Transformer Spec - BC Sub3 River Mountain 20240219~1.pdf

River Mountain Substation (Sub #3)

Substation Power Transformer T1 & T2

TECHNICAL SPECIFICATION FOR 69D-12.47GY/7.2kV

XFMR T1 & T2: 13.5/18/22.5 MVA, 55°C-rise; 15/20/25 MVA, 65°C-rise

POWER TRANSFORMER

WITH LV LTC

For Colorado River Commission

February 2024

River Mountain Transformer Specification

Table of Contents

Table of Contents

1 PART 1 - GENERAL

1.1 SUMMARY

1.2 REFERENCES

1.3 SUBMITTALS

1.4 OWNER’S REVIEWS AND MANUFACTURER REPRESENTATIVE’S SERVICES

1.5 DELIVERY, STORAGE, AND HANDLING

1.6 EXTRA MATERIALS

1.7 SPECIAL GUARANTEE

1.8 EXCEPTIONS

2 PART 2 - PRODUCTS

2.1 SERVICE CONDITIONS

2.2 TRANSFORMER Ratings

2.3 BUSHINGS

2.4 SURGE ARRESTERS

2.5 COOLING

2.6 ELECTRONIC TEMPERATURE MONITOR (ETM)

2.7 TRANSFORMER INSULATING FLUID

2.8 OIL PRESERVATION SYSTEM

2.9 WIRING AND TERMINAL CABINETS FOR ACCESSORIES

2.10 FIBER OPTIC CABLE

2.11 ENERGIZED TAP CHANGING MECHANISM (LTC - LOW VOLTAGE WINDINGS)

2.12 DE-ENERGIZED TAP CHANGING MECHANISM (HIGH VOLTAGE WINDINGS)

2.13 GROUND CONNECTIONS

2.14 TANK CONSTRUCTION

2.15 WINDING AND CORE

2.16 NAMEPLATES

2.17 GAUGES AND ACCESSORIES

2.18 CURRENT TRANSFORMERS

2.19 VALVES

2.20 PRESSURE RELIEF DEVICE

2.21 FACTORY FINISHING

2.22 EXTERNAL FASTENERS AND HARDWARE

2.23 SOURCE QUALITY CONTROL AND TESTING

SUBSTATION POWER TRANSFORMER

PART 1 - GENERAL

1.1 SUMMARY

This specification is for two (2) 60 Hz 3-phase, 2-winding transformers. The top rating of both transformers T1 & T2 is 25 MVA at 65 degrees C rise over the ambient temperature described in section “Service Conditions”. Capacity and cooling is as specified below. Voltage is 69D–

12.47GY/7.2kV.

POWER TRANSFORMER(S) TO BE DELIVERED F.O.B. “ASSEMBLED AND TESTED, ON PAD” TO

THE PROJECT SITE. THE ANTICIPATED SUBSTATION SITE IS LOCATED BOULDER CITY, NV,

AND THE SITE ELEVATION IS 2510 FEET.

1.2 REFERENCES

The following is a list of standards which may be referenced in this section and shall be used in conjunction with this specification. The list is not conclusive and additional industry standards may be required for a complete installation.

The power transformer shall be furnished in accordance with the latest version of all applicable standards, unless otherwise explicitly allowed or required.

American Institute of Steel Construction (AISC)

Application No. Description

- Steel Construction Manual

- Seismic Design Manual

American Society for Testing and Materials (ASTM)

Application No. Description

D523 Standard Test Method for Specular Gloss

D1816 Standard Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using VDE Electrodes

D2794 Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact)

D3359 Standard Test Methods for Measuring Adhesion by Tape Test

D3487 Standard Specifications for Mineral Insulating Oil Used in Electrical Apparatus

D4060 Standard Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser

D4214 Standard Test Methods for Evaluating the Degree of Chalking of Exterior Paint Films

G154 Standard Practice for Operating Fluorescent Ultraviolet (UV) Lamp Apparatus for Exposure of Nonmetallic Materials

February 2024 page 5 of 33

American Welding Society (AWS)

Application No. Description

D1.1/D1.1M Structure Welding Code – Steel

Institute of Electrical and Electronics Engineers (IEEE)

Application No. Description

C57.12.00 General Requirements for Liquid-Immersed Distribution, Power and Regulating Transformers

C57.12.10 American National Standard for Transformers 230 KV and Below 833/958

Through 8333/10 417 KVA, Single-Phase, and 750/862 Through 60 000/80

000/100 000 KVA, Three-Phase without Load Tap Changing: and 3750/4687 through 60 000/80 000/100 000 KVA with Load Tap Changing—Safety

Requirements

C57.12.70 Standard Terminal Markings and Connections for Distribution and Power Transformers

C57.12.80 Terminology for Power and Distribution Transformers

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

Transformers

C57.13 Standard Requirements for Instruments Transformers

C57.19.00 General Requirements and Test Procedure for Outdoor Power Apparatus Bushings

C57.19.01 Performance Characteristics and Dimensions for Outdoor Apparatus Bushings

C57.91 Guide for Loading Mineral-Oil-Immersed Transformers

C57.93 Guide for Installation of Liquid-Immersed Power Transformers

C57.98 Guide for Transformer Impulse Tests

C57.109 Guide for Liquid-Immersed Transformer Through-Fault Current Duration

C57.116 Guide for Transformers Directly Connected to Generators

C57.120 Loss Evaluation Guide for Power Transformer and Reactors

C57.131 Requirements for Load Tap Changers

C62.11 Metal-Oxide Surge Arrester for AC Power Circuits

C62.22 Application of Metal-Oxide Surge Arresters for Alternating-Current Systems

693 Recommended Practice for Seismic Design of Substations

Insulated Cable Engineers Association (ICEA)

Application No. Description

S-73-532 Enclosures for Electrical Equipment (1000 Volts Maximum)

