Overview
The LXK-φ80/φ100/φ120/φ150/φ180/φ200/φ240/φ260 is an indoor split-core zero sequence current transformer rated for systems up to 35kV, with a standard insulation level of 0.72/3kV. It features an epoxy cast-resin construction that provides robust electrical insulation, moisture resistance, and mechanical stability for reliable operation in indoor environments.
Designed for 50Hz or 60Hz AC systems, this CT delivers secondary outputs of 5A or 1A and offers protection accuracy classes from 10P5 to 10P20 depending on model and ratio. It is commonly used in cable earth fault protection, residual current monitoring, and grounding fault detection in switchgear, ring main units, and distribution panels—particularly where retrofit installation around existing cables is required without disconnecting conductors.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Rated insulation level | 0.72/3kV |
| Rated frequency | 50Hz / 60Hz |
| Rated secondary current | 5A or 1A |
| Protection class | 10P5, 10P10, 10P15, 10P20 |
| System voltage (max) | 35kV (with proper cable insulation) |
| Installation environment | Indoor |
| Core type | Split-core (open-type) |
| Insulation material | Epoxy cast-resin |
| Application | Zero sequence / residual current detection |
| Phase conductor requirement | All phases through single aperture |
| Secondary burden | As per selected ratio and protection class |
| Primary current | Vector sum (residual) measurement |
Model Designation
- L: Current transformer
- X: Zero sequence / residual current detection
- K: Open-type / split-core structure
- 80 / 100 / 120 / 150 / 180 / 200 / 240 / 260: Nominal aperture diameter in millimeters
Construction
The LXK series features a split-core design with a hinged or separable body that allows installation around pre-laid cable bundles without disconnection. The magnetic core and secondary winding are fully encapsulated in high-quality epoxy cast-resin, ensuring excellent dielectric strength, environmental resistance, and long-term dimensional stability. The clamping mechanism securely closes the two halves after installation, maintaining consistent magnetic coupling and measurement accuracy. This construction supports reliable zero sequence current detection in demanding indoor power distribution applications.
Technical Parameters
Service Conditions
- Installation location: indoor
- Rated frequency: 50Hz / 60Hz
- Applicable system: small-current grounding systems and cable feeder protection systems up to 35kV
- Ambient temperature: -25°C to +40°C
- Recommended environment: no severe vibration, corrosive gas, conductive dust, explosive medium, heavy moisture or serious pollution
- Conductor routing: All protected phase conductors should pass through the same CT aperture in the same direction
Technical Parameters
The LXK series is an indoor epoxy cast-resin split-core zero sequence current transformer rated for systems up to 35kV with a rated insulation level of 0.72/3kV. It operates within an ambient temperature range of -25°C to +40°C and complies with GB/T 20840.1-2010, GB/T 20840.2-2014, and IEC 61869-1/-2 standards. Secondary current options are 5A or 1A, with primary current ratios ranging from 50/1 to 400/5.
| Type | Classes | Rated Current Ratio (A) |
Rated Output (VA) |
|---|---|---|---|
| LXK-80 (80/165*57) | 10P5~10P10 | 50/5 75/5 100/5 150/5 200/5 250/5 300/5 400/5 50/1 75/1 100/1 150/1 200/1 250/1 |
5~1 |
| LXK-100 (100/180*55) | 10P5~10P10 | 5~1 | |
| LXK-100 (100/180*57) | 10P5~10P15 | 10~1 | |
| LXK-120 (120/204*57) | 10P5~10P15 | 10~1 | |
| LXK-120 (120/210*65) | 10P5~10P15 | 10~2.5 | |
| LXK-120 (120/210*100) | 10P5~10P20 | 15~2.5 | |
| LXK-120 (120/250*80) | 10P5~10P20 | 15~1 | |
| LXK-150 (150/235*57) | 10P5~10P10 | 10~1 | |
| LXK-150 (150/280*80) | 10P5~10P20 | 15~1 | |
| LXK-160 (160/250*80) | 10P5~10P20 | 10~1 | |
| LXK-180 (180/265*57) | 10P5~10P10 | 5~1 | |
| LXK-180 (180/310*80) | 10P5~10P20 | 15~1 | |
| LXK-200 (200/330*80) | 10P5~10P20 | 15~1 | |
| LXK-240 (240/350*80) | 10P5~10P20 | 15~1 | |
| LXK-260 (260/370*80) | 10P5~10P20 | 15~1.5 |
Installation & Wiring
Installation Diagram
The LXK split-core zero sequence current transformer is installed by opening the core via the fastening band, placing it around the complete cable group (all phase conductors and neutral, if applicable), then closing and evenly tightening the band to ensure full contact at the mating surface. Ensure the selected aperture fully covers the cable bundle and that the cable bending radius aligns with cabinet layout constraints.
Selection & FAQs
Selection Guide
- Confirm the system grounding method, maximum earth-fault current, relay pickup, and required protection class.
- Measure the complete phase-cable bundle and select an 80mm–260mm aperture with installation and bending clearance.
- Choose the 1A or 5A secondary and current ratio that matches the relay input and protection study.
- Calculate relay and cable-loop burden, then confirm the available 1VA–15VA output for the selected aperture and class.
- Verify all protected conductors pass through in the same direction and that the split faces close cleanly and tightly.
Frequently Asked Questions
Q1: What does the LXK split-core zero-sequence CT detect?
It measures residual current—the vector sum of the phase currents—so a protection relay can detect cable earth faults.
Q2: Can it be installed without disconnecting existing cables?
Yes. The separable core opens around the complete cable group, making it suitable for retrofit protection projects.
Q3: Which aperture sizes are available?
The series includes 80mm, 100mm, 120mm, 150mm, 180mm, 200mm, 240mm, and 260mm inner diameters.
Q4: What secondary and protection classes can be specified?
Available secondary outputs are 1A or 5A, with protection classes from 10P5 to 10P20 depending on model and ratio.
Q5: Can the LXK series be used on 35kV cables?
Yes. It can monitor properly insulated cable systems up to 35kV; the CT itself has 0.72/3kV secondary insulation.
Q6: Which conductors must pass through the aperture?
All protected phase conductors—and the neutral when required by the scheme—must pass together through the window in the same direction.
Q7: What installation error most affects protection accuracy?
Dirty, misaligned, or loosely clamped split-core faces create an air gap and can reduce sensitivity or alter relay performance.