SECTION 26 12 25
MEDIUM-VOLTAGE UNIT TRANSFORMERS
PART 1 - GENERAL
1.01
RELATED DOCUMENTS
A.
1.02
SUMMARY
A.
1.03
This Section includes Secondary Unit Substation, liquid-filled transformers with
medium-voltage primaries.
DEFINITIONS
A.
1.04
Drawings and general provisions of the Contract, including General and
Supplementary Conditions apply to this Section.
NETA ATS: Acceptance Testing Specification.
REFERENCES
A.
ANSI C37.47 - Specifications for Distribution Fuse Disconnecting Switches, Fuse
Supports, and Current-Limiting Fuses.
B.
IEEE C57.12.00 - Standard General Requirements
Distribution, Power, and Regulating Transformers (ANSI).
C.
ANSI C57.12.26 - Standard for Transformers - Pad-mounted, compartmental-type,
self-cooled, three-phase distribution transformers for use with separable insulated
high Voltage Connectors: High Voltage, 34,500 GrdY/19,920 Volts and Below;
2,500 kVA and Smaller.
D.
ANSI C57.12.27 – American National Standard Conformance Requirements for
Liquid-Filled Distribution Transformers Used in Pad-Mounted Installations,
Including Unit Substations.
E.
ANSI C57.12.28 - Switchgear and Transformers, Pad-Mounted Equipment Enclosure Integrity.
F.
IEEE C57.12.90 - Standard Test Code for Liquid-Immersed Distribution Power,
and Regulating Transformers and Guide for Short-Circuit Testing of Distribution
and Power Transformers (ANSI).
G.
ANSI/IEEE 386 - Separable Insulated Connector Systems for Power Distribution
Systems Above 600 V.
H.
ASTM D877 - Test Method for Dielectric Breakdown Voltage of Insulating Liquids
Using Disk Electrodes.
26 12 25 - 1
MEDIUM-VOLTAGE UNIT TRANSFORMERS
for
Liquid-Immersed
USAF Academy
Project No. XQPZ 10-0105C
1.05
I.
NEMA AB1 - Molded Case Circuit Breakers.
J.
CAN/CSA-C88-M90 - Electrical Power Systems and Equipment.
SUBMITTALS
A.
Product Data: Include rated nameplate data, capacities, weights, dimensions,
minimum clearances, installed devices, and features, location of each field
connection, and performance for each type and size of transformer indicated.
B.
Shop Drawings: Diagram power wiring.
C.
Coordination Drawings: Floor plans, drawn to scale, on which the following items
are shown and coordinated with each other, based on input from installers of the
items involved:
1.
2.
3.
4.
5.
6.
7.
1.06
Primary and secondary termination location
Dimensioned concrete base, outline of transformer, and required clearances
Ground rod and grounding cable locations
Primary and secondary pad (height) locations
Grounding pad (height) location
Transformer impedances
Primary and secondary voltages
D.
Qualification Data: For testing agency
E.
Source quality-control test reports
F.
Field quality-control test reports
G.
Follow-up service reports
H.
Operation and Maintenance Data: For transformer and accessories to include in
emergency, operation, and maintenance manuals
QUALITY ASSURANCE
A.
Testing Agency Qualifications:
An independent testing agency, with the
experience and capability to conduct the testing indicated, that is a member
company of the InterNational Electrical Testing Association (NETA) or is a
nationally recognized testing laboratory (NRTL) as defined by OSHA in
29 CFR 1910.7, and that is acceptable to authorities having jurisdiction.
1.
B.
Testing Agency's Field Supervisor:
Person currently certified by the
InterNational Electrical Testing Association or the National Institute for
Certification in Engineering Technologies to supervise on-site testing
specified in Part 3.
Product Options: Drawings indicate size, profiles, and dimensional requirements
of transformers and are based on the specific system indicated. Refer to
Division 1 Section "Product Requirements."
26 12 25 - 2
MEDIUM-VOLTAGE UNIT TRANSFORMERS
USAF Academy
Project No. XQPZ 10-0105C
1.07
C.
Electrical Components, Devices, and Accessories: Listed and labeled as defined
in NFPA 70, Article 100, by a testing agency acceptable to authorities having
jurisdiction, and marked for intended use.
D.
Comply with IEEE C2.
E.
Comply
with
ANSI C57.12.10,
IEEE C57.12.80.
F.
Comply with NFPA 70.
and
Store transformers so condensation will not form on or in units. Provide temporary
heating according to manufacturer's written instructions.
PROJECT CONDITIONS
A.
Service Conditions:
following:
1.
2.
3.
4.
5.
6.
7.
8.
1.09
IEEE C57.12.70,
DELIVERY, STORAGE, AND HANDLING
A.
1.08
ANSI C57.12.28,
IEEE C37.121, usual service conditions except for the
Exposure to significant solar radiation
Exposure to fumes, vapors, or dust
Exposure to explosive environments
Exposure to hot and humid climate or to excessive moisture, including steam,
salt spray, and dripping water
Exposure to excessively high or low temperatures
Unusual transportation or storage conditions
Unusual grounding-resistance conditions
Unusual space limitations
COORDINATION
A.
