Overview
The LB-10W series are outdoor-rated, oil-immersed current transformers designed for 10 kV medium-voltage AC power systems. They feature a steel-tank construction filled with high-grade mineral insulating oil, processed through vacuum filtration and vacuum oil-filling to ensure optimal dielectric strength and thermal performance in both indoor and outdoor environments.
These transformers deliver precision current measurement with accuracy classes of 0.2 and 0.5 for metering, and 10P10 for protection applications. They are suitable for energy metering, relay protection, and distribution monitoring in switchgear, outdoor substations, and pole-mounted installations. The design complies with IEC 61869-1/2 and GB/T 20840.1/20840.2 standards, supporting continuous operation at 120% of rated primary current.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System voltage class | 10 kV |
| Rated frequency | 50 Hz |
| Rated secondary current | 5 A |
| Rated primary current range | 20 A to 400 A |
| Continuous thermal rating | 120% of rated primary current |
| Accuracy classes | Metering: 0.2, 0.5; Protection: 10P10 |
| Rated burden | 10 VA, 15 VA, 20 VA per core |
| Burden power factor | cosφ = 0.8 (lagging) |
| Short-circuit withstand (Ith / Idyn) | 1.8–30 kA (1 s) / 3.0–50 kA (peak) |
| Thermal stability factor | 187.5 |
| Insulation medium | Mineral insulating oil |
| Applicable standards | IEC 61869-1/2; GB/T 20840.1/20840.2 |
Model Designation
- L: Current transformer (CT)
- B: Protective configuration (supports both metering and protection functions)
- 10: Voltage class (10 kV)
- W: Outdoor service design (weather-resistant construction)
Construction
The LB-10W features a robust steel-tank oil-immersed design suitable for indoor and outdoor service. Insulation is provided by high-grade mineral insulating oil, processed via vacuum filtration and vacuum oil-filling to eliminate moisture and air bubbles, ensuring high dielectric integrity and thermal stability. The magnetic core is toroidal (ring-type), enabling accurate current transformation with minimal phase error.
The sealed steel tank includes an oil filling valve, weather-protective cap, pressure relief vent, and an internal diaphragm system that isolates the oil from ambient air to reduce oxidation and extend service life. Natural oil circulation provides effective cooling, supported by a thermal stability factor of 187.5. External surfaces are corrosion-resistant, and the terminal chamber is fully sealed for reliable outdoor operation in harsh conditions.
Technical Parameters
Service Conditions
-
- Installation environment: Indoor installation or outdoor installation (pole-mounted, wall-mounted, or outdoor switchgear)
- Altitude: Standard rating up to 2000 m above sea level; extended altitude capability up to 4000 m with appropriate derating and engineering confirmation
- Ambient temperature: −25 °C to +40 °C
- Relative humidity: Maximum 95% (no condensation)
- Pollution level: Class II per IEC 60815 (medium pollution)
- Environmental conditions: Free from corrosive gases or vapors; free from explosive or flammable media; no severe vibration or mechanical shock that exceeds specified limits
- Weather resistance: Designed to withstand rain, snow, ice, UV radiation, and temperature cycling in outdoor installations
Technical Parameters
The LB-10W is an outdoor oil-immersed current transformer for 10 kV class AC systems (50 Hz), featuring a rated primary current range of 20–400 A, standard ambient temperature operation from −25 °C to +40 °C, and compliance with IEC standards for medium-voltage applications. It supports altitudes up to 2000 m (with options up to 4000 m) and offers dual-core configurations with combined metering and protection accuracy classes.
Current Transformer Data
Installation & Wiring
Outline Dimensions
The outline dimensions and mounting details for the LB-10W Outdoor Oil-Immersed Current Transformer are shown in the drawing above. Actual dimensions may vary depending on the current rating and specific configuration ordered.
Selection & FAQs
Selection Guide
- Confirm the 10kV system class, 50Hz frequency, insulation coordination, and outdoor site conditions.
- Select a 20A–400A primary ratio from the feeder load, overload profile, and protection settings.
- Specify class 0.2 or 0.5 for metering and 10P10 for protection, with the required VA for each core.
- Check the selected ratio’s Ith and Idyn ratings against the switchgear fault duty.
- Verify altitude, pollution level, certified dimensions, terminal allocation, grounding, and oil-maintenance access.
Frequently Asked Questions
Q1: Can the LB-10W be pole-mounted in high-altitude areas?
Yes, it supports pole-mounted outdoor installations. Standard altitude is up to 2000m, but 4000m is possible with derating. Contact us for high-altitude engineering confirmation.
Q2: What accuracy classes are available for the dual-core configuration?
The LB-10W offers combined metering and protection accuracy classes. Specific class combinations depend on your 20-400A primary current requirements. Submit your single-line diagram for factory selection.
Q3: Which pollution level does this outdoor current transformer withstand?
It is designed for Class II medium pollution environments per IEC 60815. The oil-immersed housing effectively resists rain, snow, ice, and UV radiation. This ensures long-term reliability in medium pollution zones.
Q4: Are routine factory tests performed before shipment?
Yes, standard routine tests include ratio, polarity, and insulation resistance checks per IEC standards. Extended type tests are subject to confirmation. Please specify any special testing requirements in your inquiry.
Q5: How long is the lead time for customized ratios?
Standard models ship quickly, but customized 20-400A ratios require additional manufacturing time. Exact delivery schedules are subject to order quantity and factory capacity. Contact our sales team for current lead times.
Q6: When should this 10kV current transformer be specified?
It is specified for 10kV AC outdoor switchgear and pole-mounted distribution networks. The 50Hz oil-immersed design ensures reliable current measurement and protection. It is fully compliant with international IEC standards for medium-voltage applications.