Overview
The JLSW3-35kV is a three-phase outdoor combined instrument transformer rated for 35 kV AC systems, featuring an oil-immersed insulation system. It integrates three single-phase voltage transformers (VTs) in Y/Y connection and three electromagnetic current transformers (CTs), all housed within a sealed, oil-filled tank for reliable outdoor operation.
Designed for high-accuracy metering, it meets accuracy classes 0.2 and 0.2S per GB standards and supports applications including rural substations, box-type substations, industrial distribution, and utility revenue metering. The unit complies with GB 20840.1–20840.4 series standards and requires a zinc oxide arrester within 1 m for lightning protection.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System voltage class | 35 kV |
| Rated frequency | 50 Hz / 60 Hz |
| Configuration | 3 × VT (Y/Y) + 3 × CT (A, B, C) |
| VT connection | Y/Y with grounded neutral |
| CT type | Electromagnetic, one per phase |
| Accuracy classes | 0.2 / 0.2S |
| Insulation type | Oil-immersed |
| Installation environment | Outdoor |
| Secondary VT output | 100 V or 100/√3 V |
| Secondary CT output | 1 A or 5 A |
| Applicable standards | GB 20840.1–20840.4 |
| Lightning protection | ZnO arrester required within 1 m |
Model Designation
- J: Combined instrument transformer (metering box)
- L: Current transformer element
- S: Voltage transformer element (three-phase)
- W: Outdoor installation
- 3: Three-phase configuration
- 35: Voltage class (kV)
Construction
The JLSW3-35kV features an integrated rectangular welded steel tank filled with insulating oil, housing three single-phase electromagnetic voltage transformers and three ring-type electromagnetic current transformers mounted on fixed terminal plates. The oil-immersed design ensures robust electrical insulation, effective heat dissipation, and environmental protection for long-term outdoor service.
The tank cover incorporates an integrated moisture-proof device to prevent humidity ingress, significantly enhancing reliability in humid conditions compared to conventional designs. External fittings include an oil level gauge, grounding bolt, oil drain valve, and two lifting lugs for safe handling and installation. All components are engineered to meet stringent performance and safety requirements under GB 20840 series standards.
Technical Parameters
Service Conditions
- Installation environment: Outdoor installation
- Altitude: Not exceeding 1000 m above sea level (higher altitude installations require engineering confirmation and rating adjustment)
- Ambient temperature: −25 °C to +40 °C (extended range available upon specification)
- Relative humidity: Daily average ≤ 95%, monthly average ≤ 90% (at +20 °C reference)
- Pollution level: Per IEC 60815 / GB/T 26218 as specified by project requirements
- Environmental conditions: Free from corrosive gases or vapors; free from explosive or flammable media; no severe vibration, mechanical shock, or salt spray (coastal installations require additional protection)
- Seismic requirements: Per applicable regional seismic design standards where specified
Technical Parameters
The JLSW3-35kV is an outdoor oil-immersed combined instrument transformer rated for 35 kV class AC systems (50 Hz / 60 Hz). It features standard compliance with GB 20840, operates within an ambient temperature range of −25 °C to +40 °C, and is suitable for altitudes up to 1000 m. The current transformer section supports primary currents from 50 A to 600 A with standard 5 A secondary output.
Voltage Transformer Data
| Primary Voltage (V) |
Secondary Voltage (V) |
Accuracy Class |
Burden (VA) |
Burden Power Factor |
|---|---|---|---|---|
| 35000/√3 | 100/√3 | 0.2 | 50 | cosφ = 0.8 (lagging) |
| 35000/√3 | 100/√3 | 0.2S | 50 | cosφ = 1.0 |
| 35000 | 100 | 0.2 | 50 | cosφ = 0.8 (lagging) |
| 35000 | 100 | 0.2S | 50 | cosφ = 1.0 |
Current Transformer Data
| Primary Current A |
Secondary Current A |
Accuracy Class |
Burden (VA) |
Burden Power Factor |
|---|---|---|---|---|
| 50 | 5 | 0.2 | 10 | cosφ = 0.8 |
| 75 | 5 | 0.2 | 10 | cosφ = 0.8 |
| 100 | 5 | 0.2 | 10 | cosφ = 0.8 |
| 150 | 5 | 0.2 | 15 | cosφ = 0.8 |
| 200 | 5 | 0.2 | 15 | cosφ = 0.8 |
| 300 | 5 | 0.2 | 15 | cosφ = 0.8 |
| 400 | 5 | 0.2 | 20 | cosφ = 0.8 |
| 600 | 5 | 0.2 | 20 | cosφ = 0.8 |
Installation & Wiring
Installation Diagram
The JLSW3-35kV outdoor oil-immersed combined instrument transformer is installed on a stable foundation or supporting structure using the designated mounting points shown in the dimensional drawing. Primary connections for the VT section are made via high-voltage bushing terminals, while the CT section uses through-type busbar or bolted terminals. Adequate clearance must be maintained around the unit to ensure proper insulation coordination, heat dissipation, oil level inspection, and maintenance access.
Selection & FAQs
Selection Guide
- Confirm the 35kV system, 50Hz or 60Hz frequency, Y/Y connection, grounding, and utility metering scheme.
- Specify the VT ratio and 100V or 100/√3V secondary, then select the 50A–600A CT ratio and 1A or 5A output.
- Define class 0.2 or 0.2S and calculate the burden of each voltage and current secondary circuit.
- Confirm insulation, pollution, altitude, lightning, seismic, and outdoor environmental requirements.
- Verify foundation, clearances, terminal arrangement, oil access, grounding, lifting provisions, and ZnO arrester location.
Frequently Asked Questions
Q1: Can this 35kV outdoor combined transformer be installed above 1000m altitude?
Standard models are rated for altitudes up to 1000m. For higher elevations, rating adjustments and engineering confirmation are required. Contact us for high-altitude specifications.
Q2: What primary current ranges are available for the current transformer section?
The CT section supports primary currents from 50 A to 600 A. Standard secondary output is fixed at 5 A. Specify your exact ratio requirements during inquiry.
Q3: Are there specific environmental restrictions for installing this oil-immersed transformer?
Standard models require environments free from corrosive gases and severe vibration. Coastal sites need additional salt spray protection. Confirm specific site conditions with our engineering team.
Q4: How can the ambient temperature range be adapted for extreme climates?
Standard models operate between −25 °C and +40 °C. Extended temperature ranges are available upon specific request. Provide your exact site temperature parameters for factory evaluation.
Q5: Which international standards does this 35kV combined instrument transformer comply with?
The JLSW3-35kV complies with GB 20840 standards, with pollution levels following IEC 60815. Frequency options include 50 Hz and 60 Hz. Request the full type test report for verification.
Q6: Why choose a combined transformer for 35kV outdoor applications?
It is designed for outdoor metering and protection in 35kV AC systems. The unit combines voltage and current transformation to reduce footprint. Contact sales for application drawings.
Q7: What defines a three-phase oil-immersed combined instrument transformer?
This category integrates voltage and current transformers within a single oil-filled tank. It significantly reduces substation footprint and simplifies wiring. Confirm design compatibility with your switchgear layout.
Q8: How is the voltage transformer accuracy class selected for this model?
Accuracy classes depend on your specific metering or protection requirements. Standard classes are available per GB 20840. Share your secondary burden and accuracy needs for precise selection.