qualification Standard for Welding and Brazing Procedures, Welders, Brazers, and Welding and Brazing Operators

ASTM INTERNATIONAL (ASTM)

ASTM A 53 (2012) Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless

ASTM A 343 (2014) Standard Test Method for Alternating-Current Magnetic Properties of Materials at Power Frequencies Using Wattmeter-Ammeter-Voltmeter Method and 25-cm Epstein Test Frame

ASTM A 504/A 504M (2008; R 2013) Standard Specification for Wrought Carbon Steel Wheels

ASTM A 664 (2014) Standard Practice for Identification of Standard Electrical Steel Grades in ASTM Specifications

ASTM A 717 (2012) Standard Test Method for Surface Insulation Resistivity of Single-Strip Specimens

ASTM A 876 (2012) Standard Specification for Flat-Rolled, Grain-Oriented, Silicon-Iron, Electrical Steel, Fully Processed Types

ASTM D 1535 (2014) Standard Practice for Specifying Color by the Munsell System

ASTM D 2472 (2000; R 2006) Standard Specification for Sulphur Hexafluoride

ASTM D 4059 (2000; R 2010) Standard Test Method for Analysis of Polychlorinated Biphenyls in Insulating Liquids by Gas Chromatography

AMERICAN SOCIETY OF CIVIL ENGINEERS (ASCE)

ASCE 7 (2010) Minimum Design Loads for Buildings and Other Structures

AMERICAN WELDING SOCIETY (AWS)

AWS A2.4 (2012) Standard Symbols for Welding, Brazing, and Nondestructive Examination

AWS D1.1 (2010) Structural Welding Code - Steel

AWS D1.6 (2007) Structural Welding Code - Stainless Steel

INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC)

IEC 60076-15 (2008) Power Transformers - Part 15:

Gas-filled Power Transformers

IEC 60376 (2005) Specification of Technical Grade Sulfur Hexafluoride (SF6) for use in Electrical Equipment

INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS (IEEE)

IEEE 693 (2005) Recommended Practice for Seismic Design of Substations

IEEE C37.90.1 (2012) Standard for Surge Withstand Capability (SWC) Tests for Relays and Relay Systems Associated with Electric Power Apparatus

IEEE C57.12.00 (2010) General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers

IEEE C57.12.10 (2010) Requirements for Liquid-Immersed Power Transformers

IEEE C57.12.70 (2011) Standard Terminal Markings and Connections for Distribution and Power Transformers

IEEE C57.12.80 (2010) Terminology for Power and Distribution Transformers

IEEE C57.12.90 (2010) Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers

IEEE C57.13 (2008) Requirements for Instrument Transformers

IEEE C57.19.00 (2004) General Requirements and Test Procedures for Outdoor Power Apparatus Bushings

IEEE C57.19.01 (2000; R 2010) Performance Characteristics and Dimensions for Outdoor Apparatus Bushings

IEEE C57.91 (2011) Guide for Loading

Mineral-Oil-Immersed Transformers and Step-Voltage Regulators

IEEE C57.149 (2012) Guide for the Application and Interpretation of Frequency Response Analysis for Oil-Immersed Transformers

IEEE C62.11 (2012) Metal-Oxide Surge Arresters for AC Power Circuits (> 1 kV)

MANUFACTURERS STANDARDIZATION SOCIETY OF THE VALVE AND FITTINGS

INDUSTRY (MSS)

MSS SP-72A (2010) Ball Valves with Flanged or Butt-Welding Ends for General Service

NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION (NEMA)

NEMA 250 (2014) Enclosures for Electrical Equipment (1000 Volts Maximum)

NEMA C29.1 (1988; R 2002) Test Methods for Electrical Power Insulators

NEMA C80.1 (2005) Electrical Rigid Steel Conduit

(ERSC)

NEMA CC 1 (2009) Electrical Power Connection for Substations

NEMA FB 1 (2012) Fittings, Cast Metal Boxes, and Conduit Bodies for Conduit, Electrical Metallic Tubing, and Cable

NEMA ICS 1 (2000; R 2008; E 2010) Industrial Control and Systems General Requirements

NEMA ICS 2 (2000; R 2005; Errata 2008) Standard for Controllers, Contactors, and Overload Relays Rated 600 V

NEMA ICS 5 (2000; R 2010) Control Circuit and Pilot Devices

NEMA LA 1 (2009) Surge Arresters

NEMA MW 1000 (2014) Magnet Wire

NEMA SG 4 (2009; R 2013) Alternating-Current High-Voltage Circuit Breakers

NATIONAL FIRE PROTECTION ASSOCIATION (NFPA)

NFPA 70 (2014) National Electrical Code

UNDERWRITERS LABORATORIES (UL)

UL 248-8 (2011) Low-Voltage Fuses - Part 8: Class J Fuses

UL 360 (2013; Rev thru Jan 2015) Liquid-Tight Flexible Metal Conduit

UL 489 (2013; Rev thru Mar 2014) Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures

UL 508 (1999; Rev thru Oct 2013) Industrial Control Equipment

UL 508A (2013; Rev thru Jan 2014) Industrial Control Panels

UL 514B (2012; Rev thru Nov 2014) Conduit, Tubing, and Cable Fittings

UL 969 (1995; Rev thru Sep 2014) Safety Marking and Labeling Systems

UL 4248-8 (2007; Rev thru Oct 2013) Fuseholders - Part 8: Class J

U.S. ARMY CORPS OF ENGINEERS (USACE)

