Issued 06-01-07
E.C.S.
INFORMATION SECTION
TRANSFORMERS
Section WTR00
Page 1 of 1
INDEX
SECTION WTR01: ELECTRICAL CONNECTIONS
PRIMARY ……………………………………………………………………….. Page 1
SERVICE DROPS FROM THREE-PHASE TRANSFORMER BANKS ….. Page 9
SECTION WTR02: INSTALLATION AND MAINTENANCE
GENERAL ………………………………………………………………………. Page 1
OVERHEAD TRANSFORMERS ……………………………………………... Page 1
PADMOUNTED TRANSFORMERS …………………………………………. Page 5
Issued 08-01-08
E.C.S.
INFORMATION SECTION
TRANSFORMERS
Section WTR01
Page 1 of 9
ELECTRICAL CONNECTIONS
1. PRIMARY
a. Standard Connections
Primary: 4.16 kV, 12.47 kV, 13.2 kV, 13.8 kV, 24.9 kV or 24 kV
3-Phase Wye-Wye for 120/208 or 277/480 Volt Services
0~ Angular Displacement
Additive Polarity Transformers Shown
Reverse X1 and X2 Leads for Subtractive Polarity Transformers
Section WTR01
Page 2 of 9
E.C.S.
INFORMATION SECTION
ELECTRICAL CONNECTIONS
Primary: 2.4 kV, 7.2 kV, 13.8 kV, 14.4 kV or 24 kV
3-Phase Delta-Wye for 120/208 or 2 77/480 Volt Services
30~ Angular Displacement
Additive Polarity Transformers Shown
Reverse X1 and X2 Leads for Subtractive Polarity Transformer
Issued 08-01-08
TRANSFORMERS
Issued 08-01-08
E.C.S.
INFORMATION SECTION
TRANSFORMERS
b.
Section WTR01
Page 3 of 9
ELECTRICAL CONNECTIONS
Maintenance Connections
Primary: 4.16 kV, 12.47 kV, 13.2 kV, 13.8 kV, 24.9 kV or 24 kV
3-Phase Floating Wye-Delta for 120/240 Volt Services
210~ Angular Displacement
Additive Polarity Transformers Shown
Reverse X1 and X3 Leads for Subtractive Polarity Transformers
Section WTR01
Page 4 of 9
E.C.S.
INFORMATION SECTION
ELECTRICAL CONNECTIONS
Primary: 4.16 kV, 12.47 kV, 13.2 kV, 13.8 kV, 24.9 kV or 24 kV
3-Phase Open Wye-Delta for 120/240 Volt Services
210~ Angular Displacement
Additive Polarity Transformers Shown
Reverse X1 and X3 Leads for Subtractive Polarity Transformers
A
B
C
N
a
b
c
N
Issued 08-01-08
TRANSFORMERS
E.C.S.
INFORMATION SECTION
Issued 08-01-08
TRANSFORMERS
Section WTR01
Page 5 of 9
ELECTRICAL CONNECTIONS
Primary: 2.4 kV, 7.2 kV, 13.8 kV, 14.4 kV or 24 kV
3-Phase Open Delta-Delta for 120/240 Volt Services
180~ Angular Displacement
Additive Polarity Transformers Shown
Reverse X1 and X3 Leads for Subtractiave Polarity Transformers
E.C.S.
INFORMATION SECTION
Section WTR01
Page 6 of 9
ELECTRICAL CONNECTIONS
Issued 08-01-08
TRANSFORMERS
Primary: 2.4 kV, 7.2 kV, 13.8 kV, 14.4 kV or 24 kV
3-Phase Delta-Delta for 120/240 Volt Services
180~ Angular Displacement
Additive Polarity Transformers Shown
Reverse X1 and X3 Leads for Subtractive Polarity Transformers
A
B
C
N
B
H1
X3
X2
a
b
c
N
H2
H1
X1
X3
A
X2
C
E.C.S.
