Specification covers the design, manufacture, testing at works and supply of Distribution Boxes made out of CRCA MS for controlling the L. 3 phase, 4 wire, 433 V, 50 HZ with effectively. In a newly constructed residential area, a 10kV power line is introduced into the substation. After stepping down the voltage through the transformer's low-voltage side (0. 4kV to the distribution cabinet (primary distribution cabinet), then the outgoing line is led to the. Differences Between Primary, Secondary, and Tertiary Distribution Boxes Designed for construction or large-scale projects as a main distribution point. Incorporates a complete protection system (e. "Two-level protection" mainly refers to the use of leakage protection measures, in addition to the final switch box to install leakage protection, but also in the upper level distribution box or general distribution box to install a leakage protection, generally forming two levels of protection. The complete set of products can form a complete three-level protection system for construction power, so as to. UNDERGROUND ELECTRIC DISTRIBUTION CONSTRUCTION STANDARDS 2023 EDITION THIS PAGE INTENIONALLY LEFT BLANK Underground Electric Distribution Standards TABLE OF CONTENTS – SECTION / CHAPTER LISTING SECTION I.