Product Overview
Functional Definition
The JSZW-6, JSZW-10 series voltage transformers are three-phase, indoor-type instrument transformers with epoxy resin cast insulation, designed for voltage measurement, energy metering, and relay protection applications in medium-voltage AC power systems. These transformers are suitable for 10 kV systems with rated frequency of 50 Hz, primarily used in ungrounded neutral (isolated neutral) systems.
Key Ratings
| Item | Specification (per order / nameplate) |
|---|---|
| System voltage class | 10 kV class (indoor switchgear and distribution applications) |
| Configuration | Three-phase integrated unit |
| Rated frequency | 50 Hz (60 Hz available upon request) |
| Rated voltage ratio | 10000/100 V (or as specified) |
| Accuracy classes | Metering: 0.2 / 0.5 class; Protection: 3P / 6P as specified |
| Rated burden | Per winding as specified (VA) |
| Burden power factor | cosφ = 0.8 (lagging) |
| Insulation level | 12/42/75 kV (Um/AC/LI) |
| Creepage distance | Meets Pollution Level II requirements |
| Applicable standards | GB/T 20840.3-2013; GB/T 20840.1-2010 (aligned with IEC 61869 framework) |
Working Principle
Operating on electromagnetic induction principles, the three-phase voltage transformer steps down the primary high voltage to standardized secondary voltage levels suitable for measurement instruments and protective relays. The integrated three-phase design ensures balanced voltage transformation across all phases, providing accurate voltage signals for metering, protection, and monitoring applications in ungrounded neutral systems.
System Application Position
- Medium Voltage Distribution: 10 kV switchgear and distribution panels
- Energy Metering: Revenue-grade electricity measurement systems
- Protection Circuits: Overvoltage, ground fault, and directional protection schemes
- Ungrounded Neutral Systems: Isolated neutral system voltage monitoring and protection
- SCADA Integration: Supervisory control and data acquisition systems
Structural Overview
Epoxy resin cast construction with fully-enclosed three-phase integrated design ensures superior insulation performance, moisture resistance, and mechanical strength. The compact three-phase configuration provides space-efficient installation in switchgear environments while maintaining excellent electrical clearance and creepage distances suitable for Pollution Level II environments.
Model Designation
Model Code Explanation
- J — Voltage transformer (VT/PT)
- S — Three-phase configuration
- Z — Cast-resin (epoxy) insulated
- W — Outdoor/Indoor type (W variant for specific installation)
- 10 — Voltage class (kV)
Service Conditions
The JSZW-10 series voltage transformers are designed for indoor operation under normal service conditions in medium-voltage power systems.
- Installation environment: Indoor installation only
- Altitude: Not exceeding 2000 m above sea level (higher altitude shall be specified for engineering confirmation)
- Ambient temperature: −5 °C to +40 °C; daily average not exceeding 35 °C
- Relative humidity: Daily average ≤ 95%, monthly average ≤ 90%
- Seismic performance: Meets industrial equipment seismic standards
- Environmental conditions: Free from corrosive gases or vapors; free from explosive or flammable media; no severe vibration, mechanical shock, or impact
Construction
Construction Design
- Configuration: Three-phase integrated unit
- Structure: Compact indoor type for switchgear installation
- Insulation: Fully enclosed epoxy resin cast insulation
- Core: High-quality silicon steel magnetic core
- System: Integrated primary and secondary insulation system
The epoxy resin casting provides stable insulation properties and resistance to moisture, contamination, and aging for long-term indoor service. The three-phase integrated design ensures balanced performance and compact installation footprint.
Windings & Terminal Marking
- Primary terminals: A, B, C (three-phase)
- Secondary terminals (Metering): a, b, c, n
- Secondary terminals (Protection/Auxiliary): As specified per configuration
Terminal markings follow standard VT polarity conventions. Correct terminal identification shall be observed to ensure metering and protection performance.
Technical Data
This section provides selection-oriented technical data for the JSZW-10 series indoor, three-phase, cast-resin voltage transformer used in 10 kV class AC systems (50 Hz). Data shown below is intended for preliminary selection of accuracy class combinations and rated burdens.
Definitions: Accuracy class indicates the measurement precision for metering or protection applications. Rated output (VA) is specified per secondary winding. Voltage factor defines the overvoltage capability for specified duration.
Data Reference
| Model | Rated Voltage Ratio (kV) |
Accuracy Class |
Rated Output (VA) |
Limiting Output(VA) |
|---|---|---|---|---|
| JSZW-6(10) | 6(10)/ √3/0.1/√3/0.1/3 | 0.2/6P | 25/50 | 300 |
| 0.5/6P | 50/50 | |||
| 1/6P | 100/50 |
Standards & Normative References
| Standard | Title | Application |
|---|---|---|
| GB/T 20840.3-2013 | Instrument Transformers – Part 3: Additional Requirements for Inductive Voltage Transformers | VT-specific requirements (national standard) |
| GB/T 20840.1-2010 | Instrument Transformers – Part 1: General Requirements | General requirements (national standard) |
| IEC 61869-1 | Instrument Transformers – Part 1: General Requirements | General requirements (international reference) |
| IEC 61869-3 | Instrument Transformers – Part 3: Additional Requirements for Inductive Voltage Transformers | VT-specific requirements (international reference) |
| IEC 60085 | Electrical Insulation – Thermal Evaluation | Insulation thermal evaluation reference |
Factory Test Compliance
- Routine tests per applicable GB/IEC requirements (including polarity/marking, ratio verification, and accuracy verification per specified class and burden)
- Dielectric tests per insulation coordination requirements and applicable standard
- Partial discharge test where specified by the project requirement
- Visual and dimensional inspection including marking and workmanship conformity
- Type and special tests as required by the project specification
Installation & Dimensions
- Outline dimensions and mounting details are provided in the dimensional drawings.
- The transformer shall be securely mounted using the designated fixing holes.
- Primary conductor connection shall be made via designated terminals.
- Adequate clearance shall be maintained for insulation, heat dissipation, and maintenance access.
Outlines
JSZW-6, JSZW-10
Safety Notes
- Secondary winding shall not be short-circuited during operation, as this may cause thermal damage.
- During inspection or maintenance, the primary circuit shall be de-energized and properly isolated.
- One point of the secondary circuit should be reliably grounded in accordance with applicable standards.
- All installation and maintenance work shall comply with local electrical safety regulations.
Ordering Information
When placing an order, the required configuration shall be specified according to the local grid requirements, applicable standards, and project technical specification. The following parameters shall be clearly stated for technical confirmation and production release:
- Model and rated voltage ratio (e.g., JSZW-10, 10000/100 V)
- Accuracy class (e.g., 0.2 or 0.5 for metering; 3P for protection)
- Rated burden (VA) for each secondary winding
- Insulation level (e.g., 12/42/75 kV)
- Environmental conditions (temperature, humidity, altitude, pollution level)
If local utility or project requirements apply (e.g., special insulation level, partial discharge limit, terminal arrangement, mounting constraints, documentation language, or required certificates), specify them at the ordering stage. Special configurations shall be confirmed by technical agreement and final data sheet prior to production.