City And County of San Francisco
Office Of Contract Administration
Purchasing Division
Bid Proposal No. ITSF11000455/CD
Attachment D
Switchgear and Transformers for Calaveras Dam Replacement Project
TECHNICAL SPECIFICATION FOR TRANSFORMERS
PART 1 - GENERAL
1.01
A.
SUMMARY
Provide medium voltage pad-mounted compartmental type distribution transformer.
PART 2 - PRODUCT
2.01
TRANSFORMER
A.
General Description: Outdoor type, oil filled, self-cooled, pad-mounted, compartmental
type distribution transformer as manufactured by ABB Inc., Copper Power System or
General Electric.
B.
Electrical Characteristics:
C.
1.
Self cooled rating: 75KVA
2.
Primary voltage: 12KV
3.
Secondary voltage: 240 volts, 3 phase, 3 wire, 60 Hz
4.
Minimum BIL: 95KV
5.
Nominal AC Impedance in percent: 5.75.
6.
Temperature Rise: 65 degree C
7.
High voltage taps: two 2.5% taps above and two 2.5% taps below rated
voltage
Mechanical Construction:
1.
Transformer shall consist of:
a.
Radial feed primary cable terminating compartment with
externally-clamped bushing wells with load break inserts.
b.
Secondary cable terminating compartment with externallyclamped bushings with NEMA 6 hole spades.
c.
LBOR oil switch for primary switching of transformer.
d.
Overcurrent protection with bayonet-type expulsion fuses for both
primary and secondary protection.
ITSF11000455/CD
Attachment D – 1/17/2011
1 of 3
City And County of San Francisco
Office Of Contract Administration
Purchasing Division
Bid Proposal No. ITSF11000455/CD
Attachment D
Switchgear and Transformers for Calaveras Dam Replacement Project
e.
Transformer: All compartments shall be assembled as a
completely tamperproof unit for anchoring on a pad and covered
by a one piece cover dome so that it will shed water.
2.
Construct external surfaces of transformer tank, radiators, primary and
secondary terminating compartments from 13 USS gauge or thicker steel.
3.
Transformer shall have no externally removable screws, bolts, or other
fastening devices. Transformer shall have no opening through which
foreign objects can be inserted.
4.
Transformers must be capable of being lifted, skidded, and slid into place
on the mounting pad. Provide a removable sill for skidding into place
without disturbing the entrance cables.
5.
Internally interlock primary compartment door with secondary
compartment door. In addition, make provision for field installation of
key interlock of primary compartment door with transformer
sectionalizing oil switch.
6.
Make provisions for pad locking of the secondary compartment and for
cable exit in the side of secondary compartment above pad.
D.
Finish: Finish shall be weather resistant, light gray in color. For the exterior of
transformer tank, interior and exterior of primary and secondary cable compartments,
the minimum total dry film thickness shall be 3.5 mils.
E.
Accessories shall include:
1.
One-half inch oil sampling device and one inch drain valve.
2.
Liquid level gauge.
3.
Dial type thermometer.
4.
Provision for vacuum pressure gauge.
5.
Ground pads: weld to tank wall near the base, one each in the primary and
secondary compartments, copper faced or stainless steel 2” x 3 ½”, inch
with two holes spaced on 1-3/4” centers and tapped for ½” 13NC thread.
Minimum threaded depth of holes shall be ½”.
6.
Tap changer control handle in secondary compartment.
7.
Distribution class lightning arresters.
8.
Gasketed and bolted handhole under the weatherproof cover.
9.
Pressure relieve device.
ITSF11000455/CD
Attachment D – 1/17/2011
2 of 3
City And County of San Francisco
Office Of Contract Administration
Purchasing Division
Bid Proposal No. ITSF11000455/CD
Attachment D
Switchgear and Transformers for Calaveras Dam Replacement Project
PART 3 - EXECUTION
3.01
INSTALLATION
A.
All electrical installation shall be completed by others per the approved Contract
Drawings and the transformer manufacturer’s installation instructions. The
Contractor shall furnish the required installation drawings and instructions.
END OF ATTACHMENT
ITSF11000455/CD
Attachment D – 1/17/2011
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