Product Overview
Functional Definition
The JSZW3-10 series indoor three-phase combined voltage transformers are precision electromagnetic instruments designed for accurate voltage measurement, energy metering, and relay protection applications in medium-voltage AC power systems. These transformers utilize electromagnetic induction principles to provide galvanically isolated secondary voltage signals proportional to primary voltage, serving measurement, metering, and protection functions in indoor 10 kV class distribution systems.
Key Ratings
| Item | Specification (per order / nameplate) |
|---|---|
| System voltage class | 10 kV class (indoor switchgear and distribution applications) |
| Rated frequency | 50 Hz / 60 Hz |
| Rated voltage ratio | 10000/√3 / 100/√3 / 100/√3 V (primary/secondary/auxiliary) |
| Winding configuration | Yo/Yo/Δ (JSZW3-10) or Yo/Yo/Yo/Δ (JSZW3-10F) |
| Accuracy classes | 0.2 / 0.5 / 1 for metering; 6P for protection |
| Rated output | Per winding as specified: 15 VA (0.2 class), 30 VA (0.5 class), 60 VA (1 class), 50 VA (6P class) |
| Maximum output | 300 VA |
| Insulation level | 12/42/75 kV (Um/Ud/Up) or 7.2/32/60 kV for 6 kV variant |
| Applicable standards | GB 1207; IEC 60044-2 |
| Model variants | JSZW3-10 / JSZW3-10F (winding configuration difference) |
Product Shows
Working Principle
Operating on Faraday’s law of electromagnetic induction, the combined voltage transformer features magnetic cores with primary windings connected to the system voltage and secondary windings providing standardized voltage output. The three-phase combined design integrates measurement, metering, and protection functions in a single compact assembly. The auxiliary delta winding (open delta configuration) enables zero-sequence voltage detection for ground fault protection schemes.
System Application Position
- Medium Voltage Distribution: 6-10 kV switchgear and distribution panels
- Energy Metering: Revenue-grade electricity measurement systems
- Protection Circuits: Overvoltage, undervoltage, and ground fault protection schemes
- SCADA Integration: Supervisory control and data acquisition systems
- Zero-Sequence Detection: Ground fault and insulation monitoring applications
Structural Overview
Epoxy resin cast construction with fully-enclosed design ensures superior insulation performance, moisture resistance, and mechanical strength. The three-phase combined configuration provides compact installation in constrained switchgear environments while maintaining excellent electrical clearance and creepage distances. The integral casting eliminates oil-filled construction, providing maintenance-free operation and environmental compliance.
Model Designation
Model Code Explanation
- J — Voltage transformer (VT)
- S — Three-phase combined type
- Z — Cast-resin (epoxy) insulated, fully enclosed structure
- W — Indoor installation
- 3 — Design code (platform/iteration)
- 10 — Voltage class (kV)
- F — Four-winding configuration (Yo/Yo/Yo/Δ) when present; standard JSZW3-10 is three-winding (Yo/Yo/Δ)
Variant Differences
JSZW3-10: Three-winding configuration with Yo/Yo/Δ connection (two metering windings + one open delta auxiliary winding)
JSZW3-10F: Four-winding configuration with Yo/Yo/Yo/Δ connection (three metering/protection windings + one open delta auxiliary winding)
The F variant provides an additional secondary winding for independent metering and protection circuit separation, suitable for applications requiring enhanced functional isolation.
Service Conditions
Installation Environments
The JSZW3-10 series combined voltage transformers are designed for indoor operation under normal service conditions in medium-voltage power systems.
- Installation environment: Indoor installation only; free from corrosive gases or vapors; free from explosive or flammable media; no severe vibration or mechanical shock
- Altitude: Not exceeding 3000 m above sea level (higher altitude shall be specified for engineering confirmation)
- Ambient temperature: −5 °C to +40 °C
- Relative humidity: ≤ 85% (at +20 °C reference)
- Environmental conditions: No conducting dust; no condensation that would impair insulation performance
Construction
Construction Design
- Structure: Three-phase combined type for indoor switchgear
- Insulation: Fully enclosed epoxy resin cast insulation
- Core: Three-phase core design with integral assembly
- System: Integrated primary and secondary insulation system
- Mounting: Base-mounted configuration with designated fixing points
The epoxy resin casting provides stable insulation properties and resistance to moisture, contamination, and aging for long-term indoor service. The dry-type construction eliminates oil maintenance requirements and environmental concerns associated with liquid-filled transformers.
