Overview
The LZZ-10 (AK12) is an indoor single-phase post-type epoxy cast-resin current transformer designed for 11kV and 12kV class medium-voltage switchgear. It features a fully enclosed epoxy resin casting that integrates the primary winding, secondary winding, and magnetic core into a compact, mechanically robust body with top-mounted primary terminals (P1/P2) and a lower-side secondary terminal box.
It supports accuracy classes of 0.2, 0.5, and 10P10, making it suitable for current measurement, energy metering, feeder monitoring, and relay protection in 50Hz or 60Hz AC systems. With a rated insulation level of 12/42/75kV, it complies with IEC-oriented requirements for 12kV equipment-class applications in 10kV, 11kV, and 12kV indoor switchgear installations after insulation coordination.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz or 60Hz |
| Primary current range | 50A to 630A |
| Secondary current | 5A or 1A |
| Metering accuracy classes | 0.2, 0.5 |
| Protection accuracy class | 10P10 |
| Insulation material | Epoxy cast-resin |
| Installation type | Indoor, post-type |
| Phase configuration | Single-phase |
| Application | Measurement, metering, protection, monitoring |
| Construction | Fully enclosed cast-resin body |
Model Designation
- L: Current transformer
- Z: Cast-resin insulated / indoor structure reference
- Z: Post-type / support-type structural series reference
- 10: Catalogue voltage-class reference; internationally documented as 11kV / 12kV class by insulation confirmation
- AK12: Manufacturer structural designation for the compact post-type version
Construction
The LZZ-10 (AK12) employs a fully enclosed post-type epoxy resin casting structure. The primary winding, secondary winding, and magnetic core are completely embedded within the solid epoxy resin body, providing excellent dielectric strength, moisture resistance, and mechanical durability. Primary terminals P1 and P2 are bolted at the top of the unit, while the secondary terminals are housed in a protected terminal box on the lower side, facilitating clear and secure wiring for both measurement and protection circuits. The base includes mounting provisions for fixed installation inside standard indoor metal-enclosed switchgear panels. This construction ensures stable performance under continuous operation and short-circuit conditions in medium-voltage distribution environments.
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 LZZ-10 (AK12) is an indoor post-type cast-resin current transformer designed for 10kV class systems. It features epoxy resin insulation and complies with IEC and GB standards. Primary current ranges from 50A to 630A.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA) |
Rated dynamic current (kA) |
||
|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 10P10 | ||||
| 50 | 0.2 0.5 10P10 |
10 | 15 | 10 | 7.5 | 19 |
| 75 | 11.25 | 28 | ||||
| 100 | 15 | 37.5 | ||||
| 150 | 22.5 | 56 | ||||
| 200 | 30 | 75 | ||||
| 300 | 40 | 100 | ||||
| 400 | ||||||
| 500 | ||||||
| 600 | ||||||
| 630 | ||||||
Installation & Wiring
Installation Diagram
The LZZ-10 (AK12) post-type epoxy cast-resin current transformer is designed for secure mounting inside indoor switchgear using the base mounting holes shown in the diagram. Prior to cabinet fabrication, verify primary terminal spacing, busbar or cable-lug connections, base hole positions, secondary terminal orientation, grounding point location, and required maintenance clearance against the approved outline drawing. Due to its compact post-type design, ensure adequate cabinet clearance and unobstructed access to all terminals before final assembly.
Selection & FAQs
Selection Guide
- Confirm a 10–12kV indoor system requiring 12/42/75kV insulation and the AK12 compact post-type terminal arrangement.
- Select 50A, 75A, 100A, 150A, 200A, 300A, 400A, 500A, 600A or 630A from load and protection studies.
- Choose 1A or 5A and specify class 0.2, 0.5 or 10P10 according to whether the circuit serves metering or protection.
- Verify the fixed reference output—10VA for 0.2/10P10 or 15VA for 0.5—against device and cable burden.
- Check ratio-specific withstand, cosφ 0.8 burden basis, P1/P2 busbar interface, base holes, clearances, grounding and +55°C duty.
Frequently Asked Questions
Q1: What are the installation environment requirements for this cast-resin CT?
Install indoors in medium-voltage switchgear free from severe vibration, conductive dust, and corrosive gases. Ambient temperature must remain between -5°C and +40°C. Contact us for harsh environment solutions.
Q2: How is the short-time thermal current rated for the 200A model?
The 200A primary current model features a 30kA short-time thermal current and 75kA rated dynamic current. Verify specific short-circuit requirements with our engineering team during project selection.
Q3: Which accuracy class combination is available for protection and metering?
The LZZ-10 (AK12) offers 0.2, 0.5, and 10P10 accuracy classes. Rated outputs are 10VA for 0.2, 15VA for 0.5, and 10VA for 10P10. Specify your exact burden requirements when ordering.
Q4: Can the primary current be customized beyond the standard 630A maximum?
Standard models cover 50A to 630A primary currents. For higher current ratings, please contact our sales team to discuss custom manufacturing options subject to factory confirmation.
Q5: Are these indoor post-type current transformers fully IEC compliant?
Yes, the transformer complies with both IEC and GB standards. Request the specific type test reports and compliance certificates from your sales representative before procurement.
Q6: Why specify the LZZ-10 for 10kV indoor switchgear applications?
It is specifically designed for 10kV class indoor medium-voltage networks operating at 50Hz. Confirm your specific switchgear dimensions and application details with our technical support team.
Q7: When is the 10P10 accuracy class required for this transformer?
The 10P10 class is required for protection relays during fault conditions. It provides a 10VA rated output and ensures accurate transformation up to 10 times rated current. Consult our engineers for relay coordination.