IEC 60364-5-52:2009 deals with the selection and erection of wiring systems. This third edition cancels and replaces the second edition, published in 2001, and constitutes a technical revision. The main changes with respect to the previous edition are as follows: – Subclause 521.4 introduces minor changes with regard to busbar trunking systems and powertrack systems. – Subclause 523.6 introduces minor changes with regard to the sizing of cables where harmonic currents are present. – A new sublause 523.9 concerning single-core cables with a metallic covering has been introduced. – Clause 525 introduces changes in the maximum value of voltage drop permitted between the origin of the consumer's installation and the equipment which should not be greater than that given in the relevant annex. – Clause 526 introduces minor changes to electrical connections including additional exceptions for inspection of connections and additional notes. – Clause 528 introduces additional requirements with regard to proximity of underground power and telecommunication cables. – Clause 529 introduces minor changes to selection and erection of wiring systems in relation to maintainability, including cleaning.