Common wiring methods for voltage transformers

(1) Single-phase wiring, which can be used to measure the line voltage of a system with a neutral point that is not directly grounded at 35kV or below or the relative voltage to ground in a system with a neutral point that is directly grounded at 110kV or above.
(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 or below with a neutral point that is not grounded or grounded through an arc suppression coil, especially in 10kV three-phase systems.
(3) The wiring form of YN, yn, d0 or YN, y, d0, which is formed by three single-phase three-winding voltage transformers, is widely used in 3~220kV systems. Its secondary winding is used to measure the phase-to-phase voltage and relative voltage to ground. The auxiliary secondary winding is connected to form 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 formed by the above three single-phase three-winding voltage transformers. Except for the iron core, its form is basically the same as Figure 3. It is generally only used in 3~15kV systems.
(4) Three-phase three-winding five-column voltage transformer, its primary winding and main secondary winding are connected in star shape, and the neutral point is grounded, and the auxiliary secondary winding is connected in an open triangle. Therefore, this type of voltage transformer can measure line voltage and relative voltage to ground, and the auxiliary secondary winding can be inserted into the relay and signal indicator for AC power grid insulation monitoring.