Overview
The JDJ series oil-immersed voltage transformers (JDJ-3, JDJ-6, JDJ-10, and JDJ-12) are precision electromagnetic devices engineered for accurate voltage measurement, energy metering, and relay protection in indoor 3â12 kV AC power systems. By leveraging electromagnetic induction, these transformers deliver galvanically isolated secondary signals proportional to the primary voltage, enabling safe interfacing with standardized instrumentation at 100 V or 110 V levels.
Built with a laminated silicon steel core and concentric windings immersed in high-grade insulating oil, the JDJ series ensures stable performance, excellent dielectric strength, and efficient thermal management under continuous operation in medium-voltage switchgear environments.
Key Ratings Snapshot
| Parameter | Value |
|---|---|
| System voltage class | 3 kV, 6 kV, 10 kV, or 12 kV (indoor) |
| Rated frequency | 50 Hz (60 Hz on request) |
| Rated primary voltage | 3/â3, 6/â3, 10/â3, or 12/â3 kV (line-to-ground) |
| Rated secondary voltage | 100 V (JDJ-3/6/10); 110 V (JDJ-12) |
| Accuracy classes | Metering: 0.2, 0.5; Protection: 3P (as specified) |
| Rated burden | Per winding, as ordered (VA) |
| Burden power factor | cos phi = 0.8 (lagging) |
| Insulation type | Oil-immersed with laminated core |
| Installation | Indoor only |
| Ambient temperature | -5 deg C to +40 deg C |
Model Designation
- J: Voltage transformer (VT)
- D: Single-phase
- J: Oil-immersed insulation
- 3 / 6 / 10 / 12: Voltage class in kV
Construction
The JDJ series features a post-type structure designed for secure mounting in indoor switchgear. Its core is constructed from high-permeability laminated silicon steel, with primary and secondary windings concentrically wound on a common limb to minimize leakage flux and ensure accuracy. The entire assembly is sealed within an oil-filled tank, with insulating oil providing both dielectric strength and thermal stability. Porcelain bushings bring out high- and low-voltage terminals, maintaining safe clearance and ease of connection.
The oil level is maintained 10â15 mm below the tank cover, and the sealed design prevents moisture ingress and contamination. This robust construction supports long-term reliability in standard indoor environments while meeting stringent IEC and GB standards for instrument transformers.
Technical Parameters
Service Conditions
- Installation environment: Indoor installation only
- Altitude: <= 1000 m above sea level
- Ambient temperature: -5 deg C to +40 deg C
- Relative humidity: <= 85% at +20 deg C
- Seismic withstand: 0.4g direct vibration test
- Environmental conditions: Free from corrosive gases, explosive media, severe vibration, or mechanical shock
Technical Data
| Type | Rated Voltage Ratio (V) |
Corresponding (VA) | Limit Output (VA) |
Power Frequency Withstand (kV) |
Weight (kg) |
|||
|---|---|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 1 | 3 | |||||
| JDJ-3 | 3000/100 | 20 | 30 | 50 | 120 | 240 | 24 | 46.5 |
| JDJ-6 | 6000/100 | 30 | 50 | 80 | 200 | 400 | 32 | 46.5 |
| JDJ-10 | 10000/100 | 40 | 80 | 150 | 320 | 640 | 42 | 46.5 |
| JDJ-12 | 11000/110 | 40 | 80 | 150 | 320 | 640 | 42 | 46.5 |
Installation & Wiring
Installation Diagram
Connection diagrams illustrate standard wiring configurations for metering and protection applications. Primary terminals (A/X) connect to the medium-voltage bus, while secondary terminals (a/x for metering, ad/xd for protection) interface with instrumentation. Correct polarity must be observed to ensure system accuracy and safety.
Outline Dimensions
| Dimension | Value (mm) |
|---|---|
| Total height | 520 |
| Base width | 220 |
| Mounting hole spacing | 180 x 180 |
| Primary bushing height | 280 |
| Secondary terminal box size | 120 x 80 x 60 |
| phi Mounting holes | 12 |
Selection & FAQs
Selection Guide
- Determine system voltage class (3 kV, 6 kV, 10 kV, or 12 kV) and select the corresponding JDJ model.
- Specify required secondary voltage (typically 100 V or 110 V) based on connected metering/protection equipment.
- Define accuracy class needs: e.g., 0.2/0.5 for revenue metering, 3P for protection relaying.
- Calculate total burden (VA) per winding, including meter/relay consumption and wiring losses.
- Confirm voltage factor requirements (e.g., 1.2 Un continuous, 1.9 Un for 30 seconds) per system overvoltage profile.
Frequently Asked Questions
Q1: Can this oil-immersed voltage transformer be installed outdoors?
No, it is strictly designed for indoor installation only. Ensure the environment is free from corrosive gases. Contact us for outdoor alternatives.
Q2: Which accuracy class output is required for protection relays?
Select the 3 class for protection applications. The JDJ-10 model provides up to 320 VA at this accuracy class. Confirm specific burden requirements with our engineering team.
Q3: What is the rated voltage ratio for the JDJ-12 model?
The JDJ-12 model features a rated voltage ratio of 11000/110 V. It offers a power frequency withstand of 42 kV. Verify system compatibility before ordering.
Q4: Can these transformers operate at altitudes above 1000 meters?
Standard models are rated for altitudes up to 1000 m. For higher elevations, custom design is subject to factory confirmation.
Q5: Are routine factory test reports provided with shipment?
Test reports are subject to confirmation based on order requirements. Contact our sales team for detailed testing protocols.
Q6: Where are JDJ series oil-immersed voltage transformers typically applied?
They are applied in indoor AC systems for voltage measurement and protection. Available in 3kV, 6kV, 10kV, and 12kV configurations.
Q7: How much does the 10kV JDJ-10 voltage transformer weigh?
The JDJ-10 model weighs 46.5 kg, matching the entire series. Check structural load limits during panel design.