INFORMATION SECTION
Issued 08-01-08
TRANSFORMERS
Section WTR01
Page 7 of 9
ELECTRICAL CONNECTIONS
Primary: 2.4 kV, 7.2 kV, 13.8 kV, 14.4 kV or 24 kV
3-Phase Delta-Delta for 120/240 Volt Services
0~ Angular Displacement
Additive Polarity Transformers Shown
Reverse X1 and X3 Leads for Subtractive Transformers
A
B
C
N
H1
X3
a
b
c
N
A
C
E.C.S.
INFORMATION SECTION
Section WTR01
Page 8 of 9
ELECTRICAL CONNECTIONS
Issued 08-01-08
TRANSFORMERS
Primary: 4.16 kV, 12.47 kV, 13.2 kV, 13.8 kV, 24.9 kV or 24 kV
3-Phase Wye-Wye for 120/208 or 277/480 Volt Services
0~ Angular Displacement
Addative Polarity Transformers Shown
Reverse X1 and X2 Leads for Subtractive Polarity Transformers
b'
A
C
PRIMARY
c
SERVICE
Issued 08-01-08
E.C.S.
INFORMATION SECTION
TRANSFORMERS
Section WTR01
Page 9 of 9
ELECTRICAL CONNECTIONS
2. SERVICE DROPS FROM THREE-PHASE TRANSFORMER BANKS
Low Voltage
High Voltage
(Phase-Ground)
KVA
240/480
120/240
8660 and Below
8661 and Above
8660 and Below
8661 and Above
Low-voltage Connections & Bushing Arrangement (Letters refer to illustrations below)
100 and less
167 and larger
A
B
C
D
E
F
Issued 06-01-07
E.C.S.
INFORMATION SECTION
TRANSFORMERS
Section WTR02
Page 1 of 17
INSTALLATION AND MAINTENANCE
1. GENERAL
a. Non-PCB Sticker for Distribution Transformer Identification
A white on blue sticker has been made available to identify transformers that contain non-PCB
oil. This sticker is applied by the manufacturer on new pole mounted transformers. It shall be
applied to unlabeled units by the Transformer Repair Shop only after a transformer has been
tested to contain, or filled with non-PCB transformer oil.
The sticker shall be applied by the transformer repair shops on all transformers containing nonPCB oil in the following locations:
1) Pole-mounted transformers.
-- Below the middle secondary bushing.
2) Padmounted transformers
-- Upper right-hand corner of the low voltage compartment door.
New padmounted transformers are labeled as non-PCB on the external nameplate.
Older transformers may be labeled as non-PCB in one of three ways:
IES - Blue Punch Card Label
IPW - 6 x 6 Blue and White Label
WP&L - Yellow Dot Label
b. Secondary Breakers on CSP Transformers
Voltages have been observed across the secondary terminals of distribution overhead and
padmount transformers whose primaries were energized but whose secondary breakers were
open.
Caution should be used when the secondary circuit breaker is open. There may be sufficient
coupling to the windings so that perceptible shock may be obtained from the secondary
terminals.
This voltage will generally be considerably less than 240 volts. In cases where it approaches or
exceeds 300 volts, it will be a very low capacity voltage source and very little current will be
available.
In addition to the possibility of this coupling, the secondary breaker contacts are not visible and
consequently the open circuit they are intended to provide cannot be visually confirmed.
For those reasons, transformer secondary breakers cannot be positively relied upon to
deenergize secondaries.
2. OVERHEAD TRANSFORMERS
a. Connections
1) Line-Equipment
Transformer connections should be made with a stirrup and hot line clamp. The sequence of
installation should be stirrup - hot line clamp - arrester - cutout, as shown in Figure 02-1 on
Page WTR02.3.
For transformers with tank mounted arresters, the sequence is stirrup, hot line clamp, cutout,
arrester.
Section WTR02
Page 2 of 17
E.C.S.
