Memorial Hermann Best Practices
July, 2013
SECTION 26 12 16 DRY-TYPE, MEDIUM VOLTAGE TRANSFORMERS
PART 1 - GENERAL
1.01
WORK INCLUDED
A.
Comply with the provisions of Section 26 05 00.
B.
Provide indoor ventilated dry-type secondary substation transformers.
1.02
RELATED SECTIONS
A.
Division 03: Concrete
B.
Section 26 05 00: Common Work Results for Electrical
C.
Section 26 05 13: Medium Voltage Cable
D.
Section 26 25 00: Enclosed Bus Assemblies
E.
Section 26 05 53: Identification for Electrical Systems
F.
Section 26 13 16: Medium Voltage Fusible Interrupter Switchgear
G.
Section 26 13 19: Medium Voltage Vacuum Interrupter Switchgear
H.
Section 26 23 00: Low Voltage Switchgear
I.
Section 26 24 13: Switchboards
J.
Section 26 24 19: Motor Control Centers
1.03
REFERENCES
A.
The ventilated dry-type transformers and protection devices in this specification are designed and
manufactured according to latest revision of the following standards (unless otherwise noted).
B.
ANSI C57.12.51, Requirements for Ventilated Dry-Type Power Transformers, 501 KVA and
Larger, Three-Phase with High-Voltage 601 to 34 500 Volts, Low Voltage 208Y/120 to 4160
Volts.
C.
ANSI C57.12.55, Dry-Type Transformers in Unit Installations, Including Unit Substations Conformance Standard
D.
ANSI/IEEE C57.98, Impulse Tests, Guide for Transformer (Appendix to ANSI/IEEE C57.12.90)
E.
ANSI/NFPA 70, National Electrical Code
F.
DOE Part III CFR Part 431, Energy Conversation Program for Commercial Equipment:
Distribution Transformers Energy Conservation Standards.
G.
IEEE C57.12.01, General Requirements for Dry-Type Distribution and Power Transformers
Including Those with Solid Cast and / or Resin-Encapsulated Windings
H.
IEEE C57.12.60, Trial Use Standard Test Procedures for Thermal Evaluation of Insulation
Systems For Solid-Cast and Resin-Encapsulated Power and Distribution Transformers
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I.
IEEE C57.12.91, Test Code for Dry-Type Distribution and Power Transformers
J.
IEEE C57.94, Recommended Practice for Installation, Application, Operation and Maintenance of
Dry-Type General Purpose Distribution and Power Transformers
K.
IEEE C57.96, Guide for Loading Dry-Type Distribution and Power Transformers
L.
NEMA ST 20, Dry Type Transformers for General Applications
M.
UL 1562 Transformers, Distribution Dry Type - over 600 watts
1.04
SUBMITTALS
A.
Comply with Division 01.
B.
Product data and spare parts list. Include all ratings, weights, sound ratings and cable terminal
data.
C.
Outline, nameplate, connection diagrams and other shop drawings on transformer. Include front
elevations, plan view, dimensions, and conduit entry/exit locations.
D.
Installation and operating instructions, maintenance, troubleshooting and repair procedures and
technical literature pertaining to all components or instruments provided.
E.
A certified test report containing minimum information per IEEE C57.12.91 Appendix.
F.
DOE Part III 10 CFR Part 431 compliance certificate
G.
Where applicable, provide the following additional information:
1.
Busway connection data
2.
Connection details between close-coupled assemblies
3.
Composite plan view and elevation view of close-coupled assemblies
4.
Kick interlock scheme drawing and sequence of operations
1.05
SYSTEM DESCRIPTION
A.
Transformers shall be indoor secondary unit substation type from incoming line terminals to
outgoing feeder terminals.
B.
Transformers shall be Cast Coil type, VPI type or as shown on drawings.
C.
Primary terminations shall be side wall mounted for cable connections in air-filled terminal
chambers.
D.
Secondary terminations shall be close-coupled to low voltage switchgear unless noted otherwise.
1.06
A.
1.07
A.
PROJECT RECORD DOCUMENTS
Maintain an up-to-date set of Contract documents. Note any and all revisions and deviations that
are made during the course of the project.
OPERATION AND MAINTENANCE DATA
Comply with Division 01.
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B.
