Product Overview
Functional Definition
The LMZ-0.66 fully enclosed epoxy resin cast current transformers, are precision electromagnetic instruments designed, for accurate current measurement and energy metering in low-voltage AC power systems. The series comprises four distinct product families (LMZ5, LMZ6, LMZ7, LMZ8), each offering specialized construction and installation configurations to meet diverse application requirements in 0.66 kV class distribution systems.
Key Ratings Snapshot
| Item | Specification (per order / nameplate) |
|---|---|
| System voltage class | 0.66 kV class (low-voltage distribution applications) |
| Rated frequency | 50 Hz (60 Hz available upon request) |
| Rated secondary current | 1 A or 5 A |
| Accuracy classes | Metering cores: 0.2, 0.2S, 0.5, 0.5S |
| Rated burden | 5 VA or 10 VA (depending on series and configuration) |
| Burden power factor | cosφ = 0.8 (lagging) unless otherwise specified |
| Insulation level | Per applicable 0.66 kV standard and project specification |
| Applicable standards | IEC 61869-2 / IEC 61869-3; GB/T 20840.2; GB 1208-2006; IEC 60044-1:2003 |
| Series variants | LMZ5 (unsaturated cast-resin, rectangular) / LMZ6 (unsaturated cast-resin, window type) / LMZ7 (plastic shell casting) / LMZ8 (ring-type cast-resin) |
Product Shows
Working Principle
Operating on Faraday’s law of electromagnetic induction, the LMZ series transformers feature toroidal magnetic cores with primary conductors passing through the aperture and secondary windings wound around the core. The magnetic flux generated by primary current induces proportional voltage in the secondary winding, delivering standardized output current through connected burden. The unsaturated core design (LMZ5/6/8) ensures accurate measurement across wide current ranges without magnetic saturation effects.
System Application Position
- Low Voltage Distribution: 0.4-0.66 kV switchgear, motor control centers, and distribution panels
- Energy Metering: Precision electricity measurement systems requiring 0.2S/0.5 accuracy
- Industrial Monitoring: Manufacturing facilities, process control, and load monitoring applications
- Building Automation: Commercial and residential energy management systems
- SCADA Integration: Supervisory control and data acquisition systems in low-voltage networks
Structural Form Overview
The LMZ series offers four distinct structural configurations to accommodate different installation requirements:
- LMZ5: Rectangular unsaturated cast-resin construction with bolt-on mounting for busbar integration
- LMZ6: Window-type unsaturated cast-resin design for through-busbar applications
- LMZ7: Plastic shell ring-type construction with lightweight, compact footprint
- LMZ8: Ring-type cast-resin design offering superior insulation and mechanical protection
Model Designation
Model Code Explanation
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 (kV)
LMZ5-0.66/30, 30L, 40, 50, 60, 80, 100, 125
Series Comparison
| Series | Construction Type | Installation Method | Primary Application | Temperature Range |
|---|---|---|---|---|
| LMZ5 | Unsaturated cast-resin, rectangular | Bolt-on busbar mounting | High-current metering (150-4000A) | -5°C to +40°C |
| LMZ6 | Unsaturated cast-resin, window | Through-busbar installation | Medium-current metering (600-4000A) | -5°C to +65°C |
| LMZ7 | Plastic shell ring-type | Ring-type aperture mounting | Low-current metering (5-600A) | -5°C to +55°C |
| LMZ8 | Cast-resin ring-type | Ring-type aperture mounting | Low-current metering (5-600A) | -5°C to +55°C |
Service Conditions
The LMZ series current transformers are designed for indoor operation under normal service conditions in low-voltage power systems.
