Overview
The LZJC-10 / LZJC(D)-10 / LZJC-12 / LZJC(D)-12 is an indoor support-type current transformer with epoxy cast-resin insulation, designed for 10kV, 11kV, and 12kV medium-voltage AC systems operating at 50Hz or 60Hz. It features a robust cast-resin structure that encapsulates both primary and secondary windings, ensuring high dielectric strength and mechanical stability in indoor switchgear environments.
This current transformer supports applications including current measurement, energy metering, relay protection, and differential protection. It complies with IEC 60044-1 and can meet IEC 61869-1/-2 requirements upon request, making it suitable for integration into metal-clad switchgear, feeder cabinets, and SCADA-compatible monitoring systems where reliable isolation and signal accuracy are critical.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Insulation level | 12/42/75kV (IEC 12kV-class) |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Primary current range | As per project specification |
| Accuracy classes | Metering: 0.2, 0.5; Protection: 5P, 10P |
| Burden (rated output) | Per IEC standards, configurable |
| Short-time thermal current | As per system short-circuit level |
| Dynamic withstand current | As per system requirements |
| Application | Indoor metal-clad switchgear |
| Protection type | Standard or differential (LZJC(D) variant) |
| Standards | IEC 60044-1; IEC 61869-1/-2 (optional) |
Model Designation
- L: Current transformer
- Z: Support type
- J: For metal-clad switchgear with breaker truck
- C: Support-type cast-resin current transformer structure
- C(D): Differential protection version
- 10 / 12: Voltage class for 10kV, 11kV, or 12kV medium-voltage applications
Construction
The LZJC series employs a support-type epoxy cast-resin construction, where both primary and secondary windings are fully molded within a solid epoxy resin body. This design provides excellent electrical insulation, mechanical rigidity, and resistance to moisture and contamination in indoor environments. The magnetic cores are securely fixed to the cast body using a clamp structure, ensuring stable performance under normal and fault conditions. The cast-resin housing serves dual roles: it electrically isolates the medium-voltage primary circuit from the low-voltage secondary circuit and acts as the primary mechanical support when mounted inside metal-clad switchgear or circuit breaker cabinets. This integrated construction enhances reliability and longevity in demanding medium-voltage distribution applications.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class systems
- Rated frequency: 50Hz
- Ambient temperature: -5°C to +40°C
- Installation environment: should be free from severe vibration, corrosive gas, explosive medium, conductive dust, heavy pollution and abnormal condensation.
Technical Parameters
The LZJC-10 series is an indoor epoxy cast-resin current transformer designed for 10kV, 11kV, and 12kV class systems. It operates within an ambient temperature range of -5°C to +40°C and complies with IEC and GB standards. The device supports primary currents from 5A to 1000A with multiple accuracy class combinations.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA/1s) |
Rated dynamic current (kA) |
|||
|---|---|---|---|---|---|---|---|
| 0.2S | 0.2/0.5 | 5P | 10P | ||||
| 5~400 | 0.2/10P 0.2S/10P 0.5/10P |
10 | 10 | 15 | 15 | 60×I1n | 150×I1n |
| 600 | 50×I1n | 120×I1n | |||||
| 800 | 50×I1n | 100×I1n | |||||
| 1000 | 45×I1n | 90×I1n | |||||
Installation & Wiring
Installation Diagram
The LZJC(D)-10 and LZJC-12 current transformers are installed as support-type units within indoor metal-clad switchgear, typically mounted on the breaker truck or feeder cabinet structure using the integrated mounting holes and clamp arrangement. Primary terminals (P1/P2) align with busbar connections per the approved project drawing, while secondary terminals (S1/S2 or multi-core) are oriented to allow safe and accessible wiring to protection or metering devices.
Selection & FAQs
Selection Guide
- Select the exact 10 or 12 model from approved project data. Both are published with 12/42/75kV insulation for 10kV–12kV systems, so model choice must also consider outline, switchgear interface and nameplate designation.
- Choose the ratio within the 5A–1000A reference range. The table groups 5A–400A under standard LZJC and 600A–1000A under LZJC(D), but confirm availability rather than treating this grouping as a universal model rule.
- Define metering and protection performance per core. Specify 0.2S, 0.2 or 0.5 for measurement, 10P for protection, 10VA or 15VA output, and an accuracy limit factor of 10 or 15.
- Validate any differential-protection version with relay data. For LZJC(D), obtain excitation characteristics, secondary resistance, ratio error and saturation information needed by the selected differential scheme.
- Coordinate mounting and short-circuit duty. Verify bottom-hole pattern, breaker-truck or cabinet support, busbar alignment, terminal access, earthing, thermal-current duration and peak dynamic withstand.
Frequently Asked Questions
Q1: Can this CT be installed in outdoor switchgear?
No, it is strictly for indoor medium-voltage switchgear. The epoxy cast-resin design requires an environment free from severe vibration and abnormal condensation. Contact us for outdoor alternatives.
Q2: How is the short-time thermal current rated?
It is rated between 50 and 60 times the primary current for 1 second, depending on the ampere level. Provide your system parameters for specific short-circuit factory verification.
Q3: Which accuracy class combination supports both metering and protection?
The 0.2/10P or 0.2S/10P combinations are recommended. They provide high-precision metering alongside 10P protection cores within a 10VA rated output. Confirm your specific burden requirements during ordering.
Q4: Are these current transformers compliant with international standards?
Yes, the LZJC series complies with IEC and GB standards. All units undergo standard factory routine tests before shipment. Request the specific test certificates for your project documentation.
Q5: Is primary current customization available up to 1000A?
Yes, the series supports primary currents from 5A to 1000A. Custom turns ratios are available subject to factory engineering confirmation. Please specify your exact primary and secondary current requirements.
Q6: Why choose the LZJC-12 epoxy cast-resin model?
It offers reliable epoxy resin insulation for 12kV indoor medium-voltage switchgear and power distribution systems. This cast-resin design ensures stable performance in clean environments. Inquire for detailed application drawings.
Q7: When should this transformer not be installed?
Do not install it in environments with severe vibration, corrosive gas, or conductive dust. The ambient temperature must remain strictly between -5°C and +40°C. Verify site conditions prior to installation.