Product Overview
The LAZBJ-10 / LFZBJ-10 current transformer is an indoor, fully enclosed, wall-through epoxy resin cast current transformer designed for medium-voltage AC systems in the 10kV, 11kV and 12kV class. It is used for current measurement, energy metering, feeder monitoring, and relay protection in indoor switchgear and distribution equipment.
The product adopts a wall-through support structure with epoxy resin casting insulation. The laminated core and secondary winding are encapsulated inside the resin body, while the primary conductor passes through the central aperture. Compared with older indoor wall-through CT structures, the LAZBJ-10 / LFZBJ-10 design is compact and convenient for switchgear assembly. It can be used as a replacement option for older models such as LA-10, LAJ-10, and LFZ-10 when the electrical parameters and installation dimensions are confirmed.
Product Type
| Item | Specification |
|---|---|
| Product name | Indoor Wall-Through Epoxy Resin Cast Current Transformer |
| Model series | LAZBJ-10 / LFZBJ-10 |
| Product structure | Fully enclosed, wall-through, epoxy resin cast structure |
| Voltage class | 10kV, 11kV and 12kV class medium-voltage AC systems |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Installation location | Indoor switchgear and distribution equipment |
| Typical applications | Current measurement, energy metering, relay protection, feeder monitoring, switchgear instrumentation |
Product Display
Applications
- 10kV, 11kV and 12kV class indoor medium-voltage switchgear
- Feeder cabinets, incoming panels, outgoing panels, and metering cabinets
- Current measurement and electric energy metering circuits
- Relay protection circuits requiring 10P accuracy limit performance
- SCADA, power monitoring, and distribution automation systems
- Replacement or retrofit projects where LA-10, LAJ-10, or LFZ-10 type structures need to be reviewed and upgraded
Features
- Wall-through structure: The primary circuit passes through the center aperture, making the product suitable for through-panel and through-wall switchgear layouts.
- Epoxy resin casting: The fully enclosed resin body supports stable insulation performance, mechanical strength, and indoor environmental resistance.
- Compact installation: The structure is relatively small and convenient for medium-voltage cabinet assembly and retrofit projects.
- Metering and protection cores: Accuracy combinations can include metering classes such as 0.2S, 0.2, 0.5S and 0.5, together with 10P10 protection cores.
- Flexible secondary output: 5A or 1A secondary current can be selected according to meter, relay and wiring distance requirements.
- Short-circuit withstand design: Rated short-time thermal current and rated dynamic current are selected according to current ratio and switchgear fault level.
Principle
The LAZBJ-10 / LFZBJ-10 current transformer operates according to electromagnetic induction. The primary current flowing through the wall-through aperture generates magnetic flux in the core, and the secondary winding outputs a proportional current signal to connected meters, relays, or monitoring devices. The epoxy resin casting insulation separates the primary medium-voltage circuit from the secondary low-voltage circuit.
For metering circuits, the current transformer must maintain ratio and phase accuracy under rated burden. For protection circuits, the 10P core must provide a reliable secondary current signal under fault-current conditions so that the protection relay can operate correctly.
Model Designation
The model code can be interpreted as follows:
| Code | Meaning |
|---|---|
| L | Current transformer |
| A | Wall-through / constructed multi-turn through type |
| Z | Epoxy resin casting insulation |
| B | Protection class available |
| J | Epoxy resin casting insulation / reinforced cast-resin design |
| 10 | Rated voltage class: 10kV class |
| LFZBJ-10 | Corresponding wall-through indoor cast-resin CT designation shown in parentheses in the catalogue |
Technical Data
| Item | Specification |
|---|---|
| Rated voltage | 10kV, 11kV and 12kV class indoor systems |
| Rated insulation level | 12/42/75kV |
| Rated frequency | 50Hz / 60Hz |
| Rated primary current | 20A, 30A, 40A, 50A, 75A, 100A, 150A, 200A, 300A, 400A |
| Rated secondary current | 5A or 1A |
| Accuracy class combination | 0.2S/10P10, 0.2/10P10, 0.5S/10P10, 0.5/10P10, 0.2S/0.5/10P10, 0.2/0.5/10P10 |
| Rated output | 10VA for measuring cores and 15VA for 0.5 / 10P10 reference cores, subject to configuration |
| Partial discharge requirement | According to GB1208-1997 current transformer standard where specified |
| Pollution level | Class II reference |
| Installation type | Indoor wall-through installation |
| Applicable standards | IEC 185 / IEC 60044-1 reference, GB1208-1997; IEC 61869 may be confirmed according to project requirement |
Selection Table
The following table summarizes common current ratios, accuracy-class combinations and short-circuit withstand values for LFZBJ-10 selection. Long table headers and shared parameters are wrapped into multiple lines to keep the table readable on responsive website layouts.
