Overview
The LAJ-10 / LFZBJ-10 is an indoor wall-through epoxy cast-resin current transformer designed for 10kV, 11kV, and 12kV class medium-voltage switchgear systems. It features a robust epoxy resin insulation system suitable for indoor environments, with primary conductors extending from both sides of the unit and a mounting plate for secure installation through switchgear panels or partitions.
This CT family supports both metering and protection applications, offering accuracy classes such as 0.2S, 0.2, 0.5 for measurement and 10P10 or 10P15 for relay protection. It delivers standardized secondary outputs of 5A or 1A to meters, relays, and monitoring equipment, complying with typical requirements for AC power systems operating at 50Hz or 60Hz.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz (60Hz by confirmation) |
| Rated secondary current | 5A or 1A |
| Rated primary current | 5A to 1000A (custom ratios available) |
| Metering accuracy classes | 0.2S, 0.2, 0.5 |
| Protection accuracy classes | 10P10, 10P15 |
| Installation type | Wall-through, indoor |
| Insulation material | Epoxy cast-resin |
| Typical use | Measurement, metering, relay protection |
Model Designation
- L: Current transformer
- A: Wall-through / bulkhead-type structure
- J: Design sequence or enhanced output series reference
- 10: 10kV class model reference, applicable to 10kV, 11kV and 12kV class projects upon confirmation
- LFZBJ-10: Related epoxy cast-resin wall-mounted CT designation with protection-class configuration
Construction
The LAJ-10 / LFZBJ-10 series features a compact, wall-mounted design with an epoxy cast-resin insulated body. The primary conductor passes through the transformer core and extends from both sides of the unit, enabling straightforward integration into switchgear walls or partition panels. Secondary terminals are embedded in the resin housing for reliable connection to measuring instruments or protection relays. The construction includes an integrated grounding point and mounting holes aligned with standard cabinet dimensions. The epoxy resin provides high dielectric strength, mechanical rigidity, and resistance to moisture and environmental contaminants, ensuring stable performance in indoor medium-voltage applications.
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 LAJ-10/LFZBJ-10 is an indoor epoxy 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 5A to 1000A.
| Rated primary current (A) |
Accuracy classed combination |
Rated Output (VA) |
Short-time thermal current (kA/1s) |
Rated dynamic current (kA) |
|||
|---|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 10P10 | 10P15 | ||||
| 5~200 | 0.2(S)/10P10 0.5(S)/10P10 0.2(S)/10P15 0.5(S)/10P15 |
10 | 10/20 | 15 | 15 | 90×I1n | 200×I1n |
| 300, 400 | 10 | 10/20 | 15 | 15 | 24.5 | 44 | |
| 500 | 10 | 10/20 | 15 | 15 | 32 | 80 | |
| 600 | 10 | 10/20 | 15 | 15 | 32 | 80 | |
| 800~1000 | 10 | 10/20 | 15 | 15 | 63 | 100 | |
Installation & Wiring
Installation Diagram
The LAJ-10 / LFZBJ-10 current transformer is designed for indoor wall-through or bulkhead-type installation. Mounting requires precise alignment with the switchgear panel opening, ensuring correct primary conductor routing, terminal orientation, and adequate insulation clearance as specified in the approved outline drawing.
Selection & FAQs
Selection Guide
- Confirm whether LAJ-10 or LFZBJ-10 matches the required wall-through/bulkhead outline and secondary-core arrangement.
- Select one of the listed 5A–1000A ratios from load, metering and fault studies, then choose 1A or 5A secondary current.
- Specify 0.2S/0.5 measurement and 10P10/10P15 protection as separate cores where both functions are required.
- Calculate each burden and verify the 10VA measurement plus 15VA/20VA protection output for the selected ratio and ALF.
- Approve the LAJ reference 160×220mm opening, 4-Ø14 holes, 510mm length, busbar alignment, insulation clearances and grounding.
Frequently Asked Questions
Q1: What installation environment is required for this epoxy cast-resin current transformer?
It requires indoor installation 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: Which accuracy class combination is suitable for protective relaying applications?
Select the 10P10 or 10P15 accuracy class for protection circuits. These classes ensure reliable performance during fault conditions with rated outputs of 15 VA. Confirm burden requirements before ordering.
Q3: How is the short-time thermal current rated for a 500A primary?
The rated short-time thermal current is 32 kA for 1 second at a 500A primary rating. The corresponding rated dynamic current is 80 kA. Verify specific fault levels with our engineering team.
Q4: Does this 10kV current transformer comply with international IEC standards?
Yes, the LAJ-10 and LFZBJ-10 models fully comply with IEC and GB standards for 10kV class networks. Request the specific type test reports during the procurement process.
Q5: Can the primary current be customized outside the standard 5A to 1000A range?
Standard ratings cover 5A to 1000A for indoor medium-voltage switchgear. Custom primary currents outside this range are subject to factory confirmation. Please contact our sales team for specific requirements.
Q6: Are these current transformers suitable for 11kV or 12kV distribution networks?
They are specifically designed for 10kV class networks. Application in 11kV or 12kV systems is subject to project confirmation and factory verification. Specify your exact system voltage when inquiring.
Q7: Where is the LAJ-10 epoxy resin current transformer typically applied?
It is designed for current measurement and protection in 10kV class indoor medium-voltage switchgear. The epoxy cast-resin insulation ensures reliable operation at a rated frequency of 50Hz.