TDA T9-T11 PWS DRAFT 2024-02-20.pdf

The Dalles Dam T9, T10, T11 Transformer Repair

SECTION 48 19 23.10

CLASS II GSU POWER TRANSFORMER REPAIR

PART 1 GENERAL

1.1 GENERAL INFORMATION

This Section describes the on-site repair requirements of The Dalles T9, T10, and T11 three-phase generator step-up (GSU) power transformers. GSU’s T9, T10, and T11 are sister units from the same manufacturer and can be considered identical.

1.1.1 Transformer Nameplate Information

Bank T9, T10, and T11 GSU power transformers have the following nameplate information:

a. Year manufactured: 1973

b. Manufacturer: General Electric

c. Serial number: H409355

d. kVA rating: 208,000

e. kV rating: 230 GrdY / 13.2 Delta

f. Impedance, percent: 12.9 @ 208,000 kVA

g. Phasing: Three

h. Cooling class: FOA

i. Oil quantity: 14,600 gal.

j. De-energized tap changer: Two at 2.5% steps above rated voltage and two at 2.5% steps below rated voltage.

1.1.2 Failure Investigation and Findings

In 2016 Bank T8 transformer failed in service. The government determined the root cause by conducting a forensic teardown after failure. The location of the failure is on the low voltage side of the GSU transformer where the neutral for the high voltage grounded-wye windings are connected. Phase 3 is connected to Phase 2, then Phase 2 to Phase 1, then Phase 1 to the neutral bushing as diagrammed in Figure X. See Appendix X for figures. The neutral connection failed open between the Phase 2 and Phase 1 coils. It is important to note that this is a load carrying connection and would carry approximately 2/3 of the rated high voltage current of 585 Amperes, while the neutral itself would carry 0 Amperes during balanced, fully loaded conditions.

In 2018, T10 failed as seen in the electrical test results, oil samples, and Figure X. Note Part 3 EXECUTION for differences in work execution in T10 compared to T9 and T11.

1.2 DESCRIPTION OF WORK

The work, as described herein, shall include all labor, materials, and equipment necessary to perform the following on three GSU transformers located at The Dalles Dam, designated Bank T9, T10, and T11:

a. Perform an internal inspection and prepare an inspection and repair report for each Bank T9, T10, and T11 transformers (see paragraph "INITIAL ON-SITE INTERNAL INSPECTION").

b. Perform transformer repairs (see paragraph "TRANSFORMER REPAIR")

c. Perform transformer reassembly, including re-gasketing of removed manhole covers and re-welding the top of the transformer tank if removed for repairs (see paragraph "TRANSFORMER REASSEMBLY

AND OIL FILLING").

d. Oil-fill and process existing transformer oil (see paragraph "TRANSFORMER REASSEMBLY AND OIL-FILLING").

e. Perform transformer electrical tests and oil tests (see paragraph "TRANSFORMER OIL TESTS", and paragraph "TRANSFORMER

ELECTRICAL TESTS").

f. Prepare a transformer repair report (se paragraph

“TRANSFORMER REPAIR REPORT”).

g. Perform work required to comply with SECTION 01 11 01.00 28

SUPPLEMENTARY REQUIREMENTS, SECTION 01 35 29.10 28 SAFETY AND

OCCUPATIONAL HEALTH REQUIREMENTS, and SECTION 01 57 20.00 28

ENVIRONMENT PROTECTION.