American National Standards Institute (ANSI)

Application No. Description

C57 Power Transformers – Part 2: Temperature rise

National Electrical Manufacturers Association (NEMA)

Application No. Description

250 Enclosures for Electrical Equipment (1000 Volts Maximum)

ICS 1 General Standard for industrial Control Systems

TR1 Transformers, Regulators and Reactors

WC 57 Standard for Control, Thermocouple Extensions, and Instrumentation Cables

National Electrical Code (NEC)

Application No. Description

240 Overcurrent Protection (non-applicable for current transformer secondary circuits)

310.15 Ampacity for Conductors Rated 0-2000 Volts

Chapter 9 Tables (for maximum conduit fill)

Nationally Recognized Testing Laboratories (NRTL)

Occupational Safety and Hazard Association (OSHA)

Application No. Description

3075 Controlling Electrical Hazards (including referenced sub-parts)

3146 Fall Protection in Construction

1.3 SUBMITTALS

Format of submittals shall be electronic PDF for review, unless otherwise requested. Final submittals shall be in PDF, with three (3) records prints (full-sized preferred for drawings), AutoCAD

2010 drawings, and native format settings files.

Exclusions

As applicable, provide a list of all exclusions and recommended changes including deviations from this specification and industry standard publications. Exclusions shall be approved on a case-by-case basis by the Owner.

Non-approved exceptions, unless explicitly permitted by the Owner, shall be corrected by the transformer manufacturer prior to shipment or during manufacturer’s field testing.

Action Submittals before Fabrication

Schedule (in business days)

Description

50 days before fabrication

1. Exclusions to this specification or industry standard.

50 days before fabrication

2. Descriptive information and manufacturer data sheets for equipment, material, and devices furnished. Use device and equipment tag numbers that appear on Drawings.

Schedule (in business days)

Description

50 days before fabrication

3. Certified outline drawings showing:

a. General arrangement with dimensions in feet and inches

b. Shipping and assembled horizontal and vertical center of gravity

c. Shipping and assembled weight, including weight of oil, in pounds.

d. Volume of oil in tank, radiators, and LTC in gallons

e. Special required features

f. Proposed method and location of non-slip tank coating or material on tank case

50 days before fabrication

4. Bill of material showing all components keyed to plan and section drawings

50 days before fabrication

5. Complete component parts list, including original manufacturer’s catalog numbers.

50 days before fabrication

6. Outline drawings of all bushings and surge arrestors

50 days before fabrication

7. Drawings for all nameplates

50 days before fabrication

8. Component and attachment testing seismic IEEE 693 certificate of compliance.

50 days before fabrication

9. Calculated values of positive and zero-sequence impedance (reactance and resistance) for unit

50 days before fabrication

10. Provide certified written memorandum and supporting documentation indicating equipment operating at or below 1000V and all control enclosures conforms to current NEC standards, except requirements explicitly excluded from this specification. Provide documentation in PDF format and three (3) hard copies.

Schedule (in business days)

Description

50 days before fabrication

11. Control schematics, interconnection, connection diagrams using NEMA device designations and symbols for electric circuit diagrams. Make content of schematic connection and interconnection diagrams in accordance with latest edition of NEMA ICS 1, including terminal boards, panels, and control circuits.

a. Manufacturer’s standardized schematic diagrams are not acceptable unless edited to show exact wiring of the individual units. Manual edits or “crossing out” are not acceptable.

50 days before fabrication

12. Cut sheets with part numbers for all materials and devices are required.

Cut sheets shall be original manufacturer’s printed literature with proposed item(s) clearly identified, including all options and accessories proposed.

50 days before fabrication

13. Communication elementary diagram.

a. Diagram(s) shall mimic the installation, showing all serial, parallel, fiber, Ethernet, or other communication connections. Include NEMA device designations and symbols for electric circuit diagrams in accordance with latest edition of NEMA ICS1.

b. Manufacturer’s standardized diagrams are not acceptable unless edited to show exact connections of the individual unit. Manual edits or “crossing out” are not acceptable.

c. Cut sheets with part numbers for all materials and devices are required. Cut sheets shall be original manufacturer’s printed literature with proposed item(s) clearly identified, including all options and accessories proposed.

d. Provide settings, calculations, and native format program files for the communication device.

30 days before fabrication

14. Provide settings, calculations, and native format program files for the transformer DGA.

30 days before fabrication

15. This section not used here.

30 days before fabrication

16. Provide settings, calculations, and native format program files for the ETM

(if furnished).

30 days before fabrication

17. This section not used here.

Schedule (in business days)

Description

30 days before fabrication

18. Provide settings, calculations, and native format program files for remote alarm and trip data collector.

Action Submittals after Fabrication

Schedule (in business days)

Description

20 days after testing

1. This section not used here.

20 days after testing

2. Complete, certified field test reports of each transformer supplied.

Informational Submittals

Schedule (in business days)

Description

5-6 weeks ARO 1. Preliminary transformer outline drawings. Include anticipated major dimensions, bushing location, bushing phase-phase spacing at terminals, control cabinet location, weight, gallons of oil, and installed center of gravity both vertical and horizontal. Drawings shall be provided in

AutoCAD 2010 and PDF format.

5-6 weeks ARO 2. Seismic anchorage and bracing calculations with recommendations.

Include foundation details for Owner’s transformer foundation design.

5-6 weeks ARO 3. Special guarantee or warranty in accordance with the Terms and

Conditions. Special guarantee or warranty shall be fully transferrable for entire duration of special guarantee or warranty.