Provide copies of installation, operation and maintenance procedures to owner.
C.
Submit operation and maintenance data based on factory and field testing, operation and
maintenance of specified product.
1.08
A.
1.09
QUALITY ASSURANCE (QUALIFICATIONS)
Manufacturer shall have specialized in the manufacture and assembly of ventilated dry-type
secondary substation transformers for 20 years.
REGULATORY REQUIREMENTS
A.
Transformer shall comply with all referenced documents and standards listed within this section.
B.
Installation shall comply with National Electrical Code, National Electrical Safety Code, EPA
regulations, and all local and state codes and regulations.
1.10
DELIVERY, STORAGE, AND HANDLING
A.
Deliver, store, protect, and handle products in accordance with recommended practices listed in
manufacturer's Installation and Maintenance Manuals and in ANSI/IEEE C57.94.
B.
Deliver each transformer on individual shipping skids for ease of handling. Each transformer shall
be wrapped for protection.
C.
Inspect and report concealed damage to carrier within specified time.
D.
Store in a clean, dry space. Maintain factory protection or cover with heavy canvas or plastic to
keep out dirt, water, construction debris, and traffic. (Heat enclosures to prevent condensation.)
E.
Handle in accordance with manufacturer's written instructions to avoid damaging equipment,
installed devices, and finish.
1.11
PROJECT CONDITIONS (SITE ENVIRONMENTAL CONDITIONS)
A.
Follow NEMA, NECA recommendations and good construction practice before, during and after
transformer installation.
B.
Indoor ventilated dry-type transformers shall be located in well-ventilated areas, free from excess
humidity, dust and dirt and away from hazardous materials. Ambient temperature of area will be
between minus 30 and plus 40 degrees C.
1.12
A.
1.13
A.
WARRANTY
Manufacturer warrants equipment to be free from defects in materials and workmanship for 1
year from date of installation or 18 months from date of delivery, whichever occurs first.
FIELD MEASUREMENTS
Make all necessary field measurements to verify that equipment shall fit in allocated space in full
compliance with minimum required clearances specified in National Electrical Code.
PART 2 - PRODUCTS
2.01
MANUFACTURER
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July, 2013
A.
Eaton/Cutler-Hammer
B.
Siemens
C.
Square D
D.
Cooper Power Systems
E.
ABB
2.02
A.
2.03
EQUIPMENT
Refer to drawings for: actual layout and location of equipment and components; current ratings of
devices, bus bars, and components; voltage ratings of devices, components and assemblies; and
other required details.
PRIMARY (INCOMING/LINE) SECTION
A.
The transformer shall have one integrally mounted air-filled primary terminal compartment with
clamp-type terminals. Refer to the drawings for specific wire size and type. The terminals shall be
radial feed.
1.
A set of intermediate class, 15 KV surge arrestors shall be mounted inside terminal
compartment.
2.
A set of surge protection capacitors sized by manufacturer for optimum performance with
surge arrestors shall be mounted inside terminal compartment.
B.
Where indicated on the drawings the transformer shall have an air-interrupter switch with
pothead}. Refer to the drawings for specific wire size and type. The terminals shall be radial
feed}.
1.
A set of {station} class, {15, 3.0, 6.0, 9.0 or 18 KV surge arrestors shall be mounted
inside terminal compartment.
2.
A set of surge protection capacitors sized by manufacturer for optimum performance with
surge arrestors shall be mounted inside terminal compartment.
3.
The primary switch shall be kirk key interlocked to the secondary main device such that
access to fuses is prevented unless secondary main is open. This is required only if an
alternate source of power is present.
C.
Where indicated on the drawings, the transformer shall have a double air-interrupter switch with
clamp-type terminals}. Refer to the drawings for specific wire size and type. The terminals shall
be radial feed}.
1.
A set of {intermediate} class, 15} KV surge arrestors shall be mounted inside terminal
compartment.
2.
A set of surge protection capacitors sized by manufacturer for optimum performance with
surge arrestors shall be mounted inside terminal compartment.
3.
The primary switch shall be kirk key interlocked to the secondary main device such that
access to fuses is prevented unless secondary main is open.
2.04
A.
TRANSFORMER SECTION
General construction, VPI type
1.
