SECTION III
SPECIFICATIONS
Three Phase Pad Mount Transformers
(Dead Front Configuration)
A.
General Electrical and Mechanical Features:
1.
New, not remanufactured.
2.
Three-phase, 60 HZ
3.
Mineral-oil filled, self-cooled, pad-mounted type distribution transformer,
kVA rating as shown on bid form, primary voltage 12.47 kV volts DELTA,
and with secondary voltage as shown on bid form. Transformer shall be
suitable for connection to a 12.47 kV WYE, multigrounded distribution
system.
4.
Secondary voltage as indicated on bid form.
5.
Impedance as per below:
75kVA to 500kVA – 2.5% to 3.5%
750kVA and above – as per ANSI C57.12.26 (5.3% to 6.2%)
6.
The transformer shall meet all applicable requirements of ANSI C57.12.26
except as otherwise specified herein.
7.
The maximum temperature rise above ambient at 100% KVA load shall
not exceed 65 degrees C.
B.
The primary connection shall be dead front and shall consist of six (6) 600A, fully
rated, non-loadbreak bushings. For each incoming circuit, bushings shall be
horizontally or diagonally-mounted side by side. Bushings shall be labeled as
H1A, H2A, H3A (left) and H1B, H2B, H3B (right). 600A bushings shall be
equipped with brass or tinned copper studs only – aluminum is not
acceptable.
C.
Three internal 600A load break switches, hot-stick operable from the front of the
transformer, to be located as shown in Figure 1. The switches shall be configured
as follows:
1.
Line Switch A
a.
Open (Off) – The internal 12.5kV buswork is not energized from
Source A.
b.
Closed (On) – The internal 12.5kV buswork is energized from
Source A.
2.
Line Switch B
a.
Open (Off) – The internal 12.5kV buswork is not energized form
Source B.
b.
Closed (On) – The internal 12.5kV buswork is energized from
Source B.
3.
Transformer Switch
a.
Open (Off) – The transformer is not energized from the internal
12.5kV buswork.
Revised 7/29/11
b.
Closed (On) – The transformer is energized from the internal
12.5kV buswork.
The operators for the internal 600A load break switches shall be mounted in the
primary compartment of the transformer.
The internal 600A load break switches shall be mounted in such a way as to
provide full access for hot-stick operation with a full complement of conductors on
all of the available primary bushings.
D.
Cable accessory parking stands shall be located adjacent to the bushing wells
with a minimum of 6.5 inches from the center line of the bushing to the center line
of the parking stand.
E.
The transformer windings shall be protected by three (3) dual sensing Bay-O-Net
type fuses located in the primary compartment. All Bay-O-Net fuseholders shall
be provided with plastic spill pans. The transformer shall include three spare
fuses of operation at 12.47kV.
F.
The transformer shall be equipped with an automatic pressure relief device,
pressure gauge, oil level gauge and an oil temperature gauge with resettable
drag needles.
G.
WYE connected secondaries shall have the secondary neutral brought out in the
secondary compartment through a fully insulated bushing (“XO”) and equipped
with a removable full ampacity ground strap.
H.
The four (4) low voltage bushings shall be fitted with appropriately sized spade
type terminals. Secondary bushing spades shall be designed in a staggered
arrangement with a minimum of 5 ½” horizontal clearance between spades and 3
¾” clearance from any sidewall.
The transformer must meet the requirements of ANSI 57.12.22-1989, Fig. 3 for
low voltage terminal arrangements and minimum dimensions.
I.
The transformer shall be equipped with a minimum of two (2) two-hole NEMA
ground pads located in the lower portion of the compartments, one in the primary
compartment and one in the secondary compartment.
Ground pads shall be ½ inch 13NC tapped holes, 7/16” deep. Ground pads shall
be capped before painting.
J.
The transformer shall be fitted with a one-inch upper filter press and filling plug or
cap and a one-inch drain valve with built-in sampling device. Such drain valves
shall be located at the bottom of the low voltage compartment.
K.
Transformer Termination Compartment Construction Requirements:
Revised 7/29/11
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
The transformer shall be of compartmental type construction with
completely separate compartments for both the primary and the
secondary.
The primary and secondary compartments shall be side by side, with the
secondary compartment on the right side when facing the transformer
front compartment.
