The voltage transformer is similar to the transformer, which is an instrument used to transform the voltage. However, the purpose of transformer voltage is to facilitate transportation power, so the capacity is very large, generally uses KVA or Zhaofu as the calculation unit; the purpose of the voltage transformer transformation of the voltage Protect the power supply to measure the voltage, power, and power of the line, or to protect the valuable equipment, motors and transformers in the line when the line is faulty. 

　　The common wiring method of voltage transformers has the following:

　　(1) Single terminal wiring can be used to measure the relative ground voltage of the line voltage of 35kV and below the neutral point or the neutral point directly grounding system above 110kV.

　　(2) The V/V wiring is the height of the two full insulation single-phase voltage transformers connected to the phase and the phase to form an incomplete triangle. This method is often used in the 35kV and below high-voltage three-phase system that is not grounded or passing through the curved coil, especially in the three-phase system of 10KV.

　　(3) The wiring forms of Yn, Yn, D0 or yn, Y, D0 are widely used in the 3 ~ 220kV system with three single-phase three winding transformers. Voltage, auxiliary secondary winding into an open triangle for access to AC power grid instead of monitoring instruments and relay. The wiring of a three-phase and five-pillar voltage transformer instead of the above three single -phase three -winding voltage transformers. Except for the iron core, its form is basically the same as Figure 3, which is generally only used for 3 ~ 15kV systems.

　　(4) The three-phase three winding five-pillar voltage transformers are connected to the star shape and the second winding of the primary and secondary winding, and the neutral point is grounded. Therefore, this voltage transformer can measure the wire voltage and relative ground voltage, and the auxiliary secondary winding can intervene in the relay and signal indicator for AC power grid insulation monitoring.