Section 26_12_71_00(16271)

Distribution Transformers

Rev # Description of Change Author WP # Date

26_12_71_00(16271)

26_12_71_00_European(16271) Rev History Hidden <Ctrl><Shift><8>

26_12_71_00(16271) Rev History Hidden <Ctrl><Shift><8>

7.1 Conversion of spec number 16271 to MF04 R. Lucius 11/16/05
number 26_12_71_00(16271)
8.0 Published(MF95) J. Pettus 05/09/06
8.1 Updated references, clarified alarm to power D. Dupy 01/07/08
monitoring requirements. Clarified core painting
requirements. Captured JFS1 lessons learned.
9.0 Review/Approval/Publish C. Bustos 01/14/08
9.1 Merged 50 Hz and 60 Hz specifications to create MMcGovern 02/28/11
new Baseline specifications. Alan McCall
Dwight Dupy
10.0 Published C. Bustos 03/03/11
10.1 Removed requirement for cooling fans on cast D. Campbell 10/31/12
resin transformers to be powered from source
external to transformer. Existing POR is to have
transformer fans powered from control power
transformer integral to transformer.
11.0 Published C. Bustos 11/01/12
11.1 Added Pacific Crest as approved supplier for oil- D. Campbell 2013.28.P1272 7/25/13
filled transformers in 60Hz regions and removed PCCB.51.F
General Electric (GE) as a qualified supplier per
approved WP. Added reference to 500V
transformers for OFA compressors and added
references to POR part numbers.
12.0 Published C. Bustos 7/30/13
12.1 Removed reference to 01_72_10_00(01721) – D. Campbell 11/4/13
Site Design Criteria. This spec is obsolete.
13.0 Published C. Bustos 11/6/13

1. General

1.1. Work Included

A. This Section specifies the requirements necessary to furnish and install: 1

1) Cast-coil, distribution transformers.
2) Liquid-filled [hermitically sealed or reservoir tank] [indoor or outdoor] distribution
transformers.
3) Liquid-filled, pad-mounted compartmental-type, outdoor distribution transformers.
1
Editor: Verify the type of transformer to be installed with the electrical work group. In the
past, this Section has been applied incorrectly and Intel is delivered the wrong transformer type.
This Section is used for three totally different types of transformers. Items 3 refers to pad-
mounted units, but rarely does Intel purchase and installed them.
IMCS Rev 13.0 dated 11/06/13 Page 1 of 27
Section 26_12_71_00(16271)
Distribution Transformers
 B. This specification is for use with MV/MV, MV/LV, LV/MV transformers.

C. This Specification is primarily written around requirements for 60Hz facilities and
applies to all projects as written, unless noted otherwise for 50 Hz facilities.

1.2. Related Work

A. Section 26_00_10_00(16010) – Basic Electrical Requirements

B. Section 26_05_29_71(16071) - Vibration Isolation For Electrical Systems

C. Section 26_05_53_00(16075) – Identification for Electrical Systems

D. Section 26_08_80_00(16080) – Electrical Testing

E. Section 26_13_16_43(16343) – Air Interrupter Switchgear

F. Section 26_13_19_41(16341) – Medium-Voltage Circuit Breaker Switchgear

G. Section 26_05_26_00(16060) – Grounding and Bonding for Electrical Systems

H. Section 26_05_29_00(16070) – Hangers and Supports for Electrical Systems

I. Section 26_05_13_00(16121) – Medium-Voltage Cables

J. Section 26_05_33_31(16131) – Conduit

K. Section 26_23_00_00(16430) – Low-Voltage Switchgear

L. Appendix at the end of this Section

1.3. Design Criteria, Quality Assurance, References and Regulatory

Requirements

A. In the event of a conflict between the Specifications and/or Drawings and the local or
regional regulatory rules/codes/standards, in addition to the applicable codes and/or
standards, the requirements of the more stringent shall prevail.

B. Standards, Listing, Labeling and Marking

1) For 60 Hz regions the following applies:
a. Transformers and electrical components shall be listed and labeled by a
nationally recognized testing laboratory (NRTL) such as: UL, ETL, CSA, or
FM; shall be listed and labeled as part of a UL-labeled assembly, or shall be
evaluated by a third party acceptable to the authority having jurisdiction (AHJ)
as suitable for the use intended. Apply labels at the manufacturer’s factory or
facility prior to shipment.
b. Conform to the following Standards:

IMCS Rev 13.0 dated 11/06/13 Page 2 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 i. IEEE C57.12.00-2010 – IEEE Standard General Requirements for Liquid-
Immersed Distribution, Power, and Regulating Transformers.
ii. IEEE C57.12.01-2005 – IEEE Standard General Requirements for Dry-Type
Distribution and Power Transformers Including Those with Solid-Cast
and/or Resin-Encapsulated Winding.
iii. IEEE C57.12.26-1992 (R1993) – IEEE Standard for Pad-Mounted,
Compartmental-Type, Self-Cooled, Three-Phase Distribution Transformers
for Use With Separable Insulated High-Voltage Connectors (34500 Grd
Y/19920V and Below; 2500 kVA and Smaller).
iv. IEEE C57.12.28-2005 – American National Standard Pad-Mounted
Equipment – Enclosure Integrity.
v. IEEE C57.12.90-2006 (R2009) – IEEE Standard Test Code for Liquid-
Immersed Distribution, Power and Regulating Transformers.
vi. IEEE C57.13-2008 – Standard Requirements for Instrument Transformers.
vii. IEEE Standard C57.12.91-2001(R2005) Standard Test Code for Dry-Type
Distribution and Power Transformers.
viii.IEEE C57.91-1995 (R2002) IEEE Guide for Loading Mineral-Oil-Immersed
Transformers. IEEE Std C57.91-1995/Cor 1-2002.
ix. IEEE C57.93-2007 – IEEE Guide for Installation of Liquid-Immersed Power
Transformers.
x. NECA NEIS 410-2005 – Standard for Installing and Maintaining Liquid-
Filled Transformers (ANSI).
xi. NEMA 250-2008 – Enclosures for Electrical Equipment (1000 Volts
Maximum), which contains the descriptions and applications, features and
test criteria, and design tests of all NEMA type enclosures (except for rotary
type apparatus) into a single document.
xii. NEMA 260-1996 (R2004) – Safety Labels for Pad-Mounted Switchgear and
Transformers Sited in Public Areas.
xiii.NEMA TP 1-2002 – Guide for Determining Energy Efficiency for
Distribution Transformers.
xiv. NEMA TP 2-2005 – Standard Test Method for Measuring the Energy
Consumption of Distribution Transformers.
xv. NEMA TP 3-2000 – Standard for the Labeling of Distribution Transformer
Efficiency.
xvi. NEMA TR 1-1993 (R2000) – Transformers, Regulators, and Reactors.
xvii. NEMA Type 3R or 4 – See NEMA 250.
2) For 50 Hz regions the following applies:
a. BS 148-2009 – Reclaimed Mineral Insulating Oil for Transformers and
Switchgear.
b. IEC 60296-2003 – Fluids for Electrotechnical Applications, Unused Mineral
Insulating Oils for Transformers and Switchger.
c. IEC 60076 – Power Transformers.
d. IEC 60529-2001 – Degrees of Protection Provided by Enclosures (IP Code).

1.4. Quality Assurance

A. Manufacturer: company specializing in distribution transformers with minimum

10 years of documented experience.