Windings & Terminal Marking
JSZW3-10 (Three-Winding Configuration):
- Primary terminals (A/B/C phases): A / B / C / N (grounded neutral)
- Secondary metering winding (Group 1): a1-n1 / b1-n1 / c1-n1
- Secondary metering winding (Group 2): a2-n2 / b2-n2 / c2-n2
- Auxiliary open delta winding: da-dn / db-dn (for zero-sequence voltage)
JSZW3-10F (Four-Winding Configuration):
- Primary terminals (A/B/C phases): A / B / C / N (grounded neutral)
- Secondary metering winding (Group 1): a1-n1 / b1-n1 / c1-n1
- Secondary metering winding (Group 2): a2-n2 / b2-n2 / c2-n2
- Secondary protection winding (Group 3): a3-n3 / b3-n3 / c3-n3
- Auxiliary open delta winding: da-dn / db-dn (for zero-sequence voltage)
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 JSZW3-10 series indoor, cast-resin combined voltage transformer used in 10 kV class AC systems (50/60 Hz). Data shown below is intended for preliminary selection of accuracy class combinations and rated outputs.
Notation: Voltage ratio shown as primary/secondary phase-to-neutral (line-to-ground) values; acceptance shall be based on nameplate values and factory test report.
Data Reference
| Type | Rated Voltage Ratio (V) |
Accuracy Class & Rated Output (VA) |
Max Output (VA) |
Rated Insulation Level (KV) |
|||
|---|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 1 | 6p | ||||
| JSZW3-10 | 10000/3/100/3/100/3 | 15 | 30 | 60 | 50 | 300 | 12/42/75 |
| JSZW3-6 | 6000/3/100/3 | 7.2/32/60 | |||||
| JSZW3-3 | 3000/3/100/3 | 3.6/20/40 | |||||
Standards & Normative References
| Standard | Title | Application |
|---|---|---|
| GB 1207 | Voltage Transformers | National standard for voltage transformers |
| IEC 60044-2 | Instrument Transformers – Part 2: Inductive Voltage Transformers | International VT requirements (superseded by IEC 61869-3 for new designs) |
| IEC 61869-3 | Instrument Transformers – Part 3: Additional Requirements for Inductive Voltage Transformers | Current international VT standard (reference) |
| GB/T 22071.1 | Instrument Transformers – Part 1: General Requirements | National general requirements (aligned with IEC 61869-1 framework) |
| GB/T 22071.3 | Instrument Transformers – Part 3: Voltage Transformers | National VT requirements (aligned with IEC 61869-3) |
| DL/T 866 | Technical Specifications for Voltage Transformers in Power Systems | Power industry technical specifications |
Factory Test Compliance
- Routine tests per applicable IEC/GB 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
- Zero-sequence voltage verification for open delta winding function
Installation & Dimensions
- Outline dimensions and mounting details are provided in the dimensional drawings.
- The transformer shall be securely mounted using the designated fixing holes on a stable, level foundation.
- Primary connection shall be made to the system busbars or incoming feeders via designated terminals.
- Adequate clearance shall be maintained for insulation, heat dissipation, and maintenance access.
- The primary neutral terminal (N) must be solidly grounded per applicable standards.
Installation Outline
Safety Notes
- Secondary circuit must not be short-circuited when the transformer is energized, as this may cause winding damage and compromise accuracy.
- During inspection or maintenance, the primary circuit shall be de-energized and isolated before accessing any terminals.
- The primary neutral point must be reliably grounded in accordance with applicable standards.
- All installation and maintenance work shall comply with local electrical safety regulations.
- Do not exceed the maximum rated burden on any secondary winding to avoid accuracy degradation and thermal issues.
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 designation (JSZW3-10 or JSZW3-10F)
- Rated voltage ratio (primary/secondary)
- Rated frequency (50 Hz or 60 Hz)
- Accuracy requirements (metering and/or protection accuracy class per winding)
- Rated burden (VA) for each secondary winding
- Insulation level (Um/Ud/Up per applicable standard)
Selection guidance: (1) Determine system voltage class (6 kV, 10 kV, or other) based on distribution system design. (2) Select winding configuration (JSZW3-10 three-winding or JSZW3-10F four-winding) based on functional separation requirements. (3) Specify metering and/or protection accuracy requirements (e.g., 0.2 for revenue metering; 0.5 or 1 for indication; 6P for protection). (4) Confirm rated burden (VA) for each secondary circuit based on connected meters/relays and wiring losses. (5) Verify insulation level against system coordination and applicable standards.
If local utility or project requirements apply (e.g., 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.