The principles followed for the rated current ratio of the main switch and circuit breaker (MCB) in rural lighting electrical ready board

The rated current ratio of the main switch and circuit breaker (MCB) of the lighting distribution box in rural Africa needs to be combined with the core characteristics of low load, unstable power supply, and complex environment in the local area (most areas only meet the basic lighting and small equipment electricity needs, with low per capita electricity load), and follow the core principles of "graded protection, load adaptation, reserved margin, and avoidance of leapfrog tripping". The specific details are as follows: 1 Core ratio principle: The rated current of the main switch is greater than the rated current of the circuit breaker (MCB), forming gradient protection. The main switch needs to cover the total maximum load of all branches, and the circuit breaker (MCB) needs to be accurately matched with the load of each lighting branch to ensure that only the faulty branch trips in case of a fault, without affecting the overall lighting power supply. This is a key prerequisite for avoiding large-scale power outages and meeting the demand for continuity of basic lighting in rural Africa. two Specific ratio standard: Based on the characteristics of rural lighting loads in Africa (with an average electricity consumption of less than 100W per household and low branch loads), the rated current of the main switch is usually 1-2 levels higher than that of the circuit breaker (MCB), and must meet the following requirements: ① The setting current of the main switch's long delay release must be ≥ twice the setting current of the circuit breaker (MCB)'s long delay release; ② The setting current of the instantaneous release of the main switch is ≥ 1.4 times the setting current of the instantaneous release of the circuit breaker (MCB), which strengthens the reliability of the graded protection and avoids tripping beyond the level. three Load adaptation and margin reservation: The rated current of the circuit breaker (MCB) needs to be calculated based on the actual load of the lighting branch (single-phase lighting circuit current calculation formula: current=power ÷ 220V ÷ power factor, power factor taken as 0.8-0.9), accurately matching the total power of the branch lamps; The main switch needs to be multiplied by a simultaneous factor of 0.7-0.9 (considering that the lamps are not turned on at the same time) and a safety margin factor of 1.2-1.5 on the basis of the total load of the branches, to reserve space for adding small lighting equipment in the later stage, adapt to the increasing demand of rural electricity load, and avoid long-term overheating and damage to the switch during full load operation. four Adaptation to African rural special scenarios: ① Environmental adaptation: For outdoor installed distribution boxes, the rated current of switches needs to be adjusted according to the ambient temperature (with a 10% -20% reduction in capacity in high-temperature environments) to cope with the high temperature and dusty environmental characteristics of tropical Africa; ② Power supply stability adaptation: If there are large voltage fluctuations and high risks of short circuits, current limiting circuit breaker (MCB)s are preferred for branch circuits, and models with short delay release devices are selected for main switches to ensure graded action during short circuits and reduce the impact of faults; ③ Simplified adaptation: Considering the limited maintenance conditions in rural areas, the ratio does not need to be overly complex. Standard specification switches are preferred (such as 10-16A for branch switches and 16-25A for main switches), balancing practicality and maintainability. five Auxiliary coordination requirements: The protection characteristic curves of the upper and lower switches should avoid intersecting. If the main switch is a selective type and the branch is a non selective type, the setting current of the short-circuit short delay release of the main switch should be ≥ 1.3 times the setting current of the instantaneous release of the branch to ensure that the branch will act first in case of a fault; At the same time, the rated current of the switch should be matched with the current carrying capacity of the incoming and branch wires to avoid overloading of the wires caused by selecting too many switches, or frequent tripping caused by selecting too few switches, which is in line with the actual situation of simple wiring in rural Africa. Summary: The overall ratio needs to take into account "safety and reliability, load adaptability, and easy maintenance". The core is to achieve graded protection through gradient current setting, which not only meets the low load demand of rural basic lighting in Africa, but also can cope with the problems of unstable power supply and complex environment. At the same time, a reasonable margin should be reserved to reduce maintenance costs in the later stage. Do you need me to provide you with specific examples of switch rated current selection based on typical lighting loads in rural Africa (such as under 100W per household)?