Transformer shall be vacuum pressure impregnated ventilated dry type construction for
optimum environmental protection. It shall be designed and manufactured in accordance
with ANSI C57.12.01 latest revision.
2.
Transformer shall be constructed of high-grade, grain oriented, silicon steel laminations,
with high magnetic permeability. Magnetic flux density is to be kept well below the
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3.
4.
saturation point. Core construction shall include mitered joints to keep core losses,
excitation current and noise level at a minimum.
Transformer coils shall be impregnated using the VPI process. Coils shall be pre-heated.
Individual windings shall be pressure impregnated with solvent-less polyester resin such
that the resin penetrates and seals the windings. The windings shall be subjected to
several cycles of dry vacuum followed by positive pressure of dry air or nitrogen to
provide complete impregnation of the coils with no voids or air pockets that can create
hot spots or cause corona formation. Windings shall then be oven treated to completely
cure the resin. After core and coils are assembled, spaced and adjusted, the entire
assembly shall be treated with resin and oven baked until resin is fully cured.
Core and coil assembly shall be enclosed in mild steel housing suitable for indoor or
outdoor installation in accordance with the purchase order instructions.
B.
General Construction, Cast Coil type
1.
Transformer coils shall be vacuum cast. Coils shall be cast void free to prevent partial
discharges within the resin material at up to 120 percent of nominal operating voltage.
The HV windings shall employ strip foil technology, be heated under vacuum and use
quartz powder and epoxy resin cured in an oven. The LV windings shall employ sheet
conductors, TIG welded start and finish bars with fiber glass mesh on the inside and
outside. The LV winding shall be vacuum poured and cast in a similar process to the HV
windings.
2.
The electrical insulation system shall be a 180 degree C system. Transformer design
temperature rise shall be based on a 30 degrees C average ambient over a 24-hour
period with a maximum of 40 degrees C. Solid insulation in the transformer shall consist
of inorganic materials such as glass fiber, electrical grade epoxy and Nomex. All
insulating materials must be rated for continuous 180 degree C duty or higher.
Temperature rise design shall be per ANSI C57.12.91 and verified via temperature test
on each unit or units of similar design.
3.
Transformer core shall be constructed of high-grade, grain oriented, silicon steel
laminations, with high magnetic permeability. Magnetic flux density is to be kept well
below the saturation point. Core shall be cruciform in shape, with mitered joints to keep
core losses, excitation current and noise level at a minimum.
C.
Ratings
1.
Transformers shall be sized as indicated on drawings.
2.
The average winding transformer temperature rise shall be 115 degree C.
3.
The transformer Basic Impulse Rating shall be as indicated on drawings or a minimum of
30 KV BIL for 5 KV system voltages and a minimum of 60 KV BIL for 15 KV system
voltages.
4.
Fan cooling shall only consist of wiring and 120/240 VAC controls for future fan cooling AA/FFA Rating.
5.
A winding temperature monitor/ fan controller shall be included in the fan cooling
package. The controller shall monitor all three windings, and display the individual
temperatures and the hottest winding and its temperature. The controller shall include
the following features:
a.
Three output relays for fan, alarm and trip control
b.
4-20mA output
c.
Fan Exerciser to minimize fan wear
d.
Maximum temperature memory and reset
e.
Automatic/manual fan control
f.
Audible alert
g.
Sensor and system diagnostics and watchdog
h.
RS-485 Data communications using Modbus RTU protocol
i.
Universal power supply
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2.05
STANDARD FEATURES
A.
Provide UL listed transformer.
B.
A stainless steel diagrammatic nameplate shall be mounted on instruction book holder on
transformer enclosure.
C.
Make provisions for lifting and jacking the unit into place.
D.
A base suitable for rolling and skidding parallel to centerline shall be provided.
E.
A ground pad shall be located on low voltage end of enclosure.
F.
Vibration isolation pads shall be provided to isolate the core and coil assembly from the casing.
[Furnish the transformer with spring isolators located between the core and the coil assembly and
the mounting base.]
G.
The unit shall be a 60 hertz design.
H.
The insulation system shall be rated 220 degree C.
I.
High and low voltage windings shall be copper}.
J.
Transformers in the Emergency Generator Room shall include thermostatically controlled space
heaters fed from external source which remains energized when the transformer is de-energized.
K.
