CSA C227.4:21

1 Scope 1.1 This Standard specifies the requirements for three-phase, pad-mounted distribution transformers, consisting of a transformer and a cable entrance compartment with provision for separable insulated high-voltage connectors, intended primarily for operation by electric utilities on three-phase underground distribution systems having primary voltages as shown in Clause 4.6. 1.2 This Standard applies to three-phase, 60 Hz, pad-mounted, liquid-filled distribution transformers, rated at 3000 kVA or below, up to 34.5 kV system nominal voltage, and with separable insulated high-voltage connectors. The transformers are suitable for mounting outdoors on pads without additional protective enclosures. 1.3 This Standard includes voltage ratings, kVA 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, audible sound level, and radio influence voltage (RIV). 1.4 When this equipment is intended for operation by other than an electric utility, it is the purchaser’s responsibility to ensure that the unit meets the requirements of the appropriate electrical inspection authority. 1.5 This Standard allows for the interchangeability of a dead-front, pad-mounted unit by another of the same basic physical size from a different manufacturer for transformers rated 125 kV BIL and below, without modifications to cables or pad. This Standard covers terminal arrangements for both radial and loop-feed systems, including certain minimum dimensions and certain specific dimensions. 1.6 In this Standard, “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; and “may” is used to express an option or that which is permissible within the limits of the Standard. 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.