Product Overview
The LMZ-10 / LMZJ1-10 current transformer is an indoor wall-through busbar-type epoxy resin cast current transformer designed for medium-voltage AC power systems. It is suitable for 10kV, 11kV and 12kV class switchgear and distribution systems with rated frequency of 50Hz. The product is mainly used for current measurement, electric energy metering and relay protection in indoor switchgear, distribution cabinets and busbar systems.
This series adopts a busbar through-type structure. The primary conductor or busbar passes through the central opening of the current transformer, while the secondary windings are wound on the iron core and cast together with epoxy resin insulation. The mounting plate, rating plate, earthing bolt and installation holes are integrated for cabinet installation. LMZ-10 is mainly used for common medium-voltage current ranges, while LMZJ1-10 is used for higher current ratings and extended output requirements.
Product Type
| Item | Specification |
|---|---|
| Product name | Indoor Wall-Through Busbar-Type Epoxy Resin Cast Current Transformer |
| Model series | LMZ-10 / LMZJ1-10 |
| Product structure | Wall-through busbar type, indoor epoxy resin cast structure |
| Voltage class | 10kV, 11kV and 12kV class medium-voltage systems |
| Rated frequency | 50Hz |
| Rated secondary current | 5A |
| Installation location | Indoor switchgear and distribution cabinets |
| Typical applications | Current measurement, energy metering, relay protection, busbar current monitoring |
Product Display
Applications
- 10kV, 11kV and 12kV class indoor medium-voltage distribution systems
- Medium-voltage switchgear and complete electrical cabinets
- Busbar current measurement and energy metering circuits
- Relay protection and overcurrent protection circuits
- Power monitoring systems for industrial and utility distribution rooms
- Retrofit or replacement projects requiring compact through-busbar CT installation
Features
- Wall-through busbar-type structure: The primary busbar passes through the central opening, making the product suitable for busbar current measurement and through-panel cabinet installation.
- Epoxy resin cast insulation: The iron core and secondary windings are cast in epoxy resin for stable indoor insulation performance, mechanical protection and compact installation.
- LMZ and LMZJ1 options: LMZ-10 covers common medium-voltage measurement ranges, while LMZJ1-10 supports higher primary current ratings and extended output configurations.
- Measurement and protection use: Accuracy combinations such as 0.5/3, 0.5/10P and 0.5/0.5 can be selected according to metering and relay protection requirements.
- 5A secondary output: Standard secondary current is suitable for common meters, relays and monitoring devices.
- Cabinet-friendly installation: The product includes a mounting plate, earthing bolt, rating plate and installation holes for secure switchgear assembly.
Principle
The LMZ-10 / LMZJ1-10 current transformer operates according to electromagnetic induction. The primary busbar or conductor passes through the central opening and acts as the primary circuit. When current flows through the primary conductor, magnetic flux is generated in the iron core. The secondary winding outputs a proportional 5A current signal to the connected meter, relay or protection device.
For metering circuits, the CT provides a proportional current signal within the required accuracy class. For relay protection circuits, the protection core must provide a usable secondary signal under fault-current conditions and should be selected according to the relay setting, secondary burden and system fault level.
Model Designation
The model code can be interpreted as follows:
| Code | Meaning |
|---|---|
| L | Current transformer |
| M | Busbar-type / bus-type structure |
| Z | Epoxy resin casting insulation |
| J1 | Extended output / reinforced design series |
| 10 | Rated voltage class: 10kV |
Technical Data
| Item | Specification |
|---|---|
| Rated voltage | 10kV class, suitable for 10kV, 11kV and 12kV class indoor systems |
| Rated frequency | 50Hz |
| Rated secondary current | 5A |
| Rated primary current | 300A to 5000A depending on selected model and ratio |
| Accuracy class combination | 0.5/3, 0.5/10P, 0.5/0.5 or project-specific combination |
| Rated secondary burden | 10VA, 15VA, 40VA, 60VA, 80VA or 100VA according to model and ratio |
| 10P accuracy limit factor | 10 or 15 according to protection configuration |
| Insulation type | Indoor epoxy resin casting insulation |
| Installation | Wall-through busbar mounting with fixed mounting plate |
| Applicable standard | IEC standard and GB1208-87 current transformer requirements |
Selection Table
The following table summarizes common LMZ-10 / LMZJ1-10 selection data. Long headers are wrapped into multiple lines for responsive website display. Shared parameters are grouped to reduce repeated values and improve readability.
| Type | Rated
Voltage |
Primary
Current (A) |
Rated
Secondary Current (A) |
Accuracy
Class |
Secondary
Burden Class 0.5 (VA) |
Secondary
Burden Class 3 (VA) |
Secondary
Burden |
Accuracy
Limit Factor: 10P |
|---|---|---|---|---|---|---|---|---|
| LMZ-10 | 10KV
11KV 12KV |
300–1000 | 5 | 0.5/3 | 10 | 15 | 10 | |
| 1500 | 0.5/10P | 40 | 80 | 15 | ||||
| LMZJ1-10 | 2000, 3000 4000, 5000 |
60 | 100 | |||||
| 2000–3000 | 60 | 100 | ||||||
| 4000–5000 | 60 | 100 |
Note: Final current ratio, burden, protection class and accuracy limit factor shall be confirmed according to project requirements, nameplate data and factory test report.