Coordinate size and location of concrete bases. Cast anchor-bolt inserts into
bases. Concrete, reinforcement, and formwork requirements are specified in
Division 3.
B.
Coordinate installation so no piping or conduits are installed in space allocated for
medium-voltage transformers except those directly associated with transformers.
PART 2 – PRODUCTS
2.01
MANUFACTURERS
A.
Subject to compliance with requirements, manufacturers offering products that may
be incorporated into the Work include, but are not limited to, General Electric.
26 12 25 - 3
MEDIUM-VOLTAGE UNIT TRANSFORMERS
USAF Academy
Project No. XQPZ 10-0105C
2.02
SECONDARY UNIT SUBSTATION, LIQUID-FILLED TRANSFORMERS
A.
The ratings of transformers shall be as follows:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Frequency: 60 Hz.
kVA: 750.
Impedance: 5.8% ± 5%.
Primary Voltage: 12.47 kV Delta connected.
Full-Capacity Voltage Taps: Four 2.5 percent taps, two above and two below
rated high voltage.
Primary B.I.L.: 95 kV.
Secondary Voltage: 277/480V wye connected. The neutral shall be solidly
grounded.
The transformer shall carry its continuous rating with average winding
temperature rise by resistance that shall not exceed 65°C.
Aluminum wound primary and secondary.
Altitudes above 7200 feet.
B.
The percent impedance voltage, as measured on the rated voltage connection,
shall be per ANSI C57.12.10.
C.
The dielectric coolant shall be listed less-flammable fluid meeting the requirements
of National Electrical Code Section 450-23 and the requirements of the National
Electrical Safety Code (IEEE C2-2002), Section 15. The dielectric coolant shall be
non-toxic per OECD G.L. 203, non-bio-accumulating and be readily and completely
bio-degradable per EPA OPPTS 835.3100.
1.
2.
3.
4.
5.
The base fluid shall be 100% derived from edible seed oils and food grade
performance enhancing additives. The fluid shall not require genetically
altered seeds for its base oil.
The fluid shall result in zero mortality when tested on trout fry.
The fluid shall be certified to comply with the US EPA Environmental
Technology Verification (ETV) requirements, and tested for compatibility with
transformer components.
The fluid shall be Factory Mutual Approved, UL Classified Dielectric Medium
(UL-EOUV) and UL Classified Transformer Fluid (UL-EOVK), Envirotemp
FR3™ fluid.
All transformer oil must be bulk tested for polychlorinated biphenyl’s (PCBs)
per ASTM D4059 and certified as having no detectable level of PCB.
D.
Panel type radiators for cooling shall be bolted directly to the tank for additional
cooling.
E.
The tank must be welded using precision cut, cold-rolled steel plate and equipped
with extra-heavy duty, welded-in-place lifting lugs and jacking pads. The tank base
must be designed to allow skidding or rolling in any direction.
F.
The transformer shall be of sealed tank construction of sufficient strength to
withstand a pressure of 7 psig without permanent distortion, and 15 psig without
rupturing.
26 12 25 - 4
MEDIUM-VOLTAGE UNIT TRANSFORMERS
USAF Academy
Project No. XQPZ 10-0105C
G.
The tank shall include a pressure relief valve as a means to relieve pressure in
excess of pressure resulting from normal operation. The venting and sealing
characteristics shall be as follows:
1.
2.
3.
4.
H.
The tank shall be complete with an anodized aluminum laser engraved nameplate.
This nameplate shall meet ANSI C57.12.00.
I.
The following standard accessories shall be provided:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
J.
De-energized tap changer
1.0-inch upper fill globe valve with filter press connection
1.0-inch drain/sampling valve
Automatic pressure relief valve
Welded cover with bolted manhole
Four lifting lugs
Liquid level gauge
Dial type thermometer
Pressure/vacuum gauge
Four ground pads
Primary and secondary terminals
The following additional accessories shall be provided:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
2.03
Cracking Pressure: 10 psig +/-2 psig
Resealing Pressure: 6-psig minimum
Zero leakage from reseal pressure to -8 psig
Flow at 15 psig: 700 SCFM minimum
Pressure Relief Device - 700 cfm.
Touch-up paint.
Rapid pressure rise relay.
Seal-in panel for rapid pressure rise relay.
Auxiliary contacts for pressure/vacuum gauge.
Auxiliary contacts for pressure relief device.
NEMA 4 terminal box with terminal strip (Wire items 5, 6 and 7 to this box.)
Insulation Temperature Rise: 65°C when operated at rated kVA output in a
40°C ambient temperature. Transformer shall be rated to operate at rated
kilovolt ampere in an average ambient temperature of 30°C over 24 hours
with a maximum ambient temperature of 40°C without loss of service life
expectancy.