| Rated
Primary Current (A) |
Accuracy
Class Combination |
Rated
Output |
Short-Time
Thermal Current (kA) |
Rated
Dynamic Current (kA) |
|---|---|---|---|---|
| 20 | 0.2S / 10P10 0.2 / 10P10 0.5S / 10P10 0.5 / 10P10 0.2S / 0.5 / 10P10 0.2 / 0.5 / 10P10 |
0.2S: 10 0.2: 10 0.5S: 10 0.5: 15 10P10: 15 |
2 | 5 |
| 30 | 3 | 7.5 | ||
| 40 | 4 | 10 | ||
| 50 | 6 | 15 | ||
| 75 | 8 | 15 | ||
| 100 | 12 | 20 | ||
| 150 | 15 | 30 | ||
| 200 | 20 | 37.5 | ||
| 300 | 32 | 50 | ||
| 400 | 36 | 80 |
Note: This table is for preliminary selection. Final current ratio, secondary current, rated output, protection accuracy limit factor, partial discharge requirement, and short-circuit withstand data shall be confirmed according to the nameplate, approved drawing, and factory test report.
Protection Curve
The protection curve shows the relationship between protection class accuracy limit factor and secondary output burden. When selecting a 10P protection core, the relay burden, wiring resistance and required accuracy limit factor shall be checked together to avoid incorrect protection performance under fault-current conditions.
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 10kV, 11kV and 12kV class networks
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: normally -5°C to +40°C unless otherwise specified
- The installation environment should be free from severe vibration, corrosive gas, explosive medium, conductive dust, heavy pollution and abnormal condensation.
- For high altitude, coastal, humid, high-pollution or retrofit conditions, technical confirmation is recommended before ordering.
Standards and Compliance
The LAZBJ-10 / LFZBJ-10 current transformer is designed for indoor medium-voltage wall-through current transformer applications. Catalogue data refers to IEC 185 and GB1208-1997, and project requirements may also specify IEC 60044-1 or IEC 61869 series standards according to the final technical agreement. Routine test requirements usually include ratio verification, polarity test, accuracy test, dielectric withstand test and insulation inspection.
Installation and Dimensions
The LAZBJ-10 / LFZBJ-10 current transformer is designed for wall-through installation. The selected structure and dimensions shall be confirmed according to the cabinet type and busbar layout. The catalogue shows multiple outline versions, including A-type, B-type and LFC-10 replacement-related mounting references.
Hole Dimension
| Item | Dimension / Note |
|---|---|
| Mounting reference | Wall-through hole dimension according to approved drawing |
| Main aperture | Central through-hole for primary conductor or busbar arrangement |
| Mounting holes | Confirmed by A-type, B-type or replacement drawing |
| Drawing confirmation | Required before cabinet production or retrofit replacement |
Dimensions
| Structure | Dimension
Reference |
Application Note |
|---|---|---|
| A-type | Overall dimension according to A-type drawing | Used where A-type mounting and terminal layout match the switchgear design. |
| B-type | Overall dimension according to B-type drawing | Used where B-type mounting arrangement and cable/busbar clearance are required. |
| LFC-10 replacement reference | Replacement-related outline shall be checked before retrofit | Used for retrofit projects where older structures are replaced after dimensional confirmation. |
Safety Notes
- Confirm the model, voltage class, current ratio, secondary current, accuracy combination and rated output before installation.
- Check wall-through opening, busbar clearance, mounting holes, terminal direction and maintenance access before switchgear production.
- Connect the primary and secondary terminals according to the terminal markings 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 performed by qualified medium-voltage electrical personnel.
Ordering Info
Please provide the following information when ordering or requesting a quotation:
- Product model: LAZBJ-10 or LFZBJ-10
- Rated primary current and rated secondary current
- Accuracy class combination and rated output
- Rated insulation level and applicable standard
- Required short-time thermal current and dynamic current
- Switchgear type, wall-through opening, mounting layout and terminal direction
- A-type, B-type or replacement outline requirement if specified
- Quantity, certificates, routine test reports, labeling and packaging requirements
Selection Guide
- Confirm voltage class: Select LAZBJ-10 / LAZBJ-10 / LFZBJ-10 for indoor medium-voltage networks commonly used in 10kV, 11kV and 12kV class systems.
- Confirm installation structure: Use this model when a wall-through epoxy resin cast CT is required for switchgear or retrofit installation.
- Select current ratio: Choose the primary current according to feeder load, metering range and protection settings.
- Define core functions: Specify measuring classes and protection class combinations, such as 0.2S/10P10 or 0.2S/0.5/10P10.
- Check rated burden: Confirm the connected meter, relay and cable burden against the rated output of each secondary core.
- Verify fault-current withstand: Rated thermal current and rated dynamic current shall meet or exceed the switchgear fault level.
- Confirm dimensions: Check the A-type, B-type or retrofit drawing before cabinet design or replacement.