Product Overview
The JDZC-3, JDZC-6, and JDZC-10 Voltage Transformers are fully enclosed, dry-type cast-resin voltage transformers designed for indoor 3 kV, 6 kV, and 10 kV AC power systems with a maximum system voltage of 12 kV.
The transformers feature an integrated epoxy resin cast insulation structure. The magnetic core is made of high-quality laminated silicon steel sheets, while the windings are wound with enamelled copper wire. They provide excellent insulation performance, reliable operation, stable accuracy characteristics, and strong resistance to pollution flashover.
These products are mainly used for voltage measurement, energy metering, relay protection, and insulation monitoring. Typical applications include indoor medium-voltage switchgear, box-type substations, distribution stations, and other power distribution equipment.
Product Features
Insulation and Electrical Performance
- 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. It can withstand the operating voltage, power-frequency withstand voltage, and lightning impulse withstand voltage requirements of the corresponding power system. - Oil-free dry-type construction:
The product contains no insulating oil, eliminating the risks of oil leakage, oil contamination, and fire associated with oil-filled equipment. It is suitable for modern indoor oil-free distribution systems. - Multiple voltage ratings:
Models are available for 3 kV, 6 kV, and 10 kV systems. Voltage ratios such as 10/0.1 kV and 6/0.1 kV can be configured according to system requirements. - Multiple accuracy classes:
Metering accuracy classes of 0.2, 0.5, and 1 and protection accuracy classes of 3P and 6P are available for metering, protection, and insulation-monitoring applications. - High pollution-flashover resistance:
The high-voltage terminals feature a shed-type insulation structure that increases the creepage distance and improves resistance to surface flashover in polluted indoor environments. - Low partial discharge:
The advanced casting process limits partial discharge to no more than 10 pC, helping reduce insulation ageing and improve long-term operating reliability.
Structural and Installation Features
- Fully enclosed dry-type structure:
The one-piece cast construction encloses the magnetic core, windings, and live components. It provides an IP20 protection rating and a compact structure with minimal installation space. - Modular design:
Standardized mounting dimensions simplify installation inside switchgear and support batch replacement and routine maintenance. - Clearly identified terminals:
The high-voltage terminals are clearly marked, while the low-voltage terminals are protected by a terminal cover. This arrangement simplifies wiring and helps prevent incorrect connection and accidental secondary-circuit short circuits. - Flexible installation:
The metal base includes mounting holes for secure bolt installation. The transformer can be installed horizontally or vertically inside indoor switchgear and provides reliable resistance to vibration.
Operation and Maintenance Features
- Low-maintenance operation:
The dry-type, oil-free design eliminates leakage and fire hazards. The epoxy resin 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 performance without becoming brittle or deformed. - High operational reliability:
The enamelled copper windings and high-quality laminated silicon steel core provide low operating losses, limited temperature rise, and stable accuracy. - Overvoltage withstand capability:
The transformer can withstand switching overvoltage and lightning overvoltage within its specified insulation level, helping maintain reliable metering and protection signals.
Technical Specifications
Electrical Parameters
| Parameter | Specification |
|---|---|
| Applicable System Voltage | 3 kV / 6 kV / 10 kV AC, Um = 12 kV |
| Rated Frequency | 50 Hz |
| Rated Primary Voltage | 3 kV / 6 kV / 10 kV, customizable |
| 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 | 3 kV system: 18 kV; 6 kV system: 24 kV; 10 kV system: 42 kV for 1 minute, without breakdown |
| Lightning Impulse Withstand Voltage | 3 kV system: 40 kV; 6 kV system: 60 kV; 10 kV system: 75 kV peak, without breakdown |
| Partial Discharge | ≤10 pC |
| Insulation Resistance | ≥1,000 MΩ between the high-voltage winding, low-voltage winding, 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 20840.1 | Instrument Transformers—Part 1: General Requirements |
| GB/T 20840.3 | Instrument Transformers—Part 3: Additional Requirements for Inductive Voltage Transformers |
Applications
Applicable Voltage Levels
Suitable for indoor 3 kV, 6 kV, and 10 kV AC power systems with a maximum system voltage of 12 kV.
Typical Applications
- Voltage measurement, energy metering, and relay protection in indoor medium-voltage switchgear, including KYN28 and XGN series equipment
- Voltage monitoring in box-type substations
- Power distribution systems in distribution stations
- 3 kV, 6 kV, and 10 kV systems in industrial and mining enterprises
- Commercial buildings and industrial parks
- Voltage monitoring, control, and protection signal acquisition in power automation systems
- Indoor distribution environments requiring enhanced resistance to 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 also 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 terminals according to the system design. Ensure that all connections are secure and provide reliable electrical contact. Maintain adequate electrical clearance between the high-voltage conductors, 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 in accordance with the system design and applicable electrical safety requirements. - Insulation inspection:
After installation, measure the insulation resistance between:- High-voltage winding and low-voltage winding
- High-voltage winding and earth
- Low-voltage winding 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.
- 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 transformer must be de-energized, and the secondary circuit must be safely isolated and grounded as required.
- 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 resistance to pollution flashover.
- 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 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 | JDZC-3, JDZC-6, or JDZC-10 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 | Low-Voltage Terminal Cover | Protects the secondary terminals and helps prevent incorrect connection or short circuits |
| 4 | Product Instruction Manual | Provides installation, operating, maintenance, and wiring 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 3 kV, 6 kV, and 10 kV power systems.
