Product Overview
The JDZ9-35 Voltage Transformer is a fully enclosed, epoxy resin cast, dry-type voltage transformer designed for indoor 35 kV AC power systems with a maximum system voltage of 40.5 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 widely used in 35 kV indoor medium-voltage switchgear, box-type substations, switching stations, industrial and mining facilities, and industrial park distribution systems.
The product is designed to meet the high reliability requirements of 35 kV power systems for voltage monitoring, electrical protection, and signal acquisition.
Product Features
Insulation and Electrical Performance
- Suitable for 35 kV systems: Specifically designed for 35 kV power systems with a maximum operating voltage of 40.5 kV. It can withstand the specified power-frequency and lightning impulse withstand voltage tests required for 35 kV medium-voltage 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. Partial discharge is limited to no more than 10 pC.
- Oil-free dry-type construction: The product contains no insulating oil, eliminating the risks of oil leakage, contamination, and fire associated with oil-filled equipment.
- High pollution-flashover resistance: The multi-shed insulation structure significantly increases the creepage distance and improves resistance to surface flashover in humid or polluted indoor environments.
- Multiple voltage ratios available: Standard voltage ratios such as 35/0.1 kV and 35/0.1/0.1 kV are available. Metering accuracy classes up to Class 0.2 can be supplied, while protection classes such as 3P and 6P can be customized for metering, protection, and insulation monitoring applications.
Structural and Installation Features
- Fully enclosed dry-type structure: The one-piece cast body contains no exposed live components and provides an IP20 protection rating. Its compact design is suitable for standard 35 kV switchgear installation.
- Clearly marked secondary terminals: The secondary terminals are protected by a transparent cover and clearly identified for convenient wiring. The terminal arrangement helps prevent incorrect connection and short circuits and is compatible with standard switchgear secondary-circuit wiring practices.
- 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.
- Compact cabinet arrangement: The transformer occupies limited installation space and is suitable for compact layouts inside 35 kV switchgear and other complete distribution equipment.
Operation and Maintenance Features
- Low-maintenance operation: The oil-free dry-type structure eliminates leakage and fire risks. The epoxy resin cast body provides high mechanical strength, impact resistance, and ageing resistance, reducing 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 design: The magnetic core is made from high-quality laminated silicon steel sheets, while the windings are wound with enamelled copper wire. The transformer provides low operating losses, limited temperature rise, and stable signal accuracy.
- Overvoltage withstand capability: The product can withstand switching overvoltage and lightning overvoltage within the specified insulation level, ensuring reliable metering and protection signals.
Technical Specifications
Electrical Parameters
| Parameter | Specification |
|---|---|
| Applicable System Voltage | 35 kV AC, Um = 40.5 kV |
| Rated Frequency | 50 Hz |
| Rated Primary Voltage | 35 kV |
| Rated Secondary Voltage | 100 V for metering and protection; 100/3 V for optional insulation monitoring |
| Metering Accuracy Class | Class 0.2 / 0.5 / 1 |
| Protection Accuracy Class | 3P / 6P |
| Power-Frequency Withstand Voltage | 95 kV for 1 minute at the high-voltage terminal, without breakdown |
| Lightning Impulse Withstand Voltage | 185 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 JDZ9-35 Voltage Transformer is suitable for indoor 35 kV AC power systems with a maximum system voltage of 40.5 kV.
Typical Applications
- Voltage measurement, energy metering, and relay protection in indoor 35 kV medium-voltage switchgear
- Voltage monitoring in box-type substations
- 35 kV distribution systems in switching and distribution stations
- Power distribution systems in industrial and mining facilities
- Commercial buildings and industrial parks
- Voltage signal acquisition for power automation systems
- Monitoring, control, and protection circuits
- 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.
When equipped with an auxiliary secondary winding, it can provide a voltage signal for insulation monitoring and system earth-fault detection.
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. - 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. - Low-voltage-side connection:
Connect the secondary terminals according to their markings. Metering, protection, and insulation-monitoring 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 grounded according to the system design and applicable 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 pollution.
- Regularly check 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 grounding 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 insulation-monitoring function where an auxiliary winding is provided.
- Clean dust and contamination from the transformer surface and insulating sheds.
- Prevent oil and corrosive substances from contacting the epoxy resin body.
- If cracking, discharge, overheating, or excessive voltage-ratio error 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 secondary circuit must be properly isolated, de-energized, and grounded in accordance with applicable safety 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 the high-voltage connection. 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 grounded. 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 | JDZ9-35 Voltage Transformer | Main device for voltage transformation, electrical isolation, and signal acquisition |
| 2 | Mounting Bolts and Washers | Used to secure the voltage transformer during installation |
| 3 | Transparent Secondary Terminal Cover | Protects the low-voltage terminals and helps prevent incorrect connection or short circuits |
| 4 | Product Instruction Manual | Provides installation, operating, and maintenance guidance |
| 5 | Product Certificate and Factory Test Report | Provides product quality and performance documentation, including voltage-ratio and accuracy 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 35 kV power systems.