40 days prior to testing

4. Product data for impact recording system.

40 days prior to testing

5. Product data for GPS monitoring system and real-time web-based tracking credentials and/or URL.

40 days prior to testing

6. Long-term outdoor storage requirements.

40 days prior to testing

7. Operation and Maintenance Data, including the following:

a. Location of nearest transformer repair shop approved by manufacturer.

b. Source for spare parts.

c. Approximate maximum time to supply repair parts.

d. Location of nearest service technician or engineer.

e. Drawings and specifications showing all gaskets sufficient to allow future field fabrication of same.

Schedule (in business days)

Description

40 days prior to testing

8. Commissioning Activities Plan including any field assembly required, testing, and all systems checkout.

40 days prior to testing

9. Three (3) instruction manuals covering receiving, handling, installation, operation, and maintenance of the transformer and auxiliary equipment.

Manual shall also include a complete parts list, including part names, suppliers, catalog numbers, quantities, and references by item number on drawings.

30 days prior to testing

10. Notify Owner of testing dates to schedule any required witness testing.

15 days prior to shipment

11. Shipping notification letters detailing complete routing. Include Purchase

Order identification, description of items shipped, number of cartons, shipping date, and delivery date.

5 days after testing

12. Complete set of factory tests shipped with each piece of equipment.

5 days after testing

13. Certification of insulating oil used to fill the transformer for testing, and the oil sampled with the unit if applicable, contains levels of polychlorinated biphenyl contamination that is non-detectable when tested per ASTM D4059.

5 days after testing

14. Final record drawings as electronic files (PDF and AutoCAD 2010) of each Submittal drawing.

5 days after shipment

15. Report sent to the Owner on day of shipment which lists the ambient temperature, ambient humidity, dryness of transformer, and gas pressure.

15 days after field testing

16. Manufacturer’s Certificate of Proper Installation.

1.4 OWNER’S REVIEWS AND MANUFACTURER REPRESENTATIVE’S SERVICES

Action Submittal Review

1. Manufacturer shall provide manufacturer technical representative(s) for a teleconference meeting with Owner (or similar) to deliver and discuss the approval drawings included in the action submittals (generally includes all items listed 50 days from fabrication). Representative must be familiar with the transformer details and be able to clearly communicate necessary technical clarification to the Owner.

Witness Transformer Testing

1. Manufacturer shall provide access to Owner for two (2) Owner’s representatives to witness unit testing at the transformer facility.

February 2024 page 11 of 33

2. Manufacturer shall provide airfare and all accommodations for two (2) Owner’s representatives to witness any re-testing if windings and/or core must be removed or repaired.

Manufacturer Representative Services

1. On-site technician(s) during delivery and offload on site foundation.

a. Install all equipment not installed for shipping (i.e. bushings, radiators), complete. Fill and top off oil as required.

b. Correct any damage as the result of shipping or offload. Apply touch up paint to any damaged paint.

c. Perform all field testing of transformers, controls, accessories and insulating fluid samples. Tests should clearly verify transformer damage did not occur during shipment. In general, tests will be performed in accordance with NETA ATS 2007, Parts 7.2.2 and 7.12.3.

d. Inspect equipment to insure it is installed plumb, level, and securely anchored in place.

e. Owner representative must be allowed to witness offload, finishing, and testing activities.

1.5 DELIVERY, STORAGE, AND HANDLING

Packing and Shipping

1. Delivered F.O.B. pad at site, assembled, filled with oil, and tested. Manufacturer responsible for all transportation permits, expenses, scheduling, and logistics.

2. Install redundant impact recorder(s) on transformer at the factory before factory testing to record impacts in directions that occur during shipping and offload. Remove recorders only in the presence of the Owner and once set on the site foundation. Method of impact recording shall require Owner approval.

3. Install redundant GPS monitors prior to shipment. Transformer location during the entire duration of shipment shall be accessible to the Owner in real-time via a web site. Do not remove monitors until set on the site foundation. GPS monitoring and web site access shall be online and accessible to the Owner prior to leaving the factory and for the entire duration of shipment.

4. Ship so transformer and accessories will arrive at final destination simultaneously.

5. Ship the control cabinet mounted to the tank. Provide sufficient bracing to prevent damage during shipment and off-load. Provide packaging details for Owner approval when impractical to ship the control cabinet mounted to the tank.

6. Provide internal bracing as required to prevent damage during shipping.

7. Clearly indicate shipping and in-service center of gravity in two perpendicular planes on external surface.

8. Shipped with transformer: complete bill of lading, shipping weight of each piece; unloading and placing instructions; complete Instruction and operations and maintenance manuals;

complete set of as built drawings; and all cut sheets.

9. Manufacturer shall be responsible for all damage that occurs during shipment.

10. Owner shall reserve the right to examine the transformer at any point during shipment.

11. Ship transducers, bushings, and radiators unmounted.

Storage and Protection

1. Packing methods and material shall be such that they will provide weatherproof protection during shipment and in outdoor storage areas.

2. Method of shipment preparation shall be such as to adequately protect the transformer, relays, bushings, and other auxiliary devices and accessories against corrosion, dampness, damage, and breakage.

3. Transformers shipped and/or stored filled with nitrogen shall have a readily accessible and viewable pressure gage for monitoring nitrogen pressure.

Delivery

Power transformer(s) to be delivered F.O.B. “assembled and tested, on pad” to the project site. Unit shall be off-loaded onto the transformer pad, if adequately prepared to accept the transformer.

Offload onto cribbing within the substation fence if the transformer pad is not prepared.

Manufacturer shall provide 7-day shipment notification with target date for delivery and shall update the Construction foreman with any changes in schedule. Manufacturer shall provide 72-hour shipment notification for exact day delivery.

Weekend delivery is not acceptable; hours for delivery shall be normal working hours on weekdays

Tuesday – Thursday only.

1.6 EXTRA MATERIALS.

A unit price schedule from the Manufacturer shall be provided to include all recommended spare parts, tools, and equipment for all transformers provided. Contractor shall offer an option to Owner for Contractor to provide all listed items at no more than Manufacturer’s cost plus an 8% markup.