- 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
Construction
Construction Design
LMZ5 Series – Rectangular Unsaturated Cast-Resin
- Structure: Rectangular configuration for direct busbar mounting
- Insulation: Fully enclosed epoxy cast-resin insulation
- Core: Unsaturated ring-type magnetic core (prevents saturation across wide current range)
- Mounting: Bolt-on installation with through-holes for busbar integration
LMZ6 Series – Window-Type Unsaturated Cast-Resin
- Structure: Window-type configuration for through-busbar passage
- Insulation: Fully enclosed epoxy cast-resin insulation
- Core: Unsaturated ring-type magnetic core
- Mounting: Flexible mounting feet for panel or support installation
LMZ7 Series – Plastic Shell Ring-Type
- Structure: Ring-type aperture for conductor passage
- Insulation: Plastic shell casting with integrated secondary terminal housing
- Core: Ring-type magnetic core with precision winding
- Mounting: Compact footprint with mounting base
LMZ8 Series – Cast-Resin Ring-Type
- Structure: Ring-type aperture for conductor passage
- Insulation: Fully enclosed epoxy cast-resin insulation
- Core: Ring-type magnetic core with superior mechanical strength
- Mounting: Base-mounted configuration with integrated terminal block
Windings & Terminal Marking
- Primary conductor: P1 / P2 (reference direction marked on nameplate)
- Secondary terminals: S1 / S2 (single secondary winding configuration typical for metering applications)
Terminal markings follow standard CT polarity conventions. Under normal operating conditions, the reference current direction is defined from P1 to P2. Correct terminal identification shall be observed to ensure metering accuracy.
Technical Data
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.
Definitions: Accuracy class indicates available metering precision (0.2, 0.2S, 0.5, 0.5S per IEC 61869-2). Rated output (VA) is specified per secondary winding. Secondary current is standardized at 1 A or 5 A.
Notation: Data acceptance shall be based on nameplate values and factory test report.
LMZ5 Series – Technical Data
Model Range: LMZ5-0.66/30, 30L, 40, 50, 60, 80, 100, 125
Standards: GB/T 20840.2-2014, IEC 61869-3:2012
| 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 | ||
| 150, 200, 300, 400, 600, 800 | 5 | 0.5 0.5S |
10 |
| 1000, 1200, 1500, 2000, 3000, 4000 | 1 |
LMZ6 Series – Technical Data
Model Range: LMZ6-0.66/60, 80, 100, 125
Standards: GB 1208-2006, IEC 60044-1:2003
| 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 | ||
| 600, 800, 1000, 1500 | 5 | 0.5 0.5S |
10 |
| 2000, 3000, 4000 | 1 |
LMZ7 Series – Technical Data
Model Range: LMZ7-0.66/28, 35, 44
Standards: GB/T 20840.2-2014, IEC 61869-2:2012
| 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 |
LMZ7 Series – Transformation Ratio Table
Standard ratios (primary current : secondary current):
| Primary Current (A) | Secondary 5A Ratio | Secondary 1A Ratio |
|---|---|---|
| 5 | 1:1 | 5:1 |
| 10 | 2:1 | 10:1 |
| 15 | 3:1 | 15:1 |
| 20 | 4:1 | 20:1 |
| 30 | 6:1 | 30:1 |
| 40 | 8:1 | 40:1 |
| 50 | 10:1 | 50:1 |
| 75 | 15:1 | 75:1 |
| 100 | 20:1 | 100:1 |
| 150 | 30:1 | 150:1 |
| 200 | 40:1 | 200:1 |
| 300 | 60:1 | 300:1 |
| 400 | 80:1 | 400:1 |
| 600 | 120:1 | 600:1 |
LMZ8 Series – Technical Data
Model Range: LMZ8-0.66/35, 45
Standards: GB 1208-2006, IEC 60044-1:2003
| 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 – Transformation Ratio Table
Standard ratios (identical to LMZ7 series): Refer to LMZ7 transformation ratio table above.