EM 385-1-1 (2008; Errata Jul 2012) Safety and Health Requirements Manual

1.4 SUBMITTALS

Government approval is required for submittals with a "G" designation;

submittals not having a "G" designation are for information only or as otherwise designated. When used, a designation following the "G" designation identifies the office that will review the submittal for the Government. The following shall be submitted in accordance with SECTION 01 33 00, "SUBMITTAL PROCEDURES", unless otherwise indicated below:

SD-02 Shop Drawings

a. Outline and Assembly Drawings; G, HDC

Outline and assembly drawings of the transformers shall be submitted for approval within 150 calendar days after date of award to demonstrate that the equipment will conform to the requirements and intent of the specifications. These drawings shall include the following, at a minimum:

(1) Transformer nameplate information. Drawings shall be provided for the main transformer nameplate and lifting nameplate, as required in paragraph "NAMEPLATES".

(2) Outline drawing. An outline drawing shall be provided indicating the following:

(a) Layout and dimensions of the assembled transformer, including centers of gravity with the transformer empty and filled with gas, and grounding pads. An elevation view for each side of the transformer and a plan view shall be provided.

(b) Jacking, lifting and pulling-eye locations.

(c) Locations of all ancillary equipment, dimensioned to the transformer centerlines or edges, as appropriate, including bushings, control and power cabinets, conduit entry terminal box, valves, gauges, relays, nitrogen regulator cabinet, radiators, coolers, and on-line monitors.

(d) Drawing legend and transformer weight and gas volume information.

(e) A transformer elevation view indicating clearances required for untanking or disassembling.

(3) Transformer winding layout and configuration diagram. The winding diagram shall be a sectional elevation view of sufficient detail to identify the following basic features of the core/coil construction:

(a) Core legs

(b) High-voltage winding

(c) Low-voltage winding

(d) Winding taps

(e) De-energized tap changer and lead support structure

(f) Bushing configuration and connections

(g) Shielding (if present)

(h) Pressboard or other barriers

(i) Tank wall surface

(4) Control schematic diagrams.

b. Detail Drawings; G, HDC

Detail drawings shall be submitted for approval within 210 calendar days after date of award. These drawings shall include the following:

(1) Further refinement of the outline and assembly drawings, including the routing of conduit, piping, locations of junction boxes and external devices, and low-voltage bushing housing design and interface to the existing low voltage bus. The final locations of the conduit routing and junction boxes may be included in the manufacturer's as-built drawings after manufacture of the transformer has been completed.

(2) Shipping drawing showing the outline of the transformer disassembled as required for shipment, including the following:

(a) Overall shipping dimensions, including indication of centers of gravity for the transformer in the shipping configuration. All devices remaining installed on the transformer during shipment shall be indicated.

(b) Lifting details and overall height required for the slings and crane hook, including recommended sling length and ratings.

(c) Location of temporary covers for bushings, valves and control and power cabinets left installed during shipment.

(d) Detail indicating the method of installing the SFRA test shipping bushings, their locations, and a description of the method of bracing the winding leads to these bushings during shipment.

(e) Location of impact recorders, shipping gas pressure gauge and pressure regulator system.

(3) Wiring connection diagrams showing terminal block and conductor designations. These drawings shall include detailed control, power, and conduit entry cabinet interconnections and device locations, and shall be prepared based upon the actual equipment arrangement.

(4) Seismic anchoring locations.

(5) A transformer outline drawing indicating the locations of all gaskets on the transformer, a schedule of gasket types and sizes, and a detail for each design of gasket showing the groove and compression requirements.

(6) A transformer outline drawing indicating the locations of typical welds, with structural weldment details.

(7) A drawing of the transformer fall protection system, indicating the routing of the wire rope, method of attaching and tensioning the wire rope, mounting framework and dimensions of the storage cabinet, and a materials list.

SD-05 Design Data

a. Descriptive Data; G, HDC

Descriptive data or catalog data of all accessory devices and ancillary equipment provided with the transformer shall be submitted for approval within 240 calendar days after date of award, to demonstrate fully that all parts of the equipment will conform to the requirements and intent of the specifications.

b. Spare Parts List; G, HDC

A listing of all required spare parts to be provided with the transformers shall be submitted for approval within 240 calendar days after date of award. (see paragraph "SPARE PARTS")

c. Structural Design Criteria and Seismic Calculations; G, HDC

Structural design criteria and seismic calculations shall be submitted for approval within 210 calendar days after date of award. Design criteria and calculations shall be performed by qualified civil or structural engineers who are presently registered professional engineers (PE). A cover sheet for the submittal shall be provided and stamped or sealed and signed by a

PE.

