Product Overview
The LXZ1(2)-80/100/120/140/160/180 indoor cast-resin zero sequence current transformer is designed for cable earth fault detection, residual current monitoring, and grounding protection in AC power systems. It is suitable for indoor applications with rated frequency of 50Hz or 60Hz and rated insulation level of 0.72/3kV. The product provides 5A or 1A secondary current output for protection relays, monitoring devices, and grounding fault detection systems.
This series is a through-hole, single-phase, ring-core zero sequence current transformer with epoxy resin cast insulation. During installation, the three-phase cable group passes through the central window of the transformer. Under normal operating conditions, the vector sum of the three-phase currents is close to zero. When a single-phase ground fault or insulation fault occurs, zero sequence current is generated, and the transformer outputs a proportional secondary signal for relay protection or alarm operation.
Product Type
| Item | Specification |
|---|---|
| Product name | Indoor Cast-Resin Zero Sequence Current Transformer |
| Model series | LXZ1(2)-80 / 100 / 120 / 140 / 160 / 180 |
| Product structure | Indoor epoxy resin cast ring-core zero sequence current transformer |
| Window diameter options | 80 mm, 100 mm, 120 mm, 140 mm, 160 mm, 180 mm |
| Rated insulation level | 0.72/3kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Protection class | 10P5, 10P10, 10P15, 10P20 according to selected model and ratio |
| Installation location | Indoor |
| Typical applications | Zero sequence current detection, cable earth fault protection, residual current monitoring, grounding protection |
Product Display
Main Applications
- Indoor cable feeder earth fault protection
- Zero sequence current detection in low-voltage and distribution systems
- Residual current monitoring for three-phase cable groups
- Small-current grounding system protection
- Single-phase ground fault alarm and trip circuits
- Motor feeder, generator feeder, and distribution line protection
- Switchgear, protection cabinets, and power monitoring systems
Key Technical Features
- Zero sequence protection design: Designed to detect residual current generated by single-phase grounding faults or insulation faults.
- Epoxy resin cast insulation: The ring core and secondary winding are encapsulated with cast resin for insulation performance, moisture resistance, and mechanical stability.
- Multiple aperture options: Window sizes from 80 mm to 180 mm are available for different cable diameters and installation layouts.
- 5A or 1A secondary output: Compatible with common protection relays, monitoring devices, and current input instruments.
- Protection class options: 10P5, 10P10, 10P15, and 10P20 are available according to current ratio and burden requirements.
- Indoor fixed installation: The through-hole body and mounting base support cabinet installation and cable feeder protection applications.
Working Principle
The LXZ1(2) zero sequence current transformer measures the vector sum of the currents flowing through the three-phase cable group. When the system operates normally, the three-phase currents are balanced, and the vector sum is approximately zero, so the secondary output is very small. When a single-phase ground fault occurs, the three-phase current balance is broken and zero sequence current appears. The transformer converts this residual current into a secondary signal for relay protection, alarm, or monitoring.
For correct operation, all three phase conductors must pass through the transformer window in the same direction. The cable or conductor provides the primary insulation, while the transformer body provides insulation and mechanical protection for the magnetic core and secondary winding.
Model Designation
The model code can be interpreted as follows:
| Code | Meaning |
|---|---|
| L | Current transformer |
| X | Zero sequence current transformer type |
| Z | Cast-resin insulated structure |
| 1 / 2 | Design structure code |
| 80 / 100 / 120 / 140 / 160 / 180 | Window diameter or structure size code |
Technical Data
| Item | Specification |
|---|---|
| Model series | LXZ1(2)-80/100/120/140/160/180 |
| Product type | Indoor cast-resin zero sequence current transformer |
| Rated insulation level | 0.72/3kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Protection class | 10P5, 10P10, 10P15, 10P20 |
| Ambient temperature | -25°C to +40°C |
| Insulation structure | Epoxy resin cast insulation |
| Applicable standards | GB 20840.1-2010, GB 20840.2-2014; customer-specific requirements can be confirmed by agreement |
Model Aperture and Dimension Reference
| Model | d (mm) | D (mm) | H (mm) | h (mm) | a (mm) | b (mm) | c (mm) |
|---|---|---|---|---|---|---|---|
| LXZ1-80 | 80 | 195 | 130 | 50 | 80 | – | 120 |
| LXZ2-80 | 80 | 195 | 130 | 80 | 80 | 50 | 120 |
| LXZ1-100 | 100 | 215 | 140 | 50 | 80 | – | 120 |
| LXZ2-100 | 100 | 215 | 140 | 80 | 80 | 50 | 120 |
| LXZ1-120 | 120 | 235 | 150 | 50 | 100 | – | 140 |
| LXZ2-120 | 120 | 235 | 150 | 80 | 100 | 50 | 140 |
| LXZ1-140 | 140 | 255 | 160 | 50 | 100 | – | 140 |
| LXZ2-140 | 140 | 255 | 160 | 80 | 100 | 50 | 140 |
| LXZ1-160 | 160 | 265 | 170 | 60 | 100 | – | 140 |
| LXZ2-160 | 160 | 265 | 170 | 80 | 100 | 30 | 140 |
| LXZ1-180 | 180 | 295 | 180 | 50 | 160 | – | 200 |
| LXZ2-180 | 180 | 295 | 180 | 80 | 160 | 50 | 200 |
Unit: mm. Final dimensions, mounting holes, terminal positions, and body thickness are subject to the approved outline drawing.