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Section 26_12_71_00(16271)
Distribution Transformers
 1.5. Environmental Requirements

A. The transformer shall be designed to operate at full load under the following
environmental conditions:
1) Ambient Temperature: 40 degrees C maximum, plus 35 degrees C average over 24
hours.
2) Relative Humidity: 50 percent at plus 40 degrees C Maximum, 90 percent at plus 20
degrees C maximum.
3) Altitude: below 3,000 feet (1,000 meters). Derate transformers for other altitudes
according to manufacturer’s recommendations.
4) Location:
a. Dry-Type Transformers: Indoor unless approved otherwise.
b. Liquid-Filled Transformers: Outdoor unless approved otherwise.

1.6. Submittals

A. Provide all required submittal data in electronic format on CD or DVD media in the
format indicated below. The following submittal information is required:
ITEM NO. SUBMITTAL REQUIREMENT FORMAT AS
INDICATED
26 12 71 00-01 Submit the following in addition With Bid
to other listed items:
1. Proposed submittal schedule.
2. Proposed Fabrication and
Shipment Schedule.
3. Long-lead component
receiving dates.
4. Fabrication time period.
5. Factory Test and Adjustment
period.
6. Factory Acceptance Test
(FAT) availability date.
7. Packaged system shipping
date, including expected
arrival at the jobsite..
26 12 71 00-02 Nameplate: Transformer Autocad .DWG Per
diagrammatic nameplate for each .DXF or PDF Submittal
unit Schedule
26 12 71 00-03 Design Tests: Data indicating PDF, MS Per
standard model design tests Word, MS Submittal
Excel Schedule
26 12 71 00-04 Test Report: Test report of PDF, MS Per
transformer furnished Word, MS Submittal
Excel Schedule
26 12 71 00-05 Transformer Damage: Thermal PDF, MS Per
and mechanical transformer Word, MS Submittal
damage characteristic curves. Excel Schedule
26 12 71 00-06 Shop Drawings: Dimensions, Autocad .DWG Per
efficiency, fabrication details, .DXF or PDF Submittal
IMCS Rev 13.0 dated 11/06/13 Page 4 of 27
Section 26_12_71_00(16271)
Distribution Transformers
 impedance, sound level, voltage Schedule
regulation, weight.
26 12 71 00-07 Seismic: Method of bracing Autocad .DWG Per
internal coils for seismic criteria .DXF or PDF Submittal
indicated in Section Schedule
01_72_10_00(01721).
CLOSEOUT SUBMITTALS
26 12 71 00-08 Maintenance manual including PDF, MS Before
operating and maintenance Word, MS Substantial
instructions Excel Completion
26 12 71 00-09 FM Approval Certificate PDF, MS Word Before
Substantial
Completion

1.7. Operation and Maintenance Data

A. Provide operating and maintenance instruction manuals.

2. Products

2.1. General

A. Ventilated Dry-Type Cast-Coil/Resin Secondary Distribution Transformers

1) Acceptable Manufacturers:
a. For 60 Hz regions the following applies:
i. ABB.
ii. Siemens (purchased from ABB).
iii. Square D (Schneider Electric) (purchased from ABB).
b. For 50 Hz regions the following applies:
i. Component Manufacturers (all regions except as noted)
(a) ABB, Resibloc range.
(b) Schneider Electric --- France Transfo range.
(c) Tesar.
ii. OEM Enclosure Vendors (all regions except as noted).
(a) Anord Controls Ltd – MV(medium voltage) to LV (low voltage)
transformers only.
(b) Davenham Engineering Ltd - MV to LV transformers only.
(c) ABB - MV to MV transformers only.
(d) Schneider Electric - MV to MV transformers only.
(e) ILS – MV to LV transformers only (additional supplier for Israel only).
(f) Afcon – MV to MV and MV to LV transformers (additional supplier for
Israel only).
(g) Enerco – MV to LV transformers only (additional supplier for Israel
only).
2) Product Requirements:

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Section 26_12_71_00(16271)
Distribution Transformers
 a. For 60 Hz regions the following applies:
i. Three-phase, self-cooled/forced air-cooled transformer.
(a) The 2500KVA/3300KVA cast-resin transformers purchased with the
large tripe-ended LV POR substations for logic facilities are included
with the POR part numbers in the Low Voltage, Metal Clad Switchgear
Spec (see appendix in 26_23_00_00(16430)).
(b) The transformers required for the 500V OFA compressors deviate from
the normal requirements since they are standard dry-type (not cast-resin)
transformers with no forced cooling. See details of these transformers in
26_12_71_00_EDP_01_SCHNEIDER. These are POR transformers for
logic facilities.
ii. The transformer unit shall have no clearance or combustible area restrictions
that would require the addition of a fire extinguishing system.
iii. Primary Voltage: As indicated on the Drawings. Provide four 2½ percent
full capacity taps, two above primary rated voltage, and two below primary
rated voltage taps. Taps shall be accessible through removable panels on
transformer. Primary-voltage taps shall have leads terminated at the coils
and equipped with provisions to change taps. For a given winding, the
number 1 or letter A shall be assigned to the tap providing the maximum
ratio of transformation.
iv. Impedance: as shown on the Drawings.
v. Basic Impulse Levels:
(a) Primary Voltage: 95 kV at 15 kV, 150 kV at 35 kV.
(b) Secondary Voltage: 10 kV at 480V; 60 kV at 4,160V.
vi. Transformers shall be Class AA/FA. Provide units having cooling fans
capable of allowing transformer to operate with a 33 1/3 percent increase of
capacity without exceeding temperature limits of the insulation system and
capable of delivering rated kVA continuously, either self-cooled, or fan-
cooled, when operating in a rated ambient temperature location, without
accelerated loss of life.
vii. Temperature Rise: 115 degrees C.
viii.Cooling Fans:
(a) Automatically control fan cooling equipment by a sensor attached to the
center-phase low-voltage winding. Include forced-air cooling system
fans, control wiring, LED pilot lights, and controller with test switch.
(b) Power fans from control power transformer integral to transformer.
(c) Provide adequate fusing and associated disconnect to protect fan motors.
(d) Group controls for fan system together on unit.
ix. Provide digital thermometer to indicate winding temperature in degrees C,
with maximum reading recall capability and contacts to control fans, plus
5A, 120V Form C contacts for remote monitoring of overtemperature and
fan run. Terminate power and control connections for fans in NEMA
Type 3R terminal box.
x. Maximum Sound Level (self-cooled/fan-cooled):
(a) 1500 kVA: 65/69 dB.
(b) 2000 kVA: 66/71 dB.
(c) 2500 kVA: 68/71 dB.
(d) 5000 kVA: 71/75 dB.

