1 关于配电箱：
配电箱是按电气接线要求将开关设备，测量仪表，保护电气和辅助设备组装在封闭金属或非金属箱重，购车低压配电装置的设备。配电箱应具有合理的分配电能的作用，且设计时尽量考虑各相负载均衡，启停控制对电网影响降低到最小。一般分为照明配电箱，计量给电箱，动力配电箱。
2 生产执行标准：
一般在中国我们按照GB7251标准执行，在国际上的其他地区的项目，应遵循招标方技术规格要求执行。
GB7251.1 2013 低压成套开关设备和控制设备 第1部分总则
GB7251.12 2013低压成套开关设备和控制设备 第2部分：成套电力开关和控制设备
GB7251.3 2017低压成套开关设备和控制设备 第3部分由一般人员操作的配电盘
在国际上，我们一般按照IEC61439标准执行，满足欧标标准。有时候客户项目要求也会按British Standard标准执行，BS标准的开关标准覆盖了很多方面，包括电路断路器、跳闸器、动力继电器、气体绝缘开关、手动控制开关、车用电子产品、继电器等。深入了解这些标准对于市场参与者（例如制造商和设计院）和最终用户的安全至关重要。
BS开关标准的实施旨在保证产品的质量和性能，以确保在使用开关设备时不会出现危险和故障。在制定标准的过程中，会对开关产品的性能、寿命、外部环境的影响、使用者的安全需求、电压和频率等多种因素进行综合考虑。
BS开关标准在很长一段时间内一直被视为世界上比较权&威性和可靠的标准之一。人们普遍认为采用符合BS标准的开关将为消费者提供更安全、可靠和长久使用的保障。
3 电参数及使用环境的要求：
不同国家及地区，变电站出来的电压不仅相同，所以在设计开始时，应与客户确认电压，防护等级，室内或是室外使用，以及是否属于海边，或者是海上使用。同时，我们还应考虑现场的温差，及湿度，海拔等影响。温度/湿度早晚比较大的情况时，箱内需要加装加热器除湿，必要时还需要加装性能可靠的呼吸阀。现场的复杂环境均会影响元件的选型及配电箱结构的设计。此外还应考虑配电箱的安装方式，及柜门的打开方向，配电箱壳体的材质要求等等。
4 配电箱的防护等级：
IP防护等级（Ingress Protection））系统是由IEC（International Electrotechnical Commission）所起草，将电器依其防尘防湿气之特性加以分级。IP防护等级是由两个数字所组成，第1个数字表示电器防尘、防止外物侵入的等级(这里所指的外物含工具，人的手指等均不可接触到电器之内带电部分，以免触电)，第2个数字表示电器防湿气、防水浸入的密闭程度，数字越大表示其防护等级越高。防护等级应遵照IEC60529标准执行。
IP后首数字 代表防尘等级
数字 | 防护范围 | 说明 |
0 | 无防护 | 对外界的人或物无特殊的防护 |
1 | 防止直径大于50mm的固体外物侵入 | 防止人体（如手掌）因意外而接触到电器内部的零件，防止较大尺寸（直径大于50mm）的外物侵入 |
2 | 防止直径大于12.5mm的固体外物侵入 | 防止人的手指接触到电器内部的零件，防止中等尺寸（直径大于12.5mm）的外物侵入 |
3 | 防止直径大于2.5mm的固体外物侵入 | 防止直径或厚度大于2.5mm的工具、电线及类似的小型外物侵入而接触到电器内部的零件 |
4 | 防止直径大于1.0mm的固体外物侵入 | 防止直径或厚度大于1.0mm的工具、电线及类似的小型外物侵入而接触到电器内部的零件 |
5 | 防止外物及灰尘 | 全防止外物侵入，虽不能全防止灰尘侵入，但灰尘的侵入量不会影响电器的正常运作 |
6 | 防止外物及灰尘 | 全防止外物及灰尘侵入 |
IP后第二位数字代表 防水等级
数字 | 防护范围 | 说明 |
0 | 无防护 | 对水或湿气无特殊的防护 |
1 | 防止水滴浸入 | 垂直落下的水滴（如凝结水）不会对电器造成损坏 |
2 | 倾斜15度时，仍可防止水滴浸入 | 当电器由垂直倾斜至15度时，滴水不会对电器造成损坏 |
3 | 防止喷洒的水浸入 | 防雨或防止与垂直的夹角小于60度的方向所喷洒的水侵入电器而造成损坏 |
4 | 防止飞溅的水浸入 | 防止各个方向飞溅而来的水侵入电器而造成损坏 |
5 | 防止喷射的水浸入 | 防持续至少3分钟的低压喷水 |
6 | 防止大浪浸入 | 防持续至少3分钟的大量喷水 |
5 内部元件的选择
元件的选择如热继电器的选择，需要根据脱扣电流及复杂还选择。此外，不用国家的不同标准，还应注意导线的颜色，及耐压等级，是否有要求导线为低压无卤阻燃等等。涉及到低温区域环境，如-60摄氏度的极低环境温度，还应考虑低温特性进行设计。
7 人机交互性的设计
现代设计理念要求考虑人机交互性，如配电箱安装的高度，箱内或箱外的照明灯具，各回路开关标签及运行指示灯的位置，颜色，必要时急停开关的设置及醒目的标识说明等等，都应考虑在内。
Design of low voltage distribution system
1 About distribution box：
Distribution box is a device that assembles switchgear, measuring instruments, protective electrical and auxiliary equipment in closed metal or non-metal boxes according to electrical wiring requirements and purchases low-voltage distribution devices. The distribution box should have the function of distributing power reasonably, and the load balance of each phase should be considered as far as possible in the design, and the impact of start-stop control on the grid should be minimized. Generally divided into lighting distribution box, metering power box, power distribution box.
