The use of voltage transformers and issues to be aware of

The voltage transformer is a special transformer that is defined and used. The use of voltage transformers is to convert the high voltage proportionally into a standard secondary voltage of 100V or lower for protection, metering, and instrumentation. At the same time, voltage transformers can be used to isolate high voltages from electrical workers. Although the voltage transformer is also a device that works according to the principle of electromagnetic induction, its electromagnetic structure relationship is opposite to that of a current transformer. The secondary circuit of the voltage transformer is a high impedance circuit, and the magnitude of the secondary current is determined by the impedance of the circuit. When the secondary load impedance decreases, the secondary current increases, so that the primary current automatically increases by one component to satisfy the electromagnetic equilibrium relationship between the primary and secondary sides.

Pay attention to the problems when using:

1. Safety: To ensure the safety of people in contact with measuring instruments and relays, the secondary winding of the voltage transformer must be grounded at all. Because the insulation between the primary and secondary windings is damaged after grounding, high voltages on the instruments and relays can be prevented to endanger personal safety.

2. Tests should be carried out: the voltage transformers should be tested and inspected according to the items specified in the regulations before being put into operation. For example, polarity measurement, connection group, shake insulation, nuclear phase sequence, and the like.

3 Correct wiring: The wiring of the voltage transformer should ensure its correctness. The primary winding and the circuit under test should be connected in parallel. The secondary winding should be connected in parallel with the connected measuring instrument, the voltage transformer of the voltage transformer or the voltage coil of the automatic device. Pay attention to the correctness of the polarity.

4. Appropriate capacity: the capacity of the secondary side load of the voltage transformer should be appropriate, and the load connected to the secondary side of the voltage transformer should not exceed its rated capacity. Otherwise, the error of the transformer will increase, and it is difficult to achieve the correct measurement. Sex.

5. Avoid short circuit: The secondary side of the voltage transformer is not allowed to short circuit. Since the internal impedance of the voltage transformer is small, if the secondary circuit is short-circuited, a large current will occur, which will damage the secondary equipment and even endanger personal safety. The voltage transformer can be equipped with a fuse on the secondary side to protect itself from damage due to secondary side short circuit. Where possible, fuses should also be installed on the primary side to protect the high voltage grid from jeopardizing the safety of the primary system due to transformer high voltage windings or lead failure.