Product Overview
The LZZBJ9-10A Current Transformer is a fully enclosed, post-type current transformer designed for indoor 10 kV AC power systems with a maximum system voltage of 12 kV.
Manufactured using an epoxy resin vacuum-casting process, the transformer is available with a busbar-type or through-type primary winding, while the secondary winding is wound with enamelled copper wire. It provides excellent insulation performance, a compact structure, high short-time thermal and dynamic current withstand capability, and stable accuracy characteristics.
The product is mainly used for current measurement, energy metering, relay protection, and signal acquisition in power systems. It is widely installed in indoor medium-voltage switchgear, box-type substations, distribution stations, and other electrical distribution equipment.
Product Features
Insulation and Electrical Performance
- Epoxy resin cast insulation:
Manufactured through vacuum casting using high-quality epoxy resin. The solid insulating body contains no internal air gaps and provides excellent dielectric performance. It can withstand the operating voltage, power-frequency withstand voltage, and lightning impulse withstand voltage requirements of 12 kV systems. - Long insulation service life:
The integrated dry-type structure contains no insulating oil and therefore presents no risk of oil leakage. It also provides reliable resistance to cracking and insulation ageing under normal operating conditions. - Wide range of current ratios:
Multiple primary-to-secondary current ratios are available, including 10/5 A, 20/5 A, 30/5 A, and ratios up to 2,000/5 A. Current ratios can be selected according to different metering and protection requirements. - Multiple accuracy classes:
Metering and protection accuracy classes such as 0.2S, 0.5, 5P, and 10P can be configured according to project requirements. - High short-time thermal and dynamic withstand capability:
The transformer can withstand the specified short-time thermal current and dynamic current generated during system short-circuit faults. It is suitable for high-current and high-short-circuit-capacity applications. - Low partial discharge:
The advanced casting process limits partial discharge to no more than 10 pC, helping reduce insulation ageing and improve long-term operating reliability.
Structural and Installation Features
- Fully enclosed post-type structure:
The one-piece cast construction contains no exposed live parts and provides an IP20 protection rating. It is suitable for indoor switchgear installation and helps reduce the ingress of dust and moisture. - Compact modular design:
The compact structure occupies minimal installation space and is compatible with standard 10 kV switchgear, including KYN28 series equipment. It supports convenient multi-circuit arrangements inside the cabinet. - Clearly identified secondary terminals:
The secondary winding terminals are protected by a transparent cover and clearly marked for convenient wiring. The cover helps prevent incorrect connections, short circuits, and accidental opening of the secondary circuit. - Flexible installation:
The metal mounting base includes fixing holes for secure bolt installation. The transformer can be installed horizontally or vertically inside indoor switchgear and provides reliable resistance to vibration.
Operation and Maintenance Features
- Low-maintenance operation:
The epoxy resin cast body provides high mechanical strength, impact resistance, and ageing resistance. Its oil-free construction eliminates leakage risks and helps reduce routine maintenance requirements. - Wide operating temperature range:
The transformer can operate at ambient temperatures from -30°C to +70°C. The epoxy resin maintains stable mechanical and insulation performance without becoming brittle or deformed. - Stable low-error characteristics:
Metering windings provide low and stable measurement errors and can meet Class 0.2S high-accuracy energy metering requirements. - Reliable protection performance:
Protection windings provide suitable accuracy limit factors to support reliable relay protection operation and reduce the risk of incorrect or failed tripping.
Technical Specifications
Electrical Parameters
| Parameter | Specification |
|---|---|
| Applicable System Voltage | 10 kV AC, Um = 12 kV |
| Rated Frequency | 50 Hz |
| Rated Primary Current | 10–2,000 A, customizable |
| Rated Secondary Current | 5 A or 1 A |
| Metering Accuracy Class | 0.2S / 0.2 / 0.5 |
| Protection Accuracy Class | 5P10 / 10P10 / 5P20 / 10P20 |
| Power-Frequency Withstand Voltage | 42 kV for 1 minute, phase-to-earth and phase-to-phase, without breakdown |
| Lightning Impulse Withstand Voltage | 75 kV peak, without breakdown |
| Partial Discharge | ≤10 pC |
| Short-Time Thermal Current (Ith) | 20 times the rated current for 1 second, customizable |
| Dynamic Current (Idyn) | 2.5 times Ith, customizable |
Structural and Material Parameters
| Parameter | Specification |
|---|---|
| Insulating Medium | Cast epoxy resin |
| Protection Rating | IP20 |
| Installation Type | Indoor post-type bolt mounting |
| Thermal Class | Class B, 130°C |
Environmental Parameters
| Parameter | Specification |
|---|---|
| Installation Altitude | ≤2,000 m; high-altitude versions available |
| Operating Temperature | -30°C to +70°C |
| Storage Temperature | -40°C to +85°C |
| Relative Humidity | ≤95%, non-condensing |
Applicable Standards
| Standard | Description |
|---|---|
| GB 1208 | Current Transformers |
| GB/T 20840.1 | Instrument Transformers—Part 1: General Requirements |
Applications
Applicable Voltage Level
The LZZBJ9-10A Current Transformer is suitable for indoor 10 kV AC power systems with a maximum system voltage of 12 kV.
