Category:power
Question:
a medium-pressure tap cvt why not shake the end of the insulation screen?
Answer:
Hello:
for Capacitive voltage transformer CVT must specify two points:
⑴ CVT for medium-pressure tap should be referred to a single CVT (110kV or 220kV next section) with the voltage transformer C1 and C2 the middle of the terminal A
⑵ CVT only the end of the capacitor, rather than calling it the end of screen; capacitor-type current transformer due to its production in different ways, while the outer layer of its capacitance, said capacitance screen it as the end of screen;
Note: (capacitor-type structure of the current transformer, electric screens are at the end (the most outer layer capacitance screen). Capacitive CT is widely used in porcelain box-type -shaped coil structure, in order to improve the main insulation strength, insulation placed in a certain number of concentric circular capacitive screen (the outermost screen grounded capacitors), the capacitor formed between the screen one by one in series capacitor, which is called the cable capacitance-type insulation. the adjacent capacitor between screen capacitors are equal, then its near-uniform voltage distribution. neighboring capacitor insulation thickness of the smaller screen, then the use of insulation, the better. capacitive screens a few more, then the insulation in the more uniform distribution of electric field strength. In fact, capacitance screen number can not be too much, can do to make the electric field was approximately uniform intensity distribution. Therefore, capacitor-type insulation in the electric field strength within the CT distribution of the structure, forming a capacitive screen, that is, the outermost layer of capacitive screen - the end of electric screens.
CVTs divider capacitor insulation resistance measurement:
⑴ measuring the insulation resistance of C1 + C2 - C1 pressing the first side A; the C2 end of N ground. C1 and C2 were measured without. shall medium voltage transformer high voltage winding of end of the XL vacant.
⑵ medium voltage transformer CVT measuring the insulation resistance: In the A to medium voltage transformer high voltage winding The end of the XL grounding.
Answer:
do not know if the pressure tap that? I know that the CVT is a screen at the end farthest from the live parts of which the outermost layer, which is the lowest voltage, normal operation , it should be grounded, or there will be thousands of volts of high voltage, grounding is to ensure that their normal work.
CVT shaking at the end is the end of the insulation screen screen-to-ground insulation. because of the end of screen running on the ground, so if the end of screen -to-ground insulation is low, it will not affect the normal CVT operation.
something like this, specifically Im not very clear.
Chinese:有中压抽头的cvt为什么不用摇末屏的绝缘？
类别: 电力
问题:
有中压抽头的cvt为什么不用摇末屏的绝缘？
回答:
你好：
对于电容型电压互感器CVT须指明两点：
⑴ CVT的中压抽头所指应该是单节CVT（110kV的或220kV的下节）含中压变压器的C1与C2的中间端子A’；
⑵CVT只有电容器的尾端，而不称其为末屏；电容型电流互感器由于其的制作方式不同，而将其电容的外层电容屏称其为末屏；
注：（电容型结构的电流互感器，均有末电屏（最外层电容屏）。电容型CT广泛使用的是瓷箱式“U”字形线圈结构，为了提高主绝缘的强度，在绝缘中放置一定数量的同心圆形电容屏（最外层电容屏接地），各电容屏间形成一个个串联的电容器，这叫做电缆电容型绝缘。各相邻电容屏间的电容相等，则其电压分布近于均匀。相邻电容屏间绝缘厚度越小，则绝缘的利用就越好。电容屏数越多，则绝缘中电场强度的分布就越均匀。实际上，电容屏数不能太多，只能做到使电场强度分布得近似均匀。因此，电容型CT内绝缘中电场强度的分布结构，形成了电容屏，即最外层电容屏－末电屏。
CVT的分压电容绝缘电阻的测量：
⑴测量C1＋C2的绝缘电阻——加压C1的首端A；将C2的末端N接地。C1与C2不需分别测量。须将中压变压器高压绕组的尾端XL悬空。
⑵测量CVT中压变压器的绝缘电阻：在A’端加压测量CVT中压变压器高压对二次对地绝缘电阻；须将C2的末端N悬空；将中压变压器高压绕组的尾端XL接地。
回答:
不知道中压抽头是什么？我知道CVT末屏是距离带电部分最远的最外面的那层，它是电压{zd1}的，正常运行时，应该接地，否则会有几千伏的高压，接地是为了保证其正常工作。
CVT摇末屏的绝缘是指末屏对地绝缘。因为末屏运行时就该接地，所以，如果末屏对地绝缘低，也不会影响CVT正常运行。
大概是这样，具体我也不是很清楚。