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 NATIONAL STANDARDS INSTITUTE (ANSI)

ANSI MW 1000 (2023) Magnet Wire ASTM

INTERNATIONAL (ASTM)

ASTM D 923 (2015 Reapproved in 2023) Sampling Electrical Insulating Liquids

ASTM D 1816 (2019) Standard Test Method for

Dielectric Breakdown Voltage of Insulating Liquids Using VDE Electrodes

ASTM D 1305 (2016 Reapproved in 2023)

Electrical Insulating Paper and Paperboard - Sulfate (Kraft) Layer Type

ASTM D 1933 (2003 Reapproved in 2017)

Nitrogen Gas as an Electrical Insulating Material

ASTM D 3283 (1998 Reapproved in 2020) Air as an Electrical Insulating Material

ASTM D 3487 (2016) Mineral Insulating Oil Used in Electrical Apparatus

ASTM F 104 (2003) Nonmetallic Gasket

Materials INSTITUTE OF ELECTRICAL AND ELECTRONICS

ENGINEERS (IEEE)

IEEE C57.12.00 (2021) General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers

IEEE C57.12.90 (2021) Test Code for Liquid-

Immersed Distribution, Power, and Regulating Transformers

IEEE C57.93 (2019) Guide for Installation of Liquid-Immersed Power Transformers

IEEE C57.106 (2015) Guide for Acceptance and Maintenance of Insulating Mineral Oil in Electrical Equipment

IEEE C57.125 (2015) Guide for Failure

Investigation, Documentation, and Analysis for Power Transformers and Shunt Reactors

IEEE C57.637 (2015) Guide for the Reclamation of

Mineral Insulating Oil and Criteria for Its Use

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-05 Design Data

Descriptive Data; G, HDC

Descriptive data shall include, but not necessarily be limited to, the following (as applicable):

a. Gasket material

b. Magnet wire

c. Cellulose insulation, lead bracing, insulating board and spacers

d. Insulating oil

e. Crimp or solder connection material

f. Oxidation inhibitor SD-06 Test Reports

1. Daily Field Supervisor Report; G, C

The Field Supervisor's daily report shall be submitted not later than 1 working day following completion of each day's work (see paragraph "Daily Reports").

2. Transformer Inspection and Repair Report; G, HDC

The transformer inspection and repair report shall be submitted for approval not later than 4 working days following completion of the transformer internal inspection (see paragraph "INITIAL

ON-SITE INTERNAL INSPECTION").

3. Pre-work Transformer Test Report; G, HDC

A transformer test report including the results of the transformer electrical tests and the oil tests before transformer repair shall be submitted for approval not later than 7 calendar days following completion of all tests (see paragraphs "TRANSFORMER OIL TESTS", and "TRANSFORMER

4. Transformer Repair Report; G, C

A transformer repair report shall be submitted for approval not later than 30 calendar days following completion of all site work (see paragraph "TRANSFORMER

REPAIR REPORT").

5. Post-work Transformer Test Report

A transformer test report including the results of the transformer electrical tests and the oil tests after filling and processing shall be submitted for approval not later than 7 calendar days following completion of all tests (see paragraphs "TRANSFORMER OIL TESTS", and "TRANSFORMER

SD-07 Certificates

Field Supervisor Experience; G, HDC

The Contractor's proposed field supervisor and related experience information shall be submitted for approval not later than 7 calendar days prior to commencement of site work (see paragraph "FIELD SUPERVISOR EXPERIENCE AND

RESPONSIBILITIES").

SD-08 Manufacturer's Instructions

1. Transformer Oil Filling Procedure; G, HDC

A transformer oil filling procedure detailing the heated oil vacuum-filling and winding dry-out shall be submitted for approval not later than 7 calendar days prior to commencement of transformer oil filling (see paragraph

"TRANSFORMER REASSEMBLY AND OIL FILLING").

2. Transformer Test Procedures; G, HDC

Transformer test procedures shall be submitted not later than 7 calendar days prior to the start of transformer field tests (see paragraph "TRANSFORMER ELECTRICAL TESTS").

SD-09 Movement Plan

Transformer Movement Plan; G, HDC

If transformer is required by the proposed work plan, submit a movement plan for approval not later than 30 calendar days prior to site arrival. See paragraph 3.3

PREPARATION FOR TRANSFORMER MOVEMENT.

