贵阳干式变压器：电压互感器的工作原理、分类和选择

电压互感器的工作原理、分类和选择 　　
1.工作原理
用测量仪表直接测量网的高电压时，必须用绝缘水平很高的仪表.并且操作人员触及这些仪表时，会有很大的危险。因此，在测量高电压时，常借助干仪表贵阳干式变压器，将一次侧高压转换为较低的二次电压后，再去测量。这样不仅安全，而且扩大仪表的量程。这种贵阳干式变压器叫做电压互感器。
电压互感器的结构和工作原理与小型双绕组贵阳干式变压器相同，一次绕组匝数较多，并在被测量的线路中，二次绕组匝数较少，接在高阻抗的测量仪表上(例如电压表、功率表的电压线圈、电能表的电压线圈、继电器的线圈等)。由于电压互感器二次绕组的负载是高阻扰仪表，二次电流很小，一、二次绕组中的漏阻抗压降都很小，所以电压互感器相当于一个空载运行的降压贵阳干式变压器。

2.分类
(1)按相数分，有单相和三相。三相只有小于等于10kV，为油浸绝缘，现已被浇注绝缘单相互感器所代替。
(2)按绕组数手 机：13287501888分，分为双绕组、三绕组或四绕组。单相三绕组和申级式电压互感器都是三绕组互感器。单相还有四绕组。
(3)按绝缘介质分
1)油绝缘，一般大于等于35kV时采用。
2)浇注绝缘，小于等于35kV时采用。
3)一般干式，小于等于380V时采用。
4)气体绝缘，大于等于110kV才有采用。
(4)按装置种类分，小于等于10kv多为户内式，大于等于35kV多为户外式。
(5)按结构原理分，在我国电磁式，小于等于35kV均用单级式，大于等于63kV为串级式。在110-220kV范围内，串级式和电容式都有采用；大于等于330kV只生产电容式。

3.电压互感器的选择
电压互感器的选择主要由三个方面决定:①一次侧的额定电压；②二次侧电压要求的准确级和与相对应的二次负载容量；③用途。对于配电盘仪表，可用0.5-1准确级的电压互感器。对于电能表，应选用0.5级。电压互感器除0.1,、0.2级用作试验或精密测量单独制造外，0. 5,、1、 3P、 6P级的电压互感器是指同一只电压互感器在某一负载容量范围内有对应的准确级，P为保护用。

Voltage transformer

1 How it works
Use measuring instruments to directly measure the high voltage power grid, with a high insulation level of the instrument and the operator touches the instrument, there will be a great danger. Therefore, the measurement of high voltage, often with the dry instrument transformers, the primary high voltage is converted to a lower secondary voltage measurement again. This will not only secure, but also to expand the range of the instrument. This transformer is called a voltage transformer.
Structure and working principle of the voltage transformer with a small two-winding power transformers, a more winding turns, and the measured line, the secondary winding turns less connected to the high impedance of the measuring instruments (such as voltage table, the voltage coil of the power meter, energy meter voltage coil, the relay coil, etc.). The voltage transformer secondary winding of the load is high obstruction of the instrument, the secondary current is very small, a secondary winding leakage impedance voltage drop is very small, so the voltage transformer is equivalent to a step-down transformer no-load operation .

2 Category
(1) the number of phases, single phase and three phase. Three-phase only less than or equal to 10kV, oil-immersed insulation, have been pouring insulated single-phase transformer instead.
(2) according to the winding number of points, divided into two-winding, three winding or windings. Single-phase three-winding and application-level voltage transformers are three-winding transformer. Single-phase four windings.
(3) sub-insulated medium
1) oil insulation, generally greater than equal to 35kV using.
2) pouring the insulation is less than or equal to 35kV using.
3) dry, and less than or equal to 380V use.
4) The gas-insulated, greater than or equal to 110kV have adopted.
(4) device types of points, less than or equal to the 10kv mostly indoor type, greater than or equal to 35kV more than for the outdoor type.
(5), according to the structural principle of electromagnetic in China, less than or equal to 35kV single-stage, greater than or equal to 63kV for Cascade. 110-220kV range, Cascade, and capacitive are commonly used; greater than or equal to 330kV produced only capacitive.

Choice of voltage transformer
The choice of the voltage transformer is mainly determined by three aspects: ① primary side rated voltage; the exact level (2) the secondary side voltage requirements and corresponding to the secondary load capacity; ③ use. Distribution panel meter, available of 0.5-1 accurate voltage transformer. 0.5 meter, should be used. Voltage transformer in addition to 0.1, 0.2 as a test or precision measurement of manufacturing outside alone, 0 5,, 1, 3P, 6P-level voltage transformer is the same voltage transformer has a load capacity range corresponding accurate level, P is the protection.

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