Memorial Hermann Best Practices
July, 2013
SECTION 26 12 19 PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
PART 1 - GENERAL
1.01
WORK INCLUDED
A.
Comply with the provisions of Section 26 05 00.
B.
Provide three-phase pad-mounted transformers with separable high voltage connectors (dead
front).
1.02
RELATED SECTIONS
A.
Division 03: Concrete
B.
Section 26 05 13: Medium Voltage Cable
C.
Section 26 25 00: Enclosed Bus Assemblies
D.
Section 26 05 53: Identification for Electrical Systems
E.
Section 26 13 19: Medium Voltage Vacuum Interrupter Switchgear
F.
Section 26 13 16: Medium Voltage Fusible Interrupter Switchgear
G.
Section 26 23 00: Low Voltage Switchgear
H.
Section 26 24 13: Switchboards
I.
Section 26 24 19: Motor Control Centers
1.03
REFERENCES
A.
The 3-phase, pad-mounted, dead front transformers and protection devices in this specification
are designed and manufactured according to latest revision of the following standards (unless
otherwise noted).
B.
ANSI/IEEE C57.12.00, Distribution, Power, and Regulating Transformers, General Requirements
for Liquid-Immersed
C.
ANSI C57.12.26, Pad-Mounted, Compartmental-Type, Self-Cooled, Three-Phase Distribution
Transformers for Use with Separable Insulated High Voltage Connectors, High Voltage, 34 500
Grd Y/19 920 Volts and Below; 2500 KVA and Smaller, Requirements
D.
ANSI C57.12.70, Terminals Markings and Connections for Distribution and Power Transformers
E.
ANSI/IEEE C57.12.80, Terminology for Power and Distribution Transformers
F.
ANSI/IEEE C57.12.90, Test Code for Liquid-Immersed Distribution, Power and Regulating
Transformers and Guide for Short-Circuit Testing of Distribution and Power Transformers
G.
ASTM D877, Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using Disk
Electrodes
H.
DOE Part III 10 CFR Part 431, Energy Conservation Program for Commercial Equipment:
Distribution Transformers Energy Conservation Standards
PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
26 12 19 - Page 1
Memorial Hermann Best Practices
July, 2013
1.04
SUBMITTALS
A.
Manufacturer shall provide a minimum of eight (8) copies of following documents to owner for
review and evaluation in accordance with general requirements of Division 01.
B.
Product data and spare parts list. Include all ratings, weighs, sound levels, and cable terminal
data.
C.
Outline, nameplate, connection diagrams and other drawings of the transformer. Include front and
side 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 ANSI/IEEE C57.12.90, by Transformer
Serial Number to follow shipment.
F.
DOE Part III 10 CFR Part 431 compliance certificate
G.
Where applicable, the Kirk Key interlock scheme drawing and sequence of operation.
1.05
SYSTEM DESCRIPTION
A.
Pad-mounted, compartmental-type transformer shall consist of a transformer tank and two cableterminating compartments, one each for high and low voltage. Transformer tank and
compartments shall be assembled as an integral unit for mounting on a pad.
B.
There shall be no exposed screws, bolts, or other fastening devices that are externally
removable. There shall be no openings through which foreign objects such as sticks, rods, or
wires might contact live parts. There shall be means for padlocking compartment door(s).
Construction shall restrict entry of water into compartment so as not to impair transformer
operation.
1.06
A.
1.07
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
A.
Comply with Division 01.
B.
Manufacturer shall 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 3-phase pad-mounted
transformers with separable insulated high voltage connectors for 20 years.
REGULATORY REQUIREMENTS
PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
26 12 19 - Page 2
Memorial Hermann Best Practices
July, 2013
A.
Transformer shall comply with all referenced documents and standards listed within this section.
B.
Installation shall comply with the National Electrical Code, National Electrical Safety Code, EPA
regulations, and all state and local codes.
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.
B.
Deliver each transformer on individual shipping skids for ease of handling.
C.
Inspect and report concealed damage to carrier within specified time.
D.
Handle in accordance with manufacturer's written instructions to avoid damaging equipment,
installed devices, and finish. Lift only by installed lifting eyes.
1.11
PROJECT CONDITIONS (SITE ENVIRONMENTAL CONDITIONS)
A.
Follow industry standard practices before, during, and after liquid filled pad-mounted transformer
installation.
B.
Liquid-filled pad mounted transformer shall be located in areas 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
greater of 1 year from date of installation or 18 months from date of delivery.
FIELD MEASUREMENTS
Make all necessary field measurements to verify that equipment shall fit in allocated space.
PART 2 - PRODUCTS
2.01
A.
2.02
A.
2.03
A.