INFORMATION SECTION
INSTALLATION AND MAINTENANCE
Issued 06-01-07
TRANSFORMERS
2) Grounding
The correct method of grounding overhead distribution transformers is also shown in Figure
02-1 and 02-2:
1) The primary neutral bushing (if present) shall have a direct connection to the primary
neutral conductor or pole ground.
2) The transformer case ground shall be grounded to the pole ground. The preferred
method is to extend the primary neutral bushing jumper as shown on dual bushing
transformers.
3) The primary neutral conductor shall be bonded to the pole ground.
4) The secondary neutral bushing shall be connected to the system neutral through the
case ground jumper and the secondary cable neutral.
5) The grounding jumper shall be extended from the transformer case ground to the
secondary neutral bushing if the secondary neutral case ground jumper is missing.
Issued 06-01-07
TRANSFORMERS
E.C.S.
INFORMATION SECTION
Section WTR02
Page 3 of 17
INSTALLATION AND MAINTENANCE
The following drawings illustrate the correct grounding connections.
Section WTR02
Page 4 of 17
E.C.S.
INFORMATION SECTION
INSTALLATION AND MAINTENANCE
Issued 06-01-07
TRANSFORMERS
Issued 06-01-07
E.C.S.
INFORMATION SECTION
TRANSFORMERS
Section WTR02
Page 5 of 17
INSTALLATION AND MAINTENANCE
3. PADMOUNTED TRANSFORMERS
a. General
1) Clearances
See "Clearance" Information Section.
2) Mounting
Padmount transformers are designed for operation on a level surface. Excessive pad tilts
can result in exposed conductors within the transformer causing disruptive failures or
restrictive flow of oil through cooling fins resulting in overheating and decrease transformer
life.
3) Fusing
a) Oil in dry-well fuse canisters
On occasion, oil may be found inside the dry-well fuse canisters of padmounted
transformers.
The above condition, if left uncorrected, can become a potential hazard. Current limiting
fuses are intended to isolate the transformer from the line in the event of a faulted
transformer, severe overload, or secondary fault. These fuses are designed to operate in
a dry air environment which is provided by the dry-well canister. Any oil, water or other
contaminant in the canister may cause misoperation of the fuse. A hazard may exist
when working in close proximity to the fuse while the primary compartment door is open
and the fuse(s) attempts to operate for a fault or overload. The oil-soaked fuse element
can expel gases with enough pressure to eject the fuse holder assembly from the
canister.
Single or three-phase padmounted transformers with canisters known or found to be
contaminated with oil must be removed from service and repaired. This requirement
applies to both new and used transformers. If an in-service transformer is suspected of
having a leaking canister(s), it is recommended that the unit be deenergized from a
remote location before removing the fuse(s).
Report any transformers with oil in canisters to Electric Distribution Standards utilizing
"
Report of Unsatisfactory Material", Form 75-0476A.
b) Missing fuses in dry-well canisters
Infrequently, a padmount transformer may be received without current limiting fuses in
the dry-well canisters. Manufacturers will generally place a steel or wood rod in the drywell canisters in the unusual case they do not ship the transformers with fuses in place.
The manufacturer should, but does not always, place a tag inside the transformer
compartment warning that fuses are missing.
Section WTR02
Page 6 of 17
E.C.S.
INFORMATION SECTION
INSTALLATION AND MAINTENANCE
Issued 06-01-07
TRANSFORMERS
In some locations, transformers installed without proper fuses may not be adequately
protected from secondary faults. Therefore, the following precautions are recommended
to prevent any unnecessary transformer damage:
(1) Transformer repair shops should inspect all padmount transformers for the presence
of correct size fuses prior to sending the units to the district or installation site.
(2) All crews installing transformers should inspect for the presence of the correct size
fuses before energizing any unit.
(3) Be sure to take replacement fuses out of Stores stock, and not out of padmount
transformers.
(4) If an installed unit is suspected of not being properly fused, de-energize the
transformer and make the appropriate corrections in accordance with applicable
Safety Rules and Electrical Operating Practices.
