Product Overview
The JDZX11-15/20 Voltage Transformer is a fully enclosed, epoxy resin cast, dry-type voltage transformer with a residual voltage winding, designed for indoor 15 kV and 20 kV AC power systems with a maximum system voltage of 24 kV.
Featuring an integrated high-creepage and pollution-resistant insulation design, the transformer provides voltage measurement, energy metering, relay protection, and insulation monitoring functions. It is suitable for medium-voltage switchgear, box-type substations, switching stations, and other indoor power distribution equipment.
The product is widely used in 15 kV and 20 kV distribution systems in industrial and mining enterprises, commercial buildings, and industrial parks. It is particularly suitable for insulation monitoring in systems with non-effectively earthed neutrals.
Product Features
Insulation and Electrical Performance
- Designed for 15 kV and 20 kV systems:
The transformer is designed for medium-voltage systems with a maximum operating voltage of 24 kV. It can withstand the specified power-frequency and lightning impulse withstand voltage tests required for 15 kV and 20 kV distribution systems. - Fully enclosed epoxy resin cast insulation:
The transformer is integrally formed using an epoxy resin vacuum-casting process. The solid insulation body contains no internal air gaps and provides excellent dielectric performance. - Low partial discharge:
Partial discharge is limited to no more than 10 pC, helping reduce insulation ageing and improve long-term operational reliability. - Oil-free dry-type construction:
The product contains no insulating oil, eliminating the risks of oil leakage, oil contamination, and oil-related fire hazards. It is suitable for modern indoor oil-free distribution systems. - High pollution-flashover resistance:
The multi-shed insulation structure significantly increases the creepage distance and improves resistance to surface flashover in humid or polluted environments. - Multifunctional winding configuration:
The built-in residual voltage winding provides a 100/3 V output for earth-fault detection and insulation monitoring. It is suitable for three-phase, five-limb voltage transformer connection arrangements. - Multiple voltage ratios and accuracy classes:
Standard voltage ratios such as 15/0.1/0.1/3 kV and 20/0.1/0.1/3 kV are available. Metering accuracy classes up to Class 0.2 can be supplied, while protection accuracy classes such as 3P and 6P can be customized.
Structural and Installation Features
- Fully enclosed dry-type structure:
The windings and live components are completely enclosed within the epoxy resin cast body. The product provides an IP20 protection rating and contains no insulating oil. - Compact construction:
The compact structure occupies limited installation space and is compatible with standard 15 kV and 20 kV switchgear mounting dimensions. - Clearly identified secondary terminals:
The secondary terminals are protected by a terminal cover and clearly marked for convenient wiring. Metering, protection, and residual-voltage circuits can be connected separately according to the switchgear secondary wiring design. - Secure bolt mounting:
The metal base is provided with mounting holes for horizontal bolt installation inside indoor switchgear. The structure provides reliable mechanical stability and vibration resistance.
Operation and Maintenance Features
- Low-maintenance operation:
The dry-type, oil-free design eliminates leakage and oil-related fire risks. The epoxy resin cast body provides high mechanical strength, impact resistance, and ageing resistance, helping reduce routine maintenance requirements. - Wide operating temperature range:
The transformer can operate at ambient temperatures from -30°C to +70°C. The epoxy resin maintains stable insulation and mechanical properties under both high- and low-temperature conditions. - High-reliability construction:
The magnetic core is made from high-quality laminated silicon steel sheets, while the windings are wound with enamelled copper wire. - Low operating losses:
The optimized magnetic core and winding design provide low power losses, limited temperature rise, and stable measurement accuracy. - Overvoltage withstand capability:
The transformer can withstand switching and lightning overvoltages within its specified insulation level, ensuring reliable metering, protection, and insulation-monitoring signals.