Rated Current Ratio and Output Reference
| Model Group | Protection Class | 5A Secondary Current Ratio | Rated Output Range for 5A Secondary (VA) | 1A Secondary Current Ratio | Rated Output Range for 1A Secondary (VA) |
|---|---|---|---|---|---|
| LXZ1-80/100/120/140/160/180 | 10P5 | 50/5, 75/5, 100/5, 150/5, 200/5, 250/5, 300/5, 400/5 | 5 to 40 depending on model and ratio | 50/1, 75/1, 100/1, 150/1 | 5 to 15 depending on model and ratio |
| LXZ1-80/100/120/140/160/180 | 10P10 | 50/5 to 400/5 | 2.5 to 20 depending on model and ratio | 50/1 to 150/1 | 2.5 to 7.5 depending on model and ratio |
| LXZ1-80/100/120/140/160/180 | 10P15 | 50/5 to 400/5 | 1 to 15 depending on model and ratio | 50/1 to 150/1 | 2 to 5 depending on model and ratio |
| LXZ1-80/100/120/140/160/180 | 10P20 | 50/5 to 400/5 | 1 to 10 depending on model and ratio | 50/1 to 150/1 | 1 to 3.75 depending on model and ratio |
| LXZ2-80/100/120/140/160/180 | 10P5 / 10P10 / 10P15 / 10P20 | 50/5 to 400/5 | 1 to 80 depending on model, ratio, and class | 50/1 to 150/1 | 2 to 30 depending on model, ratio, and class |
Note: The rated output varies according to aperture size, secondary current, protection class, and selected current ratio. Values beyond the catalogue table can be confirmed through technical agreement.
Service Conditions
- Installation location: indoor
- Rated insulation level: 0.72/3kV
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: -25°C to +40°C
- The installation environment should be free from severe vibration, corrosive gas, conductive dust, explosive medium, and heavy pollution.
- All three phase conductors should pass through the transformer window together in the same direction.
- The cable, busbar, or conductor should have sufficient insulation clearance and should not apply mechanical stress to the transformer body.
- For special cable diameter, grounding protection scheme, burden, or protection class requirements, technical confirmation is recommended before ordering.
Standards and Compliance
The LXZ1(2) zero sequence current transformer series is manufactured according to GB 20840.1-2010 and GB 20840.2-2014, and can also be supplied according to customer-specific project requirements. Final current ratio, rated output, protection class, routine test items, and nameplate data should be confirmed in the technical agreement.
Installation and Dimensions
The LXZ1(2) series adopts a through-hole ring-core structure. The three-phase cable group, busbar group, or conductor group passes through the central aperture, and the secondary terminals are marked as S1 and S2. The model should be selected according to the required aperture diameter, installation thickness, mounting position, and cabinet layout.
Connection and Wiring Notes
- All three phase conductors should pass through the transformer window together in the same direction.
- Do not pass only one phase conductor through the window when the transformer is used for zero sequence protection.
- Connect the secondary terminals S1 and S2 to the protection relay or monitoring device according to the wiring diagram.
- Check polarity, terminal tightening, relay setting, and secondary wiring continuity before commissioning.
- The secondary circuit of a current transformer must not be open-circuited when the primary circuit is energized.
- Secondary wiring, grounding, and terminal protection should comply with project specifications and local electrical regulations.
Installation and Safety Notes
- Confirm the model, aperture size, current ratio, secondary current, protection class, and rated output before installation.
- Ensure that the cable or conductor group can pass through the window without forcing the transformer body.
- Install the transformer in an indoor cabinet or panel according to the approved drawing.
- Keep the cable group centered as far as possible in the window to support stable residual current detection.
- Check terminal marks, mounting holes, secondary wiring, and relay connection before energizing.
- Installation and maintenance should be performed by qualified electrical personnel.
Ordering Information
Please provide the following information when ordering or requesting a quotation:
- Product model: LXZ1 or LXZ2, and aperture size 80 / 100 / 120 / 140 / 160 / 180
- Rated current ratio, such as 100/5, 200/5, 300/5, 400/5, 50/1, or 100/1
- Rated secondary current: 5A or 1A
- Required protection class: 10P5, 10P10, 10P15, or 10P20
- Rated output / burden in VA
- Rated frequency and installation environment
- Maximum outside dimension of the cable group, busbar group, or conductor group
- Relay model, protection scheme, and grounding fault detection requirements
- Quantity, drawing requirements, certificates, inspection documents, labels, or packaging requirements
Selection Guidelines
- Confirm aperture size: Select 80, 100, 120, 140, 160, or 180 according to the outside dimension of the three-phase cable or conductor group.
- Choose LXZ1 or LXZ2 structure: Select the structural type according to installation thickness, terminal position, and mounting layout.
- Confirm zero sequence application: Use this series when the protection system needs residual current or earth fault current detection.
- Confirm current ratio: Select the ratio according to the relay input and protection setting requirement.
- Select secondary current: Choose 5A or 1A according to the connected relay or monitoring device.
- Select protection class: Choose 10P5, 10P10, 10P15, or 10P20 according to the protection circuit requirement.
- Check rated burden: The total burden of relays, meters, cables, and terminal blocks should not exceed the rated output.
- Confirm dimensions: Check the outline drawing, mounting holes, and cabinet clearance before batch installation.