SD-06 Test Reports

a. Transformer Factory Acceptance Test Report; G, HDC

The transformer factory acceptance test report shall be submitted for approval not later than 14 calendar days following completion of the factory acceptance tests. (see paragraph "Factory Acceptance Test Report").

b. Bushing Design Tests; G, HDC

The transformer bushing design test reports shall be submitted for approval not later than 30 calendar days following completion of the tests (see paragraph "Bushing Design Tests"). If certified copies of bushing design tests previously conducted within five

(5) years are submitted in-lieu of new test results, they shall be submitted when the bushing selection is made, but not later than 60 calendar days prior to the performance of transformer factory acceptance tests.

c. Bushing Routine Tests; G, HDC

The transformer bushing routine test reports shall be submitted for approval not later than 30 calendar days following completion of the tests. (see paragraph "Bushing Routine Tests").

d. Bushing Current Transformer Tests; G, HDC

The transformer bushing current transformer test reports shall be submitted for approval not later than 30 calendar days following completion of the tests. (see paragraph "Bushing Current Transformer Tests").

e. Surge Arrester Design Tests; G, HDC

The surge arrester design test reports shall be submitted for approval not later than 30 calendar days following completion of the tests (see paragraph "Surge Arrester Design Tests"). If certified copies of previously conducted surge arrester design tests are submitted in-lieu of new test results, they shall be submitted not later than 30 calendar days prior to performance of transformer factory acceptance tests.

f. Surge Arrester Conformance Tests; G, HDC

The surge arrester conformance test reports shall be submitted for approval not later than 30 calendar days following completion of the tests. (see paragraph "Surge Arrester Conformance Tests").

SD-07 Certificates

a. Transformer Gas Certification; G, HDC

Transformer gas certification shall be submitted for approval a minimum of 14 calendar days prior to the delivery of transformer gas to the Detroit Dam power plant. (see paragraph "Quantity and Transformer Gas Certification").

b. Notification of the Date of the Transformer Design Review Meeting; G, HDC

The contractor shall notify the COR 30 calendar days in advance of when the transformer manufacturer will be ready for performance of a design review meeting, to be held at the manufacturer's facility. (see paragraph "TRANSFORMER DESIGN REVIEW MEETING").

c. Notification of the Date of Factory Tests; G, HDC

The contractor shall notify the COR, in writing, 30 calendar days in advance of when the transformer will be ready for factory acceptance tests, so that the tests may be witnessed by a Government Representative. If factory testing in a foreign country is proposed, the Contractor shall notify the COR in writing of the preliminary testing dates, not later than 60 days prior to the start of factory tests. (see paragraph "TRANSFORMER FACTORY

ACCEPTANCE TESTS").

d. Welder Qualifications; G, HDC

The welding operators and welders qualifications shall be submitted a minimum of 30 calendar days prior to their performance of work. (see paragraph "Welder Qualifications").

e. Weld Inspector Qualifications; G, HDC

The qualifications for the Contractor's Quality Assurance personnel responsible for performing weld inspections shall be submitted a minimum of 30 calendar days prior to the performance of weld inspections. (see paragraph "Inspection and Weld Inspector Qualifications").

SD-08 Manufacturer's Instructions

a. Factory Test Procedures; G, HDC

The transformer factory test procedures shall be submitted for approval a minimum of 60 calendar days prior to the performance of the factory acceptance tests. (see paragraph "TRANSFORMER FACTORY

ACCEPTANCE TESTS").

b. Welding Procedures; G, HDC

Welding procedures and specifications and copies of test reports shall be submitted a minimum of 30 calendar days prior to the performance of work. (see paragraph "Welding Procedure").

c. Prequalified Weld Procedures; G, HDC

Applicable prequalified weld procedures per the requirements of AWS shall be submitted a minimum of 30 calendar days prior to the performance of work. (see paragraph "Welding Procedure").

1.5 WARRANTY REQUIREMENTS

In addition to the requirements outlined in FAR 52.246-17, the manufacturer’s warranty for the power transformers shall continue for a period of five (5) years from the date of final acceptance of the work.

Transformer gas leaks exceeding the relative leakage rate specified in IEC 60076-15, Clause 13.2 shall be considered a warranty repair item. If the Government takes possession of any part of this work before final acceptance, this warranty shall continue for a period of five (5) years from the date the Government takes possession.

PART 2 PRODUCTS

2.1 TYPE AND RATING

2.1.1 General

The transformers furnished under these specifications shall be suitable for outdoor operation, forced gas-cooled/forced air-cooled type, Class GDAF, and shall be of a design that has an established record of satisfactory operation with the type of gas system specified. Gas medium shall be sulfur hexafluoride gas for electirc power equipment. The transformers shall be designed and manufactured for transportation by rail and trucking by heavy hauler, and for shipment by sea if the transformers have a probability of being transported by this method.

2.1.2 Transformer Limiting Dimensions and Equipment Arrangement

The transformer design, configuration, and dimensions shall be as indicated on the contract drawings, and the transformer shall not exceed the limiting dimensions.

2.1.3 Requirements

Except as otherwise specified herein, the transformers, accessories, and spare parts shall conform to the applicable requirements of IEEE C57.12.00, IEEE C57.12.10, IEEE C57.12.70, IEEE C57.12.80 and IEEE C57.12.90.

2.1.4 Standard Products

Material and equipment provided with the transformers shall be standard products from a manufacturer regularly engaged in their production, and shall essentially duplicate items that have been in satisfactory use for at least 3 years prior to bid opening, unless otherwise specifically approved.

All materials shall conform to the requirements of these specifications.

Materials shall be of industrial quality, free from defects and imperfections, of recent manufacture, and of the classification and grades designated. All materials, supplies, and articles not manufactured by the Contractor shall be the products of other recognized reputable manufacturers. If the Contractor desires for any reason to deviate from the standards designated in these specifications, a statement shall be submitted for approval describing the exact nature of the deviation, including complete specifications for the materials that are being proposed for use.