1.5 FIELD SUPERVISOR EXPERIENCE AND RESPONSIBILITIES

1.5.1 Experience

The field supervisor shall have been engaged in the field (site) internal repair, assembly, oil filling and testing of similar power transformers, as specified herein. Qualifying experience shall have been performed at a minimum of three projects within the previous five years. A verifying contact, name and phone number shall be provided for at least three such facilities. The Field Supervisor Experience shall be submitted for approval.

1.5.2 Responsibilities

The field supervisor shall be responsible for the performance, oversight and correctness of all site work identified in these specifications, including the following:

a. Comply with all safety, health and reporting requirements of these specifications, including powerplant safe clearance procedures, accident prevention, environmental protection, activity hazard analysis, fall protection, and confined space entry.

b. Preparation of all required submittals and documentation.

c. Securing an inventory of all materials entering the transformer to ensure no unintended foreign objects remain in the tank (see SECTION 01 11 01.00 28 SUPPLEMENTARY REQUIREMENTS, paragraph "TOOLS AND

PARTS CONTROL AND ACCOUNTABILITY PROCEDURE").

1.5.3 Daily Reports

The field supervisor shall maintain a Daily Field Supervisor Report, and provide a copy to the COR. The daily report shall include the following activities, at a minimum: inspection activities, detailed description of work performed, instructions provided, photographs, weather conditions, test results, recommendations and general observations.

a. Weather conditions

b. References to Activity Hazard Analysis

c. Inspection activities

d. Detailed description of work performed

e. Photographs

f. Tests performed with results

g. Tool equipment daily checklist

h. Problems noted

PART 2 PRODUCTS

2.1 PRODUCT DATA

Descriptive data or catalog data of all materials provided for the transformer repair shall be submitted for approval within 7 calendar days prior to performance of the work, to demonstrate fully that all materials will conform to the requirements and intent of the specifications.

2.2 WINDING CONDUCTORS

Conductors used for replacing the high-voltage neutral shall be high stranded copper conductors meeting the applicable requirements of

ANSI MW 1000, made of high-conductivity copper, made especially for the purpose, and shall have a minimum cross-sectional area and rating as that of the conductor being replaced.

2.3 CONDUCTOR INSULATION

Electrical grade insulating kraft or “crepe” paper shall meet the requirements of ASTM D 1305, shall be thermally upgraded, cellulose-based, and derived from unbleached, softwood pulp. The kraft paper shall be chemically neutral, with low ash, chloride and sulfate content, and made specifically for the use of insulating conductors in oil filled power transformers. Thermally upgraded creped kraft paper, NEMA graded glass polyester materials, or similar materials intended for permanent installation in mineral oil-immersed transformers may be used in-lieu of standard kraft paper.

Stiff electrical grade crepe-kraft paper tubing used for bracing the neutral lead shall meet the same requirements as above. If proposed for use, information detailing the tubing wall thickness, layer construction, and kV dielectric breakdown strength in oil shall be submitted for approval.

2.4 LEAD BRACING, INSULATING BOARD AND SPACERS

Lead bracing, insulating transformer board, spacers and other winding bracing components shall meet the requirements of ASTM D 1305, be manufactured of electrical grade, cellulose-based materials derived from unbleached, softwood pulp, shall be chemically neutral with low ash, chloride and sulfate content, and made specifically for the use inside oil filled power transformers. Spacing and other bracing components shall be dried and pre-impregnated, as applicable.

2.5 GASKET MATERIAL

Gaskets shall be made of nitrile material meeting the minimum requirements of ASTM F 104, classification F-229000, specifically designed for the use of sealing transformer insulating oil in oil filled power transformers. The gasket material shall be sized to allow for a minimum 20 percent compression when the man-hole cover is bolted and tightened against the compression stop (see the Transformer O&M Manual, Attachment XXX, for gasket details and locations).

