SPECIFICATION FOR THREE-PHASE PAD MOUNT TRANSFORMERS. D. Dead Front, loop feed design shall be employed.

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1 City of Cartersville Electric System P.O. Box S. Erwin St. Cartersville, GA March 2006 SPECIFICATION FOR THREE-PHASE PAD MOUNT TRANSFORMERS This specification provides standardization of physical and electrical requirements for three-phase, self-cooled, oil-immersed, pad-mounted transformers designed for underground distribution systems. The word utility describes the buyer which is the City of Cartersville Electric System; the word vendor describes the seller, vendor, supplier, or manufacturer. I. General Information A. Provisions and terminology of current revisions of ANSI Standards C , 12.10, 12.20, 12.22, 12.25, 12.26, 12.28, 12.70, 12.80, 12.90, latest revisions apply. B. Winding temperature rise above ambient shall not exceed 65 C at rated capacity. Hot spot rise shall be limited to 80 C. Excessive tank heating due to imbalanced loading or loss of a primary phase shall not occur. C. A five-legged core shall be provided. D. Dead Front, loop feed design shall be employed. II. Construction Features A. The pad-mounted, compartmental-type transformers shall consist of the transformer tank with high-voltage and low-voltage cable terminating compartment. The transformer tank and compartment shall be assembled as an integral unit for mounting on a pad. B. Transformer tank shall be sealed-tank construction with either a welded main cover or a bolted main cover and capable of withstanding a pressure of 7 psig without permanent distortion. If a welded main cover is used, a bolted temper-resistant hand-hole shall be provided. C. There shall be no exposed screws, bolts, or other fastening devices which are externally removable. There shall be no openings through which foreign objects such as sticks, rods, or wires might contact energized parts. The construction shall limit the entry of water (other than flood water) into the compartment so as not to impair the operation of the unit. Transformer shall meet tamper resistance requirements set forth in ANSI C D. Full-height, air-filled incoming and outgoing terminal compartments with hinged doors shall be located side-by-side separated by a steel barrier, with the incoming compartment on the left. The high-voltage (incoming) compartment will be accessible only after the door to the low-voltage (outgoing) compartment has been opened. To facilitate making connections and permit cable pulling, the doors and compartment hood shall be removable. Removable door sill on compartments shall be provided to permit rolling or skidding of unit into place over conduit studs or cable. E. Both compartment doors must be capable of being secured with a single padlock having a 1/2 diameter shackle and a recessed, captive pentahead bolt. The compartments will have 1

2 hinged doors equipped for latching in the open position. The high-voltage compartment door will have a pentahead bolt fastening device which is accessible only through the low-voltage compartment. F. The hinge assemblies shall be made of corrosions-resistant material. Stainless-steel hinge pins of 3/8 minimum diameter will be provided. G. All exterior nuts and bolts shall be stainless steel or chemically treated to prevent corrosion. H. Lifting provisions in accordance with ANSI Standards shall be provided; jacking and rolling provisions shall be provided. I. The nameplate is to be located in the low-voltage portion of the compartment. Information on the instruction nameplate shall comply with ANSI Standard C and shall include the kva rating, high voltage, low voltage, weight, manufacture date, serial number, impedance, type oil utilized, and state non-pcb. J. Provisions for tank grounding shall be supplied in both the high-voltage and low-voltage compartments. These provisions shall consist of: kVA and below: 1/2-13 UNC tapped hole 7/16 deep kVA and above: (2) 1/2-13 UNC tapped holes 1/2 deep K. The following accessories are to be provided on all units: 1. One-inch filling provision 2. One-inch drain valve with sampler 3. Liquid level indication 4. Pressure relief device 5. Grounding lugs L. Transformers shall be painted inside and outside; color shall be Munsell 7GY, Outdoor Green. Paint shall be of such quality as to resist rust, fading, etc., for a minimum 15-year (exposed to elements) period and comply with ANSI C M. NEMA Standard 260, Figure 2 safety labels shall be provided inside the compartment. No labels shall be placed on the exterior surface of transformer (utility will provide exterior safety label). III. Electrical Requirements A. Transformers shall be provided for wye-wye connection to 60 hertz alternating current for the following voltages as specified in the order: High Voltages Low Voltages 12,470 GRDY/ GRDY/120 12,470 GRDY/ GRDY/277 B. High voltage insulation level shall be 15kV class, 95kV BIL. Low voltage insulation level shall be 1.2kV class, 30kV BIL. Should future requirements specify a high voltage in excess of 15,000 GRDY, insulation class shall be 18kV, 125 BIL. Higher secondary voltages shall be provided with an insulation level based on latest standards for the required voltage. Dual voltage transformers shall meet insulation level requirements for the higher voltage. 2