Service Conditions
- Installation location: indoor medium-voltage switchgear
- Altitude: not over 1000m unless otherwise specified
- Ambient temperature: -5°C to +40°C
- Relative humidity: less than 85% at 20°C reference condition
- The product should be installed in a site free from severe vibration, corrosive gas, explosive medium, conductive dust, heavy pollution and abnormal condensation.
- The product has passed vibration test conditions equivalent to 0.4g three-sine waves under reference requirements.
Standards and Compliance
The LMZ-10 / LMZJ1-10 current transformer conforms to IEC standard and GB1208-87 current transformer requirements. Routine inspection items may include ratio verification, polarity check, accuracy test, insulation resistance test, power-frequency withstand test, appearance inspection and terminal marking verification. Final acceptance shall be based on the nameplate data, test certificate and technical agreement.
Installation and Dimensions
The LMZ-10 / LMZJ1-10 series is designed for indoor wall-through busbar installation. The busbar or conductor passes through the central opening, while the mounting plate provides fixed installation holes. Final dimensions, hole size, busbar clearance and mounting hole position shall be confirmed with the approved drawing before switchgear production.
Dimensions
| Type | Rated Primary Current (A) |
Accuracy Class |
L (mm) |
C (mm) |
D (mm) |
d (mm) |
A1 (mm) |
A2 (mm) |
B1 (mm) |
B2 (mm) |
Weight (kg) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| LMZ-10 | 300 | 0.5/3 0.5/10P |
220 | 125 | 136 | 33 | 140 | 170 | 206 | 236 | 7.5 |
| 400 | 136 | 43 | |||||||||
| 500–600 750–800 1000 |
0.5/10P | 225 | 132 | 173 240 |
53 63 85 |
165 | 195 | 230 | 260 | 8.2 | |
| LMZJ1-10 | 1500–2000 3000 4000 |
0.5/10P | 276 | 173 177 168 |
240 256 305 |
128 143 170 |
256 | 296 | 346 | 346 | 25.8 |
| 5000 | 276 | 168 | 305 | 170 | 300 | 340 | 420 | 420 | 26.5 |
Unit: mm. Final dimensions are subject to the approved drawing and selected specification.
Safety Notes
- Confirm the model, current ratio, accuracy class, burden and aperture size before installation.
- Check that the busbar or conductor size matches the hole dimension and insulation clearance requirements.
- Install the CT according to the approved switchgear drawing and maintain adequate phase-to-phase and phase-to-ground clearances.
- Connect secondary terminals according to polarity marks and the project wiring diagram.
- The secondary circuit of a current transformer must not be open-circuited when the primary circuit is energized.
- During meter or relay replacement, short-circuit the CT secondary circuit before disconnecting any secondary wiring.
- 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: LMZ-10 or LMZJ1-10
- Rated primary current and rated secondary current
- Accuracy class combination, such as 0.5/3 or 0.5/10P
- Rated secondary burden for each core
- Protection accuracy limit factor if 10P core is required
- Busbar size, hole dimension and switchgear layout
- Installation drawing, terminal direction and mounting plate requirement
- Quantity, certificates, routine test report, labeling and packaging requirements
Selection Guide
- Confirm system voltage: Select LMZ-10 / LMZJ1-10 for 10kV, 11kV and 12kV class indoor medium-voltage systems.
- Select model type: Use LMZ-10 for common 300A–1500A applications and LMZJ1-10 for higher current ranges up to 5000A.
- Confirm current ratio: Select the rated primary current according to feeder load, continuous current and protection range.
- Specify accuracy class: Use 0.5/3 for measurement-focused circuits and 0.5/10P where protection output is required.
- Check burden: Ensure that connected meters, relays and secondary wiring burden do not exceed the rated secondary output.
- Verify dimensions: Check hole size, busbar clearance, overall dimension and mounting hole position before switchgear production.
- Confirm documents: Specify standard, routine test report, nameplate language, drawing approval and packaging requirements if needed.