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Section 26_12_71_00(16271)
Distribution Transformers
 xi. Core:
(a) The transformer core shall be constructed of high-grade, grain-oriented
silicone steel laminations, with high magnetic permeability. Magnetic
flux density is to be kept well below the saturation point. The core shall
be cruciform in shape, with metered joints to keep core losses, exciting
current, and noise level at a minimum. The outside surfaces of the core
shall be protected from corrosion by painting with a suitable coating
after assembly.
(b) Bond the core to the frame by means of a flexible grounding strap.
(c) Provide, as a noise-reducing measure, vibration-isolating pads placed
between the core and coil assembly and the transformer base.
xii. Windings:
(a) Both primary and secondary voltage windings and all external bus-work
shall be copper or aluminum. High-voltage windings shall be separately
cast as rigid coils utilizing strip-disk winding construction. Low-voltage
windings shall utilize full-height sheet conductor material and shall be
fully encapsulated. Coils shall be supported by cast epoxy bottom
supports and space blocks and resilient top blocks, in order to absorb
thermal expansion and contraction of coils. There shall be no rigid
mechanical connection between HV and LV coils.
(b) Transformer properties shall be as follows:
(1) Thermal: Thermal strength to withstand fluctuating operating
temperatures to 130 degrees C and down to minus 30 degrees C
without damage to the insulation.
(c) The transformer shall be designed to carry short-time emergency
overloads.
(d) The windings shall not absorb moisture and shall be suitable for both
storage and operation in adverse environments, including prolonged
storage in 100 percent humidity at temperatures from
minus 40 degrees C to plus 40 degrees C and shall be capable of
immediately being switched on after such storage without predrying.
xiii.Primary Terminations: Air-filled compartment or air-interrupter switch.
Reference Section 26_13_16_43(16343). Terminals shall be copper, 4-hole-
bolted type, side-mounted on opposite side of transformer from secondary
(low voltage) terminals. Terminals shall be mounted directly on the ends of
the transformer high-voltage bus. The terminals shall be identified by H1,
H2, H3 for reference to A, B, C phases, respectively, and so indicated on the
nameplate. The air-filled chamber shall be full-height sheet steel structure
with bolted, removable front and side panels, open bottom, and sufficiently
sized for bottom feeder entrance.
xiv. Transformers will be utilized in a high-resistance neutral grounded system
and shall be fully insulated. The “XO” or neutral bus shall not be grounded
either internally or externally, and shall be accessible for connection to a
neutral grounding resistor (provided by others) to be located remote from the
transformer.
xv. Secondary Terminations:
(a) As indicated on the Drawings.
(1) Throat-Coupled Secondary Section
(i) Copper conductor.

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Section 26_12_71_00(16271)
Distribution Transformers
 (ii) Terminals shall be side-mounted on opposite side of transformer
from primary (high voltage) terminals. Connections to
secondary switchgear shall be by means of copper bus bar
having flexible sections of laminated copper strip. The air-filled
terminal chamber shall be made of sheet steel with bolted,
removable panels.
(2) Cable Connected Secondary Section
(i) Provide cable termination lug space per data sheet at end of
Section or per Drawings.
(ii) LV Bushing.
(iii) Porcelain with lug-hole pattern per ANSI P.
(3) Busway connected secondary section.
xvi. A ground cable lug shall be provided inside the termination chambers for
connecting the equipment grounding conductors and shields furnished with
the phase conductors.
xvii. Construction
(a) The transformer enclosure shall be of sheet steel panels bolted together,
suitable for outdoor installation, when indicated, and complete with the
following fittings:
(1) All ventilating openings shall be in accordance with NEMA and
National Electrical Code® standards for ventilated enclosures.
(2) Undercarriage shall be of steel plate, rigidly constructed, and fitted
with flangeless rollers and jacking pads.
(3) Lifting lugs to lift the complete transformer.
(4) Rating and connecting diagram plate.
(5) Grounding provisions shall consist of two ground pads welded on
the base or on core frames near the base. One additional ground pad
shall be furnished near each neutral bushing.
(6) High-Voltage Taps: Tap leads shall be terminated at the coils and
equipped with provisions for changing taps.
(7) Provide side, front and rear covers with removable captive screw-on
plates having formed edges on all sides. Captive screws or bolts
shall not be able to be easily knocked out of their retainers.
(8) Mounting of each assembly to base shall be capable of withstanding
seismic forces as specified.
(9) Hinge the side, front and rear covers to the transformer enclosure
frame with removable fasteners in case the covers have to be
completed taken off.
(10) When any door or panel is opened/removed, all internal
electrical components shall be rated to IP20 per IEC 60529.
xviii. Finish
(a) Clean enclosure steel members in phosphatized bath, coat with
rust-inhibiting primer, and follow with a baked enamel finish. Finish
shall have a minimum dry film thickness of 3 mils. Color shall be
ANSI 61, light grey.
xix. Factory Tests and Reports
(a) Provide certified test reports for each unit.

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Section 26_12_71_00(16271)
Distribution Transformers
 (b) Owner shall have the right to witness all tests and shall be notified at
least 5 working days in advance of any tests to allow his representative
to be present.
(c) Owner may assign an inspector to inspect the equipment, as well as to
expedite the fabrication and manufacturing of the transformer.
(d) Tests
(1) The following tests shall be performed on the transformer. Submit
certified test reports to the A/E prior to installation of the
transformer.
(i) Resistance measurements of all windings on the rated voltage
connection of each unit and at the tap extremes of one unit only.
(ii) Ratio tests on the rated voltage connection and on all tap
connections.
(iii) Polarity and phase-relation tests on the rated voltage
connections.
(iv) No-load loss at rated voltage on the rated voltage connection.
(v) Exciting current at rated voltage on the rated voltage connection.
(vi) Impedance and load loss at rated current on the rated voltage
connection of each unit and on the tap extremes of one unit only.
(vii) X/R ratio.
(viii) Applied potential tests.
(ix) Induced potential tests.
(x) Regulation at 100 percent and 80 percent power factor.
(xi) Temperature test.
xx. Nameplates: A stainless steel nameplate shall be mounted approximately at
eye level height on the transformer enclosure with a minimum of the
following information:
(a) Graphic representation of the connections of the high-voltage and low-
voltage windings.
(b) The kVA ratings at all cooling class ratings and temperature rises.
(c) Transformer impedance at rated temperature.
(d) Tap changer positions, voltages, and full-load currents at each tap
setting.
(e) Low-voltage rating and full-load current.
(f) Total weight, weight of core and coils, and weight of tank and fittings.
(g) Conductor material of each winding.
xxi. Factory-Installed Nameplates: Temporary tape labels.
xxii. Field-Installed Nameplates: The installing Contractor will provide
laminated plastic nameplates with engraved letters per the requirements of
Section 26_05_53_00(16075).
xxiii. Ambient Conditions: Transformers shall be designed for the
ambient conditions as defined in Section 01_72_10_00(1721).
b. For 50 Hz regions the following applies:
i. Indoor Dry-Type, Cast-Resin, Ventilated Distribution Transformers
(a) IEC 60076; three-phase, 50-Hz, self-cooled transformer, complete with
fan cooling.
(b) Refer to Appendix Sheet for further details.

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Section 26_12_71_00(16271)
Distribution Transformers
 (c) The transformers required for the 500V OFA compressors deviate from
the normal requirements of this section. See details of these transformers
in 26_12_71_00_EDP_01_SCHNEIDER. These are POR transformers
for logic facilities.
ii. Characteristics, MV/400V Secondary Transformers
(a) Electrical
(1) Continuous Rating AN/AF: as per Drawings.
(2) No-Load Voltage Ratio: as per Drawings.
(3) Vector Group: Dyn 11.
(4) Impedance: approximately 6.25 percent.
(5) Withstand Voltage, 50 Hz/1 minute:
(i) LV: 3 kV.
(ii) [HV at 10.5 kV: 28 kV.]
(iii) [HV at 22 kV: 50 kV.]
(6) Primary Impulse Level
(i) [HV at 10.5 kV: 75 kV.]
(ii) [HV at 22 kV: 125 kV.]
(b) System
(1) Nominal Primary Voltage: as per Drawings.
(2) Operating Voltage Range: +/- 5 percent.
(3) Nominal Secondary Voltage: 400/230V, four-wire.
(4) LT Neutral Star Point: solidly earthed.
(5) Phase/Frequency: three phase/50 Hz.
(6) System Fault Level
(i) [300 MVA at 110 kV level.]
(ii) [As per Drawings.]
(7) Neutral Star Point of [110 kV / 10.5 kV] [161 kV / 22 kV] Power
Transformer
(i) [Low resistance earthed.]
(ii) [As per Drawings.]
iii. Characteristics, MV/480V Secondary Transformers
(a) Electrical
(1) Continuous Rating AN/AF: as per Drawings.
(2) No-Load Voltage Ratio: as per Drawings.
(3) Vector Group: Dyn 11.
(4) Impedance: approximately 6.25 percent.
(5) Withstand Voltage, 50 Hz/1 minute
(i) LV: 3 kV
(ii) [HV at 10.5 kV: 28 kV.]
(iii) [HV at 22 kV: 50 kV.]
(6) Primary Impulse Level
(i) [HV at 10.5 kV: 75 kV.]
(ii) [HV at 22 kV: 125kV.]
(b) System
(1) Nominal Primary Voltage: as per Drawings.

