Issued 06-01-07
E.C.S.
Section WTR00
INFORMATION SECTION
Page 1 of 1
TRANSFORMERS 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
INFORMATION SECTION
Page 1 of 9
TRANSFORMERS
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
Section WTR01
E.C.S.
Issued 08-01-08
Page 2 of 9
INFORMATION SECTION
ELECTRICAL CONNECTIONS
TRANSFORMERS
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
INFORMATION SECTION
Page 3 of 9
TRANSFORMERS
ELECTRICAL CONNECTIONS
b. 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
Section WTR01
E.C.S.
Issued 08-01-08
P a g e 4 o f 9
INFORMATION SECTION
ELECTRICAL CONNECTIONS
TRANSFORMERS
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 c N N a b
INFORMATION SECTION
Page 5 of 9
TRANSFORMERS
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
Section WTR01
E.C.S.
Issued 08-01-08
Page 6 of 9
INFORMATION SECTION
ELECTRICAL CONNECTIONS 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 A H1 a b c N X3 X2 H2 H1 X1 X3 C X2
INFORMATION SECTION
Page 7 of 9
TRANSFORMERS
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 a b c N H1 A C X3
Section WTR01
E.C.S.
Issued 08-01-08
Page 8 of 9
INFORMATION SECTION
ELECTRICAL CONNECTIONS 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
c
INFORMATION SECTION
Page 9 of 9
TRANSFORMERS ELECTRICAL CONNECTIONS
2. SERVICE DROPS FROM THREE-PHASE TRANSFORMER BANKS
240/480 120/240
Low Voltage High Voltage (Phase-Ground)
8660 and Below 8661 and Above 8660 and Below 8661 and Above
KVA
Low-voltage Connections & Bushing Arrangement (Letters refer to illustrations below)
1 0 0 a n d l e s s A B D E
Issued
06-01-07
E.C.S.
Section WTR02
INFORMATION SECTION
Page 1 of 17
TRANSFORMERS
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 non-PCB 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.
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INFORMATION SECTION
INSTALLATION AND MAINTENANCE 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
E.C.S.
Section WTR02
INFORMATION SECTION
Page 3 of 17
TRANSFORMERS INSTALLATION AND MAINTENANCE
E.C.S.
Page 4 of 17
INFORMATION SECTION
Issued 06-01-07
E.C.S.
Section WTR02
INFORMATION SECTION
Page 5 of 17
TRANSFORMERS 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 well canisters. Manufacturers will generally place a steel or wood rod in the dry-well 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.
E.C.S.
Page 6 of 17
INFORMATION SECTION
INSTALLATION AND MAINTENANCE 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.
Issued 06-01-07
E.C.S.
Section WTR02
INFORMATION SECTION
Page 7 of 17
TRANSFORMERS 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.
Page 8 of 17
INFORMATION SECTION
INSTALLATION AND MAINTENANCE 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
1 2 3 4 5 Streetlight Tap
Phase Cable Cable Cable Cable Vacant 1 - Vacant
1 - Streetlight Cable
Neutral 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
E.C.S.
Section WTR02
INFORMATION SECTION
Page 9 of 17
TRANSFORMERS 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
E.C.S.
Page 10 of 17
INFORMATION SECTION
INSTALLATION AND MAINTENANCE TRANSFORMERS
Figure 02-5 - Three-Phase GY-GY Transformer Faceplate Layout
Three-Phase GY-GY Transformer Faceplate Layout
Pressure Relief Valve Oil Fill Plug
Primary Bushing
LFSA Loopfeed switch A-side LFSB Loopfeed switch B-side Parking Stand
Loopfeed switch handles Bayonet
Secondary Bushings/Spades Tap changer operating
handle TC
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
Issued 06-01-07
E.C.S.
Section WTR02
INFORMATION SECTION
Page 11 of 17
TRANSFORMERS 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.
E.C.S.
Page 12 of 17
INFORMATION SECTION
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.
Issued 06-01-07
E.C.S.
Section WTR02
INFORMATION SECTION
Page 13 of 17
TRANSFORMERS 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.
E.C.S.
Page 14 of 17
INFORMATION SECTION
INSTALLATION AND MAINTENANCE 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.
Section WTR02
INFORMATION SECTION
Page 15 of 17
TRANSFORMERS 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.
E.C.S.
Page 16 of 17
INFORMATION SECTION
INSTALLATION AND MAINTENANCE TRANSFORMERS
Issued
06-01-07
E.C.S.
Section WTR02
INFORMATION SECTION
Page 17 of 17
TRANSFORMERS
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.