Typical Applications
- Current measurement, energy metering, and relay protection in indoor medium-voltage switchgear, including KYN28 and XGN series equipment
- Current signal acquisition in box-type substations
- Distribution stations and switching stations
- 10 kV distribution systems in industrial and mining enterprises
- Commercial buildings and industrial parks
- Current monitoring and control in power automation systems
- Main incoming cabinets and high-current outgoing cabinets
- Distribution applications requiring high short-time thermal and dynamic current withstand capability
Main Functions
The current transformer converts high primary current into a standardized secondary current of 5 A or 1 A at a specified ratio.
It supplies current signals to:
- Energy meters
- Measuring instruments
- Relay protection devices
- Monitoring equipment
- Control systems
The transformer also provides electrical isolation between the primary and secondary systems, helping protect connected equipment and operating personnel.
Operating Conditions
Normal Operating Conditions
- Installation altitude: no more than 2,000 m
- Ambient temperature: -30°C to +70°C
- Severe or sudden temperature changes should be avoided
- Relative humidity: no more than 95%, non-condensing
- The environment should be free from corrosive gases
- Flammable or explosive substances are not permitted
- Severe vibration and mechanical impact should be avoided
- Significant dust and salt-spray contamination should be avoided
- Indoor post-type installation
- Direct sunlight, rain, and condensation should be avoided
Special Operating Conditions
Customized products are required for:
- Installation altitudes above 2,000 m
- Ambient temperatures outside the range of -30°C to +70°C
- Severe pollution or salt-spray environments
- Chemically corrosive environments
- Applications involving strong vibration or mechanical impact
- Non-standard current ratios
- Special accuracy classes
- Non-standard mounting dimensions
Installation and Maintenance
Installation Requirements
- Pre-installation inspection:
Inspect the current transformer and confirm that the cast body is free from cracks, bubbles, mechanical damage, and other visible defects. Check that all terminal markings are clear and that the supplied accessories are complete. Verify that the model, specifications, current ratio, and accuracy class match the system design requirements. - Mounting:
Position the current transformer at the specified location inside the switchgear and secure it with bolts through the mounting holes in the base. Ensure that the transformer is firmly installed without looseness or displacement. The mounting surface should be level to prevent uneven mechanical stress. - Primary-side connection:
Connect the primary busbar according to the electrical design. Ensure close contact between the busbar and the primary terminals and tighten all bolts securely to prevent overheating caused by poor electrical contact. - Secondary-side connection:
Connect the secondary winding terminals according to their markings. Metering and protection windings must be wired separately and correctly. The secondary circuit must never be left open while the primary circuit is energized. One point of the secondary circuit must be reliably grounded to prevent hazardous overvoltage. - Insulation inspection:
After installation, measure the insulation resistance between:- Primary and earth
- Secondary and earth
- Primary and secondary
Maintenance Requirements
- Regularly inspect the epoxy resin body for cracks, mechanical damage, discharge marks, and contamination.
- Check the terminals for looseness, oxidation, and abnormal heating.
- Regularly inspect the primary busbar and secondary wiring to ensure that all connections remain secure.
- Check for overheating, discoloration, unintended open circuits, and incorrect short circuits.
- Periodically test the insulation resistance and current-ratio error to confirm that the metering and protection accuracy remain within the specified limits.
- Clean dust and contamination from the transformer surface.
- Prevent oil and corrosive substances from contacting the epoxy resin body.
- Keep the equipment clean and dry.
- If cracking, electrical discharge, overheating, or excessive measurement error is detected, immediately de-energize and inspect the equipment. Replace the current transformer where necessary.
Precautions
- The secondary winding must never be left open while the primary circuit is energized. An open secondary circuit may generate a hazardous overvoltage of several thousand volts, creating a serious risk to equipment and personnel.
- During maintenance, the secondary winding must be securely short-circuited and grounded before any work is carried out.
- Avoid impact or collision with the epoxy resin body during transportation and installation. Mechanical damage may crack the epoxy resin and reduce insulation performance.
- The equipment must be reliably grounded. The grounding terminal on the metal base must be securely connected to the switchgear grounding busbar.
- Store the product in a dry, ventilated, and shaded environment. Avoid direct sunlight, high temperatures, moisture, compression, and mechanical impact.
- Installation, commissioning, and maintenance must be carried out by qualified electrical personnel in accordance with applicable electrical safety procedures.
Standard Supply List
| No. | Item | Function |
|---|---|---|
| 1 | LZZBJ9-10A Current Transformer | Main device for current transformation and electrical isolation |
| 2 | Mounting Bolts and Washers | Used to secure the current transformer during installation |
| 3 | Transparent Secondary Terminal Cover | Protects the secondary terminals and helps prevent incorrect connection or short circuits |
| 4 | Product Instruction Manual | Provides installation, operating, and maintenance guidance |
| 5 | Product Certificate and Factory Test Report | Provides evidence of product quality and performance |
Applicable Standards and Certification
The product complies with the following standards:
- GB 1208, Current Transformers
- GB/T 20840.1, Instrument Transformers—Part 1: General Requirements
- GB/T 20840.2, Instrument Transformers—Part 2: Additional Requirements for Current Transformers
The product has passed the applicable type tests, and its performance meets the operating requirements of indoor 10 kV power systems.
