Product Overview
LA-10 (LFZ1-10, LFZB1-10) is an indoor semi-enclosed cast-resin wall-through current transformer for medium-voltage distribution systems. It is designed for current measurement, electric energy metering, and relay protection in AC circuits with rated frequency 50Hz and rated voltage up to 10kV. For international documentation, it can be described for 10kV, 11kV and 12kV class indoor switchgear applications, subject to final project confirmation.
This series uses a wall-through structure in which the primary conductor passes through the transformer body and the secondary winding outputs a standardized signal for meters, relays, and monitoring devices. According to the catalogue description, 200A and below adopts a semi-enclosed resin-cast structure, while 300A and above adopts a fully enclosed resin-cast structure. This structural division allows the product to cover compact metering circuits as well as larger feeder protection applications.
From an engineering perspective, the LA-10 series combines compact installation, epoxy resin insulation, and dependable electromagnetic performance. It is particularly suitable for indoor switchgear where the transformer must maintain stable ratio accuracy, adequate insulation strength, and secure mounting within limited panel space.
Product Type
| Item | Specification |
|---|---|
| Product name | Semi-Enclosed Cast-Resin Wall-Through Current Transformer |
| Model | LA-10 (LFZ1-10, LFZB1-10) |
| Structure | Wall-through type; semi-enclosed for 200A and below, fully enclosed for 300A and above |
| Insulation | Epoxy resin cast insulation |
| Voltage class | 10kV, 11kV and 12kV class indoor systems |
| Rated insulation level | 11.5/42/75kV |
| Rated frequency | 50Hz |
| Rated secondary current | 5A |
| Typical use | Current measurement, energy metering, relay protection |
| Installation | Indoor wall-through mounting |
Product Display
The LA-10 series includes multiple structural sizes for different current ranges. Lower-current versions are compact and suitable for cabinet metering circuits, while higher-current versions provide larger conductor accommodation and stronger body structure for feeder protection applications.
Applications
- 10kV, 11kV and 12kV class indoor medium-voltage distribution systems
- Indoor switchgear, ring main units, metering panels, and feeder cabinets
- Current measurement and electric energy metering circuits
- Relay protection circuits requiring stable secondary current output
- Retrofit and replacement of wall-through type CTs in existing switchgear
Features
- Semi-enclosed cast-resin design: The 200A-and-below range uses a semi-enclosed structure, balancing compact size and insulation performance.
- Wall-through construction: The product is designed for switchgear partitions or plates where the primary conductor passes through the CT body.
- Wide current range: The series covers both smaller metering circuits and higher-current feeder applications.
- Reliable insulation: Epoxy resin casting improves insulation integrity and mechanical stability for indoor service.
- Metering and protection suitability: The CT can be specified for measurement duty or protection duty with the appropriate class and burden.
- Clear terminal identification: Marked primary and secondary terminals help maintain polarity and wiring correctness.
Principle
The LA-10 current transformer operates on electromagnetic induction. When current flows through the primary conductor, magnetic flux is generated in the core. The secondary winding induces a proportional 5A current signal for connected meters, relays, or monitoring equipment. This allows the medium-voltage primary circuit to be safely isolated from the low-voltage secondary circuit while preserving the defined current ratio.
For metering duty, the CT must keep the specified ratio and phase accuracy under rated burden. For protection duty, the CT must maintain sufficient output under fault conditions so that relay devices receive a dependable signal. This is why correct selection of accuracy class, rated output, thermal current, and dynamic current is essential.
Model Designation
The model code LA-10 (LFZ1-10, LFZB1-10) can be interpreted as follows:
| Code | Meaning |
|---|---|
| L | Current transformer |
| A | Wall-through type |
| 10 | Rated voltage class: 10kV |
| LFZ1-10 / LFZB1-10 | Associated manufacturer designations for cast-resin wall-through indoor CT variants |
Technical Data
| Item | Specification |
|---|---|
| Rated voltage class | 10kV class; suitable for 10kV, 11kV and 12kV class indoor applications by project confirmation |
| Rated insulation level | 11.5/42/75kV |
| Rated frequency | 50Hz |
| Rated secondary current | 5A |
| Rated primary current | 5A to 1500A depending on model size and structure |
| Accuracy classes | 0.2, 0.5, 1, 10P10 depending on specification |
| Rated output | Project-dependent; typical metering and protection burdens available |
| Thermal current | Up to 90 × I1n / 75 × I1n / 60 × I1n / 50 × I1n depending on current range |
| Dynamic current | Up to 160 × I1n / 135 × I1n / 110 × I1n / 90 × I1n depending on current range |
| Operating overcurrent | The current transformer can keep working at rated current of 1.1 times |
| Power-frequency withstand | Secondary-to-earth withstand voltage 2kV for 1 minute |
Selection Table
The table below is optimized for web display. Long headers are wrapped into multiple lines for better readability in responsive layouts.