All listed items shall be delivered to the site and turned over to Owner at the substation site.

Specific pricing from the Manufacturer shall be provided for the following:

Item Quantity

HV bushing complete with gaskets. Liquid-filled bushings shall be shipped in crates suitable for storage of the bushing in the upright position.

One per unit

LV bushing complete with gaskets. Liquid-filled bushings shall be shipped in crates suitable for storage of the bushing in the upright position.

One per unit

HV surge arresters One per unit

LV surge arresters One per unit

One complete motor and fan assembly, un-mounted One per unit

Equipment paint Two 1-quart cans per unit

Set of control contacts & coils One of each type per unit

Special tools required to maintain, assemble, dismantle, or move One complete set per unit

Gaskets for cover, manhole, hand-holes, radiators, and any other location where field maintenance would require re-gasketing

One complete set per unit

1.7 SPECIAL GUARANTEE

Provide manufacturer’s extended guarantee or warranty.

When operated under the conditions stipulated in the manufacturer’s operating manuals and this specification, unit shall be warranted against defects in workmanship and materials for sixty (60) months following receipt at the project site and completion of assembly and testing. This period includes all services specified here within. Warranty shall include repairs or replacement made by manufacturer’s field representatives while the unit remains on-site.

In the event that defects in workmanship and materials cause unit failure that is not field correctable or serviceable, the transformer manufacturer shall be responsible to load the transformer from the pad to the low-boy trailer, transport the unit to the nearest repair facility, transport the unit back to the site, and off-load back to the transformer foundation.

1.8 EXCEPTIONS

Manufacturer shall clearly identify in writing any requested, desired, or assumed exceptions to or alternatives or deviations from this Specification.

If applicable, the transformer shall be procured from one of the manufacturers identified on the grid operator’s approved vendor list. Alternate manufacturers will be subject to owner approval and must confirm a Mean Time Between Failure (MTBF) of greater than 600 years for large scale transformers. This shall be confirmed via the factory’s MTBF register for the last 10 years for transformers larger than 50MVA. Owner has the right to reject supplier if they do not meet this criteria.

PART 2 - PRODUCTS

2.1 SERVICE CONDITIONS

Outdoor Service Conditions

1. Located at 35°58'33.16"N, 114°48'50.53"W

2. Maximum Elevation of Installation Site Above Sea Level: 2,510 ft.

3. Maximum Ambient Air Temperature: 52°C

4. Minimum Ambient Air Temperature: -7°C

5. Mean (24-hour) Maximum Ambient Air Temperature: 24°C

6. Minimum Ambient Air Temperature: Per IEEE C57 requirements

7. Relative Humidity: 100 percent

8. Maximum Wind: 120 mph

9. Average Annual Precipitation: 6.4 inches

Transformer Usage

1. Transformers will function as a transmission power step-down to feed distributed load.

The transformers shall be designed to be able to transmit the maximum output of the corresponding unit at all possible ambient temperatures.

2. Loading

Transformer No. Load Power

(worst case PF)

T1 25 MVA

T2 25 MVA

2.2 TRANSFORMER RATINGS

Winding Capacity

Transformers T1 & T2

Temperature Rise Rating

1. Temperature rise and maximum temperatures shall be per IEEE C57.12.00. When site-specific ambient temperatures exceed the recommendations of IEEE C57.12.00, the manufacturer shall accommodate the site-specific conditions.

2. Average winding temperature rise by resistance shall not exceed 65° C.

High Voltage Windings

1. Nominal Voltage: 69 kV

2. Basic Insulation Level: 350 kV (bushings and external spacing to be for 450 kV BIL)

3. Delta connected, open to ground

Low Voltage Winding

1. Nominal Voltage: 12.47 kV

2. Basic Insulation Level: 110 kV

3. Wye connected, with neutral brought out through a bushing for external impedance grounding. Design to account for asymmetrical voltage rise due to impedance grounding.

Impedance

Impedance tolerance shall be per IEEE C57.12.00 and shall be 8.1% with +/- 10% tolerance at base

MVA rating.

Noise Level

Audible noise level when energized at capacity ratings shall meet or exceed NEMA TR1 audible noise requirements.

Transformer manufacturer should focus on optimizing transformer core design to ensure low-noise and lower no-load losses.

Losses and Loss Factor

Total transformer efficiency at rated ONAN capacity and rated voltage shall be at least 99.4% (Loss

Winding Stage 1: ONAN Stage 2: ONAF Stage 3: ONAF

H 15 MVA 20 MVA 25 MVA

X 15 MVA 20 MVA 25 MVA

February 2024 page 16 of 33

Guarantee). Failure to demonstrate compliance with this Loss Guarantee will cause Performance

Liquidated Damages to be assessed according to the agreement. In ANY event, total transformer efficiency at rated ONAN capacity and rated voltage shall be not less than 99.3925% when tested at the factory and 99.385% when tested after installation at the Project (Minimum Performance

Standard).

Transformer manufacturer shall design for a low-loss transformer. Losses will be evaluated using the following multipliers:

1. No-load loss multiplier: $3.50 per watt

2. Load loss multiplier: $1.86 per watt

3. Auxiliary power multiplier: $1.08 per watt

2.3 BUSHINGS

Design

1. H.V. Bushings: 69 kV class, 350 kV BIL

2. L.V. Bushings: 13.8 kV class, 110 kV BIL

3. Neutral Bushings: Match L.V. bushing

General

Bushings shall meet the requirements of IEEE C57.12.00, Section 6.1. Color shall be TIA/EIA 359-1, No. 70, light gray. Bushings of like voltage shall be interchangeable.

Liquid-filled bushings shall be provided with liquid level indication and provision for power factor testing without disconnecting main leads or bushing tap adaptors for the monitoring device.

