Specifications include, but are not limited to: 1. TANK – The padmount transformer shall consist of the transformer tank with a high and low voltage cable terminating compartment. The transformer tank and compartment shall be assembled as an integral unit, tamperproof and weatherproof. 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 live 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 transformer. Cable entrances shall be through the bottom of the compartment. The top of the transformer shall be ridged to assure water drainage. The tank coating shall meet all requirements in C57.12.28-2014 - IEEE Standard for Pad-Mounted Equipment - Enclosure Integrity. The transformer shall be sealed-tank construction with the main cover welded or bolted in place with adequate gasket. Cooling fins will NOT be acceptable. 2. COMPARTMENT – The high and low voltage bushing shall be located side by side in a single air-filled compartment, with the high voltage bushings on the left. The compartment shall be accessible by means of a hinged, lift-up cover. The cover shall be secured by means of a single, recessed penta-head bolt, with additional provision for a pad-lock having a 1/2" diameter shackle. Enclosure security shall meet all requirements in C57.12.28-2014 - IEEE Standard for Pad-Mounted Equipment - Enclosure Integrity. 3. RIGGING – Lifting, jacking and rolling provisions per 11) C57.12.25-1990 - American National Standard for Transformers - Pad-Mounted, Compartmental-Type, Self-Cooled, Single-Phase Distribution Transformers With Separable Insulated High-Voltage Connectors; High Voltage, 34 500 Grdy/ 19 920 Volts and Below; Low Voltage, 240/120 Volts; 167 kVA and Smaller Requirements, shall be provided. 4. INSTRUCTION NAMEPLATE – The instruction nameplate is to be located in the low voltage segment of the compartment and shall be readable with cables in place. Where the nameplate is to be mounted on a removable part, the manufacturer's name and transformer serial number shall be permanently affixed to a non-removable part. 5. GROUNDING – Provisions for tank grounding shall be supplied in both high and low voltage segments of the compartment. These provisions shall consist of steel pads and a 1/2-13 UNC tapped hole 7/16" deep. 6. HV BUSHINGS & TAPS – 6.1. 15KV: Transformers are to be dead-front, loop-feed with externally operable voltage or tap changer switches for safe operation. A universal type bushing well will be used that complies with C57.12.00-2010 - IEEE Standard for General Requirements for LiquidImmersed Distribution, Power, and Regulating Transformers, Section 6. 6.2. 25KV: Transformers are to be dead-front, loop-feed with externally operable voltage or tap changer switches for safe operation. 6.2.1. An externally fastened field replaceable primary bushing installed in a universal type bushing well will be used that complies with C57.12.00-2010 - IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers, Section 6. 6.2.2. Bushing arrangement shall be per “Type 2” arrangement as specified in C57.12.25- 1990 - American National Standard for Transformers - Pad-Mounted, Compartmental-Type, Self-Cooled, Single-Phase Distribution Transformers With Separable Insulated High-Voltage Connectors; High Voltage, 34,500 Grd-y/ 19,920 Volts and Below; Low Voltage, 240/120 Volts; 167 kVA and Smaller Requirements. 7. 25KV: DUAL VOLTAGE SELECTOR SWITCH – Dual Voltage Units shall have an appropriately labeled and identified external selector switch for switching 14,400 volt – 7,200 volt. Selector switch shall have lockable provisions. 8. LV BUSHINGS & GROUNDING – 8.1.1. Low voltage bushings shall be provided with a 5/8”-11 UNC 1.25" (min) copper stud for units <= 75kVA, and shall be provided with a 1”-14 UNC 1.75” (min) copper stud for units from 100 – 167kVA per C57.12.25-1990 - American National Standard for Transformers - Pad-Mounted, Compartmental-Type, Self-Cooled, Single-Phase Distribution Transformers With Separable Insulated High-Voltage Connectors; High Voltage, 34 500 Grd-y/ 19 920 Volts and Below; Low Voltage, 240/120 Volts; 167 kVA and Smaller Requirements, Figure 4C. 8.1.2. Leads from the windings to the secondary bushings shall have either copper or hard aluminum at the point of connection to the low voltage bushings. NOTE: Must note exceptions if not in compliance. 8.1.3. Grounding connectors shall be provided, two each installed in the tapped grounding holes as specified in C57.12.25-1990 - American National Standard for Transformers - Pad-Mounted, Compartmental-Type, Self-Cooled, Single-Phase Distribution Transformers With Separable Insulated High-Voltage Connectors; High Voltage, 34,500 Grd-y/ 19,920 Volts and Below; Low Voltage, 240/120 Volts; 167 kVA and Smaller Requirements, Paragraph 6.6.4. Low voltage removable ground strap shall be as shown in item ‘BU-1’ of Informational Publication 202-1, March 2018 “List of Materials Acceptable for Use on Systems of USDA Rural Development Electrification Borrowers. 9. PRESSURE RELIEF – Transformers shall be equipped with an automatic pressure relief device per C57.12.21-2000 - American National Standard Requirements for Pad-Mounted, Compartmental-Type Self-Cooled, Single-Phase Distribution Transformers With High Voltage Bushings; High-Voltage, 34500 GRDY/19920 Volts and Below; Low-Voltage, 240/120 Volts; 167 kVA and Smaller. 10. NEUTRAL – The neutral end of the high voltage windings shall be securely grounded to the tank internally, and shall be independent of all other connections. The low voltage neutral terminal shall be a fully insulated bushing, connected to the tank grounding plate with a removable external strap.
