Overview
The LZZBJ9-12/150b/4S (also designated AS12/150b/4S) is a 12kV indoor single-phase current transformer with epoxy resin cast insulation. It is rated for use in 10kV, 11kV, and 12kV medium-voltage power distribution systems and features a dry-type, fully enclosed support structure suitable for installation in metal-clad switchgear.
This model provides four independent secondary outputs (4S configuration), enabling simultaneous use for revenue metering, panel indication, primary protection, and backup protection. It complies with IEC 60044-1 and aligns with IEC 61869-1/-2 for international applications, ensuring reliable performance under standard indoor service conditions including humidity and pollution exposure.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV / 11kV / 12kV |
| Highest voltage for equipment | 12kV |
| Rated insulation level | 12/28/75kV or 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Secondary current | 5A or 1A |
| Secondary configuration | 4S (four independent secondaries) |
| Insulation type | Epoxy resin cast (dry-type) |
| Installation | Indoor switchgear only |
| Primary conductor | Built-in, encapsulated in resin |
| Core type | Annular, epoxy-encapsulated |
| Protection class availability | Yes (e.g., 10P10, 10P15, 10P20) |
| Accuracy compliance | IEC 60044-1 / IEC 61869-1 & -2 |
Model Designation
- L: Current transformer
- Z: Indoor / pillar-type structure
- Z: Epoxy resin casting insulation
- B: Protection level available
- J: Strengthened design
- 9: Design serial number
- 12: 12kV maximum operating voltage class
- 150b: Compact nominal width / structure dimension code
- 4S: Four-secondary schematic code
- AS12: Alternative 12kV series designation for the same platform
Construction
The LZZBJ9-12/150b/4S features a robust indoor, dry-type construction with all active components fully encapsulated in epoxy resin. The primary conductor, annular magnetic core, and four secondary windings are integrally cast into a solid, non-hygroscopic body that provides uniform electric field distribution and long-term insulation stability. This cast-resin structure eliminates air gaps and prevents moisture ingress, making it suitable for humid or polluted indoor environments typical of medium-voltage switchgear rooms. The support-type mounting design allows secure fixation within panels, while terminal blocks on the secondary side facilitate reliable wiring to meters, relays, and monitoring devices. The entire assembly forms a maintenance-free, fire-resistant unit compliant with standard indoor safety and dielectric requirements.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 12kV class networks
- Rated frequency: 50Hz
- Ambient temperature: -5°C to +40°C
- Installation environment: should be free from severe vibration, conductive dust, corrosive gas, explosive medium, heavy pollution and abnormal condensation.
Technical Parameters
The LZZBJ9-12/150b/4s is an indoor epoxy cast-resin current transformer designed for 12kV class systems. It features multiple accuracy class combinations and complies with GB 20840.2-2014 and IEC 61869-2:2012 standards.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA/1s) |
Rated dynamic current (kA) |
||
|---|---|---|---|---|---|---|
| Class 1 | Class 2 | Class 3 | ||||
| 20,30,40,50,75,100 | 0.2/0.2/5P10 | 10 | 10 | 30 | 150×I1n | 375×I1n |
| 0.2/0.5/5P15 | 10 | 20 | 20 | |||
| 0.2/0.5/5P20 | 10 | 10 | 15 | |||
| 0.2/5P10/10P15 | 10 | 10 | 15 | |||
| 0.5/5P10/10P20 | 10 | 10 | 10 | |||
| 150,200 | 0.2/0.2/5P10 | 10 | 10 | 30 | 31.5 | 80 |
| 0.2/0.5/5P15 | 10 | 20 | 20 | |||
| 0.2/0.5/5P20 | 10 | 10 | 15 | |||
| 0.2/5P10/10P15 | 10 | 10 | 15 | |||
| 0.5/5P10/10P20 | 10 | 10 | 10 | |||
| 300,400 | 0.2/0.2/5P10 | 10 | 10 | 30 | 45 | 112.5 |
| 0.2/0.5/5P15 | 10 | 15 | 20 | |||
| 0.2/0.5/5P20 | 10 | 15 | 15 | |||
| 0.2/5P10/10P15 | 10 | 15 | 20 | |||
| 0.5/5P10/10P20 | 15 | 15 | 15 | |||
| 500 | 0.2/0.2/5P10 | 10 | 10 | 30 | 63 | 130 |
| 0.2/0.5/5P15 | 10 | 15 | 20 | |||