Liquid-filled bushings are required for HV only. LV and neutral bushings shall be “solid” porcelain or polymer.

Bushings shall be designed so there will be no undue stresses on any parts due to temperature changes. Provide adequate means to accommodate conductor expansion.

Provide standard threaded stud type terminals with 0.001-inch minimum silver-plating on bushings.

Provide tin-plated NEMA 4-hole copper pad for each bushing. Bushings rated 2,000A or above shall have provisions for 4-inch, 4-hole pads.

1. High Voltage Line Bushings: On transformer cover, Segment 3, in accordance with

IEEE C57.12.10. H2 shall be on the centerline of the transformer tank.

2. High Voltage Transformer Neutral Bushing: On transformer cover in accordance with IEEE

C57.12.10.

3. Low Voltage Line Bushings: On transformer cover, Segment 1, in accordance with

IEEE C57.12.10. X2 shall be on the centerline of the transformer tank.

X3 X2 X1 X0

Transformer Bushing Plan View

H3 H2 H1

4. Low Voltage Transformer Neutral Bushing: On transformer cover in accordance with

IEEE C57.12.10

5. Core-Ground Bushing: On transformer side, preferably near the top with cover to protect from contact and inadvertent damage.

Current Ratings

Current ratings shall be based upon the continuous line current at maximum specified MVA rating.

Provide sufficient excess capacity to permit transformer loading with “moderate sacrifice of

[transformer] life expectancy” as tabulated in IEEE C57.91

Locations

High-Voltage Line Bushings: On transformer cover, Segment 3, in accordance with ANSI C57.12.10.

Low-Voltage Line Bushings: On transformer cover, Segment 1, in accordance with ANSI C57.12.10.

Low-Voltage Transformer Neutral Bushing: On transformer cover, Segment 1, in accordance with

ANSI C57.12.10.

Arrangement of bushings for Transformers shall be:

2.4 SURGE ARRESTERS

Operation Voltage MCOV Rating

69 kV 48 kV

12.47 kV 8.4 kV

Surge arrester MCOV ratings will be subject to owner revision upon review of approval prints.

Surge arresters shall be tank or bracket mounted and shall be single-phase, polymer-housed, station class, metal-oxide type. Color shall match the transformer tank and bushings, generally TIA/EIA

359-1, No. 70 light gray.

Top of arrestors shall match height of associated winding bushings and shall be in line with terminal on bushing to facilitate connection of cable jumpers.

Equip arrestors with tin-plated NEMA four-hole pads for conductor attachment and ground terminals suitable for 4/0 bare copper connection.

2.5 COOLING

The transformers shall be of type ONAN/ONAF/ONAF type cooling. Loading: Design to permit transformer loading with “moderate sacrifice of life expectancy” as tabulated in IEEE C57.91.

Cooling type and stages as identified in section “Winding Capacity”.

Controls

Provide forced air cooling, which shall be automatically controlled and actuated by transformer top-oil and winding temperature devices described. Controls shall be 120VAC, 60Hz.

Radiators

Provide removable radiators with lifting eye on each radiator. Include isolating shutoff butterfly valves at top and bottom of each radiator to permit removal of radiator without interfering with operation of transformer and without draining any oil from the tank and/or common headers.

Radiators shall include a drain plug and vent plug in each radiator at the ends away from the tank.

The bottoms and shut-off valves of all radiators shall be at least 24” above the transformer pad elevation. The mechanical tolerance of the arrangement shall be minimized to allow the exchange of all radiators/oil coolers of the same type without additional fitting.

Include one extra shut-off butterfly valve with each transformer.

Provide oil-tight blank flanges properly gasketed, for shipment of tank without radiators attached and to make flanges available when a radiator needs to be removed while in service. Valves shall comply with section “Valves”.

Fans

Provide - self-supporting fans for forced cooling. Fans shall be installed on one side of radiators; do not install on top or bottom of radiators. All fans shall direct air in the same direction across the radiator surface.

Fans shall operate at 230VAC, 60Hz, single phase, with the alarm circuits rated for 125VDC operation including two stages of alarms.

Equip individual fan motors with weatherproof plugs and receptacles for ease in removal.

Fans shall have OSHA approved safety guards.

Fan Motors, Leads, and Associated Protective Equipment

Each stage of fans shall be energized from an independent electrical circuit. Furnish fan motors with overload protection per NEC. Fan groups shall be on separate overload circuits to limit potential for complete cooling outage. Protection shall be provided via molded case circuit breakers with manual reset for each group of fans, fuses will not be accepted.

Enclose controls, fuses, and breakers for cooling equipment in one cabinet. All leads, junction boxes, and other equipment installed outside of the control cabinet shall be weatherproof and suitable for outdoor operation at substation site.

Provide loss of fan AC voltage alarm contact(s) wired to Electronic Transformer Monitor (ETM).

Loss of AC relays shall be connected on the load side of the overcurrent / overload device on each fan group circuit to detect an open circuit.

Provide a magnetic contactor for each group of fans with at least two auxiliary contacts that are independently reversible. Wire contactor coil leads to terminal blocks in control cabinet.