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Section 26_12_71_00(16271)
Distribution Transformers
 (2) Operating Voltage Range: +/- 5 percent.
(3) Nominal Secondary Voltage: 480/277V, four-wire.
(4) LT Neutral Star Point: solidly earthed.
(5) Phase/Frequency: three-phase/50 Hz.
(6) System Fault Level
(i) [300 MVA at 110 kV level.]
(ii) [As per Drawings.]
(7) Neutral Star Point of [110 kV / 10.5 kV] [161 kV / 22 kV] Power
Transformer
(i) [Low-resistance earthed.]
(ii) [As per Drawings.]
iv. Characteristics, MV/208V Secondary Transformers
(a) Electrical
(1) Continuous Rating AN/AF: as per Drawings.
(2) No-Load Voltage Ratio: as per Drawings.
(3) Vector Group: Dyn 11.
(4) Impedance: 5 percent.
(5) Withstand Voltage, 50 Hz/1 minute:
(i) LV: 3 kV.
(ii) [HV at 10.5 kV: 28 kV.]
(iii) [HV at 22 kV: 50 kV.]
(6) Primary Impulse Level
(i) [HV at 10.5 kV: 75 kV.]
(ii) [HV at 22 kV: 125kV.]
(b) System
(1) Nominal Primary Voltage: as per Drawings.
(2) Operating Voltage Range: +/- 5 percent.
(3) Nominal Secondary Voltage: 208/120V, four wire.
(4) LT Neutral Star Point: solidly earthed.
(5) Phase/Frequency: three phase/50 Hz.
(6) System Fault Level
(i) [300 MVA at 110 kV level.]
(ii) [As per Drawings.]
(7) Neutral Star Point of [110 kV / 10.5 kV] [161 kV / 22 kV] Power
Transformer
(i) [Low resistance earthed.]
(ii) [As per Drawings.]
v. Characteristics, MV/MV [3.3kV] [6.6kV] Secondary Transformers:
(a) Electrical:
(1) Continuous Rating AN/AF: as per Drawings.
(2) No-Load Voltage Ratio: as per Drawings.
(3) Vector Group: Dyn 11.
(4) Impedance: approximately 7.15 percent.
(5) Withstand Voltage, 50 Hz/1 minute:
(i) Primary

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Section 26_12_71_00(16271)
Distribution Transformers
 (ii) [HV at 10.5 kV: 28 kV.]
(iii) [HV at 22 kV: 50 kV.]
(iv) Secondary
(v) 10 kV.
(6) Primary Impulse Level
(i) [HV at 10.5 kV: 75 kV.]
(ii) [HV at 22 kV: 125kV.]
(b) System
(1) Nominal Primary Voltage: as per Drawings.
(2) Operating Voltage Range: +/- 5 percent.
(3) Nominal Secondary Voltage: as per Drawings, three wire.
(4) LT Neutral Star Point: low Impedance earthed or solidly earthed as
per Drawings.
(5) Phase/Frequency: three phase/50 Hz.
(6) System Fault Level
(i) [300 MVA at 110 kV level.]
(ii) [As per Drawings.]
(7) Neutral Star Point of [110 kV / 10.5 kV] [161 kV / 22 kV] Power
Transformer
(i) As per Drawings.
vi. Construction: The transformer enclosure shall be of sheet steel panels bolted
together, suitable for use in a unit substation and complete with the
following fittings:
(a) Lifting lugs to lift the complete transformer.
(b) Dial-type thermometer mounted behind visor on enclosure door, fitted
with maximum reading pointer and set of contacts for remote alarm and
trip complete with winding temperature sensors.
(c) Three sets of thermistors and relays for fan control, alarm, and trip.
(d) Fan control box to be mounted in the 480V, 400V, or 208V unit
substation incoming instrumentation compartment.
(e) Rating and connecting diagram plate.
(f) Earthing terminal, drilled, and tapped for 12-mm-diameter set screw.
(g) Undercarriage shall be of steel plate, rigidly constructed, and fitted with
flangeless rollers and jacking pads.
(h) Primary cable terminals shall be suitable for the connection of one three-
core copper conductor cable. The enclosure gland plate shall be on the
top directly over the transformer primary cable terminals.
(i) Flange on secondary side suitable for coupling to the 6,600V, 3,300V,
480V, 400V, or 208V switchgear cubicle, and low-voltage terminals
suitable for connecting with the three-phase and neutral switchgear
copper busbars. Refer to Section 26_13_19_41(16341), and
Section 26_23_00_00(16430).
(j) The high-voltage winding tappings shall be reconnectable by bolted
links positioned on the high-voltage side of the transformer. A warning
plate labeled DO NOT OPERATE TAPS UNLESS THE
TRANSFORMER IS DEAD shall be provided.
(k) Cooling grilles as required.

IMCS Rev 13.0 dated 11/06/13 Page 12 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 (l) Enclosure protection shall be IP 31 to IEC 60529. The top roof section
shall, in addition, be fully gasketed and shall overhang the enclosure so
that any leaks from pipework above will not enter the transformer.
(m) When any door or panel is opened/removed, all internal electrical
components shall be rated to IP20 per IEC 60529.
(n) The enclosure ventilation grilles shall be designed to prevent ingress of
water and foreign objects from touching live terminals. This protection
shall take the form of clear perspex sheeting, placed inside the grilles
opposite these live terminals, and designed so as not to affect the
ventilation requirements of the transformer during natural and forced air
operation.
(o) At the medium-voltage side, removable bus-links, manufactured from
circular solid copper bar machined flat at both ends, shall be provided
allowing temporary earthing clamps to be applied by maintenance
technicians and for testing of the cable without need for disconnection of
the cable conductors.
(p) On low-voltage busbar connections, earthing studs shall be provided,
allowing temporary earthing clamps to be applied by maintenance
technicians for protection against backfeeds when working on the
primary side.
(q) Hinged doors with key-type, tee-handle locks.
(r) Remote MV circuit breaker trip pushbutton.
(s) Transformer enclosure to be fitted with sapphire lenses, at least two on
the MV primary connection side and two on the MV or LV secondary
connection side, to enable external infra-red scanning of the MV and LV
connections to be performed safely.
vii. Windings:
(a) The transformer shall be double wound on a laminated core, insulated,
and encapsulated using fiberglass reinforced epoxy resin.
(b) The primary windings shall be connected in delta and have voltage
tappings of plus or minus 2.5 percent and plus or minus 5 percent.
(c) The secondary windings shall be connected in star and the fully-rated
star point shall be extended to the low-voltage terminations.
(d) The windings shall be insulated in Class F (minimum) materials.
viii.Rating: The transformer shall be capable of operating at 100 percent of its
AN rating continuously at all tap positions without the use of cooling fans.
ix. Cooling Fans:
(a) The transformer shall be fully equipped with cooling fans and all
necessary controls, including run test facility. There shall be capacity in
all current-carrying parts for the higher fan-cooled rating.
(b) Fan-cooled rating shall be 140 percent of natural-cooled rating.
(c) Fan power shall be 230V or 120V, one phase, 50 Hz, depending on
secondary transformer voltage. It shall be 230V, one phase, 50Hz for
either the 3,300V or 6,600V substations. The power supply to the fans
and fan controls for LV secondaries shall be provided by the unit
substation manufacturer and taken from the control voltage circuit within
the LV main circuit breaker instrumentation section. A separate 230V
supply will be provided by others for MV secondaries.

