Transformer Tank And Cover example essay topic

All requirements shall be in accordance with the latest revision of ANSI C 57.12. 00 and ANSI C 57.12. 20, except where modified by this standard. The transformer shall be bar coded in accordance with the proposed EEI "Bar Coding Distribution Transformers: A Proposed EEI Guideline". The manufacturer and serial number shall be bar coded on the nameplate. The serial number, manufacturer, and the Company Item ID (if given above) shall be bar coded on a temporary label.

The transformer shall meet interchangeability dimensions for single position mounting as shown in Figures 1 and 9 of ANSI C 57.12. 20. The two primary bushings shall be wet process porcelain cover-mounted. The primary connectors shall be tin-plated bronze of the eye-bolt type. The H 1 bushing is to be supplied with a wildlife protector and an eyebolt connector equipped with a covered hand knob tightening device. The eyebolt connector shall accept a 5/16 inch diameter knurled stud terminal with the wildlife protector in place.

The secondary bushings shall be wet process porcelain or epoxy, mounted on the tank wall. Secondary connectors shall be per ANSI C 57.12. 20, section 6.1. 2, except terminals on 75 kVA 120/240 volt units shall accommodate up to 1000 kamil-61 stranded conductor. The cover of the transformer shall be coated for wildlife protection. The coating shall have a rating of at least 10 kV AC rms.

The insulating finish shall be capable of withstanding 10 kV at a 200 volt per second rate of rise, tested per ASTM D 149-87, using electrode type 3 (1/4 inch cylindrical rods). The transformer tank and cover shall be designed to withstand an internal pressure of 20 psig without tank rupture or bushing or cover displacement, and shall withstand an internal pressure of 7 psig without permanent distortion. The transformer tank shall retain its shape when the cover is removed. Support lugs for single-position mounting shall be provided and shall be designed to provide a static-load safety factor of 5. Lifting lugs shall be provided, with location and safety factor as specified in ANSI C 57.12. 20.

The tank and cover finish shall be light gray No. 70 (Mun sell 5 BG 7.0/0.4). The interior shall be coated with a durable protective finish from the top to at least below the top liquid level. The transformer shall be equipped with a tank ground per ANSI C 57.12. 20, paragraph 6.5. 4.1 with eyebolt to accept an AWG 6 solid copper ground wire; a tank ground for ground strap connection; and a ground strap, properly sized to carry load and fault current, connected between the secondary neutral terminal and the tank ground. The grounding strap shall be supplied with a connection hole at each end.

"J" hook or slotted connection points shall not be allowed. The transformer shall be equipped with neoprene or Buna-N gaskets on all primary and secondary bushings and tank fittings. A Qualit rol 202-032-01 automatic pressure relief device, with operation indication, or approved equivalent; or a cover assembly designed for relief of excess pressure in accordance with ANSI C 57.12. 20, section 6.2.

7.2, shall be supplied on the transformer. Final core and coil assembly shall result in a rigid assembly that maintains full mechanical, electrical, and dimensional stability under fault conditions. The coil insulation system shall consist of electrical kraft paper layer insulation coated on both sides with thermosetting adhesive. Curing of the coils shall cause a permanent bond layer to layer and turn to turn. The internal primary leads shall have sufficient length to permit cover removal and lead disconnection from the high voltage bushing. These leads shall be adequately anchored to the coil assembly to minimize the risk of damaging the coil connection during cover removal.

The internal secondary leads shall be identified by appropriate markings, embossed or stamped on a visible portion of the secondary lead near the end connected to the bushing. These leads shall have sufficient length to permit series or parallel connection of the secondary windings. If the internal secondary leads are soft aluminum, a hard aluminum-alloy tab shall be welded to the bushing end of the lead for connection to the bushing. The transformer should be designed so that the voltage regulation shall not exceed 2.5% at full load and 0.8 power factor for all transformers covered in this specification. All transformers shall be filled with Type I insulating oil meeting the following requirements: a. All applicable requirements of ASTM D 3487, paragraph 82 a. b.

Minimum breakdown value of 28 kV per ASTM D 1816, paragraph 84 a using a 0.4 inch gap. c. The PCB content shall be less than 2 parts per million which shall be noted upon the nameplate of each unit. In addition, the manufacturer shall provide and install a "No PCB" identification on the tank wall, near the bottom of the tank centered below the low-voltage bushings. The decal shall be not less than 1 inch by 2 inch in size and shall indicate "No PCB's" in blue lettering on a white background, and be sufficiently durable to remain legible for the life of the transformer.