有時為了減少開關柜外形尺寸,可以有以下幾種方法:
Sometimes, in order to reduce the overall dimension of the switchgear, the following methods can be used:
1)在空氣間隙中插入一塊非金屬的絕緣隔板,從而縮小對絕緣距離的要求。但要注意的是空氣凈距離不小于60毫米,相間絕緣隔板應設置在中間位置。該方法的缺點是絕緣隔板受使用環(huán)境影響很大,存在絕緣老化的問題。
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)使用熱縮套管把高壓帶電導體整個套起來,實踐中要確保絕緣距離不小于100毫米。缺點是熱縮套管同樣存在絕緣老化的問題。
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.
綜上所述,在設計許可的情況下,盡可能地使用空氣絕緣,滿足上表的要求。
To sum up, air insulation shall be used as much as possible to meet the requirements of the above table when the design permits.
二.爬電距離
II Creepage distance
由于電力系統(tǒng)用戶往往追求高可靠性,實踐中我們要符合以下條件:
Since power system users often pursue high reliability, in practice, we should meet the following conditions:
高壓開關柜中各組件及其支持絕緣件(純瓷及絕緣件)的外絕緣爬電比距(高壓電器組件外絕緣的爬電距離與額定電壓之比)對于純瓷絕緣為18 mm/k V,對于絕緣為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.
由于這一要求比較高,很多常規(guī)的元器件往往滿足不了要求,這就要求我們告知元器件生產廠家加以定制。元器件生產廠家往往會采用不增加絕緣子高度而增多的方法。
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.
我們在選型時要注意裙邊的高度與裙距比例不能太懸殊,另外,我們還應注意開關柜使用場所的環(huán)境條件,為了防止發(fā)生凝露,我們可以在開關柜中加入帶自動控制的加熱器。
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.
三.防護等級
III Degree of protection
為了防止人體接近高壓開關柜的高壓帶電部分和觸及運動部分,在設計開關柜時,我們應考慮要達到幾級防護等級。
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.
設計時我們要注意隨著防護等級的提高,生產成本相應提高,散熱條件變差,所以不能追求高的防護等級,一般以I P 3 X和I P 4 X為宜。
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.
四.動穩(wěn)定
IV Dynamic stability
在電力系統(tǒng)中,高壓開關柜通常要能承受2 0 k A,3 2 k A,4 0 k A甚5 0 k A的額定短路開斷電流,當開關柜中通過如此大的電流時,相間及同相母線之間會產生很大的電動力。這時,我們需借助支撐絕緣子的支撐,使母線不會產生明顯位移。
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.
五.溫升
V temperature rise
電力系統(tǒng)中開關柜通常要能承受4 0 0 0 A
In the power system, the switch cabinet is usually able to withstand 400 a
及以下的正常工作電流,由于一次元器件通常處于密封的柜內運行,他們產生的熱量很難散發(fā)到柜外,所以導致柜內溫度升高。若溫度超過以下限定值,便會燒毀元器件,釀成事故。
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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