2.1.5 Ratings and Electrical Characteristics

The ratings and electrical characteristics of the transformers shall be as follows:

a. Continuous ratings, at the 65 degrees-C temperature rated temperature rise, on all taps, kVA:

GDAF Rating: 87,000

b. Frequency, Hz: 60

c. Number of phases: 3

d. Rated voltage, kV:

(1) High-voltage windings: 230

(2) Low-voltage windings: 13.8

e. Winding connections:

(1) High-voltage windings: Grounded-Wye

(2) Low-voltage windings: Delta

f. Impedance, at maximum GDAF rated current, subject to IEEE tolerances, percent: 10.0%

g. Angular displacement, low-voltage lags high-voltage by, degrees: 30

h. Basic impulse insulation levels (BIL), kV:

(1) Line ends of the high-voltage windings, not less than: XXX.X

(2) Neutral ends of the high-voltage windings, not less than:

(3) Low-voltage windings, not less than: 110

i. Taps in low voltage windings: None

j. Taps (full capacity) in high voltage winding

(1) Tap 1, percent of high-voltage rating: 105.0

(2) Tap 2, percent of high-voltage rating: 102.5

(3) Tap 3, percent of high-voltage rating: 100.0

(4) Tap 4, percent of high-voltage rating: 97.5

(5) Tap 5, percent of high-voltage rating: 95.0

k. Maximum no-load losses at rated voltage and frequency, kW: 30

l. Maximum load losses at maximum GDAF rated kVA and 1.0 power factor, kW: 165

m. Maximum average sound level at rated voltage and frequency, with all cooling groups in operation, dB: 85

n. Maximum transformer total weight, completely assembled and gas filled with all accessories installed, pounds: 170,000

2.2 STRUCTURAL DESIGN CRITERIA AND SEISMIC CALCULATIONS

Structural design criteria and seismic calculations shall be provided for the transformer design, to include the main tank, structural frame,and all major components such as bushings, and cooling equipment.

2.2.1 Structural Design Criteria

Structural design criteria shall include the following:

a. Indicate the industry design standards and allowable stresses or capacities to which steel plate, structural steel shapes, welds, bolts and studs shall conform.

b. Indicate the industry standards used in developing the seismic forces and analysis techniques used in design of the transformer and transformer components.

c. Seismic design for equipment restraint shall be in accordance with Chapter 13, "Seismic Design Requirements for Nonstructural Components," of ASCE 7 with the seismic design force computed as per Section 13.3 "Seismic Demands on Nonstructural Components". Electrical equipment restraint shall designed in accordance with the provisions in IEEE 693 Annex D, or Section 13.3 of ASCE 7 whichever produces the more adverse seismic effects. For ASCE 7, use a spectral acceleration SDS = 0.167 IP = 1.50, and z=h=1. For IEEE 693, the seismic qualification level shall be moderate.

2.2.2 Seismic Calculations

Seismic calculations shall include the following:

a. Derivation of seismic forces and load cases. Load cases used for developing seismic anchorage of the complete transformer shall account for the effect of the righting force of the weight of the transformer.

b. Calculations for use in the design of anchorage to resist overturning and base shear. The maximum uplift and shear force per anchor shall be provided in pounds or kips.

c. A schematic depicting the location of the center of gravity, the applied seismic forces relative to the base, and the location of seismic anchors.

d. Calculations for individual components and their attachment to the transformer.

2.2.3 Anchorage to Existing Concrete Pedestals for Seismic Restraint

Each transformer shall be designed for mounting on the existing embedded rails. For the purposes of performing seismic calculations, separate seismic anchorage points will be used for anchorage to the existing concrete pedestals, as indicated on drawings S-101. The separate seismic anchorage points will consist of rail stops and shear-tension supports. The shear-tension members will connect to lugs which are seismically anchored to the pedestals. It is not permissible to include the rail in seismic calculations for the resistance of shear forces in the direction perpendicular to the rail length.

2.3 THERMAL DESIGN

The temperature rise above ambient temperature of each transformer or parts thereof, when tested in accordance with its ratings, shall not exceed the limits of observable temperature rise for the insulation system classification as stated in IEC 60076-15, paragraph 11. The winding temperature rise by resistance shall not exceed the insulation class limits in IEC 60076-15, Table 2, and the hottest spot winding temperature rise shall not exceed IEC 60076-15, Table 1, on the tap connections that give the highest losses, with all coolers in operation. In addition, each transformer shall not exceed the above temperature rises when tested at the Stage 1 GDAF reduced rating with one cooling group in operation.

2.4 CORE

Each transformer core shall be constructed of high-quality, non-aging, cold-rolled, grain-oriented steel especially suitable for the purpose. The core steel laminations shall meet the requirements of ASTM A 664 and ASTM A 876, shall have a maximum thickness of 0.270 mm, and the design flux density shall not exceed 1.75 Tesla. The use of paper insulation in the core will not be acceptable. Electrical core steel core loss, rms exciting power, rms and peak exciting current, and ac permeability shall be tested in accordance with ASTM A 343. Each roll of sheet steel used shall have the surface insulation resistivity tested in accordance with ASTM A 717.

The core shall be carefully assembled and rigidly clamped to ensure adequate mechanical strength to support the windings and to prevent shifting of the laminations during shipment, and also to reduce vibration to a minimum under operating conditions. Core joints shall be interleaved. The transformer core design and construction methods shall be in such a manner to assure that the average sound level due to operation of the transformer and accessories will not exceed 85 dB at rated voltage and frequency as measured in accordance with IEEE C57.12.90.

