Use And Application Fields of Low-Voltage Current Transformers

Use and Application Fields of Low-Voltage Current Transformers

Current Transformers (CTs), especially in low-voltage distribution systems, play a pivotal role in power systems. They are not only used for current measurement but also widely applied in power system protection, monitoring, and automation control. This article will delve into the use of low-voltage current transformers and their extensive application fields.

I. Basic Overview of Low-Voltage Current Transformers

Low-voltage current transformers are current sensing units typically used to convert high currents into easily measurable low currents, such as 5A or 1A. This conversion not only facilitates current measurement but also enhances measurement accuracy and system safety. Low-voltage current transformers usually consist of a toroidal iron core made of silicon steel, wound with multiple turns of copper wire. The conductor carrying the primary current passes through the toroidal hole of the iron core, forming the primary coil. According to the principle of electromagnetic induction, when the primary current flows through the primary coil, an induced current is generated in the secondary coil, which is proportional to the primary current.

II. Precautions for the Use of Low-Voltage Current Transformers

1. Rated Voltage and Current Limits: Low-voltage current transformers are generally designed for AC circuits with a rated voltage not exceeding 0.66kV. The long-term operating current should not exceed 1.2 times the rated value, and it is permissible to operate at 1.2 times the rated current for short periods (not exceeding one hour).

2. Polarity Markings: Transformers have clear polarity markings, with primary wiring marked as P1, P2, and secondary wiring as S1, S2. Measuring instruments should be connected to the S1, S2 terminals, ensuring that the total impedance of the connected instruments does not exceed the rated load of the transformer.

3. Secondary Circuit Closure: During transformer operation, it is crucial to ensure that the secondary circuit is closed, strictly prohibiting secondary opening to prevent high voltage generation, which could endanger personnel and equipment safety.

4. Selection and Installation: Choose products based on parameters such as primary current and busbar cross-section. During installation, ensure that the primary conductor correctly passes through the transformer window hole and make secondary connections through press-clamp terminals.

III. Application Fields of Low-Voltage Current Transformers

1. Current Measurement: Low-voltage current transformers are crucial components for current measurement, widely used in the current measurement of various electrical equipment. Through transformers, high currents can be converted into standard low currents, facilitating the reading of measurement instruments such as ammeters.

2. Energy Metering: In power systems, low-voltage current transformers are paired with energy meters for accurate energy metering. By converting high currents into low currents, energy meters can measure energy consumption more precisely.

3. Protection Systems: Low-voltage current transformers are also widely used in power system protection systems. When power system faults occur, such as short circuits or overloads, transformers can quickly detect abnormal currents and cut off the circuit through protective devices (e.g., relays) to protect equipment and systems from damage.

4. Monitoring Systems: In modern power systems, low-voltage current transformers are paired with telemetry devices for remote measurement and monitoring of current signals. This helps detect and resolve issues promptly, improving power system reliability and stability.

5. Motor Protection: In motor protection circuits, low-voltage current transformers also play a vital role. They can detect motor overload currents and cut off the circuit through protective devices to prevent motor damage due to overload.

IV. Development Trends of Low-Voltage Current Transformers

With the continuous development of power systems and the improvement of intelligence levels, low-voltage current transformers are also advancing and innovating. For example, dual-winding current transformers can simultaneously output 5A or 1A current signals for current measurement and also output AC 0-20mA small current signals for direct acquisition and upload by telemetry systems. This multifunctionality makes low-voltage current transformers more versatile and flexible in power system applications.

In summary, the use of low-voltage current transformers in power systems is crucial. They not only improve the accuracy of current measurement and system safety but also promote the intelligent development of power systems. With continuous technological advancements and innovations, low-voltage current transformers will play an even more important role in the future.