Overview
The UNZ10 / UNZ2-12 is a fully enclosed epoxy cast-resin voltage transformer designed for indoor use in 6kV, 10kV, and 12kV medium-voltage power systems. It features a solid cast-resin insulation structure that encapsulates the primary winding, secondary winding, and iron core, providing excellent dielectric strength, moisture resistance, and pollution resistance.
This voltage transformer supports applications including energy metering, voltage monitoring, and relay protection, with a typical rated output ranging from 0.5/3 to 100/3000VA and a maximum output of 5000VA. It complies with international standards such as IEC61869-3:2011 and GB20840.3-2013, ensuring reliable performance in switchgear environments requiring stable secondary voltage signals.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System Voltage Class | 6kV, 10kV, 12kV |
| Insulation Structure | Fully enclosed epoxy cast-resin |
| Rated Frequency | 50Hz / 60Hz |
| Ambient Temperature Range | -5°C to +40°C |
| Rated Insulation Level (10kV) | 12/42/75kV |
| Secondary Output Voltage | 100V / 220V (project-specific) |
| Typical Rated Output | 0.5/3 — 100/3000VA |
| Maximum Output | 5000VA |
| Wiring Schemes | V/V, Y/Y/Δ |
| Installation Type | Indoor switchgear |
| Standards | IEC61869-3:2011, GB20840.3-2013 |
| Product Type | Indoor voltage/potential transformer |
Model Designation
- UNZ: Indoor epoxy cast-resin voltage transformer series code.
- 10: Model voltage code commonly used for 10kV system applications.
- 12: 12kV insulation / switchgear class expression for export product pages.
- 3K: Structure or design code, subject to final manufacturer drawing.
- 266: Dimension / design code, subject to final manufacturer drawing.
Construction
The UNZ10 / UNZ2-12 voltage transformer employs a fully enclosed epoxy cast-resin construction. All active components—including the primary winding, secondary winding, and magnetic core—are completely embedded within a solid epoxy resin body during the casting process. This monolithic structure eliminates air gaps and voids, significantly enhancing electrical insulation integrity and mechanical robustness. The cast-resin material provides inherent resistance to moisture ingress, surface tracking, and environmental contaminants, making it well-suited for indoor switchgear installations where long-term reliability and minimal maintenance are required. The design ensures uniform electric field distribution and thermal stability under continuous operating conditions.
Technical Parameters
Service Conditions
- Ambient Temperature: -5°C to +40°C
- Altitude: Up to 1000 m above sea level
- Relative Humidity: Up to 95% at 25°C
- Installation Environment: Indoor, non-corrosive, non-explosive, free from excessive dust and conductive pollutants
Technical Parameters
The UNZ10 and UNZ2-12 series are epoxy cast-resin voltage transformers rated for 12kV class systems with a power-frequency design (50Hz / 60Hz). They feature an insulation level of 12/42/75kV, operate within standard ambient temperatures (-5°C to +40°C), and are suitable for installation up to 1000 m altitude. These units comply with international standards for metering and protection applications.
Voltage Transformer Data
| Type (Ratio) |
Accuracy Class (Protection/ Measurement) |
Rated Output (VA) |
Max. Output (VA) |
Rated Insulation Level (kV) |
Rated Frequency |
|---|---|---|---|---|---|
| 10/√3 : 0.1/√3 : 0.22 | 0.5/3 | 100/3000 | 5000 when matched with 3000VA output |
12/42/75 | 50Hz / 60Hz |
| 10 : 0.1 : 0.22 | 0.5/3 | 100/3000 |
Installation & Wiring
Installation Diagram
The UNZ10 and UNZ2-12 epoxy cast-resin voltage transformers are designed for secure mounting on a flat base using the specified main mounting length of 410mm. Ensure proper alignment with the overall base length of 470mm and base width of 250mm. Primary terminals are secured with 2-M10 bolts, while secondary terminals use 4-M6 fixings. Maintain clearances as indicated in the dimension reference to ensure safe operation and compliance with insulation requirements.
Wiring Diagram
The secondary output terminals must be connected according to the selected wiring scheme. For voltage measurement and metering applications, V/V wiring is recommended. When residual-voltage detection or protection functions are required, use Y/Y/Δ wiring. Always verify terminal polarity and grounding before energizing the system. Confirm primary terminal position, cable routing, and insulation clearance during switchgear design to avoid field modifications.
Selection & FAQs
Selection Guide
- Select the primary connection: choose 10kV/100V for line-to-line measurement or 10/√3kV to 100/√3V for phase-to-earth measurement, both with the specified 220V auxiliary winding.
- Check the actual load: use the class 0.5, 100VA winding for measurement and verify that the 220V equipment’s continuous VA, power factor, inrush and voltage-regulation needs fit the 3000VA class 3.0 output.
- Do not assume residual protection: the published ratios contain no 100/3V residual winding; any Y/Y/△ or earth-fault scheme requires a corrected winding schedule and terminal drawing.
- Separate class from system voltage: published data supports a 10kV primary with 12/42/75kV insulation; 6kV and 12kV-primary claims require separate verified ratings.
- Approve mechanical and safety data: confirm UNZ10 versus UNZ2-12 designation, 470 × 250mm base, 410mm mounting length, terminal allocation, ventilation, secondary protection and grounding.
Frequently Asked Questions
Q1: Can these cast-resin voltage transformers be installed outdoors?
No, they are strictly designed for indoor installation. The environment must be non-corrosive, non-explosive, and free from excessive dust. Contact us for outdoor alternatives.
Q2: Which accuracy classes are available for protection and measurement?
The UNZ10 and UNZ2-12 offer 0.5 class for measurement and 3P class for protection. Rated outputs are 100 VA and 3000 VA respectively. Specify your exact burden requirements.
Q3: What is the rated insulation level for 12kV systems?
The standard insulation level is 12/42/75 kV. This ensures reliable performance in 6kV, 10kV, and 12kV class systems. Factory test reports are provided upon request.
Q4: Are custom primary to secondary voltage ratios available?
Standard ratios include 10/√3 : 0.1/√3 : 0.22 and 10 : 0.1 : 0.22. Custom ratio configurations are subject to confirmation. Please provide your exact ratio requirements for factory evaluation.
Q5: How are factory test certificates provided before shipment?
Standard routine tests include ratio, polarity, and insulation resistance checks. Factory test reports are provided upon request. Contact our sales team for detailed documentation.
Q6: Why choose epoxy cast-resin for 12kV switchgear?
Epoxy cast-resin provides excellent insulation and flame retardancy for indoor 12kV switchgear. These units ensure reliable metering and protection for 50Hz and 60Hz power-frequency systems.
Q7: When should we request high-altitude design modifications?
Standard models are rated for altitudes up to 1000 meters. For installations above this limit, derating or special design modifications are required. Consult our engineering team early.