Overview
The JLSW3-35kV is an outdoor oil-immersed combined instrument transformer designed for three-phase AC power systems up to 35 kV. It integrates three single-phase fully-insulated voltage transformers (VT) in Y/Y connection with three electromagnetic current transformers (CT), one per phase, all housed within a single oil-filled tank. This compact assembly delivers simultaneous voltage and current measurement for accurate energy metering in outdoor substations and distribution networks.
Engineered as an optimized upgrade over conventional designs, the JLSW3-35kV features an integrated moisture-proof device in the tank cover to block humidity ingress, enhancing insulation integrity and extending service life. The unit offers higher capacity, reduced weight and footprint, and simplified field installation compared to legacy configurations.
Key Ratings Snapshot
| Parameter | Value |
|---|---|
| System voltage class | 35 kV |
| Rated frequency | 50 Hz / 60 Hz |
| Configuration | 3 x VT (Y/Y) + 3 x CT (A,B,C) |
| VT connection | Y/Y grounded neutral |
| CT type | Electromagnetic, toroidal core |
| Accuracy classes | 0.2 / 0.2S |
| Insulation type | Oil-immersed |
| Installation environment | Outdoor |
| Secondary voltage (VT) | 100 V or 100/√3 V |
| Secondary current (CT) | 1 A or 5 A |
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 a rectangular welded steel oil-filled tank housing three single-phase electromagnetic VTs and three ring-type electromagnetic CTs mounted on fixed terminal plates. The tank includes a moisture-proof cover, oil level gauge, grounding bolt, oil drain valve, and two lifting lugs for safe hoisting during installation. All internal components are fully immersed in insulating oil for superior dielectric performance and thermal stability.
The integrated moisture-proof device actively prevents external humidity from entering the oil system, significantly improving long-term reliability in humid climates compared to standard outdoor transformers. This design ensures consistent insulation strength and minimizes maintenance requirements over the product’s operational life.
Technical Parameters
Service Conditions
- Installation environment: Outdoor installation
- Altitude: Not exceeding 1000 m above sea level
- Ambient temperature: -25 deg C to +40 deg C
- Relative humidity: Daily average <= 95%, monthly average <= 90% (at +20 deg C)
- Pollution level: Per IEC 60815 / GB/T 26218
- Environmental conditions: Free from corrosive gases, explosive media, severe vibration, or salt spray
- Seismic requirements: Per applicable regional standards where specified
Technical Data
| Rated Primary Voltage (V) |
Rated Secondary Voltage (V) |
Accuracy Class |
Rated Burden (VA) |
Burden Power Factor |
|---|---|---|---|---|
| 35000/√3 | 100/√3 | 0.2 | 50 | cos phi = 0.8 (lagging) |
| 35000/√3 | 100/√3 | 0.2S | 50 | cos phi = 1.0 |
| 35000 | 100 | 0.2 | 50 | cos phi = 0.8 (lagging) |
| 35000 | 100 | 0.2S | 50 | cos phi = 1.0 |
| Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Class |
Rated Burden (VA) |
Burden Power Factor |
|---|---|---|---|---|
| 50 | 5 | 0.2 | 10 | cos phi = 0.8 (lagging) |
| 100 | 5 | 0.2 | 10 | cos phi = 0.8 (lagging) |
| 200 | 5 | 0.2 | 15 | cos phi = 0.8 (lagging) |
| 400 | 5 | 0.2 | 20 | cos phi = 0.8 (lagging) |
| 600 | 5 | 0.2 | 20 | cos phi = 0.8 (lagging) |
Installation & Wiring
Installation Diagram
The JLSW3-35kV combined transformer must be securely mounted on a stable foundation using designated mounting points. Primary VT connections are made via high-voltage bushings, while CT primary connections use through-type busbar or bolted terminals. Maintain adequate clearance for insulation, heat dissipation, oil inspection, and maintenance access. A zinc oxide arrester must be installed within 1 meter of the unit per GB 20840.4-2015.
Outline Dimensions
| Dimension | Value (mm) |
|---|---|
| Overall height | 1850 |
| Overall width | 1200 |
| Overall depth | 800 |
| Bushing center spacing (phase-to-phase) | 400 |
| Mounting hole pattern | 800 x 600 |
| Minimum ground clearance | 300 |
Selection & FAQs
Selection Guide
- Select VT ratio based on system voltage: 35000/100 V for line-to-line or 35000/√3/100/√3 V for line-to-neutral measurement.
- Choose CT ratio (e.g., 100/5, 200/5) to cover expected load range while maintaining accuracy at minimum operating current.
- For revenue metering, specify 0.2 or 0.2S accuracy class per GB 17215 and utility requirements.
- Calculate total rated burden as sum of connected instrument VA ratings plus wiring losses based on cable length and cross-section.
- Confirm environmental suitability: altitude >1000 m, coastal, or heavy-pollution sites require enhanced specifications.
- Specify optional features early: integrated energy meters, communication interfaces, or special terminal arrangements.
Frequently Asked Questions
Q1: Can this 35kV combined transformer be installed in coastal areas?
No, the installation environment must be free from salt spray and corrosive gases. For coastal projects, please contact our engineering team for specialized anti-corrosion customization options.
Q2: Which accuracy class is suitable for high-precision revenue metering?
Select the 0.2S accuracy class for high-precision billing applications. It maintains strict accuracy across varying loads with a burden power factor of 1.0. Confirm your exact rated burden requirements during ordering.
Q3: What is the maximum altitude for standard outdoor installation?
Standard installation is limited to altitudes not exceeding 1000 meters above sea level. If your project exceeds this elevation, factory derating calculations and design modifications are required.
Q4: What routine factory tests are performed before shipment?
Standard routine tests include ratio, polarity, and insulation resistance checks per IEC standards. Specific type tests or third-party certifications are subject to confirmation. Contact sales for the detailed test report template.
Q5: Can the primary voltage be customized for non-standard 33kV systems?
Standard models are rated for 35000 or 35000/√3 V primary systems. Custom primary voltage ratios for 33kV networks are available subject to engineering confirmation. Please provide exact system parameters for a tailored quote.
Q6: What applications is this oil-immersed combined transformer designed for?
It is designed for outdoor voltage measurement and protection in 35kV power distribution networks. The oil-immersed design ensures reliable performance in standard ambient temperatures from -25°C to +40°C.
Q7: Are there specific seismic requirements for this outdoor transformer?
Seismic performance complies with applicable regional standards where specified by the client. The installation site must also be free from severe vibration. Provide local seismic zone data for factory validation.