Gaskets between metal surfaces shall be set in expansion-limiting grooves so that all contact surfaces are metal-to-metal when tightened. The gaskets shall be made of Nitrile NBR (Buna N), with the exception that gaskets for the low-voltage bushings shall be Viton, with a Durometer rating between 50 and 70. Circular cross-section gaskets shall not be acceptable for use in gasket grooves of rectangular cross-section.

Nitrile gasket sizing for rectangular cross-section grooves shall be accomplished as follows:

a. Gasket thickness is chosen so that approximately 25-percent of the gasket cross-section protrudes above the depth of the groove, referred to as the 'gasket compression area'.

b. The width of the groove minus the width of the gasket determines the space available for gasket expansion during compression. The amount of groove space available for gasket expansion during the compression process is referred to as the 'gasket expansion area', which must be greater than the gasket compression area to avoid pinching of the gasket between the metal surfaces when tightened.

c. Proper sizing coordination between the gasket groove and the gasket cross-sections results in 25-percent gasket compression, with a remaining gasket expansion area after tightening of between 5 and 10-percent.

2.6 NITROGEN GAS AND DRY-AIR

2.6.1 Nitrogen Gas

Nitrogen gas shall be in accordance with ASTM D 1933, Type III.

As identified in the referenced standard, the composition and properties of the nitrogen gas shall be as follows:

a. Nitrogen and rare gases, min. volume: 99.993%

b. Hydrogen, max. volume: 0.005%

c. Oxygen, max. volume: 0.002%

d. Dew Point, max.: -59 Degrees Celsius

2.6.2 Dry-air

Dry-air shall be in accordance with ASTM D 3283, Type I. As identified in the referenced standard, the composition and properties of the dry-air shall be as follows:

e. Oxygen, volume: 19.5% to 23.5%

f. Carbon monoxide, max. volume: 0.0020%

g. Carbon dioxide, max. volume: 0.10%

h. Nitrogen: predominantly balance

i. Dew point, max.: -58 Degrees Celsius

2.6.3 Dry-air from a Compressor

Oil-less compressors used to supply dry-air must include the following, as a minimum:

a. Desiccant system on the output of the compressor designed for removal of dirt, water, oil, and uncondensed moisture from compressed air lines.

b. Maintain a maximum -40 degrees Fahrenheit dew point, while achieving a 0 percent compressed air humidity.

c. Coalescer that removes oil and sub-micron particles down to 0.01 microns.

d. Filter that provides removal of water and contaminants down to 5 microns.

e. Provide a filtration capacity up to 30 cubic feet per minute (CFM) at 175 pounds per square inch (psi).

f. Replaceable or regenerative desiccant system which provides indication of silica gel saturation.

2.7 TRANSFORMER OIL

2.7.1 Quantity and Transformer Oil Certification

Provide top-off and make-up transformer oil as required to fill transformers T10, T9 and T11 to the proper operating level after oil filling and processing. Any remaining oil after completion of the oil-filling will remain the property of the contractor. Submit for approval the transformer oil certification documents prior to delivery of the transformer oil to The Dalles Dam, indicating that the oil furnished for placing the transformer in service has been tested to meet the requirements specified below.

2.7.2 Type of Oil

The grade of transformer oil furnished must be unused, produced from a naphthenic base crude petroleum specifically prepared and refined for use in power transformers as an insulating and cooling medium. Paraffinic and paraffinic-blends are not acceptable. Except for the oxidation inhibitor, the transformer oil must be free from additives of every kind, either natural or synthetic in any quantity, such as silicone or ester oil contamination from hoses or equipment used during oil filling and processing.

2.7.3 Oxidation Inhibitor

Oxidation inhibitor shall be '2,6 Ditertiary-Butyl Para-Cresol' (DBPC) type.

2.7.4 Chemical, Physical and Electrical Characteristics

The transformer oil provided must meet the requirements of ASTM D3487, Table 1, Type II, with an oxidation inhibitor content of between 0.25 and

0.30 percent by mass, prior to shipment.

2.7.5 Sampling

Obtain samples for testing as specified in ASTM D923.