Technical Specifications
Electrical Parameters
| Parameter | Specification |
|---|---|
| Applicable System Voltage | 15 kV / 20 kV AC, Um = 24 kV |
| Rated Frequency | 50 Hz |
| Rated Primary Voltage | 15 kV / 20 kV |
| Rated Secondary Voltage | 100 V for metering and protection; 100/3 V for residual voltage and insulation monitoring |
| Metering Accuracy Class | Class 0.2 / 0.5 / 1 |
| Protection Accuracy Class | 3P / 6P |
| Power-Frequency Withstand Voltage | 50 kV for 1 minute at the high-voltage terminal, without breakdown |
| Lightning Impulse Withstand Voltage | 95 kV peak, without breakdown |
| Partial Discharge | ≤10 pC |
| Insulation Resistance | ≥1,000 MΩ between high voltage, low voltage, and earth |
Structural and Material Parameters
| Parameter | Specification |
|---|---|
| Insulating Medium | Fully cast epoxy resin |
| Protection Rating | IP20 |
| Installation Type | Indoor post-type bolt mounting |
| Thermal Class | Class B, 130°C |
Environmental Parameters
| Parameter | Specification |
|---|---|
| Installation Altitude | ≤2,000 m; high-altitude versions available |
| Operating Temperature | -30°C to +70°C |
| Storage Temperature | -40°C to +85°C |
| Relative Humidity | ≤95%, non-condensing |
Applicable Standards
| Standard | Description |
|---|---|
| GB 1207 | Voltage Transformers |
| GB/T 20840 Series | Instrument Transformers |
Applications
Applicable Voltage Level
The JDZX11-15/20 Voltage Transformer is suitable for indoor 15 kV and 20 kV AC power systems with a maximum system voltage of 24 kV.
Typical Applications
- Voltage measurement, energy metering, and relay protection in indoor medium-voltage switchgear
- Voltage monitoring in box-type substations
- 15 kV and 20 kV distribution systems in switching stations
- Power distribution systems in industrial and mining enterprises
- Commercial buildings and industrial parks
- Insulation monitoring in systems with non-effectively earthed neutrals
- Three-phase, five-limb voltage transformer connection arrangements
- Indoor distribution environments requiring enhanced resistance to humidity and pollution flashover
Main Functions
The voltage transformer converts the system high voltage into a standardized secondary voltage, typically 100 V, at a specified ratio.
It supplies voltage signals to:
- Energy meters
- Measuring instruments
- Relay protection devices
- Monitoring equipment
- Control systems
- Insulation monitoring devices
The transformer also provides electrical isolation between the primary and secondary systems, helping protect connected equipment and operating personnel.
The residual voltage winding provides a signal for earth-fault detection and insulation monitoring, supporting the safe operation of non-effectively earthed medium-voltage systems.
Operating Conditions
Normal Operating Conditions
- Installation altitude: no more than 2,000 m
- Ambient temperature: -30°C to +70°C
- Severe or sudden temperature changes should be avoided
- Relative humidity: no more than 95%, non-condensing
- The environment should be free from corrosive gases
- Flammable or explosive substances are not permitted
- Severe vibration and mechanical impact should be avoided
- Significant dust and salt-spray contamination should be avoided
- Indoor post-type installation
- Direct sunlight, rain, and condensation should be avoided
Special Operating Conditions
Customized products are required for:
- Installation altitudes above 2,000 m
- Ambient temperatures outside the range of -30°C to +70°C
- Severe pollution or salt-spray environments
- Chemically corrosive environments
- Applications involving strong vibration or mechanical impact
- Non-standard voltage ratios
- Special accuracy classes
- Non-standard mounting dimensions
Installation and Maintenance
Installation Requirements
- Pre-installation inspection:
Inspect the voltage transformer and confirm that the cast body is free from cracks, bubbles, mechanical damage, and other visible defects. Check that all terminal markings are clear and that the supplied accessories are complete. Verify that the model, specifications, voltage ratio, and accuracy class match the system design requirements. Confirm that the residual voltage winding parameters meet the requirements of the insulation monitoring system. - Mounting:
Position the voltage transformer at the specified location inside the switchgear and secure it with bolts through the mounting holes in the base. Ensure that the transformer is firmly installed without looseness or displacement. The mounting surface should be level to avoid uneven mechanical stress. - High-voltage-side connection:
Connect the high-voltage terminal according to the system design. Ensure that all connections are secure and provide reliable electrical contact. Maintain adequate electrical clearance between the high-voltage conductor, grounded components, and other live parts to prevent electrical discharge. - Low-voltage-side connection:
Connect the secondary terminals according to their markings. Metering, protection, and residual-voltage circuits must be wired separately and correctly. The secondary circuit must not be short-circuited during operation. One point of the secondary circuit must be reliably earthed according to the system design and applicable electrical safety requirements. - Insulation inspection:
After installation, measure the insulation resistance between:- High voltage and low voltage
- High voltage and earth
- Low voltage and earth
Maintenance Requirements
- Regularly inspect the epoxy resin body for cracks, mechanical damage, discharge marks, and contamination.
