Overview
The LMZ-6 / LMZ-10 / LM-6 / LM-10 is an indoor, single-phase, through-hole current transformer with epoxy resin cast insulation. It is designed for use in 6kV, 10kV, 11kV, and 12kV medium-voltage systems operating at 50Hz or 60Hz, featuring a compact circular body that allows the primary conductor to pass directly through its central window.
This series supports measurement, energy metering, relay protection, and feeder monitoring applications in air-insulated switchgear, ring main units, and metering cabinets. It complies with IEC 61869-1 and IEC 61869-2 standards, and can be configured with accuracy classes such as 0.5, 1, or 3 for metering and 10P for protection, based on project requirements.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 6kV, 10kV, 11kV, 12kV |
| Rated insulation level | 7.2/32/60kV (6kV class); 12/42/75kV (10kV–12kV class) |
| Rated frequency | 50Hz / 60Hz |
| Rated primary current | 50A – 630A (custom ratios available) |
| Rated secondary current | 1A or 5A |
| Metering accuracy class | 0.5, 1, 3 (as specified) |
| Protection accuracy class | 10P |
| Insulation material | Epoxy resin cast |
| Application type | Measurement, metering, protection, monitoring |
| Installation environment | Indoor, air-insulated MV equipment |
| Applicable standard | IEC 61869-1, IEC 61869-2 |
| Phase configuration | Single-phase |
Model Designation
- L: Current transformer
- M: Busbar / through-hole type structure
- Z: Cast-resin insulated structure
- 6: 6kV class version (7.2/32/60kV insulation level)
- 10: 10kV class version (for 10kV, 11kV, 12kV systems; 12/42/75kV insulation level)
Construction
The LMZ-6 / LMZ-10 / LM-6 / LM-10 current transformers feature a through-hole design where the primary conductor passes through the central aperture without electrical connection to the device. The magnetic core and secondary winding are fully encapsulated in epoxy resin casting, providing high dielectric strength, excellent mechanical robustness, and resistance to moisture and environmental contamination. The compact, circular housing is optimized for installation in confined spaces within indoor medium-voltage switchgear, including ring main units and metering panels. Terminal blocks for secondary connections are integrated into the cast body, ensuring reliable and secure wiring. This construction ensures long-term operational stability under normal and fault conditions in 50Hz or 60Hz power systems.
Technical Parameters
Service Conditions
- Installation location: indoor medium-voltage switchgear
- System voltage: 6kV, 10kV, 11kV, or 12kV class
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: -5°C to +40°C reference range
- Switchgear type: suitable for air-insulated switchgear with controlled humidity and pollution level
- Environmental restrictions: the installation site should be free from severe vibration, corrosive gas, explosive medium, heavy conductive dust, and abnormal condensation.
- Special conditions: for high altitude, high humidity, coastal, high-pollution, or compact switchgear conditions, technical confirmation is recommended before ordering.
Technical Parameters
The LMZ-6/10 and LM-6/10 are indoor through-hole cast-resin current transformers designed for 6kV and 10kV class systems, featuring epoxy resin insulation, a rated primary current range of 50A to 630A, and operation within an ambient temperature range of -5°C to +40°C. They comply with standard service conditions for indoor medium-voltage switchgear and support both metering and protection applications with secondary currents of 1A or 5A.
| Rated Current Ratio (A) |
Accuracy Classes / Rated Output (VA) |
|||
|---|---|---|---|---|
| 0.5 | 5P5 10P5 |
5P10 10P10 |
5P15 10P15 |
|
| 50/5 | 1.5 | 1.5 | 0.5 | 0.1 |
| 75/5 | 2.5 | 2.5 | 1 | 0.3 |
| 100/5 | 3.75 | 3.75 | 1.5 | 0.5 |
| 150/5 | 5 | 5 | 2.5 | 1 |
| 200/5 | 7.5 | 7.5 | 3.75 | 1.5 |
| 300/5 | 10 | 10 | 5 | 2.5 |
| 400/5 | 15 | 15 | 7.5 | 5 |
Installation & Wiring
Installation Diagram
The LMZ-6/10 and LM-6/10 current transformers are designed for indoor through-hole installation in switchgear. The primary conductor, busbar, or insulated cable passes through the central window of the cast-resin body. Mounting is performed according to the approved outline drawing, ensuring proper alignment with switchgear structure, creepage distances, and electrical clearances.
Wiring Diagram
Secondary terminals are arranged in a terminal block according to the selected winding configuration (single, dual, tapped, or multi-core output). Connect secondary wiring strictly in accordance with terminal markings and the project-specific wiring diagram. Terminal identification corresponds to the specified current ratio, accuracy class, and protection class (e.g., 10P).
Selection & FAQs
Selection Guide
- Select the voltage version from the system insulation level. Use LMZ/LM-6 for 7.2/32/60kV coordination or LMZ/LM-10 for 12/42/75kV coordination in 10kV–12kV systems; do not select only by nominal network voltage.
- Choose a 50A–630A ratio and 1A or 5A secondary. Match normal feeder current and connected equipment, then calculate lead and device burden for the complete secondary loop.
- Specify measurement or protection performance. Published references are 3.75VA for classes 0.5, 1 or 3 and 5VA for 10P; confirm the exact class, accuracy limit factor and output for the ordered version.
- Define the winding and terminal arrangement. Single, dual and tapped-terminal references appear in the page, but they are configuration options rather than guaranteed features; state every required ratio, core and terminal explicitly.
- Check window fit and clearances in the switchgear. Confirm conductor or cable dimensions, aperture, 134mm or 175mm creepage reference, phase clearances, mounting, bend radius, terminal access and operating environment.
Frequently Asked Questions
Q1: Can the LMZ-10 current transformer be installed in 11kV switchgear?
Yes, it supports 6kV, 10kV, 11kV, and 12kV systems. Ensure the installation site is free from corrosive gases and abnormal condensation. Confirm specific switchgear dimensions with our engineering team.
Q2: What is the maximum rated primary current for this epoxy resin CT?
The rated primary current range is from 50A to 630A. It provides secondary currents of 1A or 5A for both metering and protection. Contact us to specify your exact ratio requirements.
Q3: When is technical confirmation required for environmental conditions?
Technical confirmation is required for extreme environments outside standard limits. The standard reference ambient temperature range is -5°C to +40°C, avoiding severe vibration and heavy conductive dust. Please provide detailed site conditions for evaluation.
Q4: Is customization available for high altitude coastal project conditions?
Yes, special conditions like high altitude or coastal areas require factory evaluation. The standard design suits controlled humidity and pollution levels. Submit your environmental parameters to our technical team for custom verification.
Q5: How are factory tests documented for the LM-6/10 before shipment?
Standard routine tests verify compliance with indoor medium-voltage switchgear requirements. Specific type tests or third-party certifications are subject to project confirmation. Contact our quality department for the detailed test report.
Q6: Are these cast-resin current transformers suitable for air-insulated switchgear?
Yes, the LMZ-10 and LM-6/10 are designed for indoor air-insulated medium-voltage switchgear. They feature epoxy resin insulation for reliable operation at 50Hz or 60Hz. Check our product catalog for more indoor CT applications.
Q7: Why choose epoxy resin insulation for this medium-voltage CT?
Epoxy resin provides high mechanical strength and moisture resistance for indoor switchgear. It ensures reliable performance across the -5°C to +40°C ambient range. Request material data sheets from our engineering team.