CSA C22.3 NO. 7:25

Preface This is the seventh edition of CSA C22.3 No. 7, Underground systems, one of a series of Standards issued under the Canadian Electrical Code, Part III. It supersedes the previous editions published in 2020, 2015, 2010, 2006, 1994, and 1986. The following are the major changes to this edition: • revised scope of standard extends to the inside of buildings or sections of buildings where installations are employed by an electric-, communication-, or cable-utility in the exercise of its function as a utility; • removed of "where practicable" clause from scope and instead captured in terminology and definitions; • new and revised definitions with an updated use of terminology; • revised the climate change adaptation content, including intent, the introduction of definitions, and the use of terms for climate and weather; • changed the term "clearance" to "separation" throughout; • adjusted climate change adaptation values for design variables (temperature, precipitation, snow, ice, wind, etc.) in Annex H; • changed nominal basic (low) voltage from 750 V to 1000 V to align with the Canadian Electrical Code, Part I; • moved maintenance requirements and references to CSA C22.3 No. 11; • revised Clauses 4.1.1, 4.1.2, and A.4.1 to address climate change, resilience, reliability, maintenance, and safety; • revised Clauses 4.2.2 and A.4.2.2 to address standards location and tree excavations/installations; • revised Clause 6.1.1 to address separation from underground systems and referencing requirements in Table 2; • added Clauses 6.1.12, A.6.1.12, 6.2.8, and A.6.2.8 to address separation from soil cell for direct buried systems; • added Clause 9.6.2 to address pressure relief of subsurface chambers; • revised Clauses 9.9.2, A.9.9.2, 9.9.3, A.9.9.3, and 9.9.4 to address subsurface chamber ventilation; • added Clauses 10.3.3 and A.10.3.3 to address ventilation for battery equipment; • revised Clause 12.2 to address clearances between submarine cables and structures; • revised Clauses 15.6.2.3 and 15.6.2.4 to address gradient control as relates to rebar, metallic objects, and equipment; • revised Tables 2 and 3 to address minimum separations; and • added Annex G to address building grounding and bonding. CSA Group acknowledges that the development of this Standard was made possible, in part, by the financial support of Electricity Canada (EC), Schneider Electric Canada Inc., IFD Corporation, Hydro-Québec, S&C Electric Canada Ltd., Fortis Alberta, Fortis BC, Maritime Electric, Newfoundland Hydro, Newfoundland Power, EPCOR, Utilities Standards Forum (USF), Alectra Utilities, and Hydro One. This Standard was prepared by the Technical Committee on Underground Systems, under the jurisdiction of the Strategic Steering Committee on Power Engineering and Electromagnetic Compatibility, and has been formally approved by the Technical Committee. 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 1.1 General This Standard applies to the lines and equipment associated with underground electric supply and communication systems located a) entirely outside of buildings; b) outside of indoor supply stations and fenced outdoor supply stations; or c) inside buildings or sections of buildings where they are employed by a utility of i) an electric system; ii) a communication system; or iii) a community antenna distribution system in the exercise of its function as a utility. This Standard, which forms part of the Canadian Electrical Code, Part III, covers the requirements for the construction of underground systems and includes electric supply and communication circuits that are installed alone, in joint use, or in proximity to each other or other facilities. 1.2 Prior editions Existing installations meeting the requirements of prior editions of this Standard need not be modified to comply with this edition of the Standard, except as might be required for safety reasons by the authority having jurisdiction. 1.3 Applications The requirements of this Standard do not constitute complete construction specifications but stipulate the minimum design requirements with regard to a) safety to persons; b) continuity of service; and c) protection of property. 1.4 Exclusion The selection, design, and installation of supply transmission cables (≥ 69 kV) are not addressed in this Standard. 1.5 Common standards Conditions not covered by this Standard are governed by equivalent Standards in common use or by the authority having jurisdiction. 1.6 Types of construction In some cases, requirements are written for specific types of construction. This does not preclude the use of other types of construction arising out of continuing advancements in the field, provided that engineering representatives can demonstrate the safety and suitability of these alternatives. 1.7 Terminology 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.