In the fields of power systems and industrial automation, accurate current measurement forms the foundation for ensuring system safety, improving energy efficiency, and enabling intelligent management.
As a globally leading manufacturer of power quality solutions and electrical sensors, ZHIMING Group deeply understands the critical role of current measurement in relay protection, energy metering, and intelligent monitoring.
Our Current Transformer product series, renowned for its exceptional accuracy, reliable stability, and broad adaptability, serves various complex scenarios from low voltage distribution to high voltage transmission. ZHIMING consistently adheres to the philosophy of “Innovation Driven, Value Sharing,” committed to providing global customers with standardized high-quality products and personalized custom solutions, ensuring your system acquires safe, precise, and efficient current sensing capabilities.
What is a Current Transformer?
A Current Transformer, abbreviated as CT, is a sensor device that operates on the principle of electromagnetic induction. It accurately converts a large primary current (ranging from tens to tens of thousands of Amperes) in a power system into a standardized small secondary current (typically 5A or 1A) according to a fixed ratio.
Core Benefits of Current Transformer
The core value delivered by using ZHIMING Current Transformers:
1. Ensures System Safety and Reliability
Electrical Isolation: A robust insulation structure effectively isolates the high voltage primary circuit from the low voltage secondary circuit, providing a solid barrier for downstream equipment and personnel safety.
2. Equipment Protection
Provides accurate current signals to relay protection devices, ensuring rapid and reliable operation to clear faults like overcurrents and short circuits, thereby protecting primary equipment.
3. Enables Accurate Metering and Energy Efficiency Management
High-Precision Measurement: Offers various accuracy classes like 0.2S, 0.5, and 1, meeting different needs from billing to general industrial metering, providing reliable data for energy audits and cost control.
4. Supports Intelligent Monitoring
Outputs standard signals for seamless integration with various smart meters, data acquisition units, and energy management systems, forming the basis for digital and intelligent power distribution.
5. Simplifies System Design and Reduces Costs
Standardization and Miniaturization: Standardized secondary current outputs enable the standardization and miniaturization of instruments and relays, reducing overall costs. The transformers themselves are compact and easy to install, saving space.
Improves Operational Efficiency: Reliable product performance reduces maintenance needs and downtime. The accurate data provided aids in predictive maintenance, enhancing overall operational efficiency.
Application Scenarios
ZHIMING Current Transformers, with their comprehensive product range, are widely used in the following critical fields:
1. Power Transmission and Distribution Systems
Used in power plants, substations, and distribution networks as high voltage current transformers and low voltage current transformers for current measurement, energy metering, and protection, ensuring safe and stable grid operation.
2. Industrial Automation and Manufacturing
Applied in distribution systems and production lines in industries like metallurgy, chemicals, and automotive manufacturing, providing signals for current monitoring and protection of Variable Frequency Drives (VFDs), motors, and large production equipment.
3. Building Automation and Commercial Complexes
Installed in distribution cabinets and energy management systems of office buildings, shopping malls, hospitals, and hotels to monitor currents of major loads like lighting, HVAC, and elevators for energy-saving control.
4. New Energy Sector
Widely used on both the DC and AC sides of photovoltaic inverters, wind farm converters, and energy storage systems for precise current measurement, serving as key components for efficient utilization of clean energy.
5. Rail Transit and Infrastructure
Used in locations with extremely high demands for power supply reliability and continuity, such as subways, high-speed rail, airports, and data centers, ensuring stable power for critical loads.
Advantages & Technical Highlights of ZHIMING Current Transformer
ZHIMING Group ensures its Current Transformers remain at the forefront of performance and reliability through continuous R&D and stringent quality control:
1. Excellent Electrical Performance
High Accuracy and Wide Range: Accuracy classes cover 0.2S, 0.5, 1, etc. Primary current range is wide, from 5A to 6300A (low voltage) and even higher (high voltage), meeting measurement needs for various applications.
2. Low Power Loss and High Stability
Use of high-performance magnetic materials like silicon steel or nanocrystalline, processed through vacuum heat treatment, ensures stable magnetic properties, low product loss, and minimal long-term accuracy drift.
3. Robust Mechanical and Safety Design
Reliable Insulation and Protection: Low-voltage current transformer housings often use high-impact, flame-retardant ABS or PC materials for good safety. High voltage current transformers may use composite insulators or optical fiber insulation technologies, with simple and reliable structures.
4. Diverse Mounting Options
Offer various mounting methods, including through-core (round window, rectangular window), busbar mounted, and base mounted, adapting to different on-site installation environments conveniently and efficiently.
5. Advanced Technology and Material Application
Dual Winding Design: Some models support dual secondary windings, allowing simultaneous local indication (e.g., 5A) and remote telemetry (e.g., 0-20mA), simplifying system structure and reducing costs.
Future-Ready: Keeping pace with trends, we offer new products like Electronic Current Transformers (ECTs), which feature simpler insulation, smaller size, lighter weight, no magnetic saturation issues, and wide frequency response, ideal for digital and smart grid needs.
6. Stringent Quality Assurance
Current transformer product design and manufacturing comply with international and national standards such as GB 1208 (equivalent to IEC 60044-1), IEC 61869, etc. Some products hold international safety certifications like CE, UL, ensuring compliance and suitability for global markets.
FAQ
Q1: Why must the secondary side of a current transformer never be open-circuited during operation?
A1: Under normal operation, the magnetomotive force from the primary current is largely counteracted by that from the secondary current. If the secondary opens, this demagnetizing effect vanishes. The core becomes highly saturated, producing a large magnetic flux that induces a dangerous high voltage in the multi-turn secondary winding, severely threatening equipment insulation and personnel safety. The core can also overheat and damage the transformer. Therefore, the secondary circuit must always remain closed during installation, testing, or maintenance.
Q2: How do I select the right current transformer for my project? What are the key parameters?
A2: Selection involves considering several key parameters:
Rated Voltage: Determined by the system voltage at the installation point, e.g., 0.66kV (low voltage) or 10kV, 35kV (high voltage).
Rated Primary Current: Should be slightly higher than the normal maximum operating current of the measured circuit, typically 1.2-1.5 times the max load current.
Rated Secondary Current: Common values are 5A or 1A. 1A is preferred for longer transmission distances or higher burden to reduce line voltage drop effects.
Accuracy Class: Energy metering usually requires 0.2S or 0.5; general measurement can use 1; relay protection focuses on the 10% error curve.
Rated Burden (VA): The total impedance of all instruments, relays, and connecting wires on the secondary side must not exceed the transformer’s rated burden; otherwise, measurement accuracy is affected.
Q3: What is the difference between a Protection Current Transformer (e.g., 10P class) and a Metering Current Transformer (e.g., 0.5 class)?
A3: They have different design goals and performance requirements:
Metering CT: Focuses on measurement accuracy within the normal current range. It should saturate early during system fault conditions to protect connected instruments from high current surges.
Protection CT: Focuses on transformation characteristics under fault conditions (currents much higher than normal). It requires the composite error not to exceed a specified limit (e.g., 10%) at a specified multiple of the primary current, ensuring correct operation of protection devices. Therefore, they are not interchangeable.
Q4: Can ZHIMING provide specially customized current transformers?
A4: Yes. ZHIMING possesses a strong R&D and engineering team capable of providing flexible personalized customization services based on specific customer requirements (such as non-standard window sizes, special ratios, extreme environmental adaptability requirements, specific mounting methods, etc.). Our goal is to be your reliable partner, not just a product supplier.
