前言:这是CSA C227的第三版。4、三相、垫装式配电变压器，带可分离绝缘高压连接器。它取代了2006年和1978年出版的前两个版本。本版本的主要变化包括:a）扩大范围，包括34.5 kV系统标称电压，并停止使用术语“绝缘等级”和“首选电压”；b） 对其他行业标准的更新参考；c） 阐明了无回路电压分接头的要求，并增加了关于带分接头的双电压互感器的信息性说明；d） 由于之前的IEEE参考文件已过时，对可选负载断路开关额定值增加了要求； e） 修改并澄清了双保险丝系统的要求，还删除了带有制造商特定零件号的表格；f） 改进了常规测试要求，以更好地与IEEE保持一致。例如，空载损耗和励磁电流将为100%额定电压，而不是105%；g） 未添加内部保险丝警告标记；h） 澄清并扩展了第10条中的附加可选项。例如，根据用户的经验和程序增加了常规局部放电测试；i） 继续包括适用于本标准涵盖的变压器的电气特性，这些特性以前在CAN/CSA中提供- C2；andj）增加了第B.5.3.1.1条，以解释熔合台的拆除。本标准的制定符合加拿大标准委员会对加拿大国家标准的要求。CSA集团已将其作为加拿大国家标准发布。范围:1.1本标准规定了三相、垫装式配电变压器的要求，该配电变压器由变压器和电缆入口隔间组成，提供可分离的绝缘高压连接器，主要供电力公司在三相地下配电系统上运行，其一次电压如第4条所示。 6.1.2本标准适用于三相、60 Hz、垫装、充液配电变压器，额定值为3000 kVA或以下，系统标称电压高达34.5 kV，并带有可分离绝缘高压连接器。变压器适合安装在户外的垫子上，无需额外的保护外壳。1.3本标准包括电压额定值、千伏安额定值、某些机械特性和试验程序。该标准还包括以下性能特征:能效（符合CAN/CSA-C802.1）、温升、负载能力、可听声级和无线电影响电压（RIV）。 1.4当本设备拟由非电力公司操作时，买方***？承包商有责任确保装置符合相应电气检查机构的要求。1.5对于额定电压为125 kV BIL及以下的变压器，本标准允许采用不同制造商提供的相同基本物理尺寸的另一个固定前端、安装在垫板上的装置进行互换，而无需对电缆或垫板进行修改。本标准涵盖径向和环形馈电系统的终端布置，包括某些最小尺寸和某些特定尺寸。 1.6在本标准中，“应”用于表示要求，即用户为遵守本标准而有义务满足的规定；“应该”用于表示建议或建议但不需要的建议；“可”用于表示一个选项或在标准范围内允许的选项。注释随附条款不包括要求或替代要求；随附条款的注释的目的是将解释性或信息性材料与文本分开。表和图的注释被视为表或图的一部分，可以作为要求编写。 附件被指定为规范性（强制性）或信息性（非强制性）以定义其应用。

Preface:This is the third edition of CSA C227.4,Three-phase, pad-mounted distribution transformers with separable insulated high-voltage connectors. It supersedes the previous editions published in 2006 and 1978.The major changes in this edition include the following:a) expanded scope to include 34.5 kV system nominal voltage, and discontinued use of the terms "insulation class" and "preferred voltages";b) updated references to other industry standards;c) clarified requirements with off-circuit voltage taps and added informative note on dual-voltage transformers with taps;d) added requirements to the optional load break switch ratings since previous IEEE references are obsolete;e) modified and clarified requirements with the two-fuse system, also removing tables with manufacturer specific part numbers;f) improved routine test requirements to better align with IEEE. For example, no-load losses and exciting current will be at 100% rated voltage instead of 105%;g) added no internal fuse warning markings;h) clarified and expanded additional optional items in Clause 10. For example, routine partial discharge testing has been added based on the experience and procedures of users;i) the continued inclusion of the electrical characteristics that apply to the transformers covered by this Standard, which were previously provided in CAN/CSA-C2; andj) added Clause B.5.3.1.1 to explain the removal of fusing tables.This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group.Scope:1.1This 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 4.6.1.2This 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.1.3This 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).1.4When 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.1.5This 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.1.6In 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.