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. It supports current measurement, electric energy metering, and relay protection in AC power systems. The compact design features primary conductors extending from both sides and a central mounting plate for secure installation through cabinet walls or partitions.
This combined product family delivers standardized 5A or 1A secondary signals to meters, relays, and monitoring devices. Configurable with metering classes (0.2S, 0.2, 0.5) and protection classes (10P10, 10P15), it ensures reliable performance across diverse indoor applications.
Key Ratings Snapshot
| Parameter | Value |
|---|---|
| Voltage Class | 10kV, 11kV, 12kV class |
| Insulation Level | 12/42/75kV |
| Frequency | 50Hz; 60Hz by agreement |
| Secondary Current | 5A or 1A |
| Primary Current Range | 5A to 1000A |
| Metering Accuracy | 0.2S, 0.2, 0.5 |
| Protection Class | 10P10, 10P15 |
| Rated Output | 10VA, 15VA, 20VA |
| Thermal Current | 90 x I1n or kA-level |
| Dynamic Current | 200 x I1n or kA-level |
Model Designation
- L: Current transformer
- A: Wall-through / bulkhead-type structure
- J: Design sequence or enhanced output series reference
- 10: 10kV class model reference (used for 10kV, 11kV, 12kV class documentation)
- LFZBJ-10: Related epoxy cast-resin wall-mounted CT with protection-class configuration
Construction
The LAJ-10 / LFZBJ-10 series features a robust epoxy cast-resin body that provides high insulation strength, mechanical stability, and moisture resistance for indoor environments. The wall-through structure includes primary terminals on both sides of the transformer body and a centrally located mounting plate for secure integration into switchgear panels.
Secondary terminals are grouped on the resin housing for easy access during wiring to meters or relays. A dedicated grounding point ensures compliance with electrical safety practices. The compact form factor minimizes space requirements while maintaining clear terminal labeling and polarity markings for field installation and maintenance.
Technical Parameters
Service Conditions
- Installation location: Indoor medium-voltage switchgear
- System voltage: 10kV, 11kV, 12kV class (by project confirmation)
- Frequency: 50Hz; 60Hz by agreement
- Ambient temperature: -5 degC to +55 degC
- Environment: Free from severe vibration, corrosive gas, explosive media, conductive dust, and insulation-damaging contamination
Technical Data
| Rated Primary Current (A) |
Accuracy Class Combination |
Rated Output (VA) |
Thermal Current Reference |
Dynamic Current Reference |
|---|---|---|---|---|
| 5-200 | 0.2S / 10P10 0.5 / 10P10 0.2S / 10P15 0.5 / 10P15 |
0.2S: 10 0.5: 10 10P10: 15 10P15: 15 |
90 x I1n | 200 x I1n |
| 300-400 | 0.2S: 10 0.5: 10 10P10: 15 10P15: 15 |
24.5kA reference | 44kA reference | |
| 500 | 0.2S: 10 0.5: 10 10P10: 20 10P15: 15 |
32kA reference | 80kA reference | |
| 600 | 0.2S: 10 0.5: 10 10P10: 20 10P15: 15 |
32kA reference | 80kA reference | |
| 800-1000 | 0.2S: 10 0.5: 10 10P10: 20 10P15: 15 |
63kA reference | 100kA reference |
Installation & Wiring
Installation Diagram
The LAJ-10 / LFZBJ-10 series is designed for wall-through or bulkhead mounting in indoor switchgear. Prior to cabinet fabrication, verify mounting plate position, hole dimensions, primary conductor routing, terminal orientation, insulation clearance, and maintenance access using the approved outline drawing. For retrofit projects, confirm dimensional compatibility even when electrical ratings match.
Outline Dimensions
| Item | LAJ-10 Reference | LFZBJ-10 Reference |
|---|---|---|
| Installation type | Wall-through mounting with primary terminals on both sides | Wall-mounted / bulkhead-type epoxy cast-resin CT structure |
| Overall length | Approx. 510mm reference | Per selected outline drawing and current ratio |
| Mounting plate width | Approx. 260mm | Per cabinet opening and drawing |
| Hole dimension | 160mm x 220mm with 4-phi14 mounting holes | Per selected variant and cabinet requirement |
| Weight | Approx. 19.2kg | Subject to final selected structure |
Selection & FAQs
Selection Guide
- Resolve LAJ-10 versus LAJ-10Q before using dimensions. The title includes Q while the body and outline refer mainly to LAJ-10; confirm whether the enhanced Q variant shares the same mounting and environmental data.
- Select a primary ratio from 5A–1000A. Match loading, 1A or 5A secondary and meter range, then select 10P10 or 10P15 according to relay duty.
- Allocate burden per core. Measurement cores are referenced at 10VA; protection output is generally 15VA, with 20VA 10P10 options listed from 500A upward.
- Validate fault values before approval. The 300A–400A thermal/dynamic pair and other references need confirmation of RMS duration and peak basis, especially where the relationship differs from surrounding rows.
- Complete a dimensional retrofit survey. Check the approximate 510mm length, 260mm plate, 160 × 220mm hole reference, four Ø14 holes, 19.2kg weight, wall opening, primary reach, terminals and clearances.
Frequently Asked Questions
Q1: Where can these wall-mounted epoxy resin current transformers be installed?
They are designed strictly for indoor medium-voltage switchgear. The environment must be free from severe vibration, corrosive gases, and conductive dust. Contact us for site assessments.
Q2: What is the short-circuit withstand capability for a 500A rated primary current?
The short-circuit capability depends on the primary current rating. For 500A, the thermal reference is 32kA and dynamic current is 80kA. Verify exact fault levels with our team.
Q3: Which accuracy class combination is recommended for protection and metering?
We recommend 0.2S/10P10 or 0.5/10P10 combinations. The 0.2S/0.5 class handles metering with 10VA output, while 10P10 provides 15VA for protection. Confirm your burden requirements.
Q4: Can these 10kV current transformers operate on 60Hz power systems?
Standard production is 50Hz, but 60Hz variants are available by prior agreement. Specify your exact system frequency in the inquiry to ensure factory compliance.
Q5: How are these current transformers tested prior to delivery?
Standard factory tests typically include ratio and insulation checks, but exact protocols are subject to confirmation. Contact our technical team for specific test certificate details.
Q6: Why is switchgear ventilation critical for these epoxy resin CTs?
These transformers require strict temperature control. The allowable ambient operating range is -5°C to +55°C. Exceeding this limit risks degrading the epoxy resin insulation.
Q7: Are these epoxy resin CTs suitable for outdoor switchgear applications?
No, the LAJ-10Q/LFZBJ-10KV series is strictly designed for indoor medium-voltage switchgear. For outdoor applications, please inquire about our weather-resistant current transformer models.