PART 3 EXECUTION

3.1 REQUIREMENTS FOR PERFORMANCE OF WORK INSIDE OF TRANSFORMER

All work performed under this contract is assumed to be performed inside of the transformer tank with the transformer in its permanent operating location, or in the erection bay inside the powerhouse. If work is required by the work plan, follow the corresponding specification section. This work is also assumed to be completed without untanking of the core/coil assembly.

Internal inspections shall be performed per the requirements of IEEE C57.93, paragraph 5.3. During final reassembly, replace all connecting hardware disturbed during transformer repairs, including devices or equipment to be replaced. Replace all disturbed hardware with graded hardware of the same dimensions. If sealing the transformer after daily activities during the repair progress, re-using old hardware is permitted. Attempt to seal the transformer from atmosphere at all times. Prior to removal of the transformer man-hole covers and entrance into the tank, the following requirements shall be met by the Contractor:

a. If work is completed in the transformer’s permanent operating location, a waterproof weather cover shall be erected over the transformer, to prevent any moisture or falling objects from entering the tank. The contractor can choose to move the transformer into the erection bay or offsite and perform the repairs. The erection bay does not require a waterproof weather cover as described above. Offsite repair not performed in a closed facility requires a waterproof cover.

b. The top of the transformer shall be thoroughly cleaned and vacuumed to minimize the possibility of contaminants entering the tank.

c. The temperature and relative humidity around the transformer shall be monitored during the performance of work.

d. All personnel entering the transformer tank shall wear 'Tyvek' suits, or equivalent, and a logbook shall be maintained of all items taken into and brought out of the transformer tank to assure nothing has inadvertently been left inside (see SECTION 01 11 01.00 28, paragraph

"TOOLS AND PARTS CONTROL AND ACCOUNTABILITY PROCEDURE").

3.2 INITIAL ON-SITE INTERNAL INSPECTION

The Contractor shall notify the Government of the desired date for the internal inspection. The Contractor shall perform a transformer internal inspection per the requirements of IEEE C57.125, paragraph 5.4. After performance of the transformer internal inspection, the Contractor shall prepare a Transformer Inspection and Repair Report that includes a summary of the internal inspection, including items identified in IEEE C57.125, Table 8, and a detailed repair procedure. The report shall include the following:

a. Evaluation of the condition of the high voltage neutral line. Included in the inspection shall be signs of severe overheating resulting in burning or paper degradation, possible.

b. Evaluation of the insulation system condition for the winding leads connected to the high voltage neutral and the insulation of low voltage flexible bushing connectors and upper leads.

c. Step-by-step repair procedure for removing the existing and replacing the high voltage neutral, including a list of required materials, method of cutting and replacing, lead insulation, and lead bracing.

d. Detail drawings and sketches of the transformer high voltage neutral with dimensioned lead configurations, including brazing/crimping details, lead insulation, and bracing for short-circuit forces.

e. Detail drawings of the replacement transformer man-hole cover gaskets.

f. Schedule, to include the following milestones:

1) Procurement of materials

2) Erection of temporary cover or transformer movement (see section

3.1 REQUIREMENTS FOR PERFORMANCE OF WORK INSIDE OF TRANSFORMER)

3) Repair of transformer

4) Oil filling process

5) Performance of tests.

3.3 PREPARATION FOR TRANSFORMER MOVEMENT

If transformer movement is required by the proposed work plan, provide, and execute the following for the movement of the transformers from the permanent operating location to the erection bay for repair:

a. Prepare a movement plan that includes loading calculations, movement path, and weights of each component in the movement. Submit this plan for government approval.

b. Remove all external connections to the transformer.

c. Drain the transformer oil into an oil storage tank.

d. The Government expects that, at a minimum, the coolers and high voltage bushings must be removed to allow for passage under the tailrace gantry crane.

