Thread Content
Changhui Instruments explains, in line with regulatory requirements, the basis for reserving backup circuits in distribution panels (cabinets, boxes) at various levels, the functions of these backup circuits, and the methods for calculating the appropriate number of backup circuits, thereby helping to ensure a more standardized and rational design of low-voltage distribution systems. Backup circuit: yunrun.com.cn/tech/2962.html 1. How much backup circuit capacity should be reserved for each level of power distribution panels (cabinets, boxes)? ①JGJ 16-2008, the Code for Electrical Design of Civil Buildings, specifies that spare circuits should be appropriately reserved in distribution panels (cabinets, boxes) at all levels, taking into account potential future development needs. 7.1.4 The design of the low-voltage distribution system shall meet the following requirements: 1 The number of levels in the low-voltage distribution from the secondary side of the transformer to the electrical loads shall not exceed three. 2 Low-voltage distribution panels or boxes at all levels should be equipped with appropriate spare circuits to account for potential future development needs. The spare circuits of the primary and secondary low-voltage distribution panels should be no less than 25% of the total circuits. ②The 2009 version of \"National Technical Measures for Design of Civil Building Projects – Electrical\" contains a similar statement: 5.1.2 Design principles for low-voltage power distribution systems 1. The design of the power distribution system should be determined by taking into account factors such as the nature of the project, its scale, load capacity, and the requirements of the client. The power supply reliability and quality shall meet the regulatory requirements, and advanced equipment that is economical, energy-efficient, environmentally friendly, and technologically mature shall be used. The wiring of the 2-system should be simple, safe to operate, easy to maintain, and possess a certain degree of flexibility ； The low-voltage distribution technology between the secondary side of the transformer and the electrical equipment generally should not exceed three levels. 3 Depending on the potential for development, appropriate numbers of spare circuits should be reserved in low-voltage distribution panels (cabinets, boxes) at all levels. In the absence of specific reservation requirements, the number of spare circuits should be considered as 25% of the total number of circuits. In short, spare circuits in distribution panels (cabinets, boxes) are generally reserved at 25% of the total number of output circuits. 2. How should the design of backup circuits for distribution panels (cabinets, boxes) be carried out? Reserve space by multiplying the number of outgoing circuits in the distribution panel/cabinet/box by 25%, and round up to the nearest whole number. For example, if a certain distribution box has 1 250A circuit, 2 100A circuits, and 5 63A circuits, how should the spare circuits be designed? No provision is made for a 250A circuit; one 100A circuit is reserved as a backup, and one 63A circuit is reserved. 3. What is the purpose of the spare circuits in the distribution panels (cabinets, boxes)? ①During the operation of the outgoing circuit, if the protection switch is damaged, it is possible to temporarily connect that circuit to a backup circuit, allowing repairs to be carried out at an appropriate time and thus reducing the duration of power outages. ②If there are many single-phase circuits in the outgoing circuits of the distribution box, and phase imbalance occurs during operation, the circuit with a higher load can be transferred to a spare circuit on the phase with a lower load, in order to achieve balanced three-phase loading. ③Within the electrical coverage area supplied by this distribution box, it may be necessary to add more electrical equipment, which can be connected temporarily or permanently, thereby enhancing the flexibility of power distribution. ④When the output circuit needs adjustment, it can be reconfigured using a spare circuit. Author: Wang Lin