Standards & Normative References
| Standard | Title | Application |
|---|---|---|
| IEC 61869-2 | Instrument Transformers – Part 2: Additional Requirements for Current Transformers | CT requirements (LMZ7 series) |
| IEC 61869-3 | Instrument Transformers – Part 3: Additional Requirements for Inductive Voltage Transformers | General requirements (LMZ5 series) |
| GB/T 20840.2 | Instrument Transformers – Part 2: Current Transformers | National CT requirements (LMZ5, LMZ7 series) |
| GB 1208-2006 | Current Transformers | National CT standard (LMZ6, LMZ8 series) |
| IEC 60044-1:2003 | Instrument Transformers – Part 1: Current Transformers | International CT requirements (LMZ6, LMZ8 series) |
| IEC 60085 | Electrical Insulation – Thermal Evaluation | Optional (insulation thermal evaluation reference) |
Factory Testing Compliance
- Routine tests per applicable IEC/GB requirements (including polarity/marking, ratio verification, and accuracy verification per specified class and burden)
- Dielectric tests per insulation coordination requirements and applicable standard
- Visual and dimensional inspection including marking and workmanship conformity
- Type and special tests as required by the project specification
Installation & Dimensions
General Installation Requirements
- Outline dimensions and mounting details are provided in the dimensional drawings for each series
- The transformer shall be securely mounted using the designated fixing holes or mounting feet
- Primary conductor shall pass through the aperture (ring-type models) or connect via busbar terminals (rectangular models)
- Adequate clearance shall be maintained for heat dissipation and maintenance access
- Secondary terminals shall be accessible for wiring and future maintenance
LMZ5 Series – Outline Dimensions
Rectangular busbar-mounting configuration
| Model | A1 (mm) | A2 (mm) | B (mm) | H (mm) | G1 (mm) | C2 (mm) |
|---|---|---|---|---|---|---|
| LMZ5/30 | 78 | 32 | 15 | 110 | 48 | 85 |
| LMZ5/30L | 108 | 32 | 17 | 135 | 80 | 117 |
| LMZ5/40 | 94 | 43 | 17 | 120 | 48 | 85 |
| LMZ5/50 | 95 | 52 | 25 | 120 | 48 | 85 |
| LMZ5/60 | 107 | 65 | 32 | 137 | 48 | 85 |
| LMZ5/80 | 135 | 85 | 32 | 137 | 48 | 85 |
| LMZ5/100 | 160 | 105 | 32 | 137 | 48 | 85 |
| LMZ5/125 | 194 | 128 | 32 | 155 | 48 | 85 |
LMZ6 Series – Outline Dimensions
Window-type configuration for through-busbar installation
| Model | A1 (mm) | A2 (mm) | A3 (mm) | B (mm) | C (mm) | H (mm) |
|---|---|---|---|---|---|---|
| LMZ6-0.66/60II | 115 | 65 | 55 | 52 | 60 | 174 |
| LMZ6-0.66/80II | 135 | 85 | 60 | 52 | 60 | 168 |
| LMZ6-0.66/100II | 155 | 105 | 75 | 52 | 60 | 182 |
| LMZ6-0.66/125II | 185 | 128 | 110 | 62 | 65 | 212 |
LMZ7 Series – Outline Dimensions
Plastic shell ring-type configuration
| Model | A1 (mm) | A2 (mm) |
|---|---|---|
| LMZ7-0.66/28 | 89.5 | 28 |
| LMZ7-0.66/35 | 94.5 | 35 |
| LMZ7-0.66/44 | 96.5 | 44 |
Note: Overall height H varies by model: /28: 118mm, /35: 125mm, /44: 124mm. Base mounting dimension: 85mm × 46mm.
LMZ8 Series – Outline Dimensions
Cast-resin ring-type configuration
| Model | A1 (mm) | A2 (mm) |
|---|---|---|
| LMZ8-0.66/35 | 100 | 35 |
| LMZ8-0.66/45 | 105 | 45 |
Note: Overall height: 140mm (±1mm). Base mounting dimension: 85mm × 45mm.