Report any such occurrences to Electric Distribution Standards utilizing "Report of
Unsatisfactory Material", Form 75-0476A.
4) Protection
When installing transformers near parking lots, driveways, alleyways, etc., place concrete
filled or galvanized steel posts at the corners for protection from vehicular traffic.
b. Single-Phase
Single-phase padmount transformers are furnished with threaded stud secondary bushings.
This design allows for space savings, minimizing of compression and bolted fittings, and
reduced cable disturbance during changeouts.
The secondary terminal blocks are aluminum alloy of inline, multi-position, set screw design,
with "slip fit" mounting for quick disconnect capability. The blocks are disconnected from the stud
via (1 or 2) Allen style set screws.
E.C.S.
INFORMATION SECTION
Issued 06-01-07
TRANSFORMERS
Section WTR02
Page 7 of 17
INSTALLATION AND MAINTENANCE
Figure 02-3
APPLICATION
KVA
STUD
DIAMETER
THREAD
STUD
LENGTH
ITEM ID
25-175
5/8"
11-UNC-2A
1-1/4"
100314
100-167
1"
14-UNS-2A
1-3/4"
102099
Each terminal block consists of five (5) main tap positions and one (1) streetlight tap position.
The mains have a range of #4 to #350 MCM AWG, the streetlight tap ranges from #8 to #4
AWG. The streetlight position pressure screw may be a regular head machine screw or hex
Allen style set screw. All hex Allen style pressure set screws have either 5/16", or 3/8" sockets.
Terminal blocks are packaged in a kit of three (3) blocks and two (2) insulating boots.
1) Block Installation
The orientation of the terminal block on the transformer studs should be such that the set
screws are directed upward to the left when facing the transformer. This aligns the cable
holes at an angle for training the cables on a proper radius, rather than directly vertical.
Once oriented, the set screws are tightened (as per manufacturer's instructions) after the
block has been fully seated on the stud. On the neutral stud the jam nut provided is run
against the terminal block. Any jam nuts on phase stud bushings should be removed, and
only one should be used on the neutral bushing. This will allow the block to bottom out fully
onto the stud and achieve optimum set-screw pressure and electrical contact over the stud
length. The insulating boots can then be placed over the phase blocks for storage.
E.C.S.
INFORMATION SECTION
Section WTR02
Page 8 of 17
INSTALLATION AND MAINTENANCE
Issued 06-01-07
TRANSFORMERS
2) Grounding
One jam nut only shall be used on the neutral stud for making the ground strap connection
(if two jam nuts are provided, discard one). Install the block such that the ground strap is
fastened between the jam nut and the back of the terminal block.
Figure 02-4
3) Cable Application
The design allows for four (4) secondary cable runs. This leaves one (1) main position
vacant on the two phase blocks; do not use. One (1) streetlight circuit is allowed per
transformer, originating from one of the two phase blocks; the other is left vacant, do not
use. See the chart below:
Cable Application Chart
Positions
Block
Phase
Neutral
1
2
3
4
5
Cable
Cable
Cable
Cable
Vacant
Streetlight Tap
1 - Vacant
1 - Streetlight Cable
Ground
Cable
Cable
Cable
Cable
Streetlight Neutral
The neutral block, however, is filled: With four (4) secondary cable neutrals, one (1)
streetlight neutral, and the "fifth" main position with the ground conductor.
Positions should be filled from the rear outward (Position #1, 2, etc.). Secondary
cables and ground conductor should be "inside" of the primary cables for clear
switching of the elbow terminators. The ground conductor should be placed in
Position 1 of the neutral block.
Issued 06-01-07
TRANSFORMERS
E.C.S.
INFORMATION SECTION
Section WTR02
Page 9 of 17
INSTALLATION AND MAINTENANCE
Cables should be dressed back to approximately 1/4" more than the block thickness.