IMCS Rev 13.0 dated 11/06/13 Page 13 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 x. Short Circuit Stress: The transformer shall be capable of withstanding,
without damage, the electromagnetic forces arising under short circuit
conditions.
xi. Equipment Finish: Transformers and their accessories shall be adequately
protected against environmental conditions and corrosion. All external metal
surfaces shall be hot-dipped galvanized and painted with two coats of
finishing paint. The enclosure finished paint color shall be identical to the
switchgear color.
xii. Electrical Tests
(a) All transformers shall be tested at the transformer manufacturer’s works
in accordance with IEC 60076.
(b) The test certificates and result sheets shall be enclosed in folders together
with all technical information relating to the transformers and their
auxiliary equipment, all drawings associated with the transformer, and
the equipment operating and maintenance instructions descriptive
leaflets.
(c) The following tests may be subject to witnessing by the Contractor and
test results shall be furnished on completion:
(1) Measurement of winding resistances.
(2) Ratio, polarity, and phase relationships.
(3) Impedance voltage.
(4) Load losses.
(5) No-load losses and no-load current.
(6) Induced overvoltage withstand.
(7) Separate source voltage withstand.
(8) Insulation resistance.
(9) Zero sequence impedance test.
(d) Test certificates shall be presented for the following type tests:
(1) Temperature rise.
(2) Impulse voltage withstand.
3) To comply with EHS requirements, provide “Arc Flash & Shock Hazard” labels as
detailed below. The marking shall be located so as to be clearly visible to qualified
persons before examination, adjustment, servicing, or maintenance of the equipment.
a. The labels are available in two sizes:
i. 10 inches by 6 inches (250 mm by 150 mm).
ii. 3 inches by 2 inches (75 mm x 50 mm).

IMCS Rev 13.0 dated 11/06/13 Page 14 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 B. Liquid-Filled Secondary Distribution Transformers
1) Acceptable Manufacturers:
a. For 60 Hz regions the following applies:
i. ABB.
ii. Pacific Crest.
b. For 50 Hz regions the following applies:
i. ABB.
ii. Pauwels.
iii. B.C. Transformers (Schneider Electric Group).
iv. France Transfo (Schneider Electric Group).
v. Enerco (additional supplier for Israel only).
vi. Ardan (additional supplier for Israel only).
2) Liquid-filled Secondary Distribution Transformers
a. For 60 Hz Regions the following applies:
i. 3-phase, self-cooled transformer; frequency, 60 Hz.
ii. Capacity: as shown on the Drawings.
iii. Primary Voltage: As indicated on the Drawings, delta connected. Provide
two each 2½ percent full capacity above normal and full capacity below
normal primary taps, with externally-operated tap changer.
iv. Secondary Voltage: as shown on the Drawings.
v. Impedance: as shown on the Drawings.
vi. Basic Impulse Level:
(a) Step-Up Type: 34.5 kV Nominal System Secondary Voltage: 150 kV
and 15kV Nominal System Primary Voltage: 95 kV.
(b) Step-Down Type: 34.5 kV Nominal System Primary Voltage: 150 kV;
for 4.16 kV Nominal System Secondary Voltage: 60 kV; for 480 V
Nominal System Secondary Voltage: 30 kV.
vii. Cooling and Temperature Rise: Class ONAN/ONAF.
(a) Units from 750 kVA to 2000 kVA shall have cooling fans capable of
allowing transformer to operate with a 25 percent increase of capacity
without exceeding 55 degrees C rise over a 40 degree C ambient.
(b) Units 2500 kVA to 7500 kVA shall have cooling fans capable of
allowing transformer to operate with a 25 percent increase of capacity
without exceeding 65 degrees C rise over a 40 degrees C ambient.
(c) Units 10000 kVA and above shall have two-stage cooling fans.
(1) The first stage shall be capable of allowing transformers to operate
with a 33 percent increase of capacity without exceeding 65 degrees
C rise over a 40 degrees C ambient.
(2) The second stage shall be capable of allowing transformers to
operate with a 66 percent increase of capacity without exceeding
65 degrees C rise over a 40 degrees C ambient.
viii.Maximum Sound Level (self-cooled/fan cooled):
(a) 1500 kVA: 58/67 dB.
(b) 2000 kVA: 61/67 dB.
(c) 2500 kVA: 62/67 dB.
(d) 3000 kVA: 63/67 dB.
(e) 5000 kVA: 65/68 dB.
IMCS Rev 13.0 dated 11/06/13 Page 15 of 27
Section 26_12_71_00(16271)
Distribution Transformers
 (f) 10000 kVA: 66/68 dB.
(g) 12000 kVA: 69/69 dB.
ix. Units with fans or shall be equipped with dial-type thermometer with
contacts to control fans. All power and control connections for fans shall
terminate in a NEMA Type 4 terminal junction box. Fan power and control
shall be 120 volts, single-phase with the source of power provided by others.
Provide dry contacts to indicate fan operation and overtemperature, and
overpressure.
x. Control panel shall have space heater.
xi. Liquid (Indoor and Outdoor Locations):
(a) Less Flammable Fluid Type: FM (Factory Mutual) Approved vegetable
oil based, biodegradable dielelectric insulating fluid having a fire point
of 300 degrees C or greater, certified as containing zero detectable PCBs.
The nameplate shall indicate the type of fluid content and other PCB
content at the time of manufacture.
xii. Accessories:
(a) Magnetic dial-type liquid level gauge (Device 71) with alarm contact.
(b) Dial-type thermometer (Device 26) with alarm contact.
(c) Stainless steel diagrammatic nameplate on side of unit.
(d) One-inch upper filter press and filling plug.
(e) One-inch drain valve with one-half-inch sampling port. Port shall be
accessible without needing to de-energize the transformer.
(f) Vacuum-pressure gauge with alarm contact.
(g) Pressure relief valve.
(h) Install terminal strip in properly rated enclosure for alarm contacts.
xiii.Windings: copper or aluminum.
xiv. Current Transformer (CT)
(a) 10 MVA and larger
(1) Low resistance ground (Neutral): C200, 400/5.
(2) Differential Protection (Primary Winding): C200, 600/5.
(3) Bus Differential Protection (Secondary Winding): C200, 600/5.
(4) Line Protection (Primary Winding): C200, 1200/5.
(b) 2.5 MVA up to 10 MVA
(1) Low resistance ground (Neutral): C200, 400/5.
(2) High resistance ground (Neutral): None.
xv. Less Flammable Fluid Type
(a) Rapid Gas Pressure Relief Relay (Device 63) with trip: Qualitrol 910.
(b) Winding thermal device (Device 49) with indication and alarm contact.
xvi. Primary Terminations: air-filled compartment. Bushings shall be porcelain
or cast-resin epoxy side mounted on opposite side of transformer from
secondary bushings. Provide standard NEMA pads.
xvii. Transformers utilized in a resistance neutral grounded system shall
be fully insulated. The “XO” or neutral bus shall not be grounded either
internally or externally, and shall be accessible for connection to a neutral
grounding resistor, provided by others, remotely located from the
transformer.
xviii. Secondary Terminations:

