Product Overview
The LAJ-10 / LFZJ-10 current transformer is an indoor, wall-through, epoxy resin cast current transformer for medium-voltage AC systems. It is used for current measurement, electric energy metering and relay protection in power systems with rated frequency of 50Hz and rated voltage class of 10kV. For international projects, it can be positioned for 10kV, 11kV and 12kV class indoor switchgear applications, subject to insulation level, system design and project specification confirmation.
The catalogue identifies this product as LAJ-10 / LFZJ-10. The 20A to 200A range is described as a semi-enclosed resin casting structure, while the 300A and above range adopts a fully enclosed resin casting structure. This makes the series suitable for both smaller metering circuits and higher-current feeder circuits where wall-through mounting and reliable insulation are required.
Product Type
| Item | Specification |
|---|---|
| Product name | Indoor Wall-Through Epoxy Resin Cast Current Transformer |
| Model series | LAJ-10 / LFZJ-10 |
| Product structure | Wall-through type, epoxy resin casting insulation |
| Voltage class | 10kV, 11kV and 12kV class indoor medium-voltage systems |
| Rated insulation level | 11.5/42/75kV |
| Rated frequency | 50Hz |
| Rated secondary current | 5A or 1A |
| Rated primary current | 20A to 6000A according to structure and specification |
| Typical applications | Current measurement, energy metering, relay protection, switchgear instrumentation |
Product Display
Applications
- 10kV, 11kV and 12kV class indoor medium-voltage distribution systems
- Indoor switchgear, feeder panels, metering cabinets and distribution cabinets
- Current measurement and electric energy metering circuits
- Relay protection circuits with 10P accuracy limit requirements
- Wall-through mounting where the primary conductor passes through the transformer body
- Retrofit or replacement projects requiring confirmation of old and new mounting dimensions
Features
- Wall-through construction: The primary conductor passes through the CT body, making it suitable for through-panel or switchgear partition installation.
- Two structure ranges: 20A to 200A is supplied as a semi-enclosed structure, while 300A and above adopts a fully enclosed resin casting structure.
- Epoxy resin insulation: The core and secondary winding are cast with resin to improve insulation performance and mechanical stability for indoor use.
- Wide current range: The product covers low primary-current metering applications and high-current feeder applications up to 6000A.
- Metering and protection cores: Accuracy combinations include metering classes such as 0.2 and 0.5, and protection classes such as 10P15.
- Dimension options: Different hole dimensions and overall dimensions are available for 20–200A and 300–1500A ranges.
Principle
The LAJ-10 / LFZJ-10 current transformer operates according to electromagnetic induction. When primary current flows through the wall-through conductor path, magnetic flux is generated in the core. The secondary winding outputs a proportional 5A or 1A current signal to meters, relays or monitoring equipment. The epoxy resin insulation separates the medium-voltage primary circuit from the low-voltage secondary circuit.
For metering applications, the CT must maintain the specified ratio and phase accuracy under the selected rated burden. For relay protection applications, the protection core must maintain the required accuracy limit factor so that the relay receives a reliable fault-current signal.
Model Designation
The model code can be interpreted as follows:
| Code | Meaning |
|---|---|
| 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 |
Technical Data
| Item | Specification |
|---|---|
| Rated voltage class | 10kV class; applicable to 10kV, 11kV and 12kV class indoor systems by project confirmation |
| Rated insulation level | 11.5/42/75kV |
| Rated frequency | 50Hz |
| Rated primary current | 20A, 30A, 40A, 50A, 100A, 150A, 200A, 300A, 600A, 1000A, 1200A, 1500A, 2000A, 3000A, 4000A, 5000A, 6000A |
| Rated secondary current | 5A or 1A |
| Accuracy class and output | According to ratio and core configuration; metering and 10P protection classes available |
| Power factor of burden | 0.8 lagging |
| Partial discharge | According to GB1208-1997 current transformer requirements where specified |
| Pollution level | Class II reference |
| Installation | Indoor wall-through mounting |
Selection Table
The following selection data is organized into current ranges. Shared accuracy combinations and output values are grouped to reduce repeated long cells and improve responsive page layout.
| Rated
Primary Current (A) |
Accuracy
Class Combination |
Rated
Output (VA) |
1s Thermal
Current |
Dynamic
Current |
|---|---|---|---|---|
| 20, 30, 40, 50, 100, 150, 200 |
0.2 / 10P10 0.2 / 10P15 0.5 / 10P10 0.5 / 10P15 |
0.2: 10 0.5: 10 or 25 10P: 15 or 25 |
75 x I1n | 188 x I1n |
| 300, 600, 1000, 1200, 1500 |
100 x I1n | 251 x I1n | ||
| 2000, 3000, 4000, 5000, 6000 |
0.5 / D D / D |
25 to 60 | 50 x I1n | 90 x I1n |
Note: The table is for preliminary selection. Final current ratio, rated output, accuracy class, thermal current, dynamic current and protection accuracy limit factor shall be confirmed according to the nameplate, approved drawing and factory test report.