2.6 ELECTRONIC TEMPERATURE MONITOR (ETM)

Should the transformer manufacturer propose such an arrangement, it shall conform to Section

“Cooling”. In addition, the ETM shall provide the following functionality:

1. Fan-balancing logic and fan anti-cycling logic

2. Auto/off/on fan control via push buttons and remote control.

3. Fans shall shut off immediately if the sudden pressure relay trip asserts

4. Program four (4) independent adjustable output contacts

5. One normally open (NO) alarm contact to close at 110C winding temperature

6. One NO trip contact to close at 130C winding temperature

7. One NO alarm contact to close for high top oil temperature, setting to be adjustable

8. Provide an alarm contact for unit failure, unit shall close for unit failure or unit powered off

9. The ETM may include the DGA function described below.

10. ETM power shall be 125 VDC and 120 VAC.

11. For SCADA integration of ETM via RJ45 port, provide a SEL-2725 Fiber Converter (2725S22X0)

2.7 TRANSFORMER INSULATING FLUID

Transformer oil shall be pure mineral oil prepared and refined by fractional distillation of petroleum, especially for use in transformers, free from moisture, acid, alkali, polychlorinated biphenyls (PCB’s), and injurious Sulphur compounds. Transformer oil shall conform to ASTM D3487

Oil shall not form a deposit under operating temperature range listed in the Section “Service

Conditions”.

Minimum Dielectric Strength shall be 30,000 volts when tested per ASTM D1816.

2.8 OIL PRESERVATION SYSTEM

Nitrogen System W/ 3 Stage Regulator, as determined by manufacturer.

An automatic nitrogen pressure oil preservation system shall be supplied with a nitrogen cylinder, a cabinet for the nitrogen cylinder, transformer tank high and low-pressure alarms, a nitrogen cylinder low pressure alarm, a nitrogen cylinder pressure gauge, and all gas pressure regulating equipment. The cabinet shall be designed and fabricated for lowering and mounting to the transformer slab or mounted to the tank wall. Material required to lower the cabinet and reconnect the nitrogen system shall be provided. Alarm contacts from each alarm relay shall be wired to terminal points in the control cabinet.

The primary regulator shall be a three-stage diaphragm type. Pressure gauges shall be provided for both the high side and the low side of the regulator. The Pemex tube is used to connect fittings inside cabinet. ½ inch valves shall be provided to permit purging the gas space and testing the seal on the transformer tank by admitting dry nitrogen under pressure.

2.9 WIRING AND TERMINAL CABINETS FOR ACCESSORIES

National Electric Code (NEC)

All equipment energized at 1000V or less and all control enclosures shall meet current NEC standards. All equipment energized at 1000V or less and all control enclosures shall meet applicable

NRTL standards and be UL listed.

Exception: Current transformer secondary circuits shall not include overcurrent protection.

Conduit

Install wiring for devices external to the control cabinet in hot-dipped galvanized rigid steel conduit.

Wiring shall terminate in a centrally located terminal cabinet mounted on the transformer tank.

Short lengths of sunlight-resistant liquid-tight flexible metallic conduit with PE or TPU coating may be used to facilitate connections to removable accessories. PVC-coated LFMC shall not be used.

Bending radius of LFMC shall exceed 12 diameters. There shall be no visible buckling due to bending in LFMC coating.

Percent fill shall not exceed the latest revision of NEC Chapter 9 requirements.

Cabinet

Provide a NEMA Type 4 control cabinet located on the sidewall of transformer at a height accessible without the use of a stepladder. Cabinet exterior shall be painted to match tank and cabinet interior shall be painted white; see section “Factory Finishing” for paint requirements. Include provision for pad locking door and an ample-sized, detachable bottom plate for conduit entrance, which will be field drilled.

Provide fixed louvers on cabinet to aid in air circulation and cooling. Louvers shall include a screen and slide-in filters to prevent entrance of blown dust and debris. Provide at least three (3) spare filters for each filter position. Filters shall be standard size and construction to facilitate routine purchase and replacement.

Provide a single-phase 120VAC, 15A waterproof, GFCI outlet mounted in the control cabinet.

Provide - LED light inside the control enclosure switched by the cabinet door. Light shall be protected all around by an impact-resistant, translucent or cage-style cover to prevent damage to the LED light source.

Control Cabinet Heaters

Provide two or more thermostat-controlled heaters in each control housing and terminal cabinet to prevent collection of condensation.

Make connections to heaters from below heaters to minimize deterioration of insulation of supply wires.

Locate heaters in the lower portion of control housing and arrange so they can be energized from an independent 120/240VAC circuit. Heaters shall be located such that they will not cause damage to equipment, insulation, or wiring within the control cabinet.

Prevent direct contact by installing perforated metal guards over heater elements. Locate away from normal inspection and working areas within the cabinet to limit the chance of personnel contact.

Control Cabinet Cooling

Install a sunshield over the control cabinet to limit solar heating. Include side and front shading if required to maintain an acceptable operating temperature for the geographic area and transformer orientation.

Provide cooling fan(s) if required to maintain an acceptable cabinet interior temperature. Fans shall be protected with suitable molded-case circuit breaker overcurrent protection. Include a filter and screen to prevent blown dust and debris from entering the cabinet. Provide at least three (3) spare filters per fan position. Filters shall be standard size and construction to facilitate routine purchase and replacement.

The use of refrigerated or evaporative air conditioning to cool the cabinet will not be accepted.

Labels

Wires, terminal blocks, relays, and devices shall be installed and labeled in accordance with manufacturer schematic and wiring diagrams.

Both ends of all wires shall be clearly labeled with printed labels. Labels shall include the destination and/or wire number and match the designation given in the schematics and interconnection wiring diagrams. All labels shall be white with upper-case black text that is at least 1/8-inch tall. Print text on one-side of the label. Wire labels shall be slip-on style shrink-tube or similar and shall not be affixed or heat-shrunk onto the wire.

Terminal Blocks

Terminal blocks shall be screw-type, and except for electrical conducting parts, fabricated from a thermosetting phenolic material that is unaffected by contact with transformer insulating oil.

Provide with bases and barriers molded integrally with brass inserts. All electrical conducting parts shall be brass, nickel plated for low contact resistance and corrosion protection. No more than two wire terminals shall terminate under each terminal screw.

