High voltage transformer is suitable for 1kv to 220kv power system to convert large voltage into small voltage or large current into small current for easy measurement, protection and use. It is mainly used to monitor the operation of electrical equipment and control system in AC circuit (usually its first side winding is called the primary winding or primary winding, and the secondary side winding is called the secondary winding or secondary winding), which is used to supply power to the voltage coil and current coil of measuring instruments and relays respectively, and correctly reflect the normal operation and fault of electrical equipment. The accuracy of the measuring instrument and the reliability of the relay protection action are largely related to the performance of the transformer. Therefore, we should be familiar with some of the main characteristics of the transformer in order to correctly select and use the transformer.
High voltage transformer is suitable for 1kv to 220kv power system to convert large voltage into small voltage or large current into small current for easy measurement, protection and use of transformers, generally divided into 3kv, 6kv, 10kv, 35kv, 66kv, 110kv, 220kv, Jiangsu area is now a trial 24kv system. 10kv and 220kv are the most widely used. The secondary input is mostly 200V or 100V or 5A or 1A. Classification: According to the function: voltage transformer: such as JDZ series Current transformer: such as LZZB series according to the filling material: oil transformer: internal filled with insulation oil dry transformer: internal filled with epoxy resin according to the sealing grade semi-closed transformer: such as the JDZ horn transformer, the terminal and other parts are exposed, and other parts are closed. Fully enclosed transformer: The whole body is enclosed. Voltage transformer: According to the principle, it is divided into two categories: electromagnetic induction type and capacitive voltage division type. According to the purpose, the voltage transformer is divided into two categories: measurement and protection.
1.Electromagnetic induction type voltage transformer. It works on the same principle as a transformer. The basic structure is also iron core and primary and secondary windings. The characteristic is that the capacity is small and relatively constant, and the normal operation is close to the no-load state. The impedance of the voltage transformer itself is very small, once the short circuit occurs on the secondary side, the current will increase sharply and burn the coil. For this reason, the primary side of the voltage transformer is connected with a fuse, and the secondary side is grounded to avoid a high potential to the ground on the secondary side when the primary and secondary side insulation is damaged. The equivalent circuit of the electromagnetic induction type voltage transformer is the same as that of the transformer.
2.Capacitive partial voltage transformer. Made on the basis of capacitive voltage divider. In order to simplify the system and reduce the cost, capacitive voltage transformer is mainly used with the coupling capacitors of the power system carrier communication. At this time, it also needs to meet the requirements of communication operation. Voltage transformers are classified by structure, including oil-filled type, dry type, three-core five-column type and single-phase type, as well as fully insulated type and semi-insulated type.
The role of the transformer has the following aspects: 1.The high voltage and high current of the primary loop into the standard bit of the secondary loop, usually rated secondary voltage is 100V, rated secondary current is 5A, so that the addressing instrument and protection device standardization, and the insulation level of the secondary equipment can be designed according to low voltage, so that the structure is lightweight and the price is cheap.
2..All secondary equipment can be connected with low voltage and small current control cables, so that the wiring in the screen is simple and easy to install. At the same time, it is convenient for centralized processing, and can realize remote control and measurement. 3.The secondary loop is not restricted by the primary loop. Can use Y shape, shape or V shape connection, so the connection is flexible and convenient. At the same time, when the secondary equipment is maintained, replaced and adjusted, the operation of the primary system does not need to be interrupted, and only the secondary wiring can be properly changed.
4.The secondary equipment and staff are isolated from the high-voltage part, and the secondary side of the transformer is grounded, thus ensuring the safety of the equipment and the person. In AC circuits, commonly used transformers convert high voltage into low voltage, large current into small current, and then for measurement, control, and protection. This can not only increase the distance of the measuring instrument, facilitate the standardization of the instrument, reduce the voltage and current of the control and protection equipment, but also separate the instrument from the equipment or high-voltage circuit to ensure the safety of the instrument, equipment and staff.
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