IMCS Rev 13.0 dated 11/06/13 Page 16 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 (a) Outdoor locations: air-filled compartment. Accommodate size,
quantity, and type of cables shown on data sheet.
(b) Indoor locations: completely assembled and close-coupled to switchgear
or bused to switchgear as indicated on the one-line diagrams. Bushings
shall be porcelain or cast-resin epoxy side mounted on opposite side of
transformer from primary bushings.
(c) Provide standard NEMA termination pads.
xix. Other Accessories: secondary current transformers.
xx. Finish: tank cleaned in phosphatized solution, coated with rust-inhibiting
primer, followed with baked enamel finish. Finish shall have a minimum
dry film thickness of 3 mils. Color per manufacturer’s standard.
xxi. When any door or panel is opened/removed, all internal electrical
components shall be rated to IP20 per IEC 60529.
xxii. Factory Tests and Reports: Provide certified test reports to
Contractor on each unit for the following:
(a) Winding resistance.
(b) Ratio, polarity, and phase relation.
(c) No-load, full-load loss tests.
(d) Exciting current, impedance, X/R ratio.
(e) Applied and induced potential tests.
xxiii. Nameplates: A stainless steel nameplate shall be mounted
approximately at eye level height on the transformer enclosure with a
minimum of the following information:
(a) Graphic representation of the connections of the high-voltage and low-
voltage windings.
(b) The kVA ratings at all cooling class ratings and temperature rises.
(c) Transformer impedance at rated temperature.
(d) Tap changer positions, voltages, and full-load currents at each tap
setting.
(e) Low-voltage rating and full-load current.
(f) Total weight, weight of core and coils, and weight of tank and fittings.
(g) Conductor material of each winding.
(h) Oil type.
xxiv. Factory-Installed Nameplates: temporary tape labels.
xxv. Field-Installed Nameplates: The installing Contractor shall provide
and install laminated plastic with engraved letters per the requirements of
Section 26_05_53_00(16075).
xxvi. Less Flammable Liquid Type Nameplates for transformers less than
10MVA: Shall bear the FM Approval Mark.
xxvii. POR Part Numbers for Logic Facilities:
(a) The part number for the Schneider Electric 7.5MVA/9.325MVA oil-
filled transformers purchased for the large triple-ended POR MV
substations is 7500UNITSUBLFXFMR.
(b) The Siemens 7.5MVA/9.325MVA oil-filled transformers purchased for
the large triple-ended POR MV substations are included with the POR
part numbers in the Medium Voltage Circuit Breaker Switchgear Spec
(see appendix in 26_13_19_41(16341)).

IMCS Rev 13.0 dated 11/06/13 Page 17 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 (c) The part number for the Schneider Electric 12/16/20MVA step-up oil-
filled transformers for D1X style EGEN buildings is
12000UNITSUBLFXFMR.
b. For 50 Hz regions the following applies:
i. ONAN sealed type transformer with integral filling, suitable for connection
to a power distribution system as per Appendix A below.
ii. Transformer design criteria:
(a) Electrical:
(1) Continuous Rating ONAN: as per Appendix A.
(2) No-Load Voltage Ratio: as per Appendix A.
(3) Vector Group: Dyn 11 (Delta/Star), star point solidly earthed.
(4) Impedance: 6.25 percent.
(5) Withstand Voltage, 50 Hz/1 minute:
(i) HV, 28 kV.
(ii) LV, 3 kV.
(6) MV System Impulse Level: 75 kV.
(7) Voltage tappings: plus or minus 2.5 per cent on the MV primary
side.
(b) Typical MV supply system, example shown below:
(1) Nominal Voltage: 10,500V.
(2) Operating Voltage Range: 9,975V to 11,025V.
(3) Phase/Frequency: three phase/50Hz.
(4) System Fault Level: 500 MVA at 10.5 kV.
(5) Connection of Main 110kV/10.5kV Power Transformer: YDY,
earthing of 10.5kV system is via 10 ohms, 600 Amp, 10 second
resistor.
iii. Transformer Construction
(a) Mounted firmly on skid outside and including:
(1) Lifting lugs to lift the complete transformer.
(2) Galvanised steel container or cast concrete containment installed
beneath the transformer and sized to contain 110 percent of the
volume of transformer oil. Designed to be easily drained of oil or
rainwater, supplied by others.
(3) Nameplate including rating, volume of oil, electrical parameters and
connection diagram. Include transformer identification nameplate.
(4) MV cable terminals shall be suitable for the connection of one three-
core copper conductor cable and shall be suitable for outdoor
installation. The enclosure gland plate shall be on the bottom
directly under the transformer MV cable terminals.
(5) LV terminals: IP56 terminal box in air and of sufficient size for the
required number of large diameter feeder cables and suitable for
outdoor installation.
(6) DGPT protection instrument in an IP 56 rated enclosure with
auxiliary contacts to indicate oil level, oil temperature (2 contacts)
and over pressure
(7) When any door or panel is opened/removed, all internal electrical
components shall be rated to IP20 per IEC 60529.

IMCS Rev 13.0 dated 11/06/13 Page 18 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 (8) Control panel shall have space heater.
(9) Pressure relief valve: Oil flow shall be directed downwards.
(10) Secondary star points shall be fully rated and brought out
separately to earthing terminals, each located in IP56 terminal boxes.
(11) Frame earthing terminal drilled and tapped for an M12
setscrew.
(12) The undercarriage shall be of sheet steel, rigidly constructed
and fitted with flangeless rollers where the transformer is installed in
a concrete bund.
(13) The manufacturer shall test the oil in accordance with BS
148/IEC 60296.
(b) Short Circuit Stress: The transformer shall be capable of withstanding,
without damage, the electromagnetic forces arising under short circuit
conditions.
(c) Equipment Finish: Transformers and their accessories shall be
adequately protected against environmental conditions and corrosion.
All external metal surfaces shall be hot-dipped galvanised and painted
with two coats of finishing paint. The enclosure finished paint colour
shall be the manufacturers standard colour.
iv. Electrical Tests
(a) All transformers shall be tested at the transformer manufacturers works
in accordance with IEC 60076.
(b) The test certificates and results sheets shall be enclosed in folders
together with all technical information relating to the transformers and
their auxiliary equipment, all drawings associated with the transformer,
and the equipment operating and maintenance instructions descriptive
leaflets.
(c) The following routine tests may be subject to witnessing by the
Contractor and test results shall be furnished on completion:
(1) Measurement of winding resistances.
(2) Ratio, polarity, and phase relationships.
(3) Impedance voltage.
(4) Load losses.
(5) No-load losses and no-load current.
(6) Induced over voltage withstand.
(7) Separate source voltage withstand.
(8) Insulation resistance.
(d) Test certificates shall be presented for the following type tests:
(1) Temperature rise.
(2) Impulse voltage withstand.