Terminals shall be rated for not less than 600 volts and 30 amps and accommodate at least No. 10 to

No. 18 AWG wire. Each terminal shall include a marking strip with the terminal designations; all terminal designations shall be inscribed in accordance with manufacturer’s schematics and wiring diagrams. Each block shall have one spare blank marking strip. Wire terminations shall be uninsulated ring compression installed with tools that require crimp completion before reset.

Equip terminals for current transformers with short-circuiting screws.

Types of blocks that depend upon spring return of deformed metal to secure terminal leads are not acceptable.

Furnish minimum twenty percent (20%) spare terminals not including any terminal blocks reserved for future equipment.

Wiring

Control, signal, and auxiliary circuits shall be insulated wire, oil- and water-resistant, and suitable for operation at 90° C, Type SIS. Conductor minimum size shall be No. 12 AWG stranded copper but shall be sized in accordance with the National Electric Code (NEC). Use non-insulated ring terminals.

Current transformer secondary circuits shall be a minimum No. 10 AWG stranded copper with non-insulated ring terminals.

Communication wiring shall be sized in accordance with manufacturer’s recommendations for installation within the control cabinet.

Where construction requires bending of wires while in service, provide multi-strand hinge wire, Type SIS.

Wires shall be trained and bundled together with wire ties. All wires shall be labeled on both ends with permanent sleeve markers indicating the opposite-end terminal.

Control and Auxiliary Voltage

1. AC voltage shall be 120/240VAC, single-phase.

2. DC voltage shall be 125VDC.

2.10 FIBER OPTIC CABLE

- Ethernet Ports on ETM and DGA (if furnished)

2.11 ENERGIZED TAP CHANGING MECHANISM (LTC - LOW VOLTAGE WINDINGS)

Transformer shall come from the factory equipped with a low-maintenance full-rated automatic on-load tap changer for the low-voltage winding. To the extent feasible to reduce voltage stresses on the LTC, preference will be for the LTC to be connected to the grounded end of the windings.

On-load tap changer shall be rated to continuously carry, without damage, the highest 65*C FA rating of the transformer.

Low maintenance means that arcs created during operation are interrupted in a vacuum switch rather than under oil. The Reinhausen RVM-II or an equivalent tap changer model is considered low maintenance. The LTC tank shall be designed such that the LTC can be removed/replaced without removal of the transformer windings/core and top cover of the main tank.

The motor drive, plus all auxiliary equipment for operation of the tap changer(s) shall be incorporated in a rigid NEMA 3R control cabinet.

A preventative autotransformer, if used, shall be round core and coil and shall use copper windings.

Tap changer control shall include the required current transformer and control devices to create a fully functional system. The control shall use a Beckwith M-2001D tap changer control with optional

Ethernet on port 3, or an OWNER-approved equivalent.

Limit-switch alarms which indicate when the transformer tap changer has reached +16R or -16L shall be provided for OWNER use.

A “failure to regulate” alarm shall be provided for OWNER use. This alarm shall indicate that the tap changer mechanism or control is not operating properly.

Potential for voltage compensation and power for control and motor operation shall be provided by

OWNER from an external source.

Taps shall be +16 steps at 5/8% per step to -16 steps at 5/8% per step for Transformers T1 & T2.

Provide an extended shaft on the LTC with provisions for the installation of a Beckwith Model M-

2948 tap position indicator, 9° per tap, 0-297° rotation with one neutral. Propose as an option the installation of a Beckwith Model M-2948 tap position indicator with Beckwith M-2025 interface between M-2001D and M-2948. Accessories on the tap changer mechanism shall include liquid level gauge with alarm and trip contacts, pressure relief with alarm contact, drain valve, fill valve, and rapid pressure sensor with seal-in relay.

A current transformer for operation of the load compensating control shall be provided in the main tank. Include a test switch and shorting switch for this CT circuit for testing purposes.

The operating mechanism shall be able to be operated manually while energized and under full load safely and with no harm to the operator or transformer.

If the mechanism can be stalled “off tap,” it shall include an alarm contact and shall be capable of operating continuously at full load.

LTC tank shall be capable of withstanding full vacuum with no leaks to main tank under normal pressure.

Only LTC designs which have been type tested with the relevant ANSI/ IEEE standards will be accepted. All LTC connected to uniformly insulated windings shall have at least same LI and AC voltage withstand levels as the related winding.

2.12 DE-ENERGIZED TAP CHANGING MECHANISM (HIGH VOLTAGE WINDINGS)

Transformer shall come from the factory equipped with a low-maintenance full-rated manually operated de-energized tap changer for the high-voltage winding. This tap changer, to the extent possible, will be located in a reasonably accessible location so as to inspect and repair any damages due to through-fault. This tap changer shall be rated to continuously carry, without damage, the highest 65*C FA rating of the transformer.

There shall be five taps that allow for +- 5% total voltage change at the high-side windings. Tap steps should be in increments of 2.5% of base voltage.

2.13 GROUND CONNECTIONS

Furnish four (4) NEMA two-hole ground pads welded on the tank wall near the base and on each corner of transformer. Locate pads so as not to interfere with jacking facilities or other equipment.

Provide solid 2-inch by 3/8-inch tin-plated copper bus bars securely attached to the transformer tank at the base of transformer tank to the top of the transformer tank. Solidly affix to the transformer tank to ensure proper grounding to the substation ground grid. Terminate 500MCM stranded tinned copper conductor from surge arresters ground terminals to the copper bus bar.

High side and low-side surge arrester grounding and bus bar will normally be separate. Where practical, run the ground bus within 1-foot horizontally from tank ground pads down to the transformer base. Drill holes in bus bar to accommodate parallel 2-hole NEMA grounding pads to the station ground grid near the transformer base.