MANUFACTURERS
Approved manufacturers are:
1.
Cooper Power System
2.
Square D
3.
ABB
4.
Eaton Corporation
5.
Siemens
EQUIPMENT
Furnish three-phase pad-mounted, dead front transformers with voltage and KVA ratings as
indicated in drawings.
PRIMARY (INCOMING LINE) SECTION
Refer to the drawings for specific wire type and size. Construction is dead front with separable
insulated high-voltage connectors.
PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
26 12 19 - Page 3
Memorial Hermann Best Practices
July, 2013
B.
Provide distribution type internal mounted surge arrestors with standard voltage ratings per the
distribution system voltage level.
C.
Incoming primary section shall be equipped with three (radial feed) or six (loop or two source
feed), as indicated on drawings, 200-ampere bushing wells in accordance with ANSI C119.2.
D.
Three current-limiting fuses in loadbreak, dry-well fuse holders. Fuse holder shall accept general
purpose, distribution, current-limiting fuses with interrupting capacity of 50,000 amperes. Fuse
holders shall be located in primary compartment and be hot-stick operable for external
replacement of fuses. Loadbreak fuse holder shall be able to interrupt a minimum of 100
amperes. Non-load break type may be used with a radial feed or loop/radial feed switch.
E.
Switches
1.
Radial feed switch shall be an internal, oil-immersed, gang-operated, two-position (ONOFF), loadbreak, manually operated switch. Switch shall be able to switch transformer
full-load current. Switch handle shall be located in primary compartment and shall be hotstick operable.
2.
Alternate source switch shall be a primary selective switch to permit energizing
transformer from either of two primary sources (but not both). Alternate source switch
shall consist of two internal, oil-immersed, gang-operated, two-position (ON OFF),
manually operated, loadbreak switches with a mechanical interlock to prevent closing
both sources. Switches shall be able to switch transformer full-load current. Switch
handles shall be located in primary compartment and shall be hot-stick operable. Six
primary bushings shall be provided.
3.
Loop feed switch shall be an internal, oil-immersed, gang-operated, loadbreak, manually
operated switch for a looped, primary cable system. Switch shall be either 2, 2-position
switches or 1, 4-position switch. Switch shall be rated as indicated in drawings to permit
sectionalizing of a looped system. Switch handle(s) shall be located in primary
compartment and shall be hot-stick operable. Six primary bushings shall be provided.
4.
Loop/Radial Switch shall be a 4-position, oil-immersed, loadbreak, manually operated
switch combing loop-and radial-switch functions. It shall consist of a transformer switch
and a loop switch. Switch shall be rated as indicated in drawings.
2.04
TRANSFORMER SECTION
A.
Furnish liquid filled pad mounted transformers as indicated on drawings.
1.
Standard transformer oil meeting requirements of ANSI C57.106 and ASTM D-3487, with
a high dielectric strength, free from impurities, and with a high flash point.
2.
Fire Resistant Hydrocarbon Fluid, (FRHF) which is non-toxic. It shall be listed as a lessflammable fluid meeting the requirements of National Electrical Code 450-23 and the
National Electrical Safety Code Section 15. It shall have a minimum fire point of 300
degree C.
3.
The insulating fluid shall be BioTemp, Envirosafe or EnviroTemp or equal environmental
friendly type fluid. It shall be listed as a less-flammable fluid meeting the requirements of
National Electrical Code 450-23 and the National Electrical Safety Code Section 15. It
shall have a minimum fire point of 300 degree.
4.
Silicone liquid polymer with a viscosity of 50 centistokes at 25 degree C, a minimum fire
point of 300 degree C, and an oxygen index of 21. It shall meet the requirements of the
National Electrical Code 450-23 and the National Electrical Safety Code Section 15.
B.
General Construction
1.
Transformer shall be liquid-filled construction. It shall be designed and manufactured in
accordance with ANSI C57.12.00 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
PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
26 12 19 - Page 4
Memorial Hermann Best Practices
July, 2013
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
saturation point. Core construction shall include mitered joints to keep core losses,
excitation current, and noise level at a minimum.
Coils shall be neatly wound under tension, utilizing adhesive-coated electrical grade
insulating paper between LV and HV layers and between LV and HV windings.
Full-height, air-filled incoming and outgoing terminal compartments with hinged doors and
separated by a steel barrier shall be located side-by-side. Incoming compartment shall be
on the left, outgoing compartment on the right.
High-voltage compartment shall be accessible only after door to low-voltage
compartment has been opened.
Compartment hood shall be removable for pulling cables and making connections.
Compartment doorsills shall be removable to permit rolling or skidding unit into place over
conduit studs in foundation.
