Overview
The LFZBJ9-10 / LAZBJ-10 is an indoor, fully enclosed wall-through current transformer with epoxy resin cast insulation, designed for 10kV, 11kV, and 12kV class medium-voltage AC systems. It features a compact structure where the primary conductor passes through a central aperture, and the laminated core with secondary winding is encapsulated in cast-resin for reliable insulation and mechanical strength.
This CT supports both metering (0.2S, 0.5S) and protection (10P10) accuracy classes, making it suitable for energy metering, feeder monitoring, relay protection, and switchgear instrumentation in indoor distribution equipment. It complies with standard requirements for indoor medium-voltage applications and can serve as a modern replacement for legacy models like LA-10 and LFZ-10 when electrical and dimensional compatibility is confirmed.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Metering accuracy classes | 0.2S, 0.2, 0.5S, 0.5 |
| Protection accuracy class | 10P10 |
| Installation location | Indoor |
| Insulation material | Epoxy resin cast |
| Primary configuration | Wall-through (single turn) |
| Secondary windings | 1 or 2 (metering + protection) |
| Thermal short-time current | Per IEC 61869-2 |
| Dynamic withstand current | Per IEC 61869-2 |
Model Designation
- L: Current transformer
- F: Wall-through / constructed multi-turn through type
- Z: Epoxy resin casting insulation
- B: Protection class available
- J: Reinforced / enhanced design
- 9: Design sequence code
- 10: Rated voltage class: 10kV class
- LAZBJ-10: Alternative model designation for the same wall-through indoor cast-resin CT series
Construction
The LFZBJ9-10 / LAZBJ-10 features a fully enclosed wall-through structure with epoxy resin casting insulation. The primary conductor passes through the central aperture without direct contact with the secondary components, ensuring galvanic isolation between high-voltage and low-voltage circuits. The magnetic core and secondary windings are completely embedded within the solid epoxy resin body, which provides excellent dielectric strength, mechanical robustness, and resistance to humidity and contamination in indoor environments. This cast-resin construction eliminates the need for external insulation maintenance and enhances long-term operational reliability under normal indoor switchgear conditions.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class networks
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: normally -5°C to +40°C unless otherwise specified
- Installation environment: should be free from severe vibration, corrosive gas, explosive medium, conductive dust, heavy pollution and abnormal condensation.
- Special conditions: For high altitude, coastal, humid, high-pollution or retrofit conditions, technical confirmation is recommended before ordering.
Technical Parameters
The LFZBJ9-10 and LAZBJ-10 are indoor wall-through cast-resin current transformers designed for 10kV–12kV systems. They operate within a standard ambient temperature range of -5°C to +40°C and comply with IEC 60044-1, GB1208-1997, and IEC 61869 (upon request). Primary current ratings span from 20A to 400A, with secondary outputs of 1A or 5A and multiple accuracy class combinations for metering and protection applications.
| Rated Primary Current (A) |
Accuracy Classes Combination |
Rated Output (VA) | Rated Short-Time Thermal Current (kA) |
Rated Dynamic Current (kA) |
||||
|---|---|---|---|---|---|---|---|---|
| 0.2S | 0.2 | 0.5S | 0.5 | 10P10 | ||||
| 20 | 0.2S/10P10 0.2/10P10 0.5S/10P10 0.5/10P10 0.2/0.5/10P10 0.2/10P10/10P10 0.5/10P10/10P10 |
10 | 10 | 10 | 15 | 15 | 2 | 5 |
| 30 | 3 | 7.5 | ||||||
| 40 | 4 | 10 | ||||||
| 50 | 6 | 15 | ||||||
| 75 | 8 | 15 | ||||||
| 100 | 12 | 20 | ||||||
| 150 | 15 | 30 | ||||||
| 200 | 20 | 37.5 | ||||||
| 300 | 32 | 50 | ||||||
| 400 | 36 | 80 | ||||||
Installation & Wiring
Installation Diagram
The LFZBJ9-10 / LAZBJ-10 current transformer is installed through the wall of the switchgear cabinet. The primary conductor or busbar passes through the central aperture, while the secondary terminals are accessible from the front or side depending on the selected structure (A-type, B-type, or retrofit). Mounting is secured using bolts aligned with the specified mounting holes, which must be verified against the approved dimensional drawing prior to cabinet fabrication or retrofit.
Selection & FAQs
Selection Guide
- Confirm that LFZBJ9-10 is the required physical version. Catalogue references to LAZBJ-10, LA-10 or LFZ-10 indicate possible application overlap, not automatic interchangeability; compare the approved outlines and terminal layouts.
- Choose the primary ratio from the 20A–400A schedule. Base the ratio on normal and future feeder load, then verify the ratio-specific short-time thermal and dynamic withstand ratings against the calculated system fault current.
- Select the secondary-current standard for the complete circuit. Specify 1A where reduced cable burden is advantageous or 5A for compatible legacy instruments; meters, relays and test blocks must match.
- Define every secondary core separately. State the required measurement class—0.2S, 0.2, 0.5S or 0.5—and whether a dedicated 10P10 protection core is needed, together with each core’s rated output.
- Complete a retrofit interface check before manufacture. Verify the 12/42/75kV insulation requirement, busbar aperture, panel opening, mounting holes, terminal access, polarity, altitude, pollution conditions and applicable standard edition.
Frequently Asked Questions
Q1: Can this epoxy resin CT be installed outdoors?
No, this model is strictly designed for indoor medium-voltage switchgear. The installation environment must be free from severe vibration, corrosive gases, and abnormal condensation. Contact us for outdoor-rated alternatives.
Q2: What are the short-circuit thermal and dynamic current ratings?
Rated short-time thermal and dynamic currents vary based on the selected primary current rating from 20A to 400A. Exact kA values are subject to confirmation based on your specific system fault levels.
Q3: Which secondary output and accuracy classes are available?
The transformer offers 1A or 5A secondary outputs with multiple accuracy class combinations for metering and protection. Please specify your required accuracy class combination during the inquiry for precise factory configuration.
Q4: Are these current transformers compliant with IEC 61869 standards?
Yes, the LFZBJ9-10 complies with IEC 60044-1 and GB1208-1997 by default, with IEC 61869 available upon specific request. Confirm your required standard compliance during the procurement process.
Q5: How does the factory handle high altitude installations?
Standard ambient temperature is -5°C to +40°C, but special conditions like high altitude require technical confirmation. Submit your specific site parameters before ordering to ensure proper design adjustments.
Q6: Why is this wall-through CT suitable for switchgear?
This cast-resin current transformer is primarily used for measurement and protection in 10kV to 12kV indoor switchgear. It supports 50Hz and 60Hz rated frequencies for diverse power networks. Verify your system frequency during the selection process.