| Rated
Primary Current (A) |
Is Short Time
Thermal Current (Ith) |
Dynamic
Current (Idyn) |
Accuracy Class
and Rated Output |
Rated
Secondary Current(A) |
Frequency
(Hz) |
Insulation
Level (kV) |
|---|---|---|---|---|---|---|
| 5, 10, 15, 20, 30, 40, 50, 75, 100, 150, 200 |
90 × I1n | 160 × I1n | 0.2 / 0.5 / 1 / 10P10 Rated output according to metering or protection requirement |
5 | 50 | 11.5/42/75 |
| 300 | 75 × I1n | 135 × I1n | 0.2 / 0.5 / 1 / 10P10 Typical metering and protection burdens available |
|||
| 500 | 60 × I1n | 110 × I1n | 0.2 / 0.5 / 1 / 10P10 Select output according to connected burden |
|||
| 600, 800, 1000, 1500 |
50 × I1n | 90 × I1n | 0.2 / 0.5 / 1 / 10P10 Final output and class per approved specification |
Structure Range
| Current Range | Structure Type | Engineering Description |
|---|---|---|
| 5A to 200A | Semi-enclosed cast-resin structure | Suitable for compact indoor wall-through applications, especially metering and lower-current protection circuits. |
| 300A to 1500A | Fully enclosed cast-resin structure | Suitable for larger primary conductors and higher-current feeder circuits requiring stronger body integrity and insulation support. |
Windings & Terminal Marking
The catalogue indicates standard polarity and terminal marking practice. The primary terminals are marked P1 and P2. The secondary terminals are marked according to winding function, such as metering and protection windings. One secondary winding may be configured for measurement and another for protection, depending on the ordered specification.
| Marking | Function | Wiring Note |
|---|---|---|
| P1 / P2 | Primary terminals | Correct polarity must be maintained for metering accuracy and relay direction. |
| 1S1 / 1S2 | Secondary winding 1 | Commonly used for metering duty, depending on ordered class. |
| 2S1 / 2S2 | Secondary winding 2 | Commonly used for protection duty, depending on ordered configuration. |
| Ground point | Protective grounding | One point of the secondary circuit should be grounded according to the system wiring standard. |
Service Conditions
- Altitude: not over 1000m above sea level
- Ambient temperature: -30°C to +40°C
- Relative humidity: less than 85% at 20°C
- Indoor installation only
- No severe vibration, corrosive gas, explosive medium, or conductive contamination
Standards and Compliance
The catalogue information indicates a 10kV-class indoor current transformer for measurement and protection applications. For project execution, compliance should be confirmed according to the required technical standard set, such as applicable GB current transformer standards or internationally specified IEC instrument transformer standards. For export projects, the technical description can be aligned with 10kV, 11kV and 12kV class switchgear requirements when insulation coordination and project conditions are verified.
Installation and Dimensions
The LA-10 series is intended for indoor wall-through installation. Different hole dimensions and overall dimensions apply to different current ranges. The catalogue distinguishes the installation outline for the 5–200A range and the 300–1500A range. Before switchgear fabrication, the opening size, hole center distance, conductor path, terminal direction, and installation clearance should be confirmed against the approved drawing.
Hole Dimension
| Model Range | Hole Dimension Type | Application Note |
|---|---|---|
| LA-10 (5–200/5) | Dimension A | For semi-enclosed lower-current structure used in compact indoor wall-through installation. |
| LA-10 (300–1500/5) | Dimension B | For higher-current structure with larger conductor passage and different mounting arrangement. |
Dimensions
| Model Range | Overall Dimension Type | Reference Note |
|---|---|---|
| LA-10 (5–200/5) | Overall Dimension A | Used for the compact semi-enclosed structure. |
| LA-10 (300–1500/5) | Overall Dimension B | Used for larger-current fully enclosed structure. |
| Approx. product weight | About 13.5kg | Reference value shown in the catalogue image; actual value may vary by configuration. |
Safety Notes
- Confirm the model, current ratio, accuracy class, rated output, and installation dimension before switchgear production.
- Check the conductor opening, hole spacing, mounting direction, and insulation clearance before installation.
- Wire the primary and secondary terminals strictly according to terminal markings and the approved schematic.
- The secondary circuit of a current transformer must never be open-circuited while the primary circuit is energized.
- Before removing meters or relays, short-circuit the CT secondary side using an approved shorting device.
- One point of the CT secondary circuit should be grounded according to local electrical safety practice.
- Installation and commissioning shall be carried out by qualified medium-voltage electrical personnel.
Ordering Info
- Product model: LA-10 (LFZ1-10, LFZB1-10)
- Rated primary current / rated secondary current
- Accuracy class and rated output for each secondary winding
- Application type: metering, protection, or combined duty
- Required Ith and Idyn values according to system short-circuit level
- Installation drawing, hole dimension, and conductor arrangement
- Service environment, altitude, and any special technical requirements
Selection Guide
- Confirm system voltage: Use this model for indoor medium-voltage systems in the 10kV, 11kV and 12kV class range after confirming insulation coordination.
- Choose the current range: Select the semi-enclosed 5–200A range for smaller circuits and the larger structure for 300–1500A circuits.
- Define the function: Confirm whether the CT is for metering, relay protection, or both.
- Select the ratio: Match the rated primary current to the actual feeder or circuit current.
- Specify accuracy and burden: Metering and protection duties require different accuracy classes and rated outputs.
- Verify withstand capability: Ith and Idyn must be compatible with the switchgear fault level.
- Confirm dimensions: Check hole dimensions and overall dimensions before panel manufacturing.