Structure Range
| Current Range | Structure | Application Note |
|---|---|---|
| 20A to 200A | Semi-enclosed resin casting structure | Suitable for smaller current ratios and compact indoor wall-through mounting. |
| 300A and above | Fully enclosed resin casting structure | Suitable for higher current feeder circuits and stronger insulation/mechanical requirements. |
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
- The installation environment should be free from severe vibration, corrosive gas, explosive medium, conductive dust, heavy pollution and abnormal condensation.
Standards and Compliance
The LAJ-10 / LFZJ-10 current transformer is designed for indoor medium-voltage current transformer applications. Catalogue data refers to GB1208-1997 and related IEC current transformer requirements. Project specifications may also request updated IEC 61869 series requirements, routine test certificates, ratio and polarity test, dielectric withstand test and accuracy verification.
Installation and Dimensions
The LAJ-10 / LFZJ-10 series is designed for indoor wall-through mounting. Different hole dimensions and overall dimensions apply to different current ranges, especially the 20–200A range and the 300–1500A range. Final mounting holes, conductor path, terminal direction and cabinet clearances should be confirmed with the approved drawing before switchgear production.
Hole Dimension
| Current Range | Hole Dimension Reference |
Drawing Note |
|---|---|---|
| 20–200A | Reference hole dimension according to catalogue drawing | Used for smaller-current semi-enclosed structure. |
| 300–1500A | Reference hole dimension according to catalogue drawing | Used for higher-current fully enclosed structure. |
Dimensions
| Current Range | Overall Dimension Reference |
Approx. Weight |
|---|---|---|
| 20–200A | Overall dimensions according to 20–200A drawing | About 12.5kg to 17kg depending on ratio |
| 300–1500A | Overall dimensions according to 300–1500A drawing | About 18kg to 20kg depending on ratio |
| 2000–6000A | High-current outline according to selected model and drawing | Subject to final specification |
Safety Notes
- Confirm the model, current ratio, secondary current, accuracy class, rated output and insulation level before installation.
- Check wall-through opening, mounting hole distance, primary conductor clearance and secondary terminal access before cabinet production.
- Connect primary and secondary terminals according to the terminal marking and project wiring diagram.
- The secondary circuit of a current transformer must not be open-circuited when the primary circuit is energized.
- Before disconnecting meters or relays, short-circuit the CT secondary circuit using an approved shorting block.
- One point of the secondary circuit should be grounded according to project and local electrical safety requirements.
- Installation and maintenance shall be carried out by qualified medium-voltage electrical personnel.
Ordering Info
Please provide the following information when ordering or requesting a quotation:
- Product model: LAJ-10 / LFZJ-10
- Rated primary current and rated secondary current
- Accuracy class combination and rated output
- Required thermal current and dynamic current
- Rated insulation level and applicable standard
- Installation drawing, hole dimension, terminal direction and cabinet layout
- Service conditions such as altitude, humidity, pollution level or special environment
- Quantity, routine test report, certificate, labeling and packaging requirements
Selection Guide
- Confirm voltage class: Select LAJ-10 / LFZJ-10 for indoor medium-voltage networks commonly used in 10kV, 11kV and 12kV class systems.
- Confirm current range: Use the 20–200A structure for smaller current circuits and the 300A-and-above structure for higher-current feeder applications.
- Select ratio: Choose the rated primary current according to continuous load current, metering range and protection setting.
- Define core function: Specify metering cores and protection cores separately, including accuracy class and rated output.
- Check burden: Confirm that meter, relay and secondary cable burden do not exceed the rated output.
- Verify withstand ratings: Thermal current and dynamic current should match the switchgear short-circuit level.
- Confirm dimensions: Check hole dimension, mounting holes, conductor path and terminal direction before production.