Overview
The LAJ-10 / LFZJ-10 is an indoor wall-through epoxy resin cast current transformer designed for 10kV, 11kV, and 12kV class medium-voltage AC systems operating at 50Hz. It features a robust epoxy resin casting insulation system that ensures reliable dielectric performance and mechanical stability in indoor switchgear environments.
This current transformer supports both metering and protection functions, with accuracy classes including 0.2, 0.5 for metering and 10P15 for protection applications. It is commonly used in feeder panels, metering cabinets, and distribution switchgear for current measurement, energy metering, and relay protection circuits where wall-through mounting is required.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV, 11kV, 12kV |
| Rated insulation level | 11.5/42/75kV |
| Rated frequency | 50Hz |
| Rated primary current | 20A to 6000A |
| Rated secondary current | 5A or 1A |
| Metering accuracy class | 0.2, 0.5 |
| Protection accuracy class | 10P15 |
| Insulation material | Epoxy resin cast |
| Installation type | Wall-through |
| Application | Indoor switchgear |
| Structure variants | Semi-enclosed (20–200A), fully enclosed (300A+) |
| System compatibility | Medium-voltage AC power systems |
Model Designation
- L: Current transformer
- A: Wall-through / constructed through type
- J: Extended output / enhanced output design
- 10: Rated voltage class: 10kV class
- LFZJ-10: Corresponding epoxy resin cast wall-through designation shown in parentheses
Construction
The LAJ-10 / LFZJ-10 current transformer employs a wall-through design where the primary conductor passes directly through the transformer body. The core and secondary winding are encapsulated in epoxy resin, providing excellent insulation properties and mechanical rigidity suitable for indoor use. For models rated from 20A to 200A, a semi-enclosed resin casting structure is used, while units rated 300A and above feature a fully enclosed resin casting structure. This construction approach ensures reliable performance across a wide range of primary currents, from low-current metering circuits to high-current feeder applications up to 6000A.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- Rated voltage: 10kV, 11kV and 12kV class systems by project confirmation
- Rated frequency: 50Hz
- Altitude: not over 1000m under standard service conditions
- Ambient temperature: -5°C to +40°C
- Relative humidity: less than 85% at 20°C reference condition
- Installation environment: should be free from severe vibration, corrosive gas, explosive medium, conductive dust, heavy pollution and abnormal condensation.
Technical Parameters
The LAJ-10 and LFZJ-10 are wall-through epoxy resin cast current transformers designed for indoor 10kV-class systems (including 11kV and 12kV by confirmation), with operating temperatures from -5°C to +40°C and altitudes up to 1000m. They comply with GB1208-1997 where specified and support primary currents from 20A to 6000A, featuring semi- or fully enclosed cast-resin structures based on current range.
| 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) |
|||
|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 1 | 10P15 | |||
| 20, 30, 40, 50, 75, 100, 150, 200 |
10 | 25 | 25 | 15 | 120 I1n | 215 I1n |
| 300 | 100 I1n | 180 I1n | ||||
| 400 | 20 | 75 I1n | 135 I1n | |||
| 500 | 60 I1n | 100 I1n | ||||
| 600, 800 | 25 | 40 | 20 | 50 I1n | 90 I1n | |
| 1000, 1200, 1500 | 40 | 40 | ||||
| 2000, 3000, 4000, 5000, 6000 |
60 | 60 | 60 | 25 | ||
| Rated Primary Current (A) |
Accuracy Classes |
L | I | D | d | A1 | A2 | B1 | B2 | Weight (kg) |
|---|---|---|---|---|---|---|---|---|---|---|
| 1000 | 0.5/D | 227 | 110 | φ190 | φ90 | 188 | 228 | 238 | 278 | 12 |
| D/D | 242 | 14.5 | ||||||||
| 1200 | 0.5/D | 2.6 | 89 | φ242 | φ130 | 256 | 296 | 306 | 346 | 15 |
| D/D | 18 | |||||||||
| 1500 | 0.5/D | 14.5 | ||||||||
| D/D | 17 | |||||||||
| 2000 | 0.5/D | 14 | ||||||||
| D/D | 16.5 | |||||||||
| 3000 | 0.5/D | φ258 | φ150 | 14 | ||||||
| D/D | 15.5 | |||||||||
| 4000 | 0.5/D | φ304 | φ195 | 345 | 385 | 395 | 435 | 16.5 | ||
| D/D | 18.5 | |||||||||
| 5000 | 0.5/D | 196 | 84 | φ347 | φ230 | 19 | ||||
| D/D | 20 | |||||||||
| 6000 | 0.5/D | 206 | 89 | φ410 | φ305 | 408 | 448 | 458 | 498 | 23.5 |
| D/D | 24.5 |
Installation & Wiring
Installation Diagram
The LAJ-10 / LFZJ-10 series is installed through a wall opening in indoor switchgear panels. The primary conductor passes directly through the center of the cast-resin body, while secondary terminals are accessible from the front or side as specified in the approved drawing. Mounting is secured using bolts through the flange around the perimeter. Ensure correct alignment of the hole dimension, conductor path, and terminal direction per the applicable catalogue drawing for the selected current range (20–200A, 300–1500A, or 2000–6000A).
Selection & FAQs
Selection Guide
- Choose the 20A–200A semi-enclosed, 300A–1500A fully enclosed, or 2000A–6000A high-current construction and matching outline.
- Select the ratio from continuous load, metering range, conductor size and fault duty, then choose 1A or 5A secondary.
- For ≤1500A, specify 0.2/0.5 measurement and 10P10/10P15 protection; obtain a complete class definition for higher-current D entries.
- Calculate each burden at the stated 0.8 lagging basis and verify the exact 10VA–60VA rating and ALF.
- Approve the wall opening, flange, conductor path, Ith/Idyn, 11.5/42/75kV insulation, ≤1000m altitude and Class II pollution.
Frequently Asked Questions
Q1: Are LAJ-10 transformers suitable for 11kV switchgear applications?
Yes, subject to project confirmation. They are designed for 10kV, 11kV, and 12kV indoor medium-voltage systems. Contact our engineering team to verify specific voltage requirements.
Q2: What are the environmental limits for installing these epoxy resin CTs?
Standard installation requires indoor environments free from corrosive gases and severe vibration. Ambient temperature must remain between -5°C and +40°C with relative humidity below 85%.
Q3: How is the short-circuit withstand capacity determined for this wall-through CT?
Rated short-time thermal and dynamic currents depend on the selected primary current rating, which ranges from 20A to 6000A. Please refer to the technical parameter table or contact us for specific ratings.
Q4: Which accuracy class should I select for protective relay circuits?
The 10P15 accuracy class is recommended for protection applications. It maintains accuracy during fault conditions up to 15 times the rated primary current.
Q5: Can the primary current ratio be customized for non-standard projects?
Custom primary current ratios are available subject to factory confirmation. Please provide your exact project specifications and single-line diagrams so our team can evaluate feasibility.
Q6: Do you issue factory test reports prior to shipment?
Routine tests are conducted prior to shipment to ensure compliance with specified standards. Contact our sales department to request detailed test reports and specific certification documents.
Q7: Why use epoxy resin cast construction for these indoor CTs?
Epoxy resin cast construction provides high dielectric strength and mechanical stability for indoor medium-voltage switchgear. The LAJ-10 features semi- or fully-enclosed structures depending on the current range.