Safety Notes
- Secondary circuit must never be left open when the transformer is energized, as dangerous high voltage may appear across the secondary terminals
- During inspection or maintenance, the secondary circuit shall be short-circuited before disconnecting any instruments
- One point of the secondary circuit should be reliably grounded in accordance with applicable standards
- All installation and maintenance work shall comply with local electrical safety regulations
- Conductor sizing through aperture (ring-type models) shall allow adequate clearance and thermal management
Ordering Information
When placing an order, the required configuration shall be specified according to the local grid requirements, applicable standards, and project technical specification. The following parameters shall be clearly stated for technical confirmation and production release:
- Series selection (LMZ5 / LMZ6 / LMZ7 / LMZ8) based on current range and installation requirements
- Model designation including aperture size or current rating
- Rated primary current / transformation ratio
- Rated secondary current (1 A or 5 A)
- Accuracy class (0.2, 0.2S, 0.5, or 0.5S)
- Rated burden (VA) for secondary circuit
- Ambient temperature range (if non-standard conditions apply)
How to Select
1. Determine series based on current range and installation method:
- LMZ5: High-current metering (150-4000A), busbar bolt-on mounting
- LMZ6: Medium-current metering (600-4000A), through-busbar window installation, extended temperature capability
- LMZ7: Low-current metering (5-600A), ring-type plastic shell, compact footprint
- LMZ8: Low-current metering (5-600A), ring-type cast-resin, superior mechanical protection
2. Select accuracy class based on application requirements:
- 0.2S / 0.2: Precision revenue metering and high-accuracy measurement systems
- 0.5S / 0.5: Standard energy metering and monitoring applications
3. Confirm rated burden (VA) for secondary circuit:
Calculate total burden including connected meters, instruments, wiring resistance, and safety margin. Select 5 VA or 10 VA rating accordingly.
4. Specify secondary current based on wiring distance and instrument compatibility:
- 5 A: Standard for short wiring distances and conventional instruments
- 1 A: Recommended for long wiring runs to minimize transmission losses
If local utility or project requirements apply (e.g., specific standards compliance, documentation language, special environmental conditions, or required certificates), specify them at the ordering stage. Special configurations shall be confirmed by technical agreement and final data sheet prior to production.
FAQs
Q1: How to select the appropriate LMZ series for a specific 0.66kV metering application?
A: Series selection depends on rated primary current range and installation constraints. LMZ5/6 series accommodate high currents (150-4000A) with busbar mounting, while LMZ7/8 series suit lower currents (5-600A) with ring-type aperture installation. Consider mechanical configuration, temperature range, and available panel space.
Q2: What are the differences between unsaturated core design (LMZ5/6) and standard core construction?
A: Unsaturated core design ensures accurate measurement across wide current ranges without magnetic saturation effects, particularly important for applications with high overload or inrush current conditions. This provides superior linearity and accuracy at current levels exceeding rated values.
Q3: How to determine rated burden (VA) for 0.66kV metering circuits?
A: Rated burden (VA) shall cover total connected load including energy meters, monitoring instruments, and wiring resistance losses. For typical single-meter installations, 5 VA is sufficient; multi-instrument circuits or long wiring runs may require 10 VA rating.
Q4: Are LMZ7 and LMZ8 series electrically equivalent for the same current rating?
A: Yes, with identical primary current, accuracy class, and secondary burden specifications, LMZ7 (plastic shell) and LMZ8 (cast-resin) are electrically equivalent. Selection between them is based on environmental requirements and mechanical protection needs.
Q5: What are the temperature rating differences between LMZ series variants?
A: LMZ5 operates -5°C to +40°C; LMZ6 offers extended range -5°C to +65°C for harsh environments; LMZ7/8 operate -5°C to +55°C. Select appropriate series based on installation environment temperature profile.
Q6: Which standards govern compliance for LMZ series transformers?
A: LMZ5/7 comply with GB/T 20840.2-2014 and IEC 61869 series; LMZ6/8 comply with GB 1208-2006 and IEC 60044-1:2003. All series maintain compliance with applicable national and international standards; nameplate and factory test report prevail for specific unit verification.
Q7: How to properly install ring-type models (LMZ7/8) for accurate metering?
A: Ensure primary conductor passes centrally through the aperture without contact with the transformer body. Maintain consistent conductor position to avoid asymmetric magnetic field effects. Verify correct polarity (P1→P2 direction) and reliably ground one secondary terminal per safety requirements.
Q8: Can LMZ series transformers be used for protection applications?
A: LMZ series are primarily designed for metering applications with accuracy classes 0.2/0.2S/0.5/0.5S. For protection applications requiring different accuracy limit factors (e.g., 5P, 10P classes), consult factory for availability and suitability confirmation.