3.4 TRANSFORMER MOVEMENT

a. Install an impact recorder on the transformer for monitoring during all movement operations.

b. Jack and skid the transformer out of the permanent operating location and load onto a heavy-haul truck for transport to the erection bay.

c. Transport the transformer to the erection bay through the door in figure XXX, and jack and skid the transformer onto cribbing with secondary oil containment.

d. Perform transformer repairs per section 3.4 TRANSFORMER REPAIR.

e. Move the transformer to its original permanent operation location.

f. After movement to its permanent operating location, inspect the impact recorder chart, vacuum process and oil-fill, install any accessories removed for movement, perform transformer cleaning and touch-up painting, and perform post-movement transformer inspections, electrical tests, and oil tests.

g. Reinstall the transformer components which were removed to facilitate its repair.

h. Provide a partial tanker with enough oil to fill the remaining space of T10 plus make-up oil for T9, T10, and T11.

3.5 CUTTING THE COVER

The confirmed failure mechanism of these transformers is the high voltage neutral conductor. Gain access to transformer high voltage neutral connections by either cutting the cover off the transformer or uncovering manholes. If cutting and removing the cover of the transformer tank is required by the proposed work plan, cut the tank cover weld with a government approved method.

3.6 TRANSFORMER REPAIR

3.6.1 Tests to be Performed Prior to Transformer Work

Winding resistance measurement tests shall be performed on each phase prior to the performance of any transformer work, for use as baseline data and post repair comparisons. Winding resistance measurements shall be performed per the requirements of paragraph "TRANSFORMER ELECTRICAL TESTS".

3.6.2 Work to be Performed Prior to Repair

Disconnect any external wiring from the transformer to the power plant. Disconnect and remove any accessories that impede the repair of the high voltage neutral.

Store all removed components using the manufacturer approved method.

3.6.3 Transformer Repair

The confirmed failure mechanism of these transformers is the high voltage neutral conductor. Gain access to transformer high voltage neutral connections. Cut the high voltage to neutral connections seen in photo X. Remove neutral conductor and phenolic tube housing the neutral conductor. Replace neutral conductor that meets the requirements of section 2.2 WINDING CONDUCTORS. Insulate replacement conductor with insulation that meets the requirements of section 2.3 CONDUCTOR INSULATION.

Replace any manhole cover gaskets and reinstall the manhole covers if removed.

Reweld the tank cover if it was removed. Replace any damaged components with exact replacements or a government approved equal.

3.7 TRANSFORMER REASSEMBLY AND OIL FILLING

3.7.1 Transformer Reassembly and Preparation for Oil Filling

After completion of the transformer repairs, the transformer shall be reassembled in preparation for oil filling. Provide new gaskets for any disturbed gasket connections. If the tank cover was removed, replace the asbestos gasket with a new fireproof rope or fiberglass rope, re-weld the tank cover cut from the transformer into the original position, and reinstall any removed components. Provide a power source to power all equipment needed to execute oil filling procedure and any required testing. After reassembly, the transformer tank shall be pressure tested for leaks using either dry-air or nitrogen. The test pressure shall be a minimum of 8 psi and no more than 10 psi, and shall be maintained for a minimum of 24 hours, and there should be no loss in gas pressure during the test period. The dial gauge used for this test shall have a scale of 0 - 10 psi. Any noticeable drop in pressure during the test period shall be brought to the attention of the COR, and the location of the leak identified. If a leak is found on any welds or components that were removed and replaced or reinstalled, fix the leak with a government approved method.

3.7.2 Transformer Oil Filling

After reassembly and pressure testing, vacuum-fill the transformer with hot oil, and dry the insulation using high-vacuum hot-oil recirculation per the requirements of IEEE C57.93, paragraphs 5.7 through 5.9 and the transformer O&M manual, Attachment XXX, and the approved Transformer Oil Filling Procedure. Supply enough oil to top off T10 and provide make-up oil during the oil filling process. The Contractor shall be responsible for the provision of all oil handling and high-vacuum processing equipment. The oil test results for T9, T10, and T11 are included in Appendix X. Prior to oil filling, hold vacuum on the transformer for a minimum of 12 hours. The transformer oil shall undergo reconditioning per IEEE C57.104.

