Overview
The ZW20Z-12 is a 12kV, 50Hz outdoor pole-mounted vacuum circuit breaker that combines vacuum arc extinguishing with SF6 gas insulation. As an improved version of the ZW20-12, it uses a sealed, explosion-proof enclosure based on the imported Toshiba (Japan) VSP5 structure with sealed lead-out bushings, keeping the internal SF6 fully isolated from the environment for maintenance-free operation.
A miniaturized spring mechanism with direct-chain drive and multi-stage tripping delivers high reliability over 10,000 operations, while low-resistance bracelet-type main contacts keep temperature rise low. Compared with the ZW20-12 it adds overcurrent protection, spring-energy indicators and aviation plugs for secondary wiring, so it pairs easily with intelligent controllers for reclosing and distribution automation across substations and industrial 10/12kV networks.
Model Designation
Model format: ZW 20 Z – 12 / 630 – 20
- ZW: Outdoor vacuum circuit breaker
- 20: Design sequence number
- Z: Spring operating mechanism
- 12: Rated voltage (kV)
- 630: Rated current (A)
- 20: Rated short-circuit breaking current (kA)
Construction
The ZW20Z-12 pairs a compact miniaturized spring mechanism (direct-chain drive, multi-stage tripping) with an internal-collecting / external-expanding bracelet main circuit for low contact resistance and temperature rise. Its Toshiba-VSP5-based sealed, explosion-proof enclosure guarantees zero SF6 leakage and stable, maintenance-free operation from -40 degC to +40 degC and at altitudes up to 3000 m. Overcurrent protection, spring-energy indicators and aviation-plug secondary links allow straightforward integration with intelligent controllers and reclosing schemes for distribution automation.
Technical Parameters
Service Conditions
- Ambient Temperature: -40 degC to +40 degC
- Altitude: <=3000 m (higher altitude on request with a correspondingly higher rated insulation level)
- Relative Humidity: Daily average <=95%
Monthly average <=90% - Wind Pressure: <=700 Pa (equivalent to wind speed 34 m/s)
- Neutral Earthing: Solidly earthed, earthed via arc-suppression coil, or earthed via low resistance
- Installation Environment: No explosive or severely polluting gas, and no chemical corrosion
Technical Data
| No. | Item | Unit | Parameter |
|---|---|---|---|
| 1 | Rated voltage | kV | 12 |
| 2 | Rated frequency | Hz | 50 |
| 3 | Rated current | A | 630 / 1250 |
| 4 | Rated short-circuit breaking current | kA | 12.5 / 16 / 20 / 25 |
| 5 | Rated peak withstand current (peak) | kA | 31.5 / 40 / 50 / 63 |
| 6 | Rated short-time withstand current (4s) | kA | 12.5 / 16 / 20 / 25 |
| 7 | Rated short-circuit making current (peak) | kA | 31.5 / 40 / 50 / 63 |
| 8 | Mechanical life | times | 10000 |
| 9 | Rated-current breaking times | times | 10000 |
| 10 | Rated short-circuit breaking times | times | 30 |
| 11 | Power-frequency withstand voltage (1 min), phase-to-phase / phase-to-earth / open | kV | 42 |
| 12 | Lightning impulse withstand voltage (peak), phase-to-phase / phase-to-earth / open | kV | 75 |
| 13 | Secondary circuit 1 min power-frequency withstand voltage | kV | 2 |
| 14 | Net weight | kg | 140 |
Installation & Wiring
Installation Diagram
The ZW20Z-12 is designed for standard pole mounting with clear phase spacing and secure anchoring points to ensure mechanical stability under wind (up to 700 Pa) and ice loading. The outline and mounting dimensions are given in the drawing below.
Outline Dimensions
| Dimension | Value (mm) |
|---|---|
| Overall width (across outgoing bushings) | 1160 |
| Overall height | 775 |
| Mechanism box height | 550 |
| Lower section height | 125 |
| Aviation-socket center spacing | 350 ± 0.5 |
| Phase-to-phase spacing (front view) | 135 / 135 |
| Phase-to-phase spacing (side view) | 275 / 275 |
| Base mounting height | 205 |
| Bushing terminal hole diameter | Φ13 |
Selection & FAQs
Selection Guide
- Confirm a 12kV, 50Hz three-phase pole-mounted application and select 630A or 1250A after load, temperature-rise and future-capacity assessment.
- Choose 12.5, 16, 20 or 25kA rated short-circuit breaking capacity above the calculated prospective fault level, and verify the corresponding peak withstand, 4s short-time withstand and peak making ratings.
- Confirm the neutral earthing arrangement (solidly earthed, via arc-suppression coil, or via low resistance) together with site wind pressure (<=700Pa) and altitude (<=3000m).
- Specify mechanism control voltage, manual/motor operation, spring-energy indication, built-in CT ratios, aviation-plug secondary circuits and controller protocol for local/remote automation and reclosing.
- Check -40 degC to +40 degC outdoor service, humidity, pollution and corrosion limits, pole strength, surge protection and grounding.
Frequently Asked Questions
Q1: What short-circuit breaking capacities are available for the ZW20Z-12?
The rated short-circuit breaking current is available in 12.5, 16, 20 or 25 kA. Select the rating above the prospective fault level at your installation point and contact us with your load profile for an engineering recommendation.
Q2: What is the difference between the ZW20Z-12 and the ZW20-12?
The ZW20Z-12 is an improved version of the ZW20-12. It adds overcurrent protection and mechanism spring-energy indicators, and uses aviation plugs for the secondary connections so it integrates more easily with intelligent controllers and reclosing schemes.
Q3: Can this breaker operate at high altitude or in extreme cold?
Yes. It operates from -40 degC to +40 degC and at altitudes up to 3000 m; for higher altitudes the rated insulation level is raised accordingly. Wind pressure must not exceed 700 Pa (about 34 m/s).
Q4: Which rated current options should I select?
Choose between 630 A and 1250 A based on your system load profile. Confirm your exact requirements with our engineering team.
Q5: Are standard factory tests performed before shipment?
Yes, routine tests are conducted per applicable IEC and GB standards. Specific type tests or third-party certifications are subject to confirmation; contact our sales team for the detailed test report.
Q6: Where is the ZW20Z-12 typically installed?
It is designed for outdoor pole-mounted 10/12kV distribution networks, ideal for substations and industrial and mining systems that require frequent operation and distribution automation.