Wiring Mode Of Voltage Transformer

The common wiring methods of voltage transformers are as follows:

(1) Single-phase wiring can be used to measure the line voltage of 35kV and below systems that are not directly grounded at the neutral point or the phase-to-ground voltage of systems above 110kV that are directly grounded at the neutral point.

(2) V/V wiring is to connect the high and low voltage windings of two fully insulated single-phase voltage transformers between phases to form an incomplete triangle. This method is often used in high-voltage three-phase systems of 35kV and below where the neutral point is not grounded or grounded by the arc suppression coil, especially in the three-phase system of 10kV.

(3) The wiring form of YN, yn, d0 or YN, y, d0 is formed by three single-phase three-winding voltage transformers, which are widely used in 3~220kV systems, and their secondary windings are used to measure phase-to-phase voltage and phase-to-ground. Voltage, auxiliary secondary windings are connected into an open triangle for access to AC power grid insulation monitoring instruments and relays. A three-phase five-column voltage transformer is used to replace the wiring composed of the above three single-phase three-winding voltage transformers. Except for the iron core, its form is basically the same as that in Figure 3, and it is generally only used for 3~15kV systems.

(4) For a three-phase three-winding five-column voltage transformer, the primary winding and the main secondary winding are connected in a star shape, and the neutral point is grounded, and the auxiliary secondary winding is connected in an open triangle. Therefore, this kind of voltage transformer can measure the line voltage and the phase-to-ground voltage, and the auxiliary secondary winding can intervene in the relay and signal indicator for the insulation monitoring of the AC power grid.