Definition of outdoor voltage transformer
Voltage transformers are similar to transformers in that they are used to transform voltage. However, the purpose of transforming the voltage of the transformer is to facilitate the transmission of electrical energy, so the capacity is very large, and it is generally calculated in kilovolt-ampere or mega-volt-ampere; while the purpose of the voltage transformer to convert the voltage is mainly used for measuring instruments and relays. The protection device is used to measure the voltage, power and power of the line, or to protect valuable equipment, motors and transformers in the line when the line fails, so the capacity of the voltage transformer is very small, generally only a few volts Dozens of volt-amperes, the maximum does not exceed one thousand volt-amperes.
Basic structure of voltage transformer
The basic structure of a voltage transformer is very similar to that of a transformer. It also has two windings, one called a primary winding and one called a secondary winding. Both windings are mounted on or around the core. There is insulation between the two windings and between the winding and the core, so that there is electrical isolation between the two windings and between the winding and the core. When the voltage transformer is in operation, the primary winding N1 is connected in parallel to the line, and the secondary winding N2 is connected to an instrument or a relay. Therefore, when measuring the voltage on the high-voltage line, although the primary voltage is high, the secondary voltage is low, which can ensure the safety of the operator and the instrument.
Precautions for use of voltage transformers
1 . Before the voltage transformer is put into operation, it should be tested and inspected according to the items specified in the regulations.
2 . The wiring of the voltage transformer should ensure its correctness. The primary winding should be connected in parallel with the circuit under test. The secondary winding should be connected in parallel with the voltage coil of the measuring instrument, relay protection device or automatic device connected. At the same time, attention should be paid to the correctness of the polarity. .
3． The capacity of the load connected to the secondary side 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 will be difficult to achieve the correct measurement.
4. The secondary side of the voltage transformer must not be short-circuited. Because the internal impedance of the voltage transformer is very small, if the secondary circuit is short-circuited, a large current will appear, 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 being damaged by a short circuit on the secondary side. Where possible, fuses should also be installed on the primary side to protect the high-voltage grid from damaging the safety of the primary system due to high-voltage windings or lead failure of the transformer.
5. In order to ensure the safety of people when touching the measuring instruments and relays, the secondary winding of the voltage transformer must be grounded a little. Because after grounding, when the insulation between the primary and secondary windings is damaged, it can prevent the high voltage of the instrument and the relay from endangering personal safety.