Test the oil to ensure the oil meets the contract requirements as outlined in paragraph "Oil Test Requirements" after reconditioning.

3.7.3 Oxidation Inhibitor

The Government will have a sample of the transformer oil that will be used for oil filling tested for the content of oxidation inhibitor, for the Contractor's use after date of award. If the oxidation inhibitor content is less than 0.2 percent by mass, additional oxidation inhibitor shall be added by the Contractor after the oil filling and shall be dissolved into transformer oil and metered gradually into the tank through the oil processing rig. The addition of the oxidation inhibitor using this method should take one or two passes to accomplish entirely. The total amount of inhibitor to be added should bring the total quantity in the transformer oil to approximately 0.3 percent by mass.

3.8 TRANSFORMER OIL TESTS

3.8.1 General

After transformer oil filling and processing, samples of the transformer insulating oil shall be taken from the transformer and sent to two independent laboratories for analysis. Oil samples shall be taken from the transformer per the requirements of ASTM D 923. Identity of samples and results of analyses shall be included in the final transformer test report. Perform the following analyses at a minimum.

a. Dissolved gases

b. Water

c. Neutralization number

d. Interfacial tension

e. PCB-in-oil

f. Dissipation factor

g. Dielectric breakdown voltage, test procedure per ASTM D 1816 – 1mm and 2mm

h. Furans

i. Dissolved metals

j. Sediment and soluble sludge

k. Oxidation stability

l. Oxidation inhibitor

m. Viscosity

n. Specific gravity

o. Color

p. Flash point

q. Corrosive sulfur

3.8.2 Oil Test Requirements

After processing, the oil shall meet all of the requirements for in Table 4 of IEEE C57.106. The exceptions that will be allowed to ASTM D 3487 are as follows:

a. Polychlorinated Biphenyls, max: same as before reconditioning

b. Oxidation inhibitor, % by mass, min: 0.26

3.8.3 ELECTRICAL TESTS

The transformer electrical tests, including test equipment, test methods, measurements, and computations, shall be in accordance with the applicable requirements of IEEE C57.12.00, IEEE C57.12.90, and IEEE C57.152 unless otherwise specified, and the Transformer Test Procedures shall be submitted for approval. The following transformer tests shall be performed prior to repairs and after completion of the transformer repairs, reassembly and oil filling, and a Transformer Test Report shall be submitted for approval.

a. Winding Resistance. Winding resistance measurements shall be performed on all tap positions.

b. Winding Insulation Resistance

c. Turns Ratio. Turns ratio measurements shall be performed on all tap positions.

d. Insulation Power Factor and Excitation Current

e. Sweep Frequency Response Analysis

f. Power Factor Test for each transformer bushing

g. Leakage Reactance Measurement Tests

See Table 1 for a tabulated list of electrical tests and time and location of performance. If the option to remove the transformer cover is not exercised, ignore rows 2 and 3.

Transformer Condition Location Tests to be Performed

1. Prework, no change Permanent operating location A, B, C, D, E, F, G

2. Postwork, cover cut off

Erection Bay or Permanent Operating Location

A

3. Postwork, cover reinstalled

Erection Bay or Permanent Operating Location

A

4. Postwork, repaired Permanent Operating A, B, C, D, E, F, G and fully assembled Location

3.9 OIL HANDLING REQUIREMENTS

3.9.1 General

The existing transformer oil was last tested in 2012 and tested as Polychlorinated Biphenyls (PCBs) free. The oil test results for PCB content are included in these specifications at the end of this section. Provide the necessary labor, material, and equipment, including but not limited to the following to drain the transformer:

a. Oil vacuum-processing equipment.

b. Clean oil hose with fittings to connect to the upper filter valve, and the lower filter/drain valve. The valves are a 1-1/2-inch brass globe valves and the lower filter/drain valve has a 3/8-inch sampling device.

