Overview
The JLS-20KV outdoor oil-immersed combined instrument transformer delivers precise, integrated current and voltage transformation for 20 kV/22 kV AC power systems. Designed for revenue-grade metering in outdoor substations, it combines two single-phase fully-insulated voltage transformers (VT) in V/V connection with two current transformers (CT) series-connected in A-phase and C-phaseâall within a compact, weather-resistant enclosure.
This electromagnetic solution ensures galvanically isolated, standardized secondary outputs for accurate active and reactive energy measurement across distribution networks, rural electrification projects, and industrial installations, offering long-term reliability under harsh environmental conditions.
Key Ratings Snapshot
| Parameter | Value |
|---|---|
| System voltage class | 20 kV / 22 kV |
| Rated frequency | 50 Hz / 60 Hz |
| CT secondary current | 1 A or 5 A |
| VT secondary voltage | 100 V / 100/sqrt(3) V (line-to-ground) |
| CT accuracy classes | 0.2, 0.2S, 0.5 |
| VT accuracy classes | 0.2, 0.5 |
| VT configuration | V/V connection (two single-phase units) |
| CT configuration | A-phase and C-phase series connection |
| Insulation type | Oil-immersed, fully insulated |
| Installation environment | Outdoor substation and distribution |
Model Designation
- J: Metering box / Combined transformer assembly
- L: Current transformer (CT) component
- S: Outdoor (Shi Wai) installation type
- 20: Voltage class (20 kV nominal)
- KV: Voltage unit designation
Construction
The JLS-20KV features an oil-immersed, fully enclosed square tank design that ensures superior dielectric strength, thermal stability, and environmental protection. The integrated structure houses both VT and CT components in a single compact unit, minimizing footprint and simplifying outdoor installation. A dedicated anti-moisture device on the tank cover prevents humidity ingress, preserving oil quality and extending service life in demanding outdoor conditions.
Key construction elements include a sealed oil tank with lifting ring, oil level indicator, grounding terminal, oil drain valve, and breathing mechanism. The design complies with stringent insulation coordination requirements, supporting reliable operation across wide temperature ranges and high humidity environments typical of outdoor distribution applications.
Technical Parameters
Service Conditions
- Installation environment: Outdoor substations and distribution facilities
- Altitude: <= 2000 m above sea level
- Ambient temperature: -40 deg C to +40 deg C
- Relative humidity: Monthly average <= 90%
- System frequency: 50 Hz / 60 Hz AC
- Environmental conditions: Free from corrosive gases, flammable media, severe pollution; no excessive vibration or mechanical shock
- Lightning protection: Zinc oxide surge arrester required within 1 meter of installation
Technical Data
| Parameter (Specify per order) |
Options / Notes |
|---|---|
| System voltage class | 20 kV or 22 kV |
| VT transformation ratio | e.g., 20000/100 V, 22000/100 V |
| CT transformation ratio | e.g., 50/5 A, 100/5 A, 150/5 A |
| CT secondary current | 1 A or 5 A |
| VT accuracy class | 0.2, 0.5, or as specified |
| CT accuracy class | 0.2, 0.2S, 0.5, or as specified |
| Rated burden (VT) | VA rating per secondary winding |
| Rated burden (CT) | VA rating per secondary core |
| Short-circuit withstand (CT) | Ith (1 s) and Idyn (peak) as required |
| Customization | Tank dimensions, terminals, markings, documentation language |
Installation & Wiring
Installation Diagram
The JLS-20KV combined transformer must be securely mounted on an outdoor support structure using designated fixing holes. Primary connections are typically made via overhead conductors or busbar terminals. Maintain adequate clearance for insulation, heat dissipation, oil monitoring, and maintenance access. Grounding terminal must connect reliably to the substation grounding grid, and a zinc oxide surge arrester must be installed within 1 meter for lightning protection.
Outline Dimensions
| Dimension | Value (mm) |
|---|---|
| Height (H) | Refer to dimensional drawing |
| Width (W) | Refer to dimensional drawing |
| Depth (D) | Refer to dimensional drawing |
| Mounting hole spacing | As per installation platform |
| Primary terminal height | As per site layout |
Selection & FAQs
Selection Guide
- Confirm system voltage class (20 kV or 22 kV) based on local grid standards.
- Select CT transformation ratio and secondary current (1 A or 5 A) to match meter input requirements.
- Choose VT secondary voltage (100 V or 100/sqrt(3) V) consistent with V/V metering configuration.
- Specify accuracy classes (e.g., 0.2S for high-precision revenue metering) per regulatory or utility mandates.
- Define rated burdens (VA) for both CT and VT to ensure compatibility with connected instruments.
- Include environmental factors (altitude, temperature, pollution) in insulation and sealing specifications.
Frequently Asked Questions
Q1: Can the JLS-20KV transformer operate in extreme cold outdoor environments?
Yes, it operates in ambient temperatures from -40°C to +40°C. Ensure the installation site is free from severe pollution and excessive vibration. Confirm specific cold-climate oil requirements with our engineers.
Q2: Which accuracy class is required for high-precision revenue metering?
Select the 0.2 or 0.2S accuracy class for the current transformer. This ensures precise measurement for billing applications. Specify the exact rated burden in VA during ordering for factory calibration.
Q3: How should lightning protection be installed for this outdoor unit?
A zinc oxide surge arrester is mandatory for lightning protection. It must be installed within 1 meter of the transformer. Verify the arrester’s voltage rating matches the 20kV or 22kV system class.
Q4: What transformation ratios are available for the voltage and current cores?
Standard VT ratios include 20000/100V and 22000/100V, while CT ratios range from 50/5A to 150/5A. Custom ratios and secondary currents (1A or 5A) are available. Contact our sales team with your single-line diagram for exact configuration.
Q5: Are routine factory tests performed before shipping the combined transformers?
Yes, standard routine tests are conducted prior to dispatch to ensure compliance. Specific type tests or third-party certifications depend on your project requirements. Please specify any special testing needs in your initial inquiry.
Q6: Where is the JLS-20KV oil-immersed combined transformer typically applied?
It is designed for outdoor substations and distribution facilities up to 2000m altitude. The unit integrates voltage and current measurement for 20kV and 22kV AC systems. Confirm site altitude and pollution levels before final selection.
Q7: What is the maximum allowable altitude for this equipment?
The standard design supports installation at altitudes up to 2000 meters above sea level. For higher elevations, derating or special design modifications are necessary. Submit your exact site coordinates for engineering evaluation.