2 Production execution standard：
Generally, in China, accordance with GB7251 standard, and in other areas of the international project, we should follow the technical specifications of the tenderer.
GB7251.1 2013 Low voltage switchgear and control equipment - Part 1 General
Low voltage switchgear and control equipment - Part 2: Switchgear and control equipment
GB7251.3 2017 Low voltage switchgear and control equipment - Part 3 Switchboards operated by general personnel
Internationally, we generally comply with IEC61439 standards to meet European standards. Sometimes customer project requirements will be implemented according to British Standard standards, BS standard switching standards cover many aspects, including circuit breakers, trip, power relays, gas insulated switches, manual control switches, automotive electronics, relays and so on. An in-depth understanding of these standards is essential for the safety of market participants (such as manufacturers and design institutes) and end users.
The implementation of BS switching standards aims to guarantee the quality and performance of products to ensure that there are no hazards and failures when using switchgear. In the process of developing the standard, many factors such as the performance of the switch product, life, the impact of the external environment, the safety needs of the user, voltage and frequency are comprehensively considered.
The BS switch standard has been regarded as one of the most authoritative and reliable standards in the world
for a long time. It is widely believed that the use of BS standard switches will provide consumers with more safety,
reliability and long-term protection.
3 Electrical parameters and operating environment requirements：
Different countries and regions, the voltage out of the substation is not only the same, so at the beginning of the design, we should confirm with the customer the voltage, protection level, indoor or outdoor use, and whether it belongs to the sea, or is used at sea. At the same time, we should also consider the on-site temperature difference, humidity, altitude and other effects. When the temperature/humidity is relatively large in the morning and evening, the box needs to be equipped with a heater dehumidification, and if necessary, it also needs to be equipped with a reliable breathing valve. The complex environment of the site will affect the selection of components and the design of distribution box structure. In addition, the installation method of the distribution box, the opening direction of the cabinet door, the material requirements of the distribution box shell and so on should be considered.
4 Protection level of distribution box：
The IP Protection (Ingress Protection) system was drafted by the International Electrotechnical Commission (IEC) to classify electrical appliances according to their dust and moisture resistance. IP protection level is composed of two numbers, the first number indicates the electrical dust, to prevent the level of foreign object intrusion (here refers to the foreign objects including tools, human fingers, etc. are not exposed to the electrical appliances within the live part, so as to avoid electric shock), the second number indicates the degree of electrical moisture, waterproof immersion, the greater the number indicates the higher the level of protection. The protection level shall comply with the IEC60529 standard.
The first digit after IP indicates the dust protection level
Digit | Range of protection | |
0 | unguard | No special protection against outside persons or objects |
1 | Prevent the invasion of solid objects larger than 50mm in diameter | Prevent the human body (such as the palm) from accidentally contacting the parts inside the electrical appliance, and prevent the intrusion of foreign objects of larger size (diameter greater than 50mm) |
2 | Prevent the invasion of solid objects larger than 12.5mm in diameter | Prevent human fingers from contacting the parts inside the appliance, and prevent the intrusion of medium size (diameter greater than 12.5mm) foreign objects |
3 | Prevent the invasion of solid objects larger than 2.5mm in diameter | Prevent tools, wires and similar small foreign objects with a diameter or thickness greater than 2.5mm from invading and contacting the parts inside the electrical appliance |
4 | Prevent the invasion of solid objects larger than 1.0mm in diameter | Prevent tools, wires and similar small foreign objects with a diameter or thickness greater than 1.0mm from invading and contacting the parts inside the electrical appliance |
5 | Prevent foreign objects and dust | Completely prevent foreign object intrusion, although it can not completely prevent dust intrusion, but the amount of dust intrusion will not affect the normal operation of the electrical appliance |
6 | Prevent foreign objects and dust | Completely prevent foreign objects and dust intrusion |
The second digit after IP indicates the waterproof rating
Digit | Range of protection | Instructions |
0 | unguard | No special protection against water or moisture |
1 | Prevent water dripping | Falling water droplets (such as condensate) will not cause damage to electrical appliances |
2 | When tilted 15 degrees, water droplets can still be prevented from immersion | When the appliance is tilted from vertical to 15 degrees, dripping water will not cause damage to the appliance |
3 | Prevent the spray water from soaking in | Prevent rain or prevent water sprayed in the direction of vertical Angle less than 60 degrees from invading electrical appliances and causing damage |
4 | Prevent splashing water from soaking in | Prevent splashing water from all directions from invading electrical appliances and causing damage |
5 | Prevent the spray water from immersing | Prevent low pressure spray lasting at least 3 minutes |
6 | Keep big waves out | Avoid spraying large amounts of water for at least 3 minutes |
5 Selection of internal components
The selection of components, such as the selection of thermal relays, needs to be selected according to the trip current and complexity. In addition, without the different standards of the country, we should also pay attention to the color of the wire, and the pressure level, whether the wire is required to be low-pressure halogen-free flame retardant and so on. When it comes to low-temperature regional environments, such as extremely low ambient temperatures of -60 degrees Celsius, the low-temperature characteristics should also be considered in the design.
7 Design of man-machine interaction
Modern design concepts require consideration of human-machine interaction, such as the height of the distribution box installation, the lighting inside or outside the box, the location of the circuit switch label and running indicator light, color, if necessary, the setting of the emergency stop switch and eye-catching identification instructions, etc., should be taken into account.