2.5 WINDINGS

2.5.1 General

Each transformer shall be manufactured with windings meeting the requirements of paragraph "Ratings and Electrical Characteristics", consisting of one high-voltage winding (H) per phase and one low-voltage winding (X) per phase. The winding conductors shall be of high-conductivity copper magnet wire meeting the applicable requirements of NEMA MW 1000, and if of a core-form design shall be of a circular coil construction. Consideration shall be given to all factors of service, such as high dielectric and mechanical strength of insulation, coil characteristics, and minimum restrictions to free circulation of SF6 gas.

Coils shall be made up, shaped, and braced to provide for expansion, contraction, and shrinkage due to temperature changes and aging in service in order to avoid abrasion of insulation and to provide resistance to movement and distortion caused by abnormal operating conditions. Adequate barriers shall be provided between windings and core and between high-voltage and low-voltage windings. End coils shall have additional protection, if required, against normal line disturbances. The delta and wye winding connections shall be made inside the transformer tank. A de-energized tap changer shall be provided, with taps located in the high-voltage windings. The tap changer contacts shall be silvered, and capable of withstanding the full short circuit current of the transformer without injury.

2.5.2 Insulation Levels

The transformers shall be designed for BIL of the windings as specified in paragraph "Ratings and Electrical Characteristics", and shall be capable of withstanding IEEE Standard dielectric tests, in accordance with paragraph "Power Transformer Tests", corresponding to the specified winding insulation levels.

2.5.3 Short Circuit Capability

The transformers shall be capable of withstanding without injury the mechanical and thermal stresses caused by short circuits on the external terminals of any winding or windings, with rated voltages maintained across the terminals of all other windings intended for connection to sources of energy, under the conditions listed in IEEE C57.12.00 (paragraph 7.1.1).

In addition to any generator fault contribution from the primary winding side, the utility indicates a fault capability at the secondary winding terminals of approximately:

XXXX.X MVA three line-ground fault

XXXX.X MVA single line-ground fault

2.6 TANK

2.6.1 Construction

Each transformer shall be provided with a gas-tight steel tank, with gas-tight covers per the requirements of IEC 60076-15 with the following features:

a. Manholes. One or more unobstructed manholes in the cover with minimum dimensions of 24 inches by 24 inches, or 24 inches minimum diameter, to afford easy access to the lower ends of bushings, terminals, and the upper portions of the coils.

b. Positioning Guides. Suitable positioning guides shall be provided inside the tank to assure the core and windings are in the correct position during assembly.

c. Pressure Design. The main transformer tank and any attached compartment that is subjected to operating pressures shall be designed and constructed to withstand, without leakage or permanent deformation, the full design range of operational pressures. Design to relevant ASME pressure vessel code.

d. Vacuum Design. The tank shall be designed and constructed for vacuum filling (essentially full vacuum) in the field. All valves, fittings and piping affected by vacuum filling shall be of correct design and construction for such filling. Auxiliary compartments, when not designed for vacuum filling, shall be so designated, and suitable isolating valves shall be provided.

2.6.3 Lifting and Moving Facilities

2.6.3.1 Lifting Facilities

Design loads for lifting eyes, lugs or hooks shall be two times the actual load to allow for possible unequal lifting forces, with a safety factor (using design loads) in accordance with IEEE C57.12.10 (paragraph 5.3.1).

Lifting eyes, lugs, or hooks shall positively keep the lifting cable in place even when the cable is slack. The transformers shall be provided with the following lifting facilities:

a. Lifting attachments on the tank.

b. Adequate means for lifting the core and coil assembly from the tank.

c. Means for lifting the complete blower assembly for replacement.

2.6.3.2 Moving Facilities

Moving features shall be furnished as required for moving each transformer to its final location as shown, and shall be in accordance with IEEE C57.12.10 (paragraph 5.3.3).

2.6.4 Valves

Each transformer shall be provided with valves conforming with IEEE C57.12.10 (paragraph 5.1.8), unless otherwise specified, below. All valves, shall be of stainless steel construction conforming to MSS SP-72A, circular flanged, reinforced PTFE valve seats, and shall be ball-type unless otherwise specifically indicated. The valves shall be designed for use with insulating gas and have a 120 degrees Celsius minimum temperature rating, and shall include provisions for locking the handle. Valve handles shall be of circular or oval design. Weather resistant locks shall be provided for all valves, keyed the same. All valves which have an outbound connection remaining open shall be provided with either a blind-flange, including a gasket and associated hardware, or a plug/cap on the NPT threaded connection. Valves shall be provided for the following at a minimum:

a. A filling / bleeding valve

b. Gas sampling valve

c. Isolation valves:

(1) Gas Blowers. At the inlet and outlet of each gas blower to permit blower isolation for maintenance purposes or removal with the transformer filled with SF6 gas.

(2) Tank Auxiliary Components . Provide isolation valves for tank auxiliary components allowing replacement with the transformer filled with SF6 gas.

2.6.5 Connections

2.6.5.1 General

All bolts, studs, machine screws, nuts, and tapped holes designed for customer connection shall be in accordance with ASME B1.1 (inch fasteners), or ASME B18.2.6M (metric fasteners). Bolting hardware shall be Grade 5 minimum, or equivalent, and and all hardware not internal to the tank shall be galvanized. Threads for sizes 1/4-inch to 1-inch, inclusive, shall be NC or UN series. The sizes and threads of all valves, pipe and fittings, conduit and fittings, tubing and fittings, and connecting equipment, shall be in accordance with ASME B1.20.1. Manufacturers' standard threads and construction may be used on small items which are integrally replaceable, except that threads for external connections to these items shall meet the above requirements.

