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The copper conductor wire and cable current carrying capacity standard was translated from the section 523 ampacity of the fifth part of the electrical installations of the International Electrotechnical Commission. The standard number is IEC60364-5-523 in 1983. Since the reform and opening up, public utilities and housing construction have developed rapidly, and household electrical equipment and other electrical equipment have increased. However, it cannot be overlooked that in the fires that occur every year, electrical fires also show an upward trend. In a few short years, the proportion of electrical fires has more than doubled, and a considerable part of this has been caused by faults in the insulation of cables and cables, overheated spontaneous combustion, poor contact, single-phase grounding of cables, and short-circuits between phases. Therefore, how to use cables and wires scientifically and reasonably, and accurately select the current carrying capacity of cables and cables, and comply with the norms for management and maintenance, is crucial. As there is no national standard for cable and wire current carrying capacity below 1000V, and the most extensive use of cable and wire is in this area, in view of this, the National Building Electrical Equipment Standardization Technical Committee has proposed the preparation of a standard plan to report national technology. The Bureau of Supervision supervised the adoption of the International Electrotechnical Commission's IEC 60364-5-523 standard as a national standard (China's cable and wire comply with the IEC cable and cable manufacturing standards).
The Standardization Technical Committee of Electrical Installations of Buildings and the International Copper Association are now compliant with the IEC60364-5-523 standard for copper-cored cable and cable current-carrying capacity and provide reference for design, production, construction and installation, quality inspection, operation and management. In 1995, the International Electrotechnical Commission began to revise the ampacity standards for the 1983 edition and has now entered the final approval stage. After a detailed comparison of the two, the following circumstances and changes have been told to the reader:
1. The applicable voltage range is changed to AC 1KV and DC 1.5KV.
2. The current carrying capacity of copper wire 1.0mm2 and aluminum core 1.0mm2, 1.5mm2 was deleted.
3. There is basically no change in the current carrying capacity, and individual variations do not exceed 7%.
4. There is no change in the cable wire type and temperature rise limit.
5. Increase the correction coefficient when the soil thermal resistance is not 2.5Km/W.
6. The textual description of the cable wiring in the table is changed to diagram.
7. Table 52-E4, E5 cancel the non-porous tray's current-carrying capacity data.
8. The following changes have been made to 523.5:
(1). 4-phase and 5-core cables can have larger current-carrying capacity only when the three-phase conductors have load current and balance;
(2) When the three-phase load is unbalanced, the temperature rise caused by the neutral current will be offset by the reduced heating of the line current. In this case, the conductor cross-section should be selected according to the maximum phase current;
(3) When there is a load current at the neutral line, and the phase current does not reduce accordingly, the neutral harmonic current is greater than 10%, and the neutral section should not be less than the phase section. See Appendix C for the larger harmonic current correction factor.
9. Increase the number of parallel conductors to achieve some balance of load current distribution.