Overview
The LXC-10/155-300-60 and LXC-10/155-300-80 are indoor cast-resin zero sequence current transformers rated for 0.72/3kV insulation level. They feature a split-core, runway-shaped long oval window designed for grouped or double-cable arrangements in medium-voltage switchgear and protection cabinets.
These transformers provide 5A or 1A secondary output with 10P5 or 10P10 protection accuracy classes, suitable for earth fault detection, residual current monitoring, and relay protection input in 50Hz or 60Hz systems. They comply with standard requirements for indoor zero sequence CT applications in ring main units, cable compartments, and retrofit installations where existing cables must remain undisturbed.
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 |
| Primary current (zero sequence) | As per selected ratio |
| Secondary burden | Dependent on model depth and ratio |
| Installation type | Indoor |
| Core type | Split-core magnetic circuit |
| Insulation material | Cast-resin |
| Window type | Long oval (double cable track) |
| Body depth options | 60 mm, 80 mm |
| Application | Zero sequence current detection, earth fault protection |
Model Designation
- L: Current transformer
- X: Zero sequence current transformer type
- C: Cast-resin / structure series code
- 10: Product design series code
- 155-300: Runway-type window structure size code
- 60 / 80: Body depth / structure thickness code
Construction
The LXC-10/155-300 series features a split-core design with two separable halves, each encapsulated in cast-resin insulation. This construction provides mechanical robustness, electrical insulation, and stable performance in indoor environments. The magnetic core is formed by clamping the two halves around the cable group after installation, creating a complete magnetic circuit without requiring cable disconnection. The long oval window—coded as 155-300—enables passage of multiple phase conductors in compact cabinet layouts while maintaining required bending radii and spacing. The resin casting ensures protection against moisture, dust, and mechanical stress, making it suitable for switchgear and protection cabinets operating under standard indoor conditions.
Technical Parameters
Service Conditions
- Installation location: indoor
- Rated insulation level: 0.72/3kV
- Rated frequency: 50Hz / 60Hz
- Ambient temperature: -25°C to +40°C
- Installation environment: Free from severe vibration, corrosive gas, conductive dust, explosive medium, heavy moisture and serious pollution.
- Cable routing: All phase conductors of the protected circuit should pass through the same transformer window in the same direction.
- Mechanical stress: The cable group should pass through the long oval window without mechanical stress on the transformer body.
- Split-core joint: The split-core joint surface should be clean, aligned and clamped firmly after installation.
Technical Parameters
The LXC-10/155-300-60/80 is an indoor double cable track type zero sequence current transformer with a rated insulation level of 0.72/3kV and cast-resin insulation. It operates within an ambient temperature range of -25°C to +40°C, complies with GB 20840.1-2010 and GB 20840.2-2014 standards, and supports primary current ratios from 20/1 up to 400/5 A.
Model: LXC-10 155-300-60
| Rated
Current Ratio |
Rated Output
10P5 (VA) |
Rated Output
10P10 (VA) |
|---|---|---|
| 50/5 | 1.5 | 0.5 |
| 75/5 | 2.5 | 0.5 |
| 100/5 | 2.5 | 1 |
| 150/5 | 3.75 | 1.5 |
| 200/5 | 5 | 1.5 |
| 300-400/5 | 7.5 | 2.5 |
| 50/1 | 1.5 | 0.5 |
| 75/1 | 2.5 | 1 |
| 100/1 | 3.75 | 1.5 |
| 150/1 | 5 | 2.5 |
Model: LXO-10 155-300-80
| Rated
Current Ratio |
Rated Output
10P5 (VA) |
Rated Output
10P10 (VA) |
|---|---|---|
| 20/5 | 0.5 | – |
| 50/5 | 2.5 | 1 |
| 75/5 | 2.5 | 1.5 |
| 100/5 | 3.75 | 1.5 |
| 150/5 | 7.5 | 2.5 |
| 200/5 | 10 | 3.75 |
| 300-400/5 | 15 | 5 |
| 20/1 | 1 | 0.5 |
| 50/1 | 2.5 | 1 |
| 75/1 | 3.75 | 1.5 |
| 100/1 | 5 | 2.5 |
| 150/1 | 7.5 | 3.75 |
Note: If user’s data go beyond the above-mentioned scopes, they may be subject to an agreement between manufacturer and purchaser.
Installation & Wiring
Installation Diagram
The LXC-10/155-300-60 and LXC-10/155-300-80 are split-core, runway-type zero sequence current transformers designed for installation around a group of phase conductors. The two cast-resin halves are opened, positioned around the cable bundle, then closed and clamped to form a complete magnetic circuit. The unit is then secured to the cabinet base or mounting bracket using the provided mounting length (280 mm) and aligned according to the approved outline drawing.
Wiring Diagram
Secondary terminals are marked as OS1/S1 and OS2/S2. OS1 (or S1) is the polarity-marked output terminal and must be connected to the relay or monitoring device input according to the required polarity. OS2 (or S2) connects to the return terminal of the protection circuit. All protected phase conductors (A, B, C) must pass through the same runway-type window in the same direction. Do not route only one phase conductor through the window when used for zero-sequence (ground fault) protection.
Selection & FAQs
Selection Guide
- Map the complete A-B-C cable arrangement against the 155–300 long-oval window and confirm bending radius, insulation clearance and cabinet mounting space.
- Select the 60mm body where depth is restricted or the 80mm body where higher output or a 20A ratio is required; verify the approved outline drawing.
- Choose a 1A or 5A secondary and a ratio suited to the expected earth-fault current and connected relay pickup range.
- Specify 10P5 or 10P10, add the relay and secondary-lead burdens, and keep the total within the exact model-and-ratio VA rating.
- Confirm all protected phase conductors follow the same direction through the window and review screen, armour, neutral and PE routing before installation.
Frequently Asked Questions
Q1: What is a double cable track zero-sequence CT?
It uses a long oval, runway-shaped aperture to surround wide or grouped cable arrangements that may not fit a conventional circular window, while measuring residual current for earth-fault protection.
Q2: What is the difference between the 60mm and 80mm versions?
The suffix identifies body depth. The 80mm model generally provides higher VA output and includes selected 20A ratio options; the 60mm model reduces installation depth.
Q3: Can the LXC be installed on an existing feeder?
Yes. Its two cast-resin halves separate and close around the installed cable group, avoiding primary cable disconnection when adequate mounting access is available.
Q4: What ratios are available?
The 60mm version covers 50/5A–400/5A and 50/1A–150/1A. The 80mm version adds selected 20/5A and 20/1A configurations; class and output depend on the chosen ratio.
Q5: Does the “10” in LXC-10 mean the CT itself has 10kV insulation?
No. The published CT insulation rating is 0.72/3kV; “10” is a product-series code. When used around insulated medium-voltage cables, the cable system retains primary insulation and all project clearances must be verified.
Q6: How must the conductors be routed?
All protected phase conductors must pass through the same window in the same direction. Screens, armour, neutral and earth conductors must follow the grounding design so residual current is neither bypassed nor introduced falsely.
Q7: What checks are essential before energizing?
Ensure the split faces are clean, aligned and firmly clamped; the CT is securely mounted; OS1/S1 polarity and wiring continuity are correct; relay settings are confirmed; and the secondary circuit is not open.