2.6.5.2 Stainless Steel

All stainless steel connecting hardware shall be installed using an anti-galling compound such as molybdenum disulfide on the threads prior to connection.

2.6.6 Steel Pipe and Fittings

Steel pipe shall conform to ASTM A 53, Weight A, Class 2. Dimensions of terminating flanges shall conform to ASME B16.1 and ASME B16.24.

2.6.7 Grounding

Provide four ground pads on the tank and four ground pads on the structural base. Provide the bonding jumper(s) between the tank and the structural base. Grounding provisions shall be in accordance with IEEE C57.12.10 (paragraph 5.5). Provide a #4/0 AWG insulated copper conductor on each transformer to connect the terminal of the neutral bushing for the high-voltage windings to one of the ground pads at the base of the tank.

The conductor shall be supported against the transformer tank a minimum of every 36-inches.

2.6.10 Structural Steel Supporting Base

Each transformer shall be provided with a structural steel supporting base with removable wheel assemblies designed for permanent mounting and moving on rails. The wheel size and spacing shall be suitable for use with the transformer rails shown on the drawings. The structural steel supporting base must span all three existing single-phase piers.

2.6.11 Wheel Assemblies

Provide each transformer with four double flanged wheels for movement over crossover plates, at which time the flanges will bear the full weight of the transformer. The wheels shall be made from solid wrought-steel blanks conforming to ASTM A 504/A 504M, Class C, rim treated. Bearings shall be roller bearings rated 250 hours and 70 RPM for 90 percent of the group with means for high-pressure grease lubrication. For non-revolving axles in steel frames, the bearing pressure shall not exceed 9,000 psi; compressive or tensile stresses in wheel mountings and axles shall not exceed 16,000 psi; and shear stresses shall not exceed 12,000 psi. Wheels shall be suitable for movement either perpendicular or parallel to a plane through the low voltage bushings and deisgned for 90 degree rotation on their pivots with respect to the transformer. The pivoting pins shall be desinged so that they will support the wheels when the transformer has been jacked to rotate the wheels.

2.6.11 Jack Ports

Each transformer base shall be provided with jack ports, bosses, or lugs, to permit jacking the complete transformer filled with gas per the requirements of IEEE C57.12.10 (paragraph 5.3.4). The design loads for jacking bosses or lugs shall be at least two times the actual loads to allow for possible unequal jacking forces.

2.6.12 Center of Gravity

Each transformer base shall be designed so that the center of gravity of the transformer, with or without gas as normally prepared for shipment, will not fall outside the base support members for a tilt of the base of 15 degrees from the horizontal.

2.7 COOLING EQUIPMENT

2.7.2 Coolers

Each transformer shall have forced-gas, forced-air (GDAF), cooling equipment of sufficient capacity to permit continuous operation of the transformer at maximum load without exceeding the allowable temperature rise. The cooling equipment shall also be adequate to provide continuous operation at 1,500 kVA load with one cooling group in service without exceeding the maximum allowable temperature rise. The cooling equipment shall be provided with not less than two separate cooling groups, which shall be supported by the structural frame. Each cooling group shall include one or more suitable gas to air heat exchangers, one gas circulating pump, and adequate forced air equipment. The coolers shall be so located on the tank as to insure uniform circulation of the gas through the transformer windings. Valves in the gas inlet and outlet connections, and provisions for venting and draining, shall be provided on each cooler to permit the removal of any cooler without taking the transformer out of service.

2.7.3 Gas Circulating Blowers

Design the gas blowers and motors to deliver the required amount of gas under the most adverse conditions. Motors must drive the blowers continuously under such conditions without exceeding their kilowatt rating or rated temperature rise. Provide blower assemblies with the following features:

a. thermal overload protection for each motor

b. easily accessible fittings for greasing when mounted in the supporting frame.

c. designed and connected so that it may be removed for repairs or replacement without taking the transformer out of service.

d. rated for continuous operation for ambient tempreatures between -20 to 50 degrees Celsius.

2.7.4 Forced-Air Equipment

The forced-air equipment shall include propeller type fans with guards and direct-connected motors, and a rigid housing with venturi openings, and louvers or baffles, if needed, to direct the air stream against the heat exchanger and to prevent recirculation of discharged air. The transformer forced-air equipment shall be designed to assure that the average sound level due to operation of the transformer and accessories with all fans and pumps in operation will not exceed 85 dB, as measured in accordance with

IEEE C57.12.90.

2.7.5 Power Supply Equipment

The power supply for fan motors and gas pumps will be Government-furnished, 480 V, 3-wire, 3 phase, 60 Hz, as indicated on the contract drawings.

Power will be direct-wired from the distribution panel located in the powerhouse to a terminal block in the cabinet.

2.8 BUSHINGS

2.8.1 General Bushing Requirements

Each transformer shall have three high-voltage, three low-voltage, and one neutral leads brought out from the tank through bushings as specified below. Bushings of the same voltage and current rating shall be interchangeable and, as applicable, conform to IEEE C57.19.00 and IEEE C57.19.01. All bushings shall meet the following requirements:

a. Bushings shall be of recent manufacture and shall be of a type and style currently manufactured by the bushing manufacturer.

b. Bushings shall be designed for outdoor service. All bushings which will be exposed to direct sunlight shall have UV resistant insulating sheds.

c. Bushings shall be so designed that there will be no stressing of any parts due to temperature changes, and adequate means shall be provided to accommodate conductor expansion.

d. Bushings shall seal gastight on the transformer tank.

e. The power factor of each bushing shall meet the requirements of IEEE C57.19.01, Table 6 as applicable.

