Wiring method of voltage transformer
The wiring method of voltage transformer can be divided into the following common types according to different combinations of primary winding wiring method and secondary winding wiring method:
1. Single-phase wiring
Single-phase wiring
It consists of a single-phase voltage transformer, which is mainly used to measure single-phase to ground voltage (such as neutral point non-effective grounding system) or line voltage. This method is simple to connect, but it cannot measure phase voltage, and is suitable for occasions where voltage accuracy is not required.
2. Three-phase wiring method
V-shaped wiring (two-phase wiring)
Two single-phase voltage transformers are connected to form Uab and Ubc line voltages respectively, which can measure line voltage but cannot directly measure phase voltage. This method is economical and simple to connect, and is widely used in 6-10kV high-voltage distribution devices.
Y0/Y0 type wiring (star wiring)
Three-phase three-column wiring: The primary windings of three single-phase voltage transformers are connected in star shape, and the secondary windings are also connected in star shape with the neutral point grounded. The line voltage and phase voltage can be measured at the same time, which is suitable for three-phase three-wire or three-phase four-wire systems.
Three-phase five-core column wiring: The primary windings of three single-phase voltage transformers are connected in star shape, and the secondary windings form a Y0/Y0/open triangle through three auxiliary windings, which can measure both line voltage and phase voltage, and provide zero-sequence voltage signals for insulation monitoring.
Open triangle wiring
The secondary windings of the three-phase voltage transformer are connected end to end to form an open triangle. During normal operation, the voltage at the open point is zero, but when the system has a single-phase grounding fault, a zero-sequence voltage will be generated, which is used for insulation monitoring and protection.
3. Other wiring methods
Three-phase five-winding wiring: Three-phase five-core column voltage transformer, the primary winding is connected in star shape, and the secondary winding contains three line voltage windings and one zero-sequence voltage winding, which is suitable for occasions where line voltage and zero-sequence voltage need to be obtained at the same time.
4. Special instructions
Wiring restrictions: When the secondary winding is short-circuited, it will cause overcurrent damage to the primary winding, so it is necessary to ensure that the secondary side short-circuit protection is reliable.
Application scenarios:
Single-phase wiring: neutral point non-effective grounding system;
V-shaped wiring: 6-10kV line measurement;
Y0/Y0 type: three-phase three-wire system measurement and protection;
Open triangle: ground fault detection.
In summary
The above wiring methods can be selected according to the actual grid wiring form and measurement requirements to ensure the accuracy of voltage measurement and the safety of the system.
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