The primary and secondary compartments shall be completely enclosed
with removable front sills and doors. Doors are to be removable only in the
fully-open position.
The high voltage compartment door shall be of the interlock type and shall
be secured by a ½ in. stainless steel pentahead bolt held in the center
frame which is accessible only after the low voltage door is opened.
The low voltage compartment door shall include a handle with a two (2)
point locking arrangement equipped with provisions for pad-locking. The
secondary compartment door handle to include a spring loaded captive
stainless steel pentahead bolt which will require loosening of the bolt to
permit operation of the handle.
An instruction nameplate shall be located on the inside of the low voltage
compartment and will clearly indicate the following:
a.
The connection diagram.
b.
The location of the protective devices.
c.
All other pertinent information related to the unit.
Footprint of transformer shall not exceed the following maximum
dimensions:
a.
78 inches wide, including radiators.
b.
70 inches deep, including radiators.
Stainless steel is to be used for all metal in contact with the foundation
(sill, side panels, and false bottom of tank area). All exposed hardware
shall be stainless steel.
Manufacturer must furnish certification that the transformer will meet ANSI
Standard on enclosure security standards.
The tank wall inside the compartment shall be painted light grey.
L.
The transformer tank shall include a fully gasketed cover that is fully detachable
for access to the interior of the tank, or approved alternate. It shall have a wraparound guard that is removable only when the compartment doors are opened
and shall enclose the tank cover nuts, or approved alternate.
M.
The transformer shall be equipped with lifting lugs or other suitable means for
safely lifting the unit.
N.
Each transformer shall meet, or exceed, Western Underground Committee Guide
2-13 for security and tamper-resistant operation.
O.
The transformer shall be provided with all required safety stickers and warning
labels.
Revised 7/29/11
P.
The transformer coating shall meet or exceed the latest EEI finishing guidelines
for pad mounted equipment and the successful vendor must provide certified test
reports insuring this requirement is met.
Color shall be Munsell No: 7.0 GY 3.29/1.5 (Ameritech Telephone Green) on the
outside. Inside the termination compartment, the tank wall, at minimum, shall be
painted light grey.
The manufacturer must furnish certification that the transformer will meet ANSI
Standard C57.12.29-1988 on finish.
Q.
The successful vendor shall provide certified test reports, which shall include
core and winding losses, on the transformer supplied under this bid.
R.
Manufacturers are to submit certification that the transformer does not contain
any measurable concentrations of PCBs.
S.
Transformer losses will be evaluated and combined with bid costs to determine
successful bidder(s), using the City’s Transformer Loss Evaluation formula
(Figure 2).
T.
Manufacturer will stencil appropriate part # on front of transformer (min. 3” high
numbers).
U.
Transformers shall include three – 5/8” holes located in the bottom sill below the
primary bushings for future installation of fault indicators. The holes shall be in a
horizontal pattern and centered in the sill below the primary compartment. The
holes shall be covered by a tamper-proof cover.
Revised 7/29/11
TRANSFORMER LOSS EVALUATION
(20 Year)
Lfe
=
Core and related no load losses
Lcu
=
Load Losses
Lt
=
Lfe
Pd
=
Typical Values
Cost of demand/losses/KW demand only
=
$ 8.82/KW
Pe
=
Cost of energy losses/KWHR; incremental =
+
Lcu
=
Total Losses
$ .02249
Combined loss cost calculation:
Assume load factor = 60% loss factor = 30%)
Pd
(Lfe)Pe =
Pd
(Lcu)Pe =
=
demand only =
energy cost
=
Lfe x 8760 x $ .02249
(A.)
Total, core loss cost
=
demand only =
energy cost
(B.)
Lfe x $ 8.82 x 12
Lcu x $ 8.82 x 12
= Lcu x 8760 x .3 x $ .02249
Total, load loss cost
=$
/Yr.
=$
/Yr.
=$
/Yr.
=$
/Yr.
=$
/Yr.
=$
/Yr.
Summary of cost Losses:
(A.)
Annual cost of No Load Losses
____________________
(B.)
Annual cost of Load Losses
____________________
Total Annual Cost (Lt = Lfe
+ Lcu)
=
____________________
TOTAL ANNUAL COST $________________ x 20 Years $ _______________
Figure 2
Revised 7/29/11