Provide solid 2-inch by 3/8-inch (minimum) tin-plated copper bus bars extending from the bottom of the tank to each of the neutral bushings. Bus thickness for low-voltage bushing grounding shall be such as to withstand the transformer impedance limited secondary side line-to-ground fault for at least 2 seconds to allow for fault clearing by backup protective schemes. Note: Ground bus bar shall be sized by the transformer manufacturer to withstand the anticipated maximum single-line to ground fault current for a 2 second duration. The H0 and X0 bushing grounding and bus bar shall be separate. Bus shall be electrically insulated from the transformer tank with 1.2 kV nominal, 30 kV

BIL insulators. Drill holes in bus bar to accommodate parallel 2-hole NEMA grounding pads to the station ground grid near the transformer base. Furnish provisions to attach an 500MCM copper ground lead from the neutral bushings to external impedance device (resistor or reactor).

ALL visible copper ground bus, conductor, and fittings shall be tin-plated.

2.14 TANK CONSTRUCTION

The unit shall be a single tank, constructed to withstand operating pressures, stresses, and full vacuum. All seams shall be double welded, inside and outside, and a minimum of 6-inches from any corner. Corner welds are not acceptable, except as approved on a case-by-case basis during bidding by the Owner.

Main Cover

Construct main cover so welded main tank cover can be removed and re-welded without damage to core and coil assemblies.

Furnish a minimum of one manhole with sloped cover, 15-inch minimum diameter, for access to lower ends of bushings, terminals, and upper portion of core and coil assembly. Bolt on manhole covers, do not weld.

Furnish gasketed surfaces with gasketed recess and gasket compression limit stops.

Furnish guides for guiding of core assembly and coils when untanking transformer for inspection.

Clearly show and label the center of gravity marks in two perpendicular planes and permanently mark on transformer for both shipping assembly and fully assembled transformer.

Main Cover Safety

Main cover will be accessed by field crews for installation, maintenance, and inspections.

Provide provisions for fall protection tie-offs in accordance with OSHA requirements such as the

Tuff Built Fall Arrestor system (Part # 30137, with base welded to tank) or similar. Tie-offs shall be located in such a manner that they can be accessed from a boom truck (“squirt boom”, not elbow-type) bucket. Fall protection tie-offs shall also be included in close proximity to equipment that will be maintained and accessed during the life of the transformer (bushings, tank manhole, etc.).

Include non-slip surfacing on areas that will be accessed for maintenance and inspection.

Transformer manufacturer is responsible to propose location, style, and recommendations for permanent, non-slip surfacing.

Lifting Lugs

Provide lifting lugs of adequate strength, size, and so arranged on transformer tank to provide a suitable lift of transformer unit.

Provide lifting eyes for lifting cover and for lifting core and coil assembly.

Moving and Handling Facilities

Provide suitable jacking facilities on transformer tank. Include pulling eyes and smooth base for skidding and rolling transformer in any direction.

2.15 WINDING AND CORE

Winding and Core Construction

Windings and leads shall be copper. Aluminum will not be accepted for winding material or current-carrying parts.

Winding and Core Design: All core and coil assemblies shall be power class, round core/circular coil design and construction. High and low voltage windings shall be either disk or helical construction;

layer/barrel windings are not acceptable.

Core Ground

A single-point core ground shall be brought to a side-mounted bushing on the tank exterior. The bushing shall be protected from accidental damage by contact and installed near the top of the tank such that the grounding lead from the core to the bushing is visible and accessible via the cover manhole.

Fault Withstand

Transformer shall be capable of withstanding the thermal and mechanical stresses caused by a two

(2) second short-circuit on the terminals of any winding or combination of windings with rated voltage maintained on un-shorted windings without incurring damage.

Phase Rotation and Phase Shift

The phase rotation shall be A-B-C counter-clockwise.

The phase shift between the H and X windings shall be 30-degrees.

2.16 NAMEPLATES

All external nameplates shall be per IEEE C57.12.00, etched stainless steel, black-filled, mounted on transformer, and include the following information:

1. Diagram of connections, including polarities

2. Voltage of taps and corresponding ampere rating

3. Impedances and corresponding MVA capacity ratings

4. Weights: Core and coils, tank and fittings, oil, and total weight

5. Quantity of oil (U.S. gallons)

6. Permissible vacuum

7. Rated kVA at each cooling step and temperature rise.

8. Ambient temperature design criteria.

9. Serial number and date of manufacturer.

10. CT connections, ratings, and polarity.

11. Other information as prescribed in IEEE C57.12.00.

2.17 GAUGES AND ACCESSORIES

General

Furnish standard accessories located in accordance with IEEE C57.91.

Group dial type gauges, valves, and tap-charger handle together on the same side of transformer as the control cabinet for easy viewing. Ensure gauges are accessible and easily field maintainable so that un-tanking is not required for removal of gauges. None of these items shall protrude beyond the floor space determined by the radiating surfaces.

Gauges installed above 96 inches from base shall be tilted down at an angle of 30 degrees from the vertical.

Each gauge, dial, etc., shall have a legible, weatherproof nameplate.

Locate wells for thermometer bulbs and liquid-level gauge floats outside main tank so removal is not required for un-tanking.

Service Life of Accessories shall be comparable with transformer.

Shock mount, or construct sufficiently rugged, gauges, meters, relays, recorders, thermal breakers, other instruments, and cabinets constituting or associated with control of fans, inert gas equipment and all other temperature and pressure alarm systems to protect them from damage or wear which could be caused by normal transformer shock and vibration.

Wire for Alarm and Auxiliary Circuits in accordance with the specification section “Wiring”.

Valves shall hold hot oil without leaking and shall withstand, when submerged, an air test of

125 psig.

Magnetic Liquid-Level Gauge

Provide as specified in 5.1.2 of IEEE C57.12.10, except with two stages of contacts. Unit shall be

Qualitrol series 032/042, or Owner-approved substitute.

The first stage contact should alarm for low oil, the second stage should be for low oil level tripping.

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