C. Liquid-Filled, Pad-Mounted Compartmental-Type, Outdoor Distribution Transformers 2

1) For 60 Hz regions the following applies:
a. Acceptable Manufacturers:
2
Editor: This transformer is similar to pad-mounted transformers utilities use to serve
smaller commercial buildings. A good application for this type of transformer is for a warehouse
or project building that is usually fed from a radial feeder via pad-mounted switchgear. Note the
differences between this Article and Article B.
IMCS Rev 13.0 dated 11/06/13 Page 19 of 27
Section 26_12_71_00(16271)
Distribution Transformers
 i. ABB
ii. Pacific Crest.
b. Temperature Ratings: Average temperature rise shall not exceed 65 degrees C
when transformer is operated at full nameplate rating in a 30 degree C ambient
(average), 40 degree C maximum per ANSI standards.
c. Transformer Cooling and Power Rating:
i. Self-cooled (OA).
ii. Power ratings as shown on the Drawings.
d. Primary Voltage:
i. Two 2½ percent full capacity above and below normal primary taps.
ii. Tap changer shall be adjustable only with the transformer de-energized,
including provisions for a padlock provided by others; locate handle in high-
voltage compartment.
iii. Basic Impulse Level (BIL):
(a) 15.0 kV Primary Voltage: 95 kV BIL.
(b) 25.0 kV Primary Voltage: 150 kV BIL.
iv. Voltage ratings as shown on the Drawings.
e. Secondary Voltage:
i. BIL: 30 kV.
ii. Voltage ratings as indicated on the Drawings.
f. Frequency: 60 Hz.
g. Impedance: as shown on the Drawings.
h. Sound Level: maximum sound levels per NEMA TR 1.

kVA Rating Sound Level

75 51 dB
112½ 55 dB
150 55 dB
225 55 dB
300 55 dB
500 56 dB
750 58 dB
1,000 58 dB
1,500 60 dB
2,000 61 dB
2,500 62 dB
i. Enclosure:
i. Compartmental type, tamper- and weatherproof for mounting on a pad.
ii. Transformer tank plus high- and low-voltage terminal compartment shall be
assembled as an integral unit.
iii. There shall be no exposed bolts, screws, or other fastening devices which are
externally removable.

IMCS Rev 13.0 dated 11/06/13 Page 20 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 iv. High- and low-voltage compartments shall be located side by side, separated
by a steel barrier.
v. Low-voltage compartment shall be on the right when viewed from the front.
vi. Compartments shall be full-height, air-filled, and with individual doors.
Compartments shall be 30 inches deep.
vii. High-voltage door shall not be accessible until low-voltage door is opened.
Low-voltage door shall have three-point latching mechanism with vault-type
handle with provisions for a single padlock. Doors shall have liftoff
stainless-steel hinges and door stops to hold doors open. Doors shall open at
least 100 degrees of arc.
viii.Front sill shall be removable to allow transformer to be rolled or skidded
over conduit stubs.
ix. Cabinet security for outdoor units shall be in accordance with the test
procedures and requirements of IEEE C57.12.28. Secure the access door by
one or more captive ½-inch to 13 UNC pentahead bolts made of a corrosion
resistant material. Entry into the low-voltage section of 4,160V or 480V
units shall require two separate procedures; the first procedure shall consist
of opening the low-voltage door and the second procedure shall be
contingent upon completion of the first procedure and shall consist of
opening a second secured door or removal of an approved non-hygroscopic
drop-in barrier. The second door or barrier shall be stenciled 4,160 V or
480V.
x. When any door or panel is opened/removed, all internal electrical
components shall be rated to IP20 per IEC 60529.
j. Windings:
i. High- and Low-Voltage Windings: aluminum or copper.
ii. Assembly shall be of wound coil construction.
k. Core:
i. Constructed of high-grade, high-magnetic permeability, grain-oriented
silicon steel laminations.
ii. Magnetic flux density shall be kept well below the saturation point.
iii. Core shall be three legged for delta-wye transformers.
iv. The core shall be grounded to the tank by means of a flexible grounding
strap.
l. Transformer Tank and Radiators:
i. Design the tank and radiators to withstand 7-psig pressure per ANSI and
NEMA standards.
ii. Tank cover shall be welded on top cover with nonorganic gasket provided
between tank and cover.
iii. Provide hand-hole with gasket in top of tank.
iv. Tank shall remain effectively sealed for a top oil temperature range of 50
degrees C to 105 degrees C.
v. Weld the radiators to the back and sides of the transformer as required.
vi. Base shall permit jacking, rolling, or skidding. Jacking pads shall be flush
with the enclosure. Provide four lifting lugs.
vii. Tanks shall be shot-blasted prior to application of primer and final finish.
Final finish shall be enamel, ANSI 61, light gray, 3-mil dry film thickness.
m. Coolant:

IMCS Rev 13.0 dated 11/06/13 Page 21 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 i. Transformers shall be vacuum dried prior to filling and vacuum filled with
degassed and dried fluids.
ii. Less Flammable Fluid Type: FM (Factory Mutual) Approved vegetable oil
based, biodegradable dielelectric insulating fluid having a fire point of 300
degrees C or greater, certified as containing zero detectable PCBs. The
nameplate shall indicate the type of fluid content and other PCB content at
the time of manufacture.
n. Primary (High-Voltage) Terminations: Air-filled compartment. Bushings shall
be porcelain or cast-resin epoxy. Provide 200A externally clamped universal
design primary bushing wells. Bushing wells shall accept loadbreak-bushing
inserts per ANSI requirements.
o. Loadbreak On/Off Switch: Construct outdoor transformer units with a 200A
continuous full load current (10,000A symmetrical momentary and close and
latch current) three-phase gang-operated on/off switch located in the high-voltage
compartment, and suitable for hot stick operation with the cables in place. The
basic impulse insulation level shall be the same as the primary winding. The
switch shall be hookstick operable and switch positions shall be clearly and
permanently identified.
p. Transformers utilized in a high-resistance neutral grounded system shall be fully
insulated. The "XO" or neutral bus shall not be grounded either internally or
externally, and shall be accessible for connection to a neutral grounding resistor
(provided by others) to be located remote from the transformer.
q. Secondary (Low-Voltage) Terminations:
i. Bushings: cast-resin epoxy, with blade-type spade terminals with NEMA
standard hole-spacing.
ii. Low-voltage neutral shall be an insulated bushing grounded to the
transformer tank by a removable grounding strap.
r. Accessories:
i. Copper ground pads with NEMA-spaced holes externally attached to the
tank on both the low- and high-voltage face of tank transformer.
ii. Stainless steel diagrammatic nameplate mounted in low-voltage
compartment of each unit per ANSI requirements.
iii. Factory-Installed Nameplates: temporary tape labels.
iv. Field-Installed Nameplates: The installing Contractor shall provide and
install laminated plastic with engraved letters per the requirements of
Section 26_05_53_00(16075).
v. 1-inch drain valve with ½-inch sample port. Port shall be accessible without
needing to de-energize the transformer.
vi. 1-inch fill plug.
vii. Liquid-level gauge.
viii.Pressure vacuum gauge.
ix. Pressure relief device.
x. Alarm contacts on gauges.
xi. Additional ¼-inch, National Pipe Thread (NPT) or National Fine (NF) thread
with gasket, inlet port on the tank wall above the 140ºC top oil level,
according to the manufacturer’s calculation, and shall be located so as not to
interfere with the use of the low-voltage terminals or the operating handle of
the low-voltage circuit breaker. This port is to be used for adding N2 to the
transformer when required.
IMCS Rev 13.0 dated 11/06/13 Page 22 of 27
Section 26_12_71_00(16271)
Distribution Transformers
 s. Standards and Factory Tests:
i. Transformer shall comply with all applicable portions of NEMA and ANSI
standards and shall include the following tests as minimum:
(a) Turns ratio.
(b) Polarity and phase rotation.
(c) No-load loss.
(d) Full-load loss.
(e) Excitation.
(f) Impedance and resistance.
(g) High potential.
(h) Induced potential.
ii. Provide certified test reports for each unit as part of the operations and
maintenance manual.
2) For 50 Hz regions the following applies:
i. None specified.

