电动伸缩门是一种长期在户外使用的设备，工作电压为220 V（过去也有380 V），其电机是处于移动状态。据悉，在高峰运行期间电动门每小时需开合数十次，这种工作特点势必导致线路极易老化。此外，在雨季电机不锈钢缝隙也容易漏水、积水、造成漏电，发生电击事故。当然这只是电动门发生电击事故的一个原因。应该说这是设备问题、物业管理问题，看起来与配电设计风马牛不相及，其实不然。
The electric telescopic door is a long - term outdoor equipment with a operating voltage of 220 V (380 V in the past), and its motor is in a moving state. It is reported that the electric door should be opened ten times per hour during the peak operation, which is bound to lead to the very easy aging of the line. In addition, during the rainy season, the stainless steel crevice in the rainy season is easy to leak, water, cause electricity leakage and electric shock. Of course, it's just one of the reasons why electric doors have an electric shock. It should be said that this is a problem of equipment and property management, which seems to be different from the distribution design.
为什么要做配电设计？对此答案很多，但是保护人身和设备安全应该是最根本的原因和目的。特别对于电气设备外露导电部分，正常时是不带点的却因绝缘损坏而带故障电压，这时人或动物接触此外露导电部分则会遭到电击，通常将这种电击称为“间接接触电击”。对此，设计人员应尽力做好防护。
Why do you want to do distribution design? There are a lot of answers to this, but the protection of people and equipment should be the most fundamental cause and purpose. Especially for the exposed part of the electrical equipment, it is normal without any point, but it is damaged by the insulation. With the breakdown voltage, people or animals will be subjected to electric shock when exposed to the exposed part. This kind of electric shock is usually called "indirect contact electric shock". In this regard, the designers should do their best to protect them.
应提及的是：GB 50054 – 2011《低压配电设计规范》（2012年6月1日起实施）中将电气装置的电击防护分为“直接接触防护”与“间接接触防护”，而在2012年12月1日起实施的GB 16895. 21 – 2011/ IEC 60364 – 4 – 41：2005《低压电气装置  第4 – 41部分：安全防护 电击防护》特别指出：
We should mention is: GB 50054 - 2011 "low voltage distribution design specification" (June 1, 2012 onwards), electrical apparatus, electric shock protection is divided into "protection against direct contact and indirect contact protection", and in December 1, 2012 implementation of GB 16895.21 - 2011/ IEC 60364 - 4 - fourth - 41:2005 "low voltage electrical installations Part 41 safety protection: protection against electric shock" in particular:
“——正常条件下的电击防护称直接接触防护（本部分改称为基本保护）；
"- the protection of electric shock under normal conditions is called direct contact protection (this part is called the basic protection).
——故障条件下的电击防护称间接接触防护（本部分改称故障保护）。”
The protection of electric shock under the condition of failure is called indirect contact protection (this part is called fault protection). "
在本文中对电击防护的称谓仍是按照 GB 50054 – 2011中的规定实施。
The appellation for electric shock protection in this article is still in accordance with the provisions of GB 50054 - 2011.
低压配电系统的接地形式，对间接接触防护的自动切断电源措施极为重要
The grounding form of low voltage distribution system is very important for the measures of automatic cutting off power supply for indirect contact protection
在现行的配电设计中，最常采用的间接接触防护措施是自动切断电源，也就是通常在配电设计中采用各类保护电器对人身、线路及设备进行保护。该保护措施对于不同的低压配电系统的接地形式，其间接接触防护电气的动作特性各不相同。
In the current distribution design, the most commonly used indirect contact protection measures is to automatically cut off the power supply, that is, usually in the distribution design, all kinds of protective appliances are used to protect the body, line and equipment. The protection measures are different in the grounding form of different low-voltage distribution systems, and their indirect contact protection electrical characteristics are different.
TN 系统中配电线路的间接接触防护电器的动作特性应符合下式要求：
In the TN system, the action characteristics of the indirect contact protective electrical apparatus for distribution lines should conform to the requirements of the next type.
Zs Ia ≤ U0
Zs Ia = U0
式中:Zs —— 接地故障回路的阻抗,Ω;
Type: Zs - the impedance of the grounding fault loop, omega;
Ia —— 保证间接接触保护电器在规定时间内切断故障回路的动作电流，A；
Ia - guarantee the action current of the indirect contact protection electrical apparatus to cut off the fault loop within the specified time, A;
U0 —— 相导体对地标称电压，V。
U0 - the nominal voltage of the phase conductor to the earth, V.
由此可看出，TN系统发生接地故障时，电流的切断与接地电阻的阻值无关。
Thus, it can be seen that the cut off of the current has nothing to do with the resistance value of the grounding resistance when the ground fault occurs in the TN system.
