Overview
The LZZBJ9-10C3, LZZBJ9-10C3Q3 and LZZBJ9-10C3Q4 are indoor epoxy cast-resin current transformers designed for 10kV, 11kV and 12kV class medium-voltage AC power systems. These fully enclosed, post-type devices feature a reinforced epoxy resin insulated body, providing reliable electrical insulation and mechanical robustness for indoor switchgear environments.
They support secondary currents of 1A or 5A and offer multi-core configurations with accuracy classes such as 0.2S, 0.5 and 5P20 for metering and protection applications. Commonly used in metal-clad switchgear for feeder monitoring, energy metering, relay protection and SCADA integration, these transformers comply with standard requirements for indoor medium-voltage instrumentation and protection circuits.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV / 11kV / 12kV |
| Insulation level | 24/65/125kV (or 12/42/75kV per nameplate) |
| Rated frequency | 50Hz / 60Hz |
| Primary current | 1000A to 3150A (per model) |
| Secondary current | 1A or 5A |
| Accuracy classes | 0.2S, 0.5, 5P20 (multi-core combinations) |
| Installation type | Indoor support-type in switchgear |
| Construction | Epoxy cast-resin, fully enclosed |
Model Designation
- L: Current transformer
- Z: Indoor type / post-type structure
- Z: Epoxy resin cast insulation / fully enclosed structure
- B: Protection class available
- J: Reinforced / enhanced design
- 9: Design sequence code
- 10: 10kV catalogue voltage class (covers 10kV, 11kV, 12kV systems)
- C3: Structure code for this product platform
- Q3 / Q4: Outline and installation variants for different switchgear layouts
Construction
The LZZBJ9-10C3 series features a fully enclosed, post-type construction with an epoxy cast-resin insulated body. This design integrates both the insulation support and current transformation functions into a single compact unit suitable for indoor switchgear mounting. The primary conductor passes through the center of the resin-molded core, while the secondary windings are embedded within the cast structure and terminated at a lower terminal block. The top primary terminals connect directly to the switchgear busbar system. The use of high-quality epoxy resin ensures stable dielectric performance, moisture resistance, and long-term mechanical integrity under normal indoor operating conditions.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV 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 LZZBJ9-10C3 is an indoor epoxy cast-resin current transformer designed for 10kV 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 | ||||
| 5~300 | 0.2/5P20/5P20 | 20 | 20 | 20 | 150×I1n | 375×I1n |
| 0.5/0.2/5P20/5P20 | 20 | 20 | 20 | |||
| 0.5/5P20/5P20 | 20 | 20 | 20 | |||
| 5P20/5P20/5P20 | 20 | 20 | 20 | |||
| 400~800 | 0.2/5P20/5P20 | 30 | 20 | 20 | 63 | 130 |
| 0.5/0.2/5P20/5P20 | 20 | 20 | 20 | |||
| 0.5/5P20/5P20 | 30 | 20 | 20 | |||
| 5P20/5P20/5P20 | 30 | 30 | 30 | |||
| 1000~1250 | 0.2/5P20/5P20 | 20 | 30 | 20 | 80 | 160 |
| 0.5/0.2/5P20/5P20 | 20 | 20 | 20 | |||
| 0.5/5P20/5P20 | 30 | 30 | 20 | |||
| 5P20/5P20/5P20 | 30 | 30 | 30 | |||
| 1500~3150 | 0.2/5P20/5P20 | 20 | 30 | 30 | 100 | 160 |
| 0.5/0.2/5P20/5P20 | 30 | 30 | 30 | |||
| 0.5/5P20/5P20 | 30 | 30 | 30 | |||
| 5P20/5P20/5P20 | 20 | 30 | 30 | |||
Installation & Wiring
Installation Diagram
The LZZBJ9-10C3, LZZBJ9-10C3Q3/Q4 current transformer is installed as an indoor post-type unit with top-mounted primary terminals and secondary terminals located at the base. Mounting is typically achieved via through-bolts aligned with the switchgear structure, using either a 425mm or 390mm mounting length depending on the terminal arrangement for the specific current range. Ensure alignment with busbar connections and maintain required phase-to-phase and phase-to-ground clearances.
Selection & FAQs
Selection Guide
- Resolve the insulation requirement first: the source lists both 24/65/125kV and 12/42/75kV, so the nameplate and project coordination must prevail.
- Select C3, C3Q3 or C3Q4 from the approved outline, 425mm/390mm mounting length and switchgear primary-terminal arrangement.
- Choose a 5A–3150A ratio and assign three 1A/5A cores to 0.2S/0.5 measurement and one or two 5P20 protection functions.
- Calculate each circuit burden and select a complete 20VA/30VA per-core combination without exceeding the verified accuracy duty.
- Confirm ratio-specific fault withstand, standard/high-current busbar interface, ≤1500m altitude, phase clearances, grounding and shorting blocks.
Frequently Asked Questions
Q1: What are the ambient temperature limits for installing this cast-resin current transformer?
The operating ambient temperature ranges from -5°C to +40°C. Ensure the installation environment is free from severe vibration, conductive dust, and corrosive gases. Contact us for extreme climate adaptations.
Q2: Which accuracy class combinations are available for the LZZBJ9-10C3 series?
Multiple combinations are available, including 0.2/5P20, 0.5/0.2/5P20, and 5P20/5P20. All cores feature a rated output of 20VA. Specify your exact protection and metering requirements during inquiry.
Q3: How does this 10kV CT perform under short-circuit fault conditions?
It withstands a short-time thermal current of 150×I1n for 1 second and a rated dynamic current of 375×I1n. Verify your specific primary current rating to confirm exact short-circuit tolerances.
Q4: What international standards does this indoor epoxy current transformer comply with?
The LZZBJ9-10C3 complies with GB 20840.2-2014 and IEC 61869-2:2012 standards. Factory test reports are provided upon shipment. Request specific certification documents during the procurement process.
Q5: Can the rated primary current be customized up to 800A?
Yes, the series supports rated primary currents ranging from 5A to 800A. Custom ratios and terminal configurations are subject to factory confirmation. Provide your single-line diagram for precise engineering review.
Q6: Where is the LZZBJ9-10C3 current transformer typically applied?
It is designed for indoor medium-voltage switchgear in 10kV class, 50Hz networks. Ensure the installation location avoids heavy pollution and abnormal condensation. Contact our sales team for project-specific application guidance.