Overview
The JLS-20KV is an outdoor oil-immersed combined instrument transformer rated for 20 kV (also suitable for 22 kV) AC power systems. It integrates two single-phase voltage transformers in a V/V connection and two current transformers in A-phase and C-phase, all housed in a fully-insulated, oil-immersed enclosure for reliable outdoor operation.
Designed for revenue-grade metering, it offers CT accuracy classes of 0.2, 0.2S, or 0.5 and VT accuracy classes of 0.2 or 0.5. It complies with GB/T 20840 and GB 17201 standards and is suited for outdoor substations, rural electrification, industrial facilities, and urban distribution networks requiring precise three-phase energy measurement.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| 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/√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 |
| Moisture protection | Integrated anti-moisture device on tank cover |
| Installation environment | Outdoor substation and distribution applications |
| Applicable standards | GB 17201-2006, GB/T 20840.1-2010, GB/T 20840.2-2014, GB/T 20840.3-2013 |
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, also applicable to 22 kV systems)
- KV: Voltage unit designation
Construction
The JLS-20KV features an outdoor oil-immersed combined design with a sealed square oil tank that includes a lifting ring on the top cover. Both the voltage and current transformer components are immersed in insulating transformer oil, ensuring stable dielectric performance and effective thermal management. The unit incorporates two single-phase fully-insulated voltage transformers wired in V/V configuration and two electromagnetic current transformers connected in series on A-phase and C-phase. An anti-moisture device with a breathing mechanism is mounted on the tank cover to prevent moisture ingress, significantly enhancing reliability in harsh outdoor conditions. Additional features include an oil level indicator, grounding terminal, oil drain valve, and fixed mounting on a pole plate within the tank assembly.
Technical Parameters
Service Conditions
- Installation environment: Outdoor installation in substations and distribution facilities
- Altitude: ≤ 2000 m above sea level (higher altitude shall be specified for engineering confirmation)
- Ambient temperature: −40 °C to +40 °C
- Relative humidity: Monthly average ≤ 90%
- System frequency: 50 Hz / 60 Hz AC systems
- Environmental conditions: Free from corrosive gases, flammable media, and severe pollution; no excessive vibration or mechanical shock
- Lightning protection: Zinc oxide surge arrester required within 1 meter of installation for lightning protection
Technical Parameters
The JLS-20KV is an outdoor oil-immersed combined instrument transformer designed for 20 kV / 22 kV class AC systems operating at 50 Hz or 60 Hz. It features oil insulation, a service temperature range of −40 °C to +40 °C, and is rated for altitudes up to 2000 m. The unit complies with applicable IEC and national standards and supports primary current ratings from 50 A to 1200 A.
Model Variants
| Type (Ratio) |
Rated Voltage (kV) |
Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Class (Protection/ Measurement) |
Burden (VA) |
|---|---|---|---|---|---|
| JLS-20KV | 20 / √3 | 50–1200 | 5 | 0.5 / 3P | 10 / 15 |
Voltage Transformer Data
| Type (Ratio) |
Rated Voltage (kV) |
Rated Secondary Voltage (V) |
Rated Output (VA) |
Accuracy Class (Protection/ Measurement) |
Burden (VA) |
|---|---|---|---|---|---|
| Single-phase VT | 20 / √3 | 100 / √3 | 50 | 0.5 | 10 |
Current Transformer Data
| Type (Ratio) |
Rated Primary Current (A) |
Rated Secondary Current (A) |
Accuracy Class (Protection/ Measurement) |
Burden (VA) |
Short-Time Thermal Current |
Dynamic Current |
|---|---|---|---|---|---|---|
| CT winding | 50–1200 | 5 | 3P / 0.5 | 15 | 20 kA / 1 s | 50 kA |
Selection Table
| Current Range |
Rated Current Ratio (A) |
Rated Insulation Level (kV) |
Moisture Protection |
|---|---|---|---|
| 50–1200 A | 50/5 – 1200/5 | 24 | With anti-moisture device |
Installation & Wiring
Outline Dimensions
The outline dimensions and mounting hole positions for the JLS-20KV outdoor oil-immersed combined instrument transformer are shown in the drawing above. Refer to this diagram for accurate spatial planning, support structure design, and alignment of fixing brackets during installation.
Selection & FAQs
Selection Guide
- Select system voltage class (20 kV or 22 kV) based on local grid standards and project specifications.
- Define VT and CT transformation ratios according to metering requirements, including primary and secondary voltages/currents.
- Specify accuracy classes for both VT (e.g., 0.2, 0.5) and CT (e.g., 0.2, 0.2S, 0.5) as required by the application.
- Confirm rated secondary current (1 A or 5 A) and burden values (in VA) for each winding/core to match connected metering devices.
- Provide environmental conditions such as altitude, temperature range, and pollution severity to ensure proper insulation level selection.
- Include any customization needs—such as tank dimensions, terminal layout, oil specs, or documentation language—at the ordering stage.
Frequently Asked Questions
Q1: What are the altitude and temperature limits for outdoor installation?
The JLS-20KV operates at altitudes up to 2000 m and temperatures from −40 °C to +40 °C. Higher altitudes require specific engineering confirmation.
Q2: How should lightning protection be configured for this combined transformer?
A zinc oxide surge arrester is required. It must be installed within 1 meter of the unit to ensure proper lightning protection. Contact us for recommended arrester pairing details.
Q3: Which primary current ratings are available for the 20 kV combined transformer?
Primary currents range from 50 A to 1200 A for 20 kV and 22 kV class systems. Custom ratios are available subject to factory confirmation.
Q4: Are the JLS-20KV transformers compliant with international IEC standards?
Yes, they are fully compliant. The design meets applicable IEC and national standards for 50 Hz and 60 Hz AC systems. Provide your specific regional certification requirements for verification.
Q5: Can the secondary burden and accuracy class be customized for projects?
Customization is supported. You can select specific accuracy classes for protection or measurement, along with defined VA burdens. Send your technical specifications to our team for configuration.
Q6: Where should the zinc oxide surge arrester be installed?
It must be placed within 1 meter of the transformer. This proximity protects the 20 kV oil-immersed unit from voltage spikes. Verify arrester specifications during the procurement phase.
Q7: Why must the installation environment be free from corrosive gases?
This is required to maintain oil insulation integrity. The environment must lack corrosive gases and severe pollution to prevent equipment degradation. Ensure site conditions meet these parameters before ordering.