c. Vacuum hose to connect to the oil processing equipment and the 3-inch vacuum connection on the transformer.

d. Clean oil storage tank per the requirements of paragraph "Transformer Oil Storage Tank".

e. Temporary oil containment for the oil vacuum-processing equipment trailer, oil storage tank, and any removed transformer components that touch oil per the requirements of paragraph "Oil Containment".

f. A method of providing dry-air to the transformer as the oil is displaced during draining. The dry-air must be in accordance with paragraph "DRY-AIR".

3.9.2 Transformer Oil Storage Tank

Provide a transformer oil storage tank for the duration of the work as necessary. The transformer oil storage tank must be double-walled, sized to contain all of the transformer oil from the transformer, and the interior walls of the storage tank lined with a chemical resistant coating. Submit for approval a transformer oil storage tank inspection and certification report prior to usage that includes the following:

a. Tank catalog data, including manufacturer's name, tank construction, and storage volume.

b. Certification of passing a 3-psi air pressure leak test performed within 30 calendar days of submittal.

c. Certification that the tank interior was cleaned utilizing a caustic wash, or similar process that does not react with the tank lining, to remove all impurities.

d. Certification that the tank has been inspected, including the interior for cleanliness, and is suitable for use in storage of transformer insulating oil. No impurities are to be present in the storage tank prior to the introduction of insulating oil.

3.9.3 Oil Containment

Provide one-piece spill containment berms under the oil vacuum-processing equipment trailer, oil storage tank, transformer, and any removed transformer components that touch oil, sized to completely surround the equipment. The berms must be manufactured from a reinforced geomembrane of a minimum 30 mil thickness, chemically resistant to transformer oil, with supported collapsible walls. During the oil handling operations, all hose joints located outside of the spill containment berms must have interlocking connections, be wrapped with an absorbent material, with 5-gallon buckets located beneath the joint to help avoid oil spills. Submit an oil spill plan and provide the necessary equipment to contain an oil spill, as required in Section 01 57 19, TEMPORARY ENVIRONMENTAL CONTROLS.

3.9.4 Oil Draining

Drain the transformer insulating oil from the transformer tank into a storage tank that meets the requirements of paragraph "Transformer Oil Storage Tank".

Locate the storage tank in an acceptable laydown area as shown on drawing G-

101. Provide oil containment for all oil handling operations, oil storage, and any equipment used for transfer of the oil from the transformer to the storage tank. During the draining process, displace the oil in the transformer tank with dry-air that meets the requirements of paragraph "DRY-

AIR".

3.9.5 Initial Dew Point

After the transformer has been drained and filled with dry-air for 24 hours, perform a dew point check and determine the insulation moisture content and submit for approval. Perform the dew point check with the Government QA representative present per the methods of IEEE C57.93, Annex C, Determination of Insulation Dryness.

3.10 COMPLETION OF WORK REQUIREMENTS

Move the transformer back to permanent operating location. Perform postwork electrical tests and oil tests. Submit all test results to government for approval.

A transformer repair report shall be prepared detailing work performed to repair the transformer. The report should include the following at a minimum:

drawings of the transformer depicting what components were replaced and what connections were changed, photos depicting the existing high voltage neutral slated for replacement, photos of the new high voltage neutral installed, detailed procedure of installation, detailed description of work performed, detailed description of any problems noted, and the solutions applied. This report shall include the following information, as a minimum:

a. Method for performing the high voltage neutral replacement without removing the tank cover, or whether removing the tank cover is required.

b. Decision and justification for performing the work in place in the permanent operating location or moving the transformer to the erection bay.

c. Detailed process of the required high voltage neutral removal and replacement.

d. Materials list, including catalog info, manufacturing contacts and associated costs.

-- End of Section --

APPENDIX A PHOTOS

3.10 COMPLETION OF WORK REQUIREMENTS