2.8.2 Bushing Ratings

The high-voltage and neutral bushings provided shall be designed to withstand the standard withstand test voltages as indicated in Table 1 of IEEE C57.19.01, suitable for the installation mounting methods used for the transformer, and tested in accordance with paragraph "Bushing Tests."

2.8.2.1 High-Voltage Bushing Minimum Requirements

a. Insulation class, kV: 230

b. BIL rating, kV: XXX.X

c. Minimum current rating, Amperes: XXX.X

d. Creepage distance: Light contamination

e. Test tap suitable for power factor testing

2.8.2.2 High-Voltage Neutral Bushing Minimum Requirements

a. Insulation class, kV: 230

b. BIL rating, kV: XXX.X

c. Minimum current rating, Amperes: XXX.X

d. Creepage distance: Light contamination

f. Test tap suitable for power factor testing

2.8.2.3 Low-Voltage Bushings Minimum Requirements

a. Insulation class, kV: 13.4

b. BIL rating, kV: XXX.X

c. Minimum current rating, Amperes: XXXX.X

d. Thermal rating, degrees Celsius temperature rise: XXX.X

e. Viton gaskets used for installation

f. Solid bulk designs, if provided, shall be of a low-corona design

2.8.3 Bushing Terminal Connections

Provide all necessary hardware for connection to the overhead lines and bus as designed under this Contract. Additional requirements include:

a. Provide high-voltage and high-voltage neutral bushings with threaded copper terminal studs with dimensions in compliance with

IEEE C57.19.01.

a. Tin plate low voltage bushing terminals.

b. Provide a threaded copper electrical bronze terminal stud and a bronze alloy bolted stud-to-cable terminal connector capable of accepting the #4/0 neutral grounding connector to the tank ground pad.

2.8.4 Core Ground Bushings

Provide two external bushings for core grounding; one for the main core ground, and one for the core frame ground meeting the following requirements::

a. Insulation class, kV: X.X

b. BIL rating, kV: XX.X

c. Minimum current rating, Amperes: XXX.X

d. Manufactured with an integral cast copper stud with tin plating and insulating body of epoxy or solid porcelain.

e. Provide tapped holes connected to a removable #4 NAWG equivalent ground strap between the terminal and tank wall

f. Mount bushings adjacent and under a removable, weatherpoof metal cover.

g. Label each bushing.

2.8.7 SFRA Test Shipping Bushings

For the purposes of performing SFRA testing with each transformer in the shipping configuration, include a test bushing connected to the winding leads for each shipping cover installed after the bushings have been removed, so that the SFRA tests can be performed just prior to transformer shipment and immediately after transformer delivery to the Detroit Dam power plant. This assembly shall permit the SFRA testing on the transformer without having to gain entrance into, or modifying the transformer shipping assembly. Brace the winding leads inside the transformer tank to assure there is no movement during shipment which could damage the bushings, or potentially alter the SFRA test results. During shipment, ground the external terminals of the test bushings to the tank.

Perform testing per the requirements of paragraph "Sweep Frequency Response Analysis Tests". SFRA Test Shipping Bushings shall be of the same manufacture and rating as the core ground bushing.

2.9 BUSHING-TYPE CURRENT TRANSFORMERS

Provide bushing-type current transformers conforming to the requirements of IEEE C57.13 and additional requirements in NEMA SG 4 with ratings:

a. 0.3B-1.8 minimum accuracy classification for metering service

b. C400 relaying accuracy

c. 1.33 continuous thermal rating factor based upon a 30 degree Celsius average ambient air temperature

2.9.1 High-Voltage Neutral Bushing

Provide one 200:5 A bushing-type current transformer for the transformer high-voltage neutral bushing.

2.10 LOW-VOLTAGE BUSHING THROAT

Design the low-voltage bushing flange to mate to the new bushing enclosure.

Design the bushing flange to utilize inch fasteners for the bolted connection.

2.11 LOW-VOLTAGE BUSHING ENCLOSURE

Provide a bushing enclosure with removable access cover. Size the access cover to allow sufficient access to power factor test the bushings with equipment such as with a Doble brand Power Factor test set. The bus side of the enclosure must create a waterproof connection to the bus provided under this Contract.

2.11 SURGE ARRESTERS

2.11.1 General

Provide one single-pole surge arrester and all mounting provisions for mounting on the powerhouse wall for each transformer high-voltage line connection designed for use on a three-phase 60 HZ system conforming to the applicable provisions of IEEE C62.11 and NEMA LA 1. Arresters must meet the test requirements as included in paragraph "Surge Arrester Tests".

2.11.2 Ratings and Requirements

Provide arresters with the following ratings and requirements:

a. Designed for usual service conditions (paragraph 4.1 of IEEE C62.11)

b. Porcelain, outdoor, station class, metal-oxide type suitable for protecting a gas-insulated power transformer from overvoltages produced by lightning and switching operations

c. Self supporting

d. Wind withstand: 130 kilometers per hour

e. Seismic acceleration withstand in any direction, but not simultaneously: 0.5g

f. Maximum continuous line-to-ground operating voltage (MCOV), kV:

at least 84

g. Duty Cycle Rating, kV: at least 108

h. Pressure relief diaphragm, constructed to meet the requirements of IEEE C62.11, which will protect the porcelain from excessive internal pressure

2.11.3 Mounting

Mount on new powerhouse-wall mounted brackets with electrical isolation to ground for interconnection to discharge counters. Orient vents away from adjacent electrical components and the powerhouse wall.

