Preface This is the fourth edition of CSA C227.3, Low-profile, single-phase, pad-mounted distribution transformers with separable insulated high-voltage connectors.? It supersedes the previous editions published in 1991, 1979, and 1974.? Scope 1.1 This Standard specifies the requirements for single-phase, pad-mounted distribution transformers with separable insulated high-voltage connectors and intended primarily for operation by electric utilities. Note: The operation of transformers complying with this Standard by other than an electric utility can be subject to additional requirements by the electrical inspection authority having jurisdiction. 1.2 This Standard applies to single-phase, pad-mounted, 60 Hz, liquid-filled distribution transformers with separable insulated high-voltage connectors designed for operating on an effectively grounded wye system, rated at 167 kV.A or less, with an insulation class of 18 kV or less, and suitable for mounting outdoors on pads without additional protective enclosures. 1.3 This Standard includes voltage ratings, kV.A ratings, certain mechanical characteristics, and test procedures. The Standard also includes the following performance characteristics: energy efficiency (in accordance with CAN/CSA-C802.1), temperature rise, loading capabilities, sound level, and radio influence voltage (RIV). 1.4 This Standard covers equipment intended primarily for operation on effectively grounded underground distribution systems having preferred rated voltages as shown in Table 1 and a secondary distribution voltage of 240/120 V, three-wire. 1.5 This Standard is intended to allow for interchangeability between pad-mounted units of the same basic physical size but made by different manufacturers, without modifying the cables or the pad. This Standard covers terminal arrangements for a loop-feed system, including certain minimum dimensions and certain specific dimensions, but does not ensure that the cable entrance compartment of one manufacturer\'s transformer matches that of another. 1.6 In CSA Standards, \"shall\" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; \"should\" is used to express a recommendation or that which is advised but not required; \"may\" is used to express an option or that which is permissible within the limits of the standard; and \"can\" is used to express possibility or capability. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.