Transformers shall be designed to meet the sound level standards for dry-type transformers as
defined in NEMA TR1.
L.
Transformer primary shall have four 2-1/2 percent full capacity taps, two above and two below
rated nominal voltage. No load taps shall be available on internal terminal board located behind
removable panels on front of transformer case. Taps shall be for de-energized operation only.
M.
The temperature rise of primary winding at rated KVA loading shall not exceed maximum rise
selected above during operation at 30 degrees C average ambient, which does not exceed 40
degrees C in a 24 hour period.
N.
A winding temperature indicator shall be included in the fan cooling package.
2.06
A.
2.07
LOSS EVALUATION
A loss evaluation report from the factory for each unit shall be provided and shall be factory
certified as to the information.
ACCESSORIES
A.
Provide 240 VAC space heaters with thermostat.
B.
Provide a 3 KVA control power transformer with a fused primary - 480 VAC to 120/240 VAC,
single phase.
C.
The transformer is to be supplied in a knockdown case design, for ease in fitting through limited
openings, and shall be of heavy gauge sheet steel construction, equipped with hinged doors for
access to the core and coils. Front and rear panels shall incorporate ventilating grills. Grills in
outdoor transformers shall be louvered to prevent water entering the enclosure. Enclosures shall
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be category C, suitable for installation in areas accessible to authorized personnel only. Base is
to allow safe means for lifting, jacking, rolling or skidding.
2.08
SECONDARY (OUTGOING / LOAD) SECTION
A.
The transformer shall have one integrally mounted air-filled secondary terminal compartment with
clamp-type terminals. Refer to the drawings for specific wire size and type. The compartment
may be part of the transformer housing if a separate compartment is not required.
B.
The transformer shall have an integral transition section which shall allow a close couple
connection to the secondary low voltage switchgear line up. See applicable specification for
equipment.
C.
The connection to the secondary low voltage equipment shall be made by {copper cable.
2.09
A.
2.10
FINISH
Finish shall be ANSI 61 gray paint.
FACTORY TESTING
A.
Each transformer shall receive the following standard commercial tests in accordance with ANSI
C57.12.91, latest revision, with test results available by transformer serial number upon request.
1.
Resistance measurements of all windings on the rated voltage connection of each unit
and at the tap extremes of one unit only of a given rating on this project
2.
Ratio tests on the rated voltage connection and on all tap connections
3.
Polarity and phase-relation tests on the rated voltage connections
4.
No-load loss at rated voltage on the rated voltage connection
5.
Exciting current at rated voltage on the rated voltage connection
6.
Applied potential test
7.
Induced potential tests
B.
The following special tests shall be performed on each transformer in accordance with applicable
ANSI standards:
1.
Impulse test on the high voltage winding
2.
Temperature test at self-cooled rating
3.
Temperature test at maximum cooled rating
4.
Sound level test at self-cooled rating
5.
Insulation Resistance (megger) test
6.
Partial Discharge test
PART 3 - EXECUTION
3.01
EXAMINATION
A.
Verify that the dry-type secondary substation transformers are ready to install.
B.
Check concrete pads for uniformity and level surface.
C.
Verify field measurements are as instructed by manufacturer.
D.
Verify that required utilities are available, in proper location and ready for use.
E.
Beginning of installation means installer accepts conditions.
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3.02
INSTALLATION
A.
Install per manufacturer's instructions and ANSI/IEEE C57.94.
B.
Install required safety labels including arc flash information.
3.03
FIELD TESTING
A.
Field testing shall be performed as recommended by NETA, the manufacturer, and/or electrical
testing specifications.
B.
Inspect installed transformers for anchoring, alignment, grounding and physical damage.
C.
Check tightness of all accessible mechanical and electrical connections with calibrated torque
wrench. Minimum acceptable values are specified in manufacturer's instructions.
3.04
ADJUSTING
A.
Adjust all access doors, operating handles, etc for free mechanical operation as described in
manufacturer's instructions.
B.
Adjust primary taps so that secondary voltage is within 2 percent of rated voltage.
C.
Return extra Kirk Keys to Engineer before energizing equipment.
3.05
CLEANING
A.
Clean interiors of enclosures to remove construction debris, dirt, shipping materials.
B.
Repaint scratched or marred exterior surfaces to match original finish.
END OF SECTION
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