Compartments hinged doors shall be equipped to latch in open position. High-voltage
compartment door shall have a fastening device that is accessible only through lowvoltage compartment. Three point latching of the secondary door shall provide a secure,
rigid fit.
Door hinge assemblies shall be made of corrosion-resistant material. 3/8 inch (minimum)
diameter stainless-steel hinge pins shall be used.
Both compartment doors shall be able to be locked with a single padlock having a
maximum 1/2-inch diameter shackle.
Provide lifting provisions in accordance with ANSI Standards, as well as jacking and
rolling provisions.
Instruction nameplate shall be located in low-voltage portion of compartment and shall be
readable with cables in place. Where the nameplate is mounted on a removable part,
manufacturer's name, and transformer serial number shall be permanently affixed to a
non-removable part.
Transformer tank shall be sealed-tank construction with a welded main cover.
A bolted tamper-resistant hand-hole shall be provided in tank cover for access to internal
connections.
Provisions for tank grounding shall be supplied in both high- and low-voltage
compartments. These provisions shall consist of:
a.
For 500 KVA and below, 1/2-13 UNC tapped hole 7/16-inch deep;
b.
For 750 KVA and above: 2, 1/2-13 UNC tapped holes 1/2-inch deep.
C.
Ratings
1.
The transformer voltage and KVA shall be as indicated on the drawings.
2.
The transformer Basic Impulse Level shall be as indicated on the drawings and at a
minimum of 60 kV for 5 kV systems and 95 kV for 15 kV systems.
D.
Standard features
1.
Primary and secondary windings shall be copper
2.
Tap changer control shall be for de-energized operation only. It shall be externally
operable with a wrench and require at least two operator actions to change taps.
Transformer shall have four 2 1/2 % taps; two above and two below nominal voltage. Tap
changer shall be lockable
3.
Impedance shall be 5.75%
4.
Paint, ANSI 61
5.
60 Hz
6.
55/65 degree C Rise
7.
Delta - Wye connection unless indicated otherwise on drawings
8.
Primary taps: Two, 2 1/2 percent above and two, 2 1/2 percent below
E.
Accessories
1.
1-inch filling provision
2.
1-inch drain provision
3.
Pressure relief valve
PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
26 12 19 - Page 5
Memorial Hermann Best Practices
July, 2013
4.
5.
6.
7.
8.
9.
2.05
Liquid level indication
One-inch drain valve and sampler
Dial-type thermometer
Liquid-level gauge
Pressure-vacuum gauge
Internal lightning arrestors,
SECONDARY (OUTGOING / LOAD) SECTION
A.
Low voltage bushings shall be tinned, spade-type with 9/16-inch holes spaced on 1-3/4-inch
centers in accordance with latest revisions of applicable ANSI standards.
B.
For wye-wye connected units, high- and low-voltage neutrals shall be connected internally and
brought out through a bushing in secondary compartment.
2.06
A.
2.07
FINISH
The tank paint finish shall be neat clean and highly resistant to corrosion. Metal surfaces shall be
thoroughly cleaned of all foreign matter prior to painting. Finish shall be ANSI 61 gray paint.
TESTING
A.
No load loss
B.
Excitation current at rated voltage
C.
Polarity check
D.
Ratio check
E.
Low frequency dielectric tests at high and low voltage
F.
Mechanical leak test
G.
Load loss
H.
Impedance
I.
Production line impulse test
PART 3 - EXECUTION
3.01
EXAMINATION
A.
Verify that transformers are ready to install.
B.
Verify field measurements are as shown on Drawings.
C.
Verify that required utilities are available, in proper location and ready for use.
3.02
INSTALLATION
A.
Install per manufacturer's instructions.
B.
Install on concrete pad sized as recommended by the manufacturer.
PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
26 12 19 - Page 6
Memorial Hermann Best Practices
July, 2013
C.
Install an oil spill containment system where indicated on drawings and/or as required by EPA
regulations.
D.
Install all 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.
Test dielectric liquid to ASTM D877, using 25,000 volts minimum breakdown voltage, after
installing transformer and before energizing it from system.
C.
Inspect installed transformers for anchoring, alignment, grounding, and physical damage.
D.
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 switches, access doors, operating handles for free mechanical and/or electrical
operation as described in manufacturer's instructions.
B.
Adjust primary taps so that secondary voltage is within 2 percent of rated voltage.
3.05
CLEANING
A.
Clean transformers to remove construction debris, dirt, shipping materials.
B.
Repaint scratched or marred exterior surfaces to match original finish.
END OF SECTION
PAD-MOUNTED, LIQUID-FILLED, MEDIUM-VOLTAGE TRANSFORMERS
26 12 19 - Page 7