2.10.4 Mounting Brackets

Provide new mounting brackets similar to the existing brackets. Design brackets to support the surge arresters, mount on the powerhouse downstream. Submit detailed loading analysis, description of powerhouse wall anchoring, dimensions, and materials with the transformer detailed design criteria.

2.11.4 Construction

2.11.4.1 General

The entire arrester construction shall be such as to assure permanent and continuous performance free of the influence of moisture and weather conditions. The design of the arrester shall be such that a uniform potential drop will exist across each section of the arrester regardless of any distortion of the electrostatic field due to the presence of fog, water, snow, sleet, or ice on the arrester porcelain, or uneven drying of the surface of the porcelain. No chemical action shall take place, nor shall the surge arrester show deterioration, as a result of ordinary operation of the arrester. No maintenance, upkeep, or attendance shall be necessary due to operation, other than routine inspection.

2.11.4.2 Housing

The arrester units shall be composed of a suitable wet process porcelain housing with metal end fittings enclosing the internal parts. The porcelain shall be of wet process, free from laminations, cavities, or other flaws affecting their mechanical or dielectric strength, and shall be well vitrified and nonporous. Seals shall be provided between the porcelain housing and metal end fittings, and any materials used therefore shall maintain their effectiveness over long periods. The metal end fittings shall be attached to the housing with solder or cement as appropriate for the construction used. The unit shall have a pressure relief diaphragm, constructed to meet the requirements of IEEE C62.11, which will protect the porcelain from excessive internal pressure. The arresters shall be rated and tested for Class I pressure-relief test currents. The color of all external porcelain shall be gray.

2.11.4.3 Line Terminal Cap

Each arrester shall be equipped with a metal line terminal cap at the line end of the arrester unit. The line terminal cap shall have the line conductor clamp terminal included as an integral part, or shall provide for attaching a separate clamp type terminal using a minimum of two attachment bolts. When a separate terminal clamp is used, all necessary hardware shall be included.

2.11.4.5 Metal Parts

Use corrosion-resistant metal or galvanized iron or steel for exposed metal parts, with the exception of conductor terminals. Iron and steel parts, including bolts, washers, and locking devices, shall be given a protective zinc coating which shall be capable of meeting the tests specified in Section 6 of NEMA C29.1.

2.11.4.6 Nameplates

Provide a corrosion resistant nameplate and, when the arrester is composed of a number of units, provide an individual namplate for each unit. Attach the main nameplate to the lower arrester unit or base with at least the information identified in IEEE C62.11.

2.11.5 Assembly

Provide all bolts with effective lock washers or other approved locking devices to maintain bolts and nuts in place. Mark and identify all parts for ease of assembly in the field.

2.11.6 Grounding

Provide a #4/0 insulated copper conductor from each surge arrester ground connection to a discharge counter. Connect the bottom of the three discharge counters together, and terminate a single #4/0 insulated copper conductor to the existing powerhouse ground conductors. The minimum spacing between conductor supports shall be 36-inches. Conductor terminations shall be made with appropriate compression fittings for cable to pad; using a simple plate to compress the ends is not acceptable.

2.11.7 Discharge Counters

Provided each arrester with an analog discharge counter to record the operations utilizing a current meter to continuously measure the grading current. The counter and ammeter shall be housed in a Type 4 enclosure, meeting the requirements of NEMA 250, and shall be mounted on the powerhouse wall to allow the counter and ammeter to be read from the ground without requiring the use of tools or unbolting the enclosure. Each discharge counter shall include a nameplate, meeting the requirements of paragraph "Device Nameplates".

2.12 TRANSFORMER MOUNTED ACCESSORIES

2.12.1 General

Dials, indicators, and gages installed on the transformer shall be mounted on the Segment 3 side at a height of approximately 60 inches above the rail with the wheels installed, unless otherwise indicated, and arranged for convenient reading standing at the level of the rails. All indicators and gauges shall have glass faces. The following accessory devices shall be furnished, and shall be included in the price for the transformers.

Accessories shall be provided per the requirements of IEEE C57.12.10 (paragraph 5), unless otherwise indicated.

2.12.2 Analog Temperature Indicating Equipment

Locate thermowells for the sensing elements of all analog indicating equipment on Segment 2, 3, or 4 sidewall.

2.12.3.1 Gas Temperature Indicator

Each transformer shall be provided with a dial-type indicating thermometer (gas temperature indicator) with its sensing element located in the path of the hottest gas. The dial indicator shall cover a range of 0 to at least 10 deg. C above maximum allowable gas temperature. Temperature shall be pressure-compensated. Provide output contacts for:

a. a 4-20mA transducer for remote indication

b. High gas temperature alarm

c. High gas temperature trip

2.12.3.2 Winding Temperature Equipment

a. General. Each transformer shall be provided with two winding temperature indicators (WTI), with associated equipment, for use in remote indicating and recording or logging of the temperatures of the low and high voltage transformer phase windings, and for use as an over-temperature alarm and trip.