- Check the high-voltage terminals for looseness, oxidation, or abnormal heating.
- Inspect the insulating sheds for accumulated dust or contamination.
- Regularly inspect the high-voltage and low-voltage wiring to ensure that all connections remain secure and free from overheating or discoloration.
- Confirm that the secondary-circuit earthing remains reliable.
- Periodically test the insulation resistance and voltage ratio to verify that the metering and protection accuracy remain within the specified limits.
- Check the residual voltage circuit and insulation-monitoring function regularly.
- Clean dust and contamination from the transformer surface and insulating sheds.
- Prevent oil and corrosive substances from contacting the epoxy resin body.
- If cracking, electrical discharge, overheating, excessive voltage-ratio error, or functional failure is detected, immediately de-energize and inspect the equipment. Replace the transformer where necessary.
Precautions
- The secondary winding must not be short-circuited while the transformer is energized. A secondary short circuit may produce excessive current and create a serious risk to equipment and personnel. During maintenance, the transformer must be de-energized, and the secondary circuit must be safely isolated and earthed in accordance with applicable procedures.
- Avoid impact or collision with the epoxy resin body, high-voltage terminals, and insulating sheds during transportation and installation. Mechanical damage may reduce insulation performance and pollution-flashover resistance.
- Use suitable insulated conductors for high-voltage connections. Maintain adequate electrical clearance from grounded components and other live parts to prevent phase-to-phase or phase-to-earth discharge.
- The equipment must be reliably earthed. The grounding terminal on the metal base must be securely connected to the switchgear grounding busbar.
- Store the product in a dry, ventilated, and shaded environment. Avoid direct sunlight, high temperatures, moisture, compression, and mechanical impact.
- Installation, commissioning, and maintenance must be carried out by qualified electrical personnel in accordance with applicable electrical safety procedures.
Standard Supply List
| No. | Item | Function |
|---|---|---|
| 1 | JDZX11-15/20 Voltage Transformer | Main device for voltage transformation, electrical isolation, and insulation monitoring |
| 2 | Mounting Bolts and Washers | Used to secure the voltage transformer during installation |
| 3 | Secondary Terminal Cover | Protects the low-voltage terminals and helps prevent incorrect connection or short circuits |
| 4 | Product Instruction Manual | Provides installation, operating, maintenance, and insulation-monitoring circuit wiring guidance |
| 5 | Product Certificate and Factory Test Report | Provides product quality and performance documentation, including voltage-ratio, accuracy, and residual-voltage circuit test data |
Applicable Standards and Certification
The product complies with the following standards:
- GB 1207, Voltage Transformers
- GB/T 20840.1, Instrument Transformers—Part 1: General Requirements
- GB/T 20840.3, Instrument Transformers—Part 3: Additional Requirements for Inductive Voltage Transformers
The product has passed the applicable type tests, and its performance meets the operating requirements of indoor 15 kV and 20 kV power systems.