Liquid level gauge.
Dial type thermometer.
Altitudes above 7200 feet,
IDENTIFICATION DEVICES
A.
Nameplates: Engraved, laser-scribed anodized nameplate for each transformer,
mounted with corrosion-resistant screws. Nameplates and label products are
specified in Division 26 Section “Basic Materials and Methods.”
26 12 25 - 5
MEDIUM-VOLTAGE UNIT TRANSFORMERS
USAF Academy
Project No. XQPZ 10-0105C
2.04
SOURCE QUALITY CONTROL
A.
Factory Tests: Perform design and routine tests according to standards specified
for components.
Conduct transformer tests according to ANSI C57.12.50
IEEE C57.12.90.
B.
Perform the following factory-certified tests on each transformer:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Resistance measurements of all windings on rated-voltage connection and on
tap extreme connections.
Ratios on rated-voltage connection and on tap extreme connections.
Polarity and phase relation on rated-voltage connection.
No-load loss at rated voltage on rated-voltage connection.
Excitation current at rated voltage on rated-voltage connection.
Impedance and load loss at rated current on rated-voltage connection and on
tap extreme connections.
Applied potential.
Induced potential.
Temperature Test: If transformer is supplied with auxiliary cooling equipment
to provide more than one rating, test at lowest kilovolt-ampere Class OA or
Class AA rating and highest kilovolt-ampere Class OA/FA or Class AA/FA
rating.
Note: Temperature test is not required if record of temperature test on an
essentially duplicate unit is available.
PART 3 - EXECUTION
3.01
3.02
EXAMINATION
A.
Examine areas and conditions for compliance with requirements for mediumvoltage transformers.
B.
Examine roughing-in of conduits and grounding systems to verify that bus entries
comply with layout requirements
C.
Examine walls, floors, roofs, and concrete bases for suitable mounting conditions
where transformers will be installed.
D.
Verify that ground connections are in place and that requirements in Division 26
Section "Grounding and Bonding for Electrical Systems" have been met.
Maximum ground resistance shall be 5 ohms at location of transformer.
E.
Proceed with installation only after unsatisfactory conditions have been corrected.
INSTALLATION
A.
Install transformers on concrete bases. Anchor transformers to concrete bases
according to manufacturer's written instructions.
26 12 25 - 6
MEDIUM-VOLTAGE UNIT TRANSFORMERS
USAF Academy
Project No. XQPZ 10-0105C
3.03
IDENTIFICATION
A.
3.04
CONNECTIONS
A.
3.05
Identify field-installed wiring and components and provide warning signs as
specified in Division 26 Section "Basic Electrical Materials and Methods."
Ground equipment according to Division 26 Section "Grounding and Bonding for
Electrical Systems."
FIELD QUALITY CONTROL
A.
Testing Agency: Engage a qualified testing and inspecting agency to perform field
tests and inspections and prepare test reports.
B.
Perform the following field tests and inspections and prepare test reports:
1.
2.
3.
4.
C.
Remove and replace malfunctioning units and retest as specified above.
D.
Test Reports: Prepare written reports to record the following:
1.
2.
3.
3.06
After installing transformers but before primary is energized, verify that
grounding system at substation is tested at specified value or less.
After installing transformers and after electrical circuitry has been energized,
test for compliance with requirements.
Perform visual and mechanical inspection and electrical test stated in
NETA ATS. Certify compliance with test parameters.
Test and adjust controls and safeties. Replace damaged and malfunctioning
controls and equipment.
Test procedures used.
Test results that comply with requirements.
Test results that do not comply with requirements and corrective actions
taken to achieve compliance with requirements.
FOLLOW-UP SERVICE
A.
Voltage Monitoring and Adjusting:
If requested by the Construction
Representative, perform the following voltage monitoring after Substantial
Completion but not more than six months after Final Acceptance:
1.
During a period of normal load cycles as evaluated by Construction
Representative, perform seven days of three-phase voltage recording at
secondary terminals of each transformer. Use voltmeters with calibration
traceable to National Institute of Science and Technology standards and with
a chart speed of not less than 1 inch (25 mm) per hour. Voltage unbalance
greater than 1 percent between phases, or deviation of any phase voltage
from nominal value by more than plus or minus 5 percent during test period,
is unacceptable.
26 12 25 - 7
MEDIUM-VOLTAGE UNIT TRANSFORMERS
USAF Academy
Project No. XQPZ 10-0105C
2.
Corrective Actions: If test results are unacceptable, perform the following
corrective actions, as appropriate:
a.
b.
3.
4.
Adjust transformer taps.
Prepare written request for voltage adjustment by electric utility.
Retests: After corrective actions have been performed, repeat monitoring
until satisfactory results are obtained.
Report: Prepare written report covering monitoring and corrective actions
performed.
END OF SECTION 26 12 25
26 12 25 - 8
MEDIUM-VOLTAGE UNIT TRANSFORMERS
USAF Academy
Project No. XQPZ 10-0105C