Overview
The LAJ-10Q / LFZJ-10Q is an indoor wall-through current transformer with epoxy resin cast insulation, designed for 10kV class medium-voltage AC systems operating at 50Hz or 60Hz. It supports rated voltage applications of 10kV, 11kV, and 12kV in indoor switchgear, subject to project-specific insulation verification.
This transformer delivers stable performance for current and power measurement as well as relay protection, meeting standard accuracy classes including 0.2, 0.5, 1, and protection class 10P10. It is engineered for integration into compact indoor switchgear, distribution cabinets, and medium-voltage assemblies requiring reliable metering and protection coordination.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV (applicable to 10kV, 11kV, 12kV by confirmation) |
| Rated frequency | 50Hz / 60Hz |
| Primary current | Up to high-current ranges (specific ratios per drawing) |
| Secondary current | 5A or 1A |
| Accuracy class (metering) | 0.2, 0.5, 1 |
| Protection class | 10P10 |
| Insulation type | Epoxy resin cast |
| Installation type | Indoor wall-through |
| Application | Current/power measurement, relay protection |
Model Designation
- L: Current transformer
- A: Wall-through type
- J: Extended output / enhanced output design
- 10: Rated voltage class: 10kV class
- Q: Stiffening / reinforced type
- LFZJ-10Q: Alternate catalogue designation for the same product family
Construction
The LAJ-10Q / LFZJ-10Q features a robust epoxy resin cast insulated structure, ensuring high dielectric strength and environmental resistance suitable for indoor medium-voltage environments. For primary currents up to 300A, the unit typically employs a semi-enclosed design, while higher current ratings utilize a fully enclosed single-wire configuration to enhance external insulation performance. The compact wall-through form factor allows seamless integration into fixed cabinet panels, where the primary conductor passes directly through the transformer body. This construction supports reliable operation in industrial substations, switchgear, and complete electrical assemblies requiring precise metering and dependable protection functionality.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- Ambient frequency: 50Hz or 60Hz
- Installation environment: should be free from severe vibration, corrosive gas, explosive medium, conductive dust, and abnormal condensation.
- International project considerations: final service conditions should be checked against altitude, pollution degree, humidity, and insulation coordination requirements.
Technical Parameters
The LAJ-10Q and LFZJ-10Q are indoor wall-through cast-resin current transformers rated for 10kV class systems. They feature a rated insulation level of 11.5/42/75kV, operate at 50Hz or 60Hz, and support primary current ratios from 5/5 A up to 1500/5 A. Designed for standard indoor environments, they comply with GB5583-85 and IEC44-4 for partial discharge performance.
| Rated Primary Current (A) |
Accuracy Class and Rated Output (VA) |
Rated Short-Time Thermal Current Ith/1s (r.m.s.) |
Rated Dynamic Current Idyn (Peak) |
|||
|---|---|---|---|---|---|---|
| Class 0.2 |
Class 0.5 |
Class 1 |
Class 10P15 |
|||
| 20~200 | 10 | 25 | 25 | 15 | 120 I1n | 215 I1n |
| 300 | 100 I1n | 180 I1n | ||||
| 400 | 15 | 75 I1n | 135 I1n | |||
| 500 | 60 I1n | 110 I1n | ||||
| 600, 800 | 25 | 20 | 50 I1n | 90 I1n | ||
Installation & Wiring
Outline Dimensions
The LAJ-10Q and LFZJ-10Q wall-through cast-resin current transformers are available in two outline dimension groups corresponding to different current ranges. Group A applies to 5–300/5 ratios, while Group B is used for 400–800/5 and higher ratios. Cabinet cut-outs and mounting layouts must be selected based on the specific current ratio and referenced product drawing to ensure proper fit and clearances.
Selection & FAQs
Selection Guide
- Select Group A or Group B outline from the exact current ratio, cabinet cutout, conductor clearance and approved drawing.
- Choose a listed 5/5A–1500/5A ratio; treat a 1A secondary as a special option because the detailed table only documents 5A.
- Select one class 0.2, 0.5, 1 or 10P10 duty per winding, or confirm separate cores when both measurement and protection are required.
- Verify 10VA–25VA burden at power factor 0.8 and convert Ith/Idyn multiples to actual kA.
- Confirm 11.5/42/75kV insulation, Class 2 pollution, ≤60pC partial discharge, structure boundary, mounting and terminal orientation.
Frequently Asked Questions
Q1: Which accuracy class is suitable for protection relays?
Class 10P15 is recommended for protection relays. It provides a 15 VA rated output and ensures accurate transformation during fault conditions. Confirm specific burden requirements with our engineering team.
Q2: Can these cast-resin CTs be installed outdoors?
No, they are strictly designed for indoor medium-voltage switchgear. The environment must be free from corrosive gases, conductive dust, and abnormal condensation. Please specify your exact site conditions for alternative outdoor options.
Q3: What is the short-circuit thermal current rating?
The rated short-time thermal current is 120 times the rated primary current for 1 second. The dynamic peak current reaches 215 times the primary current. Verify exact multipliers for your specific primary current ratio with our technical team.
Q4: How are these CTs tested before shipment?
Standard factory tests include partial discharge measurements complying with IEC 44-4 and routine insulation checks. Specific international certification requirements depend on the destination country. Contact our sales team for detailed test reports.
Q5: Is it possible to customize the primary current ratio?
Yes, we support standard primary current ratios ranging from 5/5 A up to 1500/5 A. Custom ratios outside this standard range are subject to factory confirmation. Provide your exact technical parameters for a tailored quote.
Q6: Are these wall-through transformers suitable for 11kV switchgear?
Yes, they feature an 11.5/42/75kV rated insulation level suitable for 10kV and 11kV class systems. They are ideal for indoor medium-voltage switchgear applications. Confirm exact insulation coordination requirements for your specific project.