Overview
The LMZ Series 0.66kV indoor epoxy resin cast current transformers are precision electromagnetic devices engineered for accurate current measurement and energy metering in low-voltage AC power systems. Designed for 0.66 kV class distribution networks, the series includes four distinct families—LMZ5, LMZ6, LMZ7, and LMZ8—each tailored to specific installation and performance needs. These transformers operate on Faraday’s law of electromagnetic induction, utilizing toroidal magnetic cores to deliver standardized secondary output (1 A or 5 A) proportional to primary current, ensuring high fidelity across wide load ranges without saturation.
Suitable for applications ranging from industrial motor control centers to commercial building automation systems, the LMZ series complies with international standards including IEC 61869-2/3 and GB/T 20840.2. The fully enclosed cast-resin or plastic-shell construction provides robust insulation, mechanical stability, and long-term reliability in indoor environments. With accuracy classes as tight as 0.2S, these CTs support precision metering, SCADA integration, and real-time load monitoring in 0.4–0.66 kV switchgear and distribution panels.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System voltage class | 0.66 kV |
| Rated frequency | 50 Hz (60 Hz optional) |
| Rated secondary current | 1 A or 5 A |
| Accuracy classes | 0.2, 0.2S, 0.5, 0.5S |
| Rated burden | 5 VA or 10 VA |
| Burden power factor | cosφ = 0.8 (lagging) |
| Insulation level | Per 0.66 kV standard |
| Applicable standards | IEC 61869-2/3, GB/T 20840.2, GB 1208-2006 |
Model Designation
L — Current transformer (CT)
M — Busbar mounting type
Z — Cast-resin insulated structure
5 — Series design code (unsaturated core, rectangular configuration)
0.66 — Voltage class in kV
Construction
The LMZ series features four structural variants using either epoxy cast-resin or plastic shell insulation. The LMZ5 and LMZ6 models employ unsaturated cast-resin construction—rectangular and window-type respectively—with fully enclosed epoxy resin providing high dielectric strength and environmental protection. The LMZ7 uses a lightweight plastic shell with integrated terminal housing, while the LMZ8 offers a ring-type design with superior mechanical robustness through full cast-resin encapsulation. All variants utilize ring-type magnetic cores to prevent saturation, ensure linearity, and maintain accuracy under varying load conditions. Secondary terminals (S1/S2) and primary direction markers (P1/P2) follow standard polarity conventions for correct metering orientation.
Technical Parameters
Service Conditions
- Installation environment: Indoor installation only
- Altitude: Not exceeding 1000 m above sea level (higher altitude shall be specified for engineering confirmation)
- Ambient temperature:
- LMZ5: -5°C to +40°C
- LMZ6: -5°C to +65°C (extended temperature capability)
- LMZ7: -5°C to +55°C
- LMZ8: -5°C to +55°C
- Relative humidity: Daily average ≤ 95%, monthly average ≤ 90% (at +20°C reference)
- Environmental conditions: Free from corrosive gases or vapors; free from explosive or flammable media; no severe vibration, mechanical shock, or impact
Technical Parameters
This section provides selection-oriented technical data for the LMZ series indoor current transformers used in 0.66 kV class AC systems (50 Hz). Data shown below is intended for preliminary selection of accuracy class, rated burden, and current range configuration.