| 0.2/0.5/5P20 | 10 | 15 | 15 | |||
| 0.2/5P10/10P15 | 10 | 15 | 20 | |||
| 0.5/5P10/10P20 | 15 | 15 | 15 | |||
| 600,800 | 0.2/0.2/5P10 | 10 | 10 | 30 | 63 | 130 |
| 0.2/0.5/5P15 | 10 | 15 | 20 | |||
| 0.2/0.5/5P20 | 10 | 15 | 15 | |||
| 0.2/5P10/10P15 | 10 | 15 | 20 | |||
| 0.5/5P10/10P20 | 15 | 15 | 15 | |||
| 1000,1200,1250 | 0.2/0.2/5P10 | 15 | 15 | 30 | 80 | 160 |
| 0.2/0.5/5P15 | 15 | 20 | 20 | |||
| 0.2/0.5/5P20 | 15 | 20 | 15 | |||
| 0.2/5P10/10P15 | 15 | 15 | 20 | |||
| 0.5/5P10/10P20 | 20 | 15 | 15 | |||
Installation & Wiring
Installation Diagram
The LZZBJ9-12/150b/4S or AS12/150b/4S current transformer is installed as a compact support-type unit within indoor switchgear. It features top-mounted primary terminals and a bottom-mounted secondary terminal box. Due to the 4S multi-secondary configuration, adequate clearance must be provided around the secondary terminal area for safe and reliable wiring. The switchgear manufacturer must verify busbar spacing, primary terminal orientation, mounting hole alignment, and secondary cable routing prior to installation.
Selection & FAQs
Selection Guide
- Confirm whether the project requires 12/28/75kV or 12/42/75kV insulation; both appear in the source and must not be treated as identical.
- Select a 20A–1250A ratio from load range, metering performance and fault level, then verify the compact 150b busbar interface.
- Define all four 1A/5A secondary circuits by function, accuracy class, output and terminal marking rather than relying on the 4S label alone.
- Obtain a complete per-core winding schedule because the source’s accuracy and burden combinations often contain only three entries.
- Check thermal/dynamic duty, terminal-box wiring clearance, P1/P2 orientation, mounting holes, creepage, indoor environment and approved test standard.
Frequently Asked Questions
Q1: Which accuracy class combination is best for protection and metering?
Select a multi-core combination like 0.2/0.5/5P10 for integrated metering and protection. It provides 10VA for Class 1, 20VA for Class 2, and 20VA for Class 3. Contact us to verify your specific burden requirements.
Q2: What are the ambient temperature and installation environment limits?
The transformer operates between -5°C and +40°C in indoor medium-voltage switchgear. The installation site must be free from severe vibration, conductive dust, and corrosive gases. Confirm site conditions with our engineering team if abnormal.
Q3: How does this CT handle short-circuit thermal and dynamic currents?
It withstands a short-time thermal current of 150×I1n for 1 second and a rated dynamic current of 375×I1n. These ratings ensure robust performance during fault conditions. Verify exact primary current ratings for your specific project.
Q4: Which international standards does this cast-resin current transformer comply with?
The LZZBJ9-12/150b/4S complies with IEC 61869-2:2012 and GB 20840.2-2014 standards. It is fully certified for 12kV class indoor networks. Request the specific type test reports for your procurement documentation.
Q5: Can the rated primary current be customized below 100A?
Yes, standard rated primary currents include 20A, 30A, 40A, 50A, 75A, and 100A. Custom ratios are subject to factory confirmation based on your switchgear specifications. Please provide your exact requirements for a tailored quote.
Q6: What applications is this 12kV indoor current transformer designed for?
It is specifically designed for indoor medium-voltage switchgear in 12kV class, 50Hz power networks. The epoxy cast-resin insulation ensures reliable performance for current measurement and protection. Check our catalog for similar 12kV transformer models.
Q7: Why choose an epoxy cast-resin design for indoor switchgear?
Epoxy cast-resin provides excellent insulation, flame retardancy, and moisture resistance for indoor 12kV applications. The LZZBJ9-12 model ensures compact integration within medium-voltage panels. Contact our sales team for technical datasheets.