Sch 2Requirements for underground lines and certain other powerlines

Schedule 2—Requirements for underground lines and certain other powerlines (regulations 49 and 50) listed standards means the standards (both national and international), codes, guides and other documents listed in the Appendix at the end of this Schedule as published as referred to in the Appendix or, if no such reference is included in the Appendix, as published from time to time. 2—Design—general (1) Underground lines must be designed so that— (a) cables have safe levels of electrical insulation; and (b) cables will carry load currents for which they are designed without failure; and (c) cables will pass short circuit current which will enable the correct operation of protective devices; and (d) the required clearances between a building or structure and an underground powerline as prescribed by regulation 82 are maintained, and so as to comply with the listed standards or achieve, to the satisfaction of the Technical Regulator, the same or better safety and technical outcomes. (2) In determining electrical service conditions and the physical environment under which the line will operate, due care must be given to the consideration of extremes that may occur, the likelihood of their occurrence and the associated risks. 3—Cables and accessories Cables and their accessories must, so as to ensure safe operational performance, conform to the listed standards or achieve, to the satisfaction of the Technical Regulator, the same or better safety and technical outcomes. 4—Cable ratings (1) The rating of a cable must be sufficient to pass the electrical load for which it is designed without failure or excessive heating. (2) Rating of cables must be determined in accordance with the listed standards. 5—Short circuit rating of conductors and cable screens (1) The cable conductors and cable screens must be of sufficient size to pass short circuit currents without overheating for the time taken for the operation of the protective device. (2) The short circuit capacity of cable must be determined in accordance with the listed standards. 6—Installation—general Underground lines must be installed in a safe manner in accordance with this Schedule and the listed standards or so as to achieve, to the satisfaction of the Technical Regulator, the same or better safety and technical outcomes. 7—Installation of underground lines (1) An underground line must be installed in accordance with Table 1 below and, subject to this clause, at the depth fixed for the designated voltage and cable type. (2) For the mechanical cover and enclosures referred to in Table 1 below, 1 of the following must be used: (a) a layer of concrete at least 50 mm thick with a characteristic strength defined by AS 3600 and AS 1012 and determined to be not less than 15 MPa at 28 days placed not less than 50 mm and not more than 150 mm above the cable and overlapping the cable by at least 40 mm on each side; or (b) concrete slabs of at least 40 mm thickness with a characteristic strength defined as AS 3600 and AS 1012 and determined to be not less than 15 MPa at 28 days with— (i) each slab touching the next so that there are no spaces left between slabs; and (ii) the slabs being placed not less than 50 mm and not more than 150 mm above the cable and overlapping the cable by at least 40 mm on each side of the cable; or (c) a plastic or composite material that offers comparable protection (depending on depth of installation). (3) The enclosure referred to in the last column of Table 1 must be a medium or heavy galvanised steel tube conforming to AS 1074 or a non‑metallic heavy duty conduit conforming to AS/NZS 2053 (depending on depth of installation). (4) If it is impractical to lay an underground line at a depth which complies with Table 1 then they may be laid at a lesser depth provided that additional covers or enclosures are installed to provide equivalent protection to that prescribed. (5) The underground line, from where it enters the ground to a position where it complies with the requirements of depth and protection in Table 1, must be protected by a cover or enclosure described above. (6) Table