Overview
The JSZX18-6R and JSZX18-10R are indoor epoxy cast-resin three-phase voltage transformers with integral primary fuses, rated for 7.2kV and 12kV system classes respectively. These units operate in 50/60Hz AC power systems and support nominal voltages of 6kV, 6.6kV, 10kV, and 11kV.
Designed for accurate voltage measurement, metering, monitoring, and relay protection, the JSZX18 series meets standard requirements for medium-voltage switchgear applications. It is commonly deployed in indoor substations, ring main units, industrial control panels, and energy metering circuits where compactness, safety, and reliability are essential.
Key Ratings Snapshot
| Parameter | Rating |
|---|---|
| System Voltage Class | 7.2kV / 12kV |
| Primary Voltage (Rated) | 6kV, 6.6kV, 10kV, 11kV |
| Secondary Voltage (Standard) | 100V or 110V (line-to-line) |
| Frequency | 50/60Hz |
| Insulation Type | Epoxy cast-resin |
| Phase Configuration | Three-phase (three single-phase units on common base) |
| Primary Protection | Integral high-voltage fuses |
| Application | Voltage measurement, metering, protection |
| Installation Environment | Indoor, metal-enclosed switchgear |
| Accuracy Class | 0.2, 0.5, 1, 3 (as per IEC/ANSI standards) |
| Thermal Burden | Per standard ratings (e.g., 50VA, 100VA) |
| Short-Time Withstand Voltage | Per IEC 61869-3 / IEEE C57.13 |
Construction
The JSZX18 series uses a cast-resin insulated body with three phase units mounted on a common baseplate. The primary side is fuse-protected, which helps improve equipment safety and provides a compact, factory-integrated solution for switchgear manufacturers. The epoxy cast construction offers good insulation stability, mechanical strength, and resistance to moisture and normal indoor environmental conditions.
Technical Parameters
Service Conditions
- Ambient temperature: -5°C to +40°C
- Altitude: up to 1000 m above sea level
- Relative humidity: daily average not exceeding 95%, monthly average not exceeding 90%
- Installation environment: indoor, non-corrosive, non-explosive, free from excessive dust and conductive pollution
- Seismic intensity: not exceeding degree 8 (according to IEC 60068-2-57)
Technical Parameters
The JSZX18-6R and JSZX18-10R are indoor fused three-phase epoxy cast-resin voltage transformers designed for metering and protection applications. They operate within a temperature range of -5°C to +40°C at altitudes up to 1000 m, comply with IEC 61869 standards, and support rated insulation levels of 7.2/32/60 kV and 12/42/75 kV respectively.
Voltage Transformer Data
| Model | Voltage Class |
Typical Voltage Ratio |
Rated Insulation Level (kV) |
Accuracy Class (Protection/ Measurement) |
Rated Output (VA) |
|---|---|---|---|---|---|
| JSZX18-6R | 7.2kV class | 6kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 6.6kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 |
7.2 / 32 / 60 | 3 x 0.2/3P – 15/100 3 x 0.2/6P – 15/100 3 x 0.5/3P – 30/100 |
3 x 400 |
| JSZX18-10R | 12kV class | 10kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 11kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 |
12 / 42 / 75 | 3 x 0.5/3P – 30/100 3 x 0.5/6P – 30/100 3 x 1.0/3P – 60/100 |
3 x 630 |
| JSZX18-6R Residual-voltage version |
7.2kV class | 6kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 / 100V/3 6.6kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 / 100V/3 |
7.2 / 32 / 60 | 3 x 0.2/0.5/3P – 10/10/100 3 x 0.2/0.5/6P – 10/15/100 |
3 x 400 |
| JSZX18-10R Residual-voltage version |
12kV class | 10kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 / 100V/3 11kV/sqrt3 / 100V/sqrt3 / 100V/sqrt3 / 100V/3 |
12 / 42 / 75 | 3 x 0.2/0.5/3P – 10/10/100 3 x 0.2/0.5/6P – 10/15/100 |
3 x 630 |
Installation & Wiring
Installation Diagram
The JSZX18-6R and JSZX18-10R indoor fused three-phase epoxy cast-resin VT/PT units are designed for wall-mounted or support-frame installation in dry, indoor environments. Ensure adequate clearance around the unit for ventilation and maintenance access as specified in the technical documentation.
Wiring Diagram
Primary terminals are marked A, B, and C for three-phase connection. Secondary terminals are labeled a-n, b-n, and c-n for each phase output, with ‘n’ representing the common neutral point. Fuses are integrated on the primary side and accessible via the front panel. Ensure all wiring complies with local electrical codes and that secondary circuits are not left open-circuited during operation.
Selection & FAQs
Selection Guide
- Match system voltage: choose JSZX18-6R for 6kV/6.6kV or JSZX18-10R for 10kV/11kV, with the corresponding 7.2kV or 12kV insulation class.
- Select standard or residual version: use the standard two-secondary package for measurement and phase-voltage protection, or add 100/3V windings when open-delta residual voltage is required.
- Coordinate each winding: specify class 0.2, 0.5 or 1 measurement and class 3P or 6P protection with the listed per-phase VA and connected relay burden.
- Verify fuse and thermal data: obtain the primary-fuse ratings and confirm whether 3 × 400VA or 3 × 630VA is stated per phase; neither value is an accuracy burden.
- Approve assembly details: confirm mounting orientation, common-base dimensions, fuse access, terminal diagram, neutral grounding, secondary protection and 1000m site limit.
Frequently Asked Questions
Q1: Can the JSZX18-10R operate in high-humidity indoor environments?
Yes, it handles high humidity. The monthly average relative humidity must not exceed 90%, with daily averages up to 95%. Ensure installation in non-corrosive, dust-free areas per IEC standards. Contact us for specific environmental assessments.
Q2: Which accuracy class is recommended for protective relaying applications?
Select the 3P or 6P accuracy class for protection. These classes ensure reliable performance during fault conditions up to the rated voltage factor. Specify your exact protection requirements during ordering for factory configuration.
Q3: What is the maximum installation altitude for these voltage transformers?
The standard maximum altitude is 1000 meters above sea level. For installations exceeding this elevation, derating factors apply to insulation and thermal performance. Please provide your site altitude for engineering verification.
Q4: Can we customize the voltage ratio for 6.6kV systems?
Yes, custom ratios are available. The JSZX18-6R supports a standard 6.6kV/√3 to 100V/√3 ratio. Submit your specific primary and secondary voltage requirements to our sales team for technical validation.
Q5: What international standards do these epoxy cast-resin transformers comply with?
They fully comply with IEC 61869 standards for instrument transformers. Seismic performance is also verified according to IEC 60068-2-57. Request the specific type test and routine test certificates with your inquiry.
Q6: Are these epoxy cast-resin transformers suitable for indoor switchgear metering?
Yes, they are specifically designed for indoor metering and protection. The three-phase fused design integrates seamlessly into 7.2kV and 12kV indoor switchgear. Confirm your switchgear dimensions with our engineers for fitment checks.