How to select the specification of the transformer? What's the effect?

Instrument transformer, also known as instrument transformer, is a generic term for voltage transformer and voltage transformer. It can change high voltage into low voltage, and large current into small current for measuring or protecting systems. To help you fully understand, this article will summarize the basic knowledge of transformer. If you are interested in the content that will be covered in this article, please continue reading.

1、 Model and specification of transformer

1. Model of low-voltage voltage transformer

There are LMZ1-0.5, LMZ1-0.66, LMZJ1-0.5, LMK-0.66, BH-0.66, SDH-0.66, etc. There are also some special enterprise models, such as ALH-0.66, AKH-0.66, and so on.

2. Full set voltage transformer model

AKH-0.66-I、AKH-0.66-II、AKH-0.66-III、AKH-0.66-M8、AKH-0.66-P、AKH-0.66-S、AKH-0.66-SM、AKH-0.66-L、AKH-0.66-G、AKH-0.66-K

2、 Method of selecting voltage transformer

1. Selection based on rated current: The rated current of the voltage transformer should be greater than the rated current of the placement point line.

2. Selection based on transformation ratio: Selection of current transformer transformation ratio by current IC shall be calculated based on primary load. In order to ensure the accuracy of the voltage transformer, a larger transformation ratio can be selected.

3. The accuracy level of voltage transformers should be selected and calibrated based on measurement accuracy. Selection principle of accuracy level: the accuracy level of voltage transformer used for charging measurement shall not be less than 0.5 level; Class 1.0-3.0 voltage transformers shall be used to monitor the current of the load current in each incoming and outgoing line.

4. According to the selection of dynamic and thermal stability: it is necessary to check the dynamic and thermal stability of the voltage transformer. The dynamic stability rate KES and thermal stability rate KT are proposed in the manufacturer's product performance parameters.

5. Selection based on short-circuit capacity: The secondary short-circuit capacity of the voltage transformer is greater than the specific secondary load, and the specific secondary load should be 25 to 100% of the secondary short-circuit capacity.

3、 Main functions of transformer

Converting high voltage or large current into standard low voltage or standard small current in proportion facilitates standardization and miniaturization of testing instruments, maintenance equipment, and automatic control equipment. At the same time, transformers can also be used to separate high-voltage systems to ensure the safety of individuals and equipment.

In order to transmit electrical energy, power supply systems typically choose AC and high current circuits to send power to customers, and cannot be measured directly with instruments. The function of the transformer is to reduce the AC current and large current to values that can be measured directly with the instrument, facilitating direct measurement by the instrument, and providing power for relay protection and protection devices. The power supply system transformer is a special transformer that transmits high-voltage and large current information from the power grid to the low-voltage and small current secondary sides, detection instruments, relay protection, and protection devices. It is a connecting element of the primary and secondary systems. The primary windings are connected to the power grid, and the secondary windings are respectively connected to detection instruments, protection devices, and so on. The transformer cooperates with testing instruments and measuring devices to measure the voltage, current, and electrical energy of the primary system; Cooperating with relay protection and automatic devices, it can form electrical protection and automatic control for various grid faults. The operational reliability of electromagnetic valve protection equipment directly affects the measurement and accuracy of the power supply system.

In power supply lines, the current difference ranges from a few amperes to tens of thousands of amperes, and the voltage difference ranges from a few volts to several million volts. The current and voltage in the circuit are very high, and direct measurement is very dangerous. In order to facilitate secondary instrument measurement, it is necessary to convert to a relatively uniform current and voltage, and use a transformer to play the role of variable voltage and electrical isolation.