IEEE DRAFT C57.12.20 : D10C 2004

Introduction
1 Overview
  1.1 Scope
  1.2 Purpose
2 References
3 Definitions
  3.1 A Fault
  3.2 A Test
  3.3 Back-Up Protection
  3.4 Enclosures
  3.5 Internal Fusible Element
4 Ratings
  4.1 Kilovolt-Ampere Ratings
  4.2 Voltage Ratings and Tap Ratings
5 Basic Lightning Impulse Insulation Levels and Dielectric
  Test Levels
  5.1 Basic Lightning Impulse
  5.2 Dielectric Test
6 Tests
  6.1 General
  6.2 Dielectric Tests
7 Construction
  7.1 Bushings and Terminals
      7.1.1 Bushings
      7.1.2 Terminals
      7.1.3 Neutral Termination
      7.1.4 Terminal Boards
  7.2 Accessory Equipment
      7.2.1 Tap Changer
      7.2.2 Series-Multiple Connections
      7.2.3 Liquid-Level Marking
      7.2.4 Lifting Lugs
      7.2.5 Relief of Excessive Pressure
      7.2.6 Enclosure Integrity
  7.3 Polarity, Terminal Markings, and Angular Displacement
      7.3.1 Polarity
      7.3.2 Angular Displacement
      7.3.3 Terminal Markings
      7.3.4 Instruction Nameplate
      7.3.5 Kilovolt-Ampere Rating on Tank
      7.3.6 Connections for Shipment by the Manufacturer
  7.4 Oil Preservation
  7.5 Tanks
      7.5.1 Covers and Handholes
      7.5.2 Support Lugs
      7.5.3 Tank Finish
      7.5.4 Tank Grounding Provisions
8 Storage and Installation
  8.1 Storage
  8.2 Installation
9 Design Tests for Fault Current Capability of Overhead
  Distribution Transformer Enclosures
  9.1 Objective
  9.2 General Requirements
  9.3 Tests
  9.4 Test Number 1- An Arcing Fault in an Enclosure
      9.4.1 First Fault
      9.4.2 Second Fault
  9.5 Test Number 2- For Enclosures with Internal Fusible Elements
      9.5.1 "A" Fault
      9.5.2 "B" Fault
  9.6 Test Results
Tables
Figures
Annex A (informative) Auxiliary Mounting Devices
Figure A.1 Support Lug C
Figure A.2 Type C Adapter Plates
Figure A.3 T-Crossarm Hangers and Kickers (T1 and K1)
Figure A.4 T-Crossarm Hangers and Kickers (T2 and K2)
Figure A.5 Crossarm Hangers
Annex B (informative) Bibliography

Describes certain electrical, dimensional, and mechanical characteristics and safety features of single and three phase, 60-Hz, mineral oil immersed, self-cooled, overhead type distribution transformers 500 kVA and smaller, High Voltages 34 500 volts and below and Low Voltages 7970/13 800Y volts and below.