Overview
The LJW-10, LJWD-12, and LJW-13.8kV are oil-immersed, steel-enclosed outdoor current transformers designed for 10kV to 13.8kV power systems operating at 50Hz. These units utilize 25# transformer oil as the primary insulation medium within an elliptical oil tank, ensuring reliable dielectric performance and thermal stability in outdoor environments.
Offering high accuracy classes including 0.2S, 0.5S, and protection ratings such as 5P10 and 10P20, these transformers support precise current measurement, energy metering, feeder monitoring, and relay protection applications. They comply with relevant IEC and GB standards for outdoor switchgear installations, delivering dependable operation under typical environmental conditions.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| Voltage class | 10kV / 12kV / 13.8kV |
| Rated frequency | 50Hz |
| Secondary current | 1A or 5A |
| Insulation medium | 25# transformer oil |
| Metering accuracy classes | 0.2S, 0.5S, 0.2, 0.5, 1.0 |
| Protection accuracy classes | 5P10, 10P20 |
| Installation type | Outdoor |
| Ambient temperature range | -25°C to +40°C |
| Maximum altitude | ≤4000m |
| Humidity limit | ≤85% |
Model Designation
- L: Current transformer (CT)
- J: Oil-immersed type
- W: Outdoor installation
- D: With protective winding (in LJWD models)
- 10 / 12 / 13.8: Rated system voltage in kV
Construction
The transformer features a robust steel enclosure housing an elliptical oil tank filled with 25# transformer oil for insulation and cooling. Ring-type magnetic cores are used, each equipped with multiple secondary windings to support separate metering and protection functions. Primary terminals are clearly marked P1 and P2, while secondary terminals are labeled S1 and S2. The design ensures mechanical strength and weather resistance suitable for long-term outdoor service. Secondary circuits must never be opened during operation to prevent hazardous overvoltages.
Technical Parameters
Service Conditions
- Ambient Temperature Range: -40°C to +40°C
- Altitude: Up to 1000 m above sea level
- Relative Humidity: Up to 100% at 25°C
- Installation Environment: Outdoor, steel-enclosed, oil-immersed
- Pollution Degree: Heavy industrial and coastal areas
- Seismic Activity: Withstand seismic intensity up to 8 degrees (Modified Mercalli Scale)
Technical Parameters
The LJW-10 and LJWD-12 series are 13.8kV oil-immersed, steel-enclosed outdoor current transformers designed for operation in ambient temperatures from -40°C to +40°C and altitudes up to 1000 m. They comply with IEC 61869 standards and support primary current ratings ranging from 10 A to 3000 A.
| Rated Primary Current (A) |
Accuracy Classes |
Rated Output (VA) | Short-Time Thermal Current (kA/1s) |
Rated Dynamic Current (kA) |
|||
|---|---|---|---|---|---|---|---|
| 0.2S | 0.2 | 0.5 | 10P | ||||
| 5–400 | 0.2/10P 0.2S/10P 0.5/10P |
10 | 10 | 15 | 15 | 60 I1n | 150 I1n |
| 600 | 50 I1n | 120 I1n | |||||
| 10–20 20–40 | 0.5 0.2 0.2S 0.5/10P 0.2/10P 0.2S/10P |
10 | 15 | 20 | – | 64 I1n | 160 I1n |
| 25–50 30–60 | |||||||
| 50–100 75–150 | 5 | 10 | 15 | 15 | |||
| 100–200 150–300 | |||||||
Installation & Wiring
Installation Diagram
Wiring Diagram
The LJW-10 and LJWD-12 current transformers are designed for outdoor, pole-mounted or substation installation. Mounting is achieved using the provided steel brackets and hardware, ensuring secure attachment to a vertical support structure. Primary conductors pass through the central aperture, while secondary wiring is connected via the terminal box located at the base of the unit. Ensure all connections comply with local electrical codes and manufacturer torque specifications.
Selection & FAQs
Selection Guide
- Confirm the required 10kV, 12kV, or 13.8kV model, system frequency, insulation level, and outdoor service conditions.
- Select the primary ratio from the load and fault study, then choose a 1A or 5A secondary and any required dual-ratio arrangement.
- Specify metering and protection accuracy, rated output, and terminal allocation for each secondary winding.
- Verify Ith and Idyn against the prospective short-circuit level and protection clearing time.
- Confirm mounting brackets, terminal polarity, grounding, oil handling, secondary sealing, and any high-altitude or coastal requirements.
Frequently Asked Questions
Q1: Are these outdoor current transformers suitable for heavy pollution environments?
Yes, they are designed for heavy industrial and coastal pollution areas. The steel-enclosed, oil-immersed construction ensures reliable outdoor operation. Contact us for specific pollution degree requirements.
Q2: What is the short-time thermal current rating for 400A primary?
The rated short-time thermal current is 60 times the primary rated current for 1 second. For a 400A primary, this equals 24 kA. Confirm exact dynamic current needs with our engineering team.
Q3: Which accuracy class should I select for protective relaying?
Select the 10P accuracy class for protection and relaying applications. It provides a rated output of 15 VA. Please specify your exact burden requirements during ordering.
Q4: Can the primary current rating be customized above 600A?
Yes, the series supports primary current ratings ranging from 10 A up to 3000 A. Custom ratios are available subject to factory confirmation. Provide your exact primary and secondary current needs.
Q5: Does this 13.8kV current transformer comply with IEC 61869?
Yes, both LJW-10 and LJWD-12 models fully comply with IEC 61869 standards. Standard factory test reports are provided with shipment. Request specific certification documents from your sales representative.
Q6: How high above sea level can this CT operate?
The maximum rated altitude is 1000 m above sea level. For installations exceeding this altitude, derating factors apply. Contact our technical team for high-altitude project evaluations.
Q7: Why choose an oil-immersed steel-enclosed design for outdoor substations?
This design offers superior mechanical strength and weather resistance for harsh outdoor conditions. It withstands seismic intensity up to 8 degrees. Discuss your specific substation environmental needs with us.