Conductor strands should protrude out the top side slightly (1/4" Max.) to ensure
adequate strand contact.
4) Tooling
Tool requirements include a crescent wrench for the jam nuts, screwdriver and an Allen style
socket ratchet wrench.
c. Three-Phase
1) Dimensions
a) Cabinet Size
Section WTR02
Page 10 of 17
E.C.S.
INFORMATION SECTION
INSTALLATION AND MAINTENANCE
Issued 06-01-07
TRANSFORMERS
Figure 02-5 - Three-Phase GY-GY Transformer Faceplate Layout
Three-Phase GY-GY Transformer Faceplate Layout
Pressure Relief Valve
Primary Bushing
Oil Fill Plug
LFSA Loopfeed switch A-side
LFSB Loopfeed switch B-side
Parking Stand
Loopfeed switch handles
Bayonet
Tap changer operating
handle
TC
switch
Secondary
Bushings/Spades
Ground Nut Locations as
per para. 9b.
HV Compartment Dimensions (in.) ______
HV Voltage
D
E
F
G
12.4 KV
3.5
6.5
4.5
6.0
12.4X24.9
4.5
6.5
4.5
6.0
24.9 KV _______ 4.5 ___ 6.5__ 4.5 __ 6.0
E.C.S.
INFORMATION SECTION
Issued 06-01-07
TRANSFORMERS
Section WTR02
Page 11 of 17
INSTALLATION AND MAINTENANCE
b) Footprint
The following table shows the approximate dimensions of 12.47 kvV padmounted
transformers. Dual voltage transformers (24.9 kV or 12.47 kV) have similar dimensions
except for a few heights and weights. The heights off 150 kVA to 500 kVA duals are 67
inches. The weights of duals are usually 500 pounds to 1,200 pounds heavier,
depending on the size of the transformer.
Figure 02-6 - Three-Phase Padmounted Transformer Cabinet Dimensions
E.C.S.
INFORMATION SECTION
Section WTR02
Page 12 of 17
Issued 06-01-07
INSTALLATION AND MAINTENANCE
TRANSFORMERS
Dimensions in Inches
Type
Kva
Voltage
A
B
C
D
E
Height
Weight
Cooper
75
277/480v
42
69
43
26
19
60
2,320 #
Cooper
75
120/208v
42
69
43
26
19
60
2,884 #
Cooper
150
277/480v
42
69
43
26
19
60
2,845 #
Cooper
150
120/208v
51
69
43
26
19
60
2,697 #
Cooper
300
277/480v
56
73
43
30
18
60
4,668 #
Cooper
300
120/208v
53
73
43
30
18
60
3,547 #
Cooper
500
277/480v
64
73
43
30
18
60
5,688 #
Cooper
500
120/208v
57
73
43
30
18
60
4,841 #
Cooper
750
277/480v
65
72
43
29
18
73
8,233 #
Cooper
750
120/208v
61
72
43
29
18
73
7,262 #
Cooper
1000
277/480v
68
78
44
34
22
73
10,634 #
Howard
1000
120/208v
76
72
42
30
24
Cooper
1500
277/480v
72
72
43
29
22
73
11,084 #
Cooper
2500
Dual 277/480v
96*
85
55
30
22
73
16,817 #
Cooper
2500
24.9kv 277/480
73
85
55
30
22
73
16,000 #
2500
24.9/12.47 Step
96
96
48
48
22
73
23,000 #
5000
24.9/12.47 Step
114
96
48
48
22
73
26,541 #
*=About 2' of cooling fins
2) Foundation
a) Use of Table and Drawings Figure 02-7 on Page WTR02.14.
(1) Pad Selection
For initial installation of a 75 kVA to 500 kVA transformer use the dimensions given
for PAD I. PAD I will also accommodate a 750 kVA sized transformer for future
growth. For initial installation of a 750 kVA to 2,500 kVA sized transformers use the
dimensions given for PAD II.