3. Execution

3.1. Inspection

A. Verify field measurements as shown on the Drawings and as instructed by manufacturer.

B. Verify that surfaces and pads are ready to receive work.

C. Verify that required utilities are available, in proper location, and ready for use.

D. Beginning of installation means installer accepts conditions.

3.2. Installation

A. Install in accordance with manufacturer’s instructions.

B. Provide any required anchoring.

C. Vibration Isolation: Follow the requirements of Section 26_05_29_71(16071).

D. Connection to Substation Switchboard/Switchgear

1) Connect transformer to switchboard/switchgear with buses and bolt the pieces
together to form a unified substation per the manufacturer’s instructions.

E. Nameplates
1) Provide and install nameplates per the requirements of
Section 26_05_53_00(16075).

F. Safety Labels
1) For 60 Hz regions the following applies:
a. Install safety labels to NEMA 260.
IMCS Rev 13.0 dated 11/06/13 Page 23 of 27
Section 26_12_71_00(16271)
Distribution Transformers
 2) For 50 Hz regions the following applies:
a. Install safety labels.

3.3. Adjusting

A. Adjust primary taps so that secondary voltage is within 2½ percent above nominal
voltage at no load.

3.4. Field Quality Control

A. Visual and Mechanical Inspection:

1) Inspect for physical damage. Remove shipping blocks and dampers.
2) Compare equipment nameplate information with latest single-line diagram and report
discrepancies.
3) Verify proper auxiliary device operation such as fans, indicators and tap changers.
4) Check tightness of accessible bolted electrical joints and adjust any vibration
isolators to manufacturer’s specifications.
5) Perform specific inspections and mechanical test as recommended by manufacturer.

B. Test distribution transformers in accordance with the requirements of

Section 26_08_80_00(16080).

3.5. Operational Acceptance Test Report

A. Use the OAT form at the end of this Section to record progress and results of installation
for completing the Operational Acceptance Test for each unit.

IMCS Rev 13.0 dated 11/06/13 Page 24 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 Appendix
60 Hz Transformer Details List (Summary)

Rated output, kVA

Type of transformer [Dry-type, cast-coil] [Oil-filled] [Pad-Mounted]
Type of cooling, dry-type cast-coil AA/FA
transformer
Type of cooling, oil filled transformer OA/FA
Type of cooling, pad-mounted OA
transformer
Number of phases Three
Frequency 60 Hz
Nominal primary voltage, principal tap
Secondary voltage
Primary connections Delta
Secondary connections Wye
Secondary winding [Solidly grounded] [Low resistance grounded] [High
resistance grounded]
Incoming conductors
Outgoing conductors
[Secondary connection] [Close-coupled to switchgear bus]
Taps Off-circuit tap changer on primary windings, all taps fully
rated and insulated; four 2.5 percent (two above and two
below nominal voltage)
Ambient temperature 40 degrees C, maximum
Sound level

IMCS Rev 13.0 dated 11/06/13 Page 25 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 Appendix
50 Hz Transformer Details List (Summary)

Rated output, kVA

Type of transformer [Dry-type, cast-resin] [Oil-filled]
Type of cooling, dry-type cast-resin AN/AF
transformer
Type of cooling, oil filled transformer ONAN
Number of phases Three
Frequency 50 Hz
Nominal primary voltage, principal tap
Secondary off-load voltage
Primary connections Delta
Secondary connections Star
Phase relationship Dyn 11
Secondary star point Brought out, fully rated, and insulated.
Secondary winding [Solidly grounded] [Low resistance earthed]
Incomer arrangement, dry-type cast-resin Top-entry MV cable entry with terminals suitable for the
transformer connection of one three-core _____-square mm
XLPE/SWA/PVC copper conductor cable rated ____ / ____V
Incomer arrangement, oil-filled Bottom-entry MV cable box with terminals suitable for the
transformer connection of one three-core _____-square-mm
XLPE/SWA/PVC copper conductor cable rated
8,700/15,000V
Off-loading arrangement, dry-type cast- Secondary connections arranged to connect with three-phase
resin transformer and neutral busbars for coupling to the main incoming breaker
in the 6,600V, 3,300V, 480V, 400V or 208V switchboard
Off-loading arrangement, oil-filled Bottom-entry LV cable box with connection terminals
transformer arranged to connect with three-phase and neutral single core
_____- sqmm XLPE/AWA/PVC copper conductor cables,
_____ per phase and ____ per neutral, for coupling to the
main incoming breaker in a remote downstream LV
switchboard
Secondary Lugs, Size and Quantity Per
Phase
Tappings Off-circuit tap changer on primary windings, all taps fully
rated and insulated; four 2.5 percent (two above and two
below nominal voltage)
Ambient temperature 40 degrees C, maximum
Winding Double wound
Load Heavy industrial motive power and lighting load
Sound level Test in accordance with IEC 60076-10

IMCS Rev 13.0 dated 11/06/13 Page 26 of 27

Section 26_12_71_00(16271)
Distribution Transformers
 Operational Acceptance Test Report
Section 26 12 71 00
Distribution Transformers

CM/GC Contractor Test Date

Equipment ID: Equipment Type: Transformer

Tag number

1. Check for proper anchorage, required area clearances, and proper alignment. Yes No
2. Inspect equipment for cleanliness and physical condition. Inspect doors and
panels for dents, scratches, & other damage. All penetrations and knockouts Yes No
properly plugged and conduits seal.
3. Verify equipment identification tags are installed. Yes No
4. Verify nameplate data with single-line diagram. Yes No
5. Verify conduits are sized per Drawing package and meet NEC ®/IEC. Color-
Yes No
coded and labeled per Section 26_05_53_00(16075).
6. Verify conduits are installed and supported per
Sections 26_00_10_00(16010), Section 26_05_33_31(16131), Yes No
Section 26_05_29_00(16070) and NEC®/IEC.
7. Verify grounding and bonding is installed per Section 26_05_26_00(16060)
Yes No
and NEC®/IEC.
8. Verify that the test organization has tested the transformer per Section
Yes No
26_08_80_00(16080).
9. Verify all bus and cable connections are torqued to manufacturer’s
Yes No
specifications.
10. Ensure shipping restraints are removed. Yes No
11. Verify that the pressure-gauge for the oil compartment has the correct
Yes No
positive pressure indicated.
12. Verify that the OAT is complete for the medium-voltage cable per Section
Yes No
26_05_13_00(16121).
Note: Attach Test Reports. Note: Generate SOR for each checked above.

Signature and date of persons performing and witnessing test(s) - Witness shall be by GC or Owner’s Rep.

Performer: Date: Performer: Date:

Witness: Date: Witness: Date:

End of Section

IMCS Rev 13.0 dated 11/06/13 Page 27 of 27

Section 26_12_71_00(16271)
Distribution Transformers