3 C. Taps are not required unless specified for units under 500 kva rating. For 500 kva transformers and larger, provide two 2 1/2% taps above and two 2 1/2% taps below rated primary voltage. The tap changer handle shall be located in the primary compartment. D. Allowable percent impedance for transformers under 750 kva rating shall be within the range of 1.2% to 5.7%. For transformers 750 kva rating and larger, percent impedance shall be within the range of 1.5% to 5.75%. IV. Bushings and Terminals A. Electrical characteristics of transformer bushings and terminals shall be as listed below: Basic Impulse 60 Cycle Insulation Insulation Level Dry One-Minute Class (kv) Dry Withstand (kv) Withstand (kv) B. Bushings and terminals shall be located on the tank wall that is common to the high-voltage and low-voltage compartments. The location and sequence shall be as shown in Figure 1. C. Unless otherwise specified, the incoming high-voltage section shall be equipped with six (6) 200-ampere bushing wells in accordance with ANSI Standard C Six (6) screw-out loadbreak inserts shall be provided. Inserts shall be designed to mate with RTE SBT IV, G.E. Sure-Make, or equivalent elbows. Bushings shall be located as shown in Figure 1. A minimum of five accessory brackets (parking stands) shall be provided at the same height and in the same plane as the high-voltage bushings. D. Low-voltage line and neutral bushings shall be externally clamped with spades. Low-voltage line and neutral terminals shall be arranged for vertical take-off and mounted in a staggered configuration on the tank wall. Minimum horizontal and vertical spacing between terminals shall be as shown in Figure 1. Terminals shall be one piece NEMA standard tinned terminal spades. Terminals used on 112 ½ kva rated units and larger shall be braced from above. A minimum of six inches (6 ) shall be maintained between the tank wall and the center of hole nearest the tank on the spade. (NOTE: CHANGE FROM 6 TO ADEQUATE SPACING) Minimum Qty. of kva Rating Holes for Spades Under 112 ½ ½ and larger 12 E. The low-voltage neutral bushing shall be an insulated bushing with high-voltage and lowvoltage neutrals tied together internally by a removable link and brought out through the lowvoltage X0H0 bushing with a removable external ground connection. The ground strap shall be adequate to carry the fault current based on the rating of the transformer. F. Terminal designations shall be as defined by ANSI Standard C , Terminal Markings for Electrical Apparatus, with each terminal clearly marked with oil resistant yellow paint. The identification of terminal connections shall be shown on the instruction nameplate. G. The angular displacement between the high-voltage and low-voltage terminal shall be zero degrees. H. All terminals shall have adequate and safe clearance from compartment doors when closed. 3

4 V. Fusing. A. Transformers rated 1500 kva and below shall be equipped with fuse holders for three bay-onet type (RTE, G.E., Kerney DEWL ) oil-immersed expulsion fuses accessible through the primary compartment. The fuses shall be removable using a hot-stick for external replacement of fuse cartridges. Fuse holders shall be located in the upper portion of the compartment, above the loadbreak bushings. A drip shield shall be provided to keep oil from dripping onto the bushings. B. Three bay-o-net type fuses shall be provided according to the following table. kva rating Fuse Size/Type Preference 45 5A DEWL Kearney or equivalent 75 5A DEWL Kearney or equivalent 112½ 8A DEWL Kearney or equivalent A DEWL Kearney or equivalent A DEWL Kearney or equivalent A DEWL Kearney or equivalent A DEWL Kearney or equivalent A DEWL Kearney or equivalent A RTE Cooper C12 or equivalent A RTE Cooper C14 or equivalent 2000 N/A N/A 2500 N/A N/A C. Internal current limiting fuses ( CLF ) shall not be provided unless specified in the order. In those cases where they are so specified, the statement CURRENT LIMITING FUSE INSIDE TANK shall be stenciled in yellow characters of at least 1 height immediately below the bayonet fuse holders. VI. Dielectric Fluid VII. Testing A. The liquid supplied in these transformers shall be a non-pcb type, as defined by Federal Regulation No. 40CFR 761, dated May 31, 1979, and subsequent revisions. Should any other oil be identified as a hazardous substance, it shall not be used B. The liquid contained in these transformers shall be identified as a non-pcb type with a separate label, no larger than three inches (3 ) by five inches (5 ), affixed to the transformer tank in the immediate vicinity of the nameplate. A. Routine tests on all transformers shall be as specified in the latest revision of Section 8 of ANSI C ANSI Test Code C shall be followed for all testing procedures. B. Loss evaluation tests including Full Load Loss (LL) in Watts at 85 C and No Load Loss (NL) in Watts at 85 C shall be provided with bid submittal so that cost of ownership can be determined by utility. Method of determining cost of ownership is determined by utility and is subject to change at any time without notice to vendor. As of this specification revision, owner s Total Ownership Cost (TOC) formula is as follows: TOC = Initial Cost * NL + 1 * LL C. Dielectric test shall be in accordance with ANSI Standard C

5 VIII. Shipping IX. Warranty D. Doors shall be opened and closed several times before vendor delivers unit, checking for misalignment, warping, improper hinging, etc. A. Transformers shall be shipped with a single transformer per pallet and delivered on a flat-bed truck situated for side unloading. B. For transformers 1000 kva and above, 36 hours notice shall be given before delivery to allow utility to arrange unloading. C. Certified test reports for each transformer, identified by serial number and rated kva, must be submitted to utility within 30 days of delivery of transformer to utility. A. Each transformer shall be guaranteed by vendor against failure due to any cause, except misapplication, abuse, or acts of God, for a minimum of one (1) year after delivery of transformer to utility or after delivery of certified test report to utility, whichever is later. B. Acceptance tests will be performed by owner to verify compliance with specifications stated herein and with quoted losses. Any transformers found not meeting these specifications or exceeding quoted losses may be refused by utility within thirty (30) days of delivery or transformer or delivery of certified test report, whichever is later. Transformers may be returned to vendor for full credit, vendor is to pay all original delivery and return transportation costs. X. Deviations to Specifications Vendors quoting transformers to this specification shall indicate any areas where deviations are required by their design and shall include sufficient information to permit full evaluation of same. This data shall accompany bid submittal from bidder. Approval drawings from manufacturer may be required on any specification changes. XI.IFD IFD(internal fault detection )shall be added to all transformers at factory and repair shops. 5