(2) Pad Dimensions
Dimension "A" specifies the depth of the pad, dimension "B" specifies the width of
the pad, dimension "C" specifies the distance from the right edge of the pad to the
right edge of the pad opening, dimension "D" specifies the width of the pad opening,
and dimension "E" specifies the depth of the pad opening.
E.C.S.
INFORMATION SECTION
Issued 06-01-07
TRANSFORMERS
Section WTR02
Page 13 of 17
INSTALLATION AND MAINTENANCE
In all cases the depth of the opening for Pads I and II will be 17 inches. The distance
from the front of the pad to the front edge of the pad openings will be 13 inches.
The outside pad dimension are selected to insure that the transformer cooling fins
will not extend beyond the perimeter of the pad when following the transformer
setting instructions.
Typically, there will be about six (6) inches of the concrete pad extending beyond the
fin perimeter of the transformer on the right side with respect to the width, and in
front with respect to the depth.
Section WTR02
Page 14 of 17
E.C.S.
INFORMATION SECTION
INSTALLATION AND MAINTENANCE
Issued 06-01-07
TRANSFORMERS
Figure 02-7
•
Maximum number of Secondary Conduits Allowed is eight. If more than eight are required,
authorization from Distribution Engineer required.
1. Size and number of conduits must be obtained from Alliant Energy Engineering.
2. When oil sump is required, excavate 18 inches under and around pad, and fill with coarse, crushed
rock. (Check with local municipal codes to determine if oil sump is required.)
3. Concrete shall have a minimum strength of 4000 lb./sq.in. after 28 days cure time.
4. Top of pad must be level.
Issued 06-01-07
E.C.S.
INFORMATION SECTION
TRANSFORMERS
Section WTR02
Page 15 of 17
INSTALLATION AND MAINTENANCE
5. The pad shall be reinforced with #4 wire, 4 inch by 4 inch mesh with additional 3/8 inch reinforcing
rod around the cable opening. The mesh shall not be less than one inch from the edges and
opening, and installed three inches below the surface. If the #4 wire, 4 inch by 4 inch mesh is not
available, two layers of #10 wire, 6 inch by 6 inch mesh staggered by 2 inches horizontally may be
substituted for the #4 wire.
6. The pad shall have all edges and corners rounded off.
b) Method of Positioning Transformer on the pad:
The following steps are required in setting the transformer properly on the pads:
Step 1:
Line up the right side of the transformer secondary cable compartment with the right edge of the
pad opening, making sure that the pad opening is not exposed outside of the cable
compartment. This is shown by the dotted (MN) in Figure 02-8 on Page WTR02.16. This will
insure that the secondary compartment is completely open at all times.
Step 2:
Line up the rear panelling of the cable compartment with the back edge of the pad opening as
shown in Figure 02-8 on Page WTR02.16 by the dotted line (XY). This will insure that the tank
will completely rest on solid concrete for weight support.
Figure 02-8 on Page WTR02.16 shows the setting of a typical transformer on the pad using the
positioning method mentioned above.
Section WTR02
Page 16 of 17
E.C.S.
INFORMATION SECTION
INSTALLATION AND MAINTENANCE
Issued 06-01-07
TRANSFORMERS
Figure 02-8
Issued 06-01-07
E.C.S.
INFORMATION SECTION
TRANSFORMERS
Section WTR02
Page 17 of 17
INSTALLATION AND MAINTENANCE
c) Pad Opening Dimensions and Location
The width and depth of the pad opening are based upon the smallest cable compartment, width
and depth, of the kVA sizes for which that pad is designed. This will leave a minimum eight (8)
inches of opening in the primary side of the cable compartment for the largest transformer
compartment width for which the pad is designed. The thirteen (13) inch dimension from the
front of the pad to the front of the pad opening will insure that larger cable compartments will not
extend over the front edge of the pad, using the prescribed method of positioning the
transformer.
Other references:
(1) Electrical Material Specifications No. 0025.
(2) Electric Service Information Manuals.
(END)