对于 TT 系统，其保护电气动作特性应满足下式要求：
For the TT system, its protective electrical action characteristics should meet the following requirements:
RA Ia ≤ 50V
RA Ia = 50V
式中：RA —— 外露可导电部分的姐弟电阻和保护导体电阻之和，Ω。
Type: RA - the resistance of the sister and brother of the exposed conductive part and the sum of the resistance of the conductor, Omega.
在实际设计中最常用的是TN 系统，由于门卫室及电动门是一个很小的用户，往往是不重视其接地故障电流的计算，当然也不会去按上述要求进行接地故障灵敏度校核，这些可能造成电动门发生接地故障时保护电器不动作，给人身带来电击的危险和伤害。
In the actual design is the most commonly used in the TN system, as the guard room and the electric door is a very small user, often do not pay attention to the calculation of the ground fault current, and certainly not to the requirements according to the ground fault sensitivity check, these may cause protection of electrical action electric door grounding fault when people bring to the risk of electric shock and damage.
电动门一般是由门卫室或岗亭的配电箱供电，常选用无选择性的A型开关，通常无法在发生接地故障时自动切断电源，为了使其具有选择性，不妨选具有选择性的B型开关作为电源的保护电器！
The electric door is powered by the guard room or booth distribution box, often use the A type switch non selective, usually not in the ground fault occurs automatically cut off power supply, in order to make the selective, may wish to choose the type of B with selective switch for protection of electric power supply!
顺便说一下，配电断路器有A、B两类：A型开关只有过载长延时及瞬时脱口二段保护，属非选择性开关；B类则具有过载长延时、短延时及瞬时脱口三段保护，为选择性断路器。如果电源开关选用B类断路器，是可根据接地故障电流的大小来整定脱口电流的数值及动作时间。
By the way, there are two kinds of distribution circuit breakers: A and B: the A switch is only overload, long delay and instantaneous two phase protection. It is a non selective switch. B has overload, long delay, short delay and instantaneous trip three stage protection. It is a selective circuit breaker. If the power switch selects the B type circuit breaker, it is possible to adjust the value and action time of the deport current according to the size of the grounding fault current.
TN 系统在采用自动切断电源措施时，一定要辅以等电位联结
The TN system must be assisted by equipotential bonding when it is used to cut off the power of the power automatically.
现今，大部分建筑物的配电设计都采用TN系统。规程、规范都规定：TN 系统在采用自动切断电源措施时，一定要辅以等电位联结。
Nowadays, TN system is used in most of the distribution design of buildings. Regulations and specifications stipulate that the TN system must be supplemented by equipotential bonding when the power supply is automatically cut off.
规范GB 16895.21 – 2011 / IEC 60364 – 4 – 41：2005及GB 50054 – 2011 都规定在低压配电系统中采用自动切断电源的防电击的防护措施，以及该措施失效时附加保护措施。对于 TN 系统而言，等电位联结是十分重要且必须的附加保护之一。
Specifications GB 16895.21 – 2011 / IEC 60364 – 4 – 41:2005 and GB 50054 – 2011 provide protection measures against electric shocks for automatic power cuts in low-voltage distribution systems, and additional protection measures when failure is applied. For the TN system, the equipotential bonding is one of the most important and necessary additional protections.
为了说明原因，还得从 TN 系统的接线特点说起。
In order to explain the reasons, we also have to talk about the connection characteristics of the TN system.
TN 系统的第一个字母表示电源的一点（通常是中性点N）与大地直接连接，第二个字母则表示电气装置外露可导电部分通过保护线与该接地点相连接，也就是说，TN 系统电源侧的 PE 线是与负荷侧全程贯通的。这样，当电源侧或负荷侧某处发生接地故障，故障电压会通过 PE 线传到其他负荷的外露可导电金属外壳，例如电动伸缩门的金属外壳。TN 系统这种“城门失火，殃及池鱼”的特点，设计者应给予关注。浙江小女孩爬在未运行的电动门上玩耍、深圳一名保安无意触及静止的电动门均遭电击，不幸身亡，经查门卫处的配电箱并未发生过故障，恐怕都与系统内传到的危险故障电压有关啊！
The first letter of the TN system that a power supply (usually neutral N) is directly connected with the earth, the second letter said electrical device exposed conductive parts through the protection line and the ground is connected, that is to say, TN system power supply side and load side line PE is the whole process through the. In this way, when the grounding fault occurs on the power side or the load side, the fault voltage will be transmitted to other load exposed metal shells through the PE line, such as the metal shell of the electric telescopic door. TN system the gates of fire, the characteristics of adverse impacts, the designer should be given attention. The little girl in Zhejiang climbed on the unfunctioning electric door. A security guard in Shenzhen didn't touch a stationary electric door. It was all killed by electric shock. There was no fault in the distribution box at the door guard. I'm afraid it's all related to the dangerous breakdown voltage in the system.
根据电气设备和电气装置防间接接触电击
Protection against indirect contact electric shock based on electrical equipment and electrical equipment