LMZ5 Series – Technical Data
| Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Classes |
Rated Output (VA) |
|---|---|---|---|
| 150, 200, 300, 400, 600, 800 | 5 | 0.2 0.2S |
5 |
| 1000, 1200, 1500, 2000, 3000, 4000 | 1 | 0.2 0.2S |
5 |
| 150, 200, 300, 400, 600, 800 | 5 | 0.5 0.5S |
10 |
| 1000, 1200, 1500, 2000, 3000, 4000 | 1 | 0.5 0.5S |
10 |
LMZ6 Series – Technical Data
| Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Classes |
Rated Output (VA) |
|---|---|---|---|
| 600, 800, 1000, 1500 | 5 | 0.2 0.2S |
5 |
| 2000, 3000, 4000 | 1 | 0.2 0.2S |
5 |
| 600, 800, 1000, 1500 | 5 | 0.5 0.5S |
10 |
| 2000, 3000, 4000 | 1 | 0.5 0.5S |
10 |
LMZ7 Series – Technical Data
| Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Classes |
Rated Output (VA) |
|---|---|---|---|
| 5, 10, 15, 20, 30, 40, 50, 75, 100, 150, 200, 300, 400, 600 |
5, 1 | 0.2, 0.2S, 0.5, 0.5S | 5 |
LMZ8 Series – Technical Data
| Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Classes |
Rated Output (VA) |
|---|---|---|---|
| 5, 10, 15, 20, 30, 40, 50, 75,
100, 150, 200, 300, 400, 600 |
5, 1 | 0.2, 0.2S, 0.5, 0.5S | 5 |
Note: If user’s requirements exceed the parameters listed above, they may be subject to technical agreement between manufacturer and purchaser.
Installation & Wiring
Outline Dimensions
The LMZ Series 0.66kV indoor epoxy resin cast current transformers are available in multiple configurations: rectangular busbar-mounting (LMZ5), window-type for through-busbar installation (LMZ6), plastic shell ring-type (LMZ7), and cast-resin ring-type (LMZ8). Dimensional details for each model are provided in the tables above, including key parameters such as A1, A2, B, H, G1, C2, and aperture sizes. Ensure mounting surfaces accommodate the specified base dimensions and allow sufficient clearance for heat dissipation and maintenance access.
Wiring Diagram
Connect the primary conductor through the central aperture (for ring-type models) or to the busbar terminals (for rectangular models). The secondary terminals are clearly marked and must be connected to the measuring or protective devices with appropriately sized wiring. Always ensure one point of the secondary circuit is reliably grounded per applicable standards. Never leave the secondary circuit open when the transformer is energized.
Selection & FAQs
Selection Guide
- Choose LMZ5, LMZ6, LMZ7, or LMZ8 by conductor type, aperture, mounting arrangement, temperature, and panel space.
- Select the 5A–4000A ratio from the operating current and required measurement range.
- Choose a 1A or 5A secondary and specify class 0.2/0.2S or 0.5/0.5S as required.
- Calculate instrument and cable burden, then select the available 5VA or 10VA configuration.
- Confirm outline dimensions, conductor alignment, polarity, terminal access, grounding, and ambient limits for the selected family.
Frequently Asked Questions
Q1: Which accuracy class should I select for revenue billing?
Select the 0.2S accuracy class for billing applications. It maintains high precision across a wider current range. Confirm specific rated burden with our engineering team.
Q2: Can this 0.66kV current transformer be installed outdoors?
No, the LMZ series is strictly for indoor installation only. It requires an environment free from corrosive gases and severe vibration. Please select an outdoor-rated model for external use.
Q3: What is the maximum installation altitude for this transformer?
The standard maximum altitude is 1000 meters above sea level. For installations exceeding this height, please specify the exact altitude for engineering confirmation and derating calculations.
Q4: When should I select the LMZ6 model over others?
Select the LMZ6 model when ambient temperatures reach up to +65°C. Standard LMZ5, LMZ7, and LMZ8 models are limited to a maximum operating temperature of +55°C.
Q5: Are custom primary current ratings above 4000A available?
Standard LMZ5 configurations go up to 4000A. For higher primary current requirements, please contact our sales team to discuss custom engineering and manufacturing feasibility.
Q6: How do I obtain type test certificates?
Type test documentation is available upon request. Please contact our technical sales team to verify specific certification standards and request the relevant test reports.
Q7: Where are these epoxy resin current transformers typically applied?
They are primarily applied in 0.66 kV indoor AC power systems. Ideal locations include switchgear, control panels, and industrial distribution networks.