Sometimes, in order to reduce the overall dimension of the switchgear, the following methods can be used:
1) Insert a non-metallic insulating diaphragm into the air gap to reduce the requirements for insulation distance. However, it should be noted that the clear air distance shall not be less than 60mm, and the phase to phase insulating partition shall be set in the middle. The disadvantage of this method is that the insulating diaphragm is greatly affected by the service environment, and there is the problem of insulation aging.
2) Use heat shrinkable sleeve to cover the whole high-voltage live conductor. In practice, ensure that the insulation distance is not less than 100mm. The disadvantage is that the heat shrinkable sleeve also has the problem of insulation aging.
To sum up, air insulation shall be used as much as possible to meet the requirements of the above table when the design permits.
II Creepage distance
Since power system users often pursue high reliability, in practice, we should meet the following conditions:
高压开关柜中各组件及其支持绝缘件(纯瓷及绝缘件)的外绝缘爬电比距(高压电器组件外绝缘的爬电距离与额定电压之比)对于纯瓷绝缘为18 mm/k V，对于绝缘为20 mm/k V。
The external insulation creepage distance (the ratio of the creepage distance of the external insulation of the high-voltage electrical components to the rated voltage) of each component and its supporting insulating parts (pure porcelain and insulating parts) in the high-voltage switchgear is 18 mm / kV for pure porcelain insulation and 20 mm / kV for insulation.
As this requirement is relatively high, many conventional components often can not meet the requirements, which requires us to inform the component manufacturer to customize. Component manufacturers often adopt the method of increasing without increasing the insulator height.
When selecting the type, we should pay attention to the ratio of skirt height to skirt distance. In addition, we should also pay attention to the environmental conditions of the place where the switchgear is used. In order to prevent condensation, we can add a heater with automatic control in the switchgear.
III Degree of protection
In order to prevent the human body from approaching the high-voltage live part and touching the moving part of the high-voltage switchgear, we should consider how many levels of protection should be achieved when designing the switchgear.
设计时我们要注意随着防护等级的提高，生产成本相应提高，散热条件变差，所以不能追求高的防护等级，一般以I P 3 X和I P 4 X为宜。
In the design, we should pay attention to that with the improvement of protection level, the production cost increases accordingly and the heat dissipation conditions become worse. Therefore, we cannot pursue high protection level. Generally, IP3X and IP4X are appropriate.
IV Dynamic stability
在电力系统中，高压开关柜通常要能承受2 0 k A，3 2 k A，4 0 k A甚至5 0 k A的额定短路开断电流，当开关柜中通过如此大的电流时，相间及同相母线之间会产生很大的电动力。这时，我们需借助支撑绝缘子的支撑，使母线不会产生明显位移。
In the power system, the high-voltage switchgear usually can withstand the rated short-circuit breaking current of 20 Ka, 32 Ka, 40 Ka or even 50 Ka. When such a large current passes through the switchgear, great electric power will be generated between phases and in-phase buses. At this time, we need the support of the support insulator to prevent the bus from obvious displacement.
V temperature rise
电力系统中开关柜通常要能承受4 0 0 0 A
In the power system, the switch cabinet is usually able to withstand 400 a
And below the normal working current, because the primary components usually operate in a sealed cabinet, the heat generated by them is difficult to be dissipated outside the cabinet, resulting in an increase in the temperature in the cabinet. If the temperature exceeds the following limit values, the components will be burned, resulting in accidents.
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