Voltage transformer wiring method

(1) Single term wiring can be used to measure the line voltage of systems with neutral points not directly grounded at 35kV and below, or the phase to ground voltage of systems with neutral points directly grounded at 110kV and above.

(2) V/V wiring is the process of connecting the high and low voltage windings of two fully insulated single-phase voltage transformers to form an incomplete triangle between phases. This method is commonly used in high-voltage three-phase systems of 35kV and below with ungrounded neutral points or grounded through arc suppression coils, especially in 10kV three-phase systems.

(3) Three single-phase three winding voltage transformers are used to form the wiring form of YN, yn, d0 or YN, y, d0, which is widely used in 3-220kV systems. The secondary winding is used to measure phase to phase voltage and phase to ground voltage, and the auxiliary secondary winding is connected to an open triangle for connection to insulation monitoring instruments and relays in AC power grids. Using a three-phase five column voltage transformer instead of the wiring composed of the three single-phase three winding voltage transformers mentioned above, except for the iron core, its form is basically the same as Figure 3 and is generally only used for 3-15kV systems.

(4) A three-phase three winding five column voltage transformer, with its primary winding and main secondary winding connected in a star shape, and the neutral point grounded, and the auxiliary secondary winding connected in an open delta shape. Therefore, this type of voltage transformer can measure line voltage and phase to ground voltage, and the auxiliary secondary winding can be used as a relay and signal indicator for insulation monitoring in the AC power grid.