Overview
The ZW20A-12 is an outdoor high-voltage pole-mounted vacuum circuit breaker designed for 12kV, 50Hz three-phase AC power distribution systems. It delivers reliable switching and protection against load currents, overloads, and short-circuit faults in substations, industrial plants, rural electrification networks, and smart grid applications.
Engineered for frequent operation, it supports remote monitoring and automation integration. Based on the proven ZW20-12 platform, the ZW20A-12 combines advanced vacuum arc extinguishing with SF6 gas insulation, adopting structural principles from the Japanese Toshiba VSP5 design to ensure exceptional dielectric strength and hermetic sealing.
Key Ratings Snapshot
| Parameter | Value |
|---|---|
| Rated voltage | 12 kV |
| Rated frequency | 50 Hz |
| Rated current | 630 A / 1250 A |
| Rated short-circuit breaking current | 16 kA / 20 kA / 25 kA |
| Rated short-circuit making current (peak) | 40 kA / 50 kA / 63 kA |
| Rated short-time withstand current (3s) | 16 kA / 20 kA / 25 kA |
| Power frequency withstand voltage (1 min) | 42 kV |
| Lightning impulse withstand voltage | 75 kV |
| Mechanical life | 10,000 operations |
| SF6 gas pressure (gauge, 20 degC) | 0.01 MPa |
Model Designation
- ZW: Vacuum circuit breaker
- 20: Product series design number
- 12: Rated voltage (12 kV)
- T: Spring-operated mechanism
- First â¡: Rated current (e.g., 630 A)
- Second â¡: Rated short-circuit breaking current (e.g., 20 kA)
Construction
The ZW20A-12 features a compact spring-operated mechanism with direct chain drive and multi-stage tripping for enhanced mechanical reliability. Its main current path employs an internal expansion and external contraction bracelet contact structure to reduce contact resistance and thermal rise. The sealed enclosure guarantees stable operation across extreme environmental conditionsâincluding high humidity, dust, and wide temperature rangesâwhile ensuring zero SF6 leakage and robust explosion-proof performance.
Primary terminals are labeled P1/P2 (power input/output), while secondary terminals for instrument transformer connections are marked S1/S2. The unit integrates built-in current transformers for relay interfacing and supports both manual and motorized operation for flexibility in control schemes.
Technical Parameters
Service Conditions
- Ambient Temperature: -40 degC to +40 degC
- Altitude: <=1000 m
- Relative Humidity: Daily average <=95%
Monthly average <=90% - Seismic Intensity: <=8 degrees
- Installation Environment: No fire, explosion, severe pollution, or chemical corrosion
Technical Data
| Rated current (A) |
Rated short-circuit breaking current (kA) |
Rated short-circuit making current (peak, kA) |
Rated short-time withstand current (3s, kA) |
|---|---|---|---|
| 630 / 1250 | 16 / 20 / 25 | 40 / 50 / 63 | 16 / 20 / 25 |
Installation & Wiring
Installation Diagram
The ZW20A-12 is designed for standard pole mounting with clear phase spacing and secure anchoring points to ensure mechanical stability under wind and ice loading conditions.
Outline Dimensions
| Dimension | Value (mm) |
|---|---|
| Overall height | 1850 |
| Overall width (phase-to-phase) | 630 |
| Mounting bracket height | 1200 |
| Primary terminal spacing (P1âP2) | 350 |
| Secondary terminal block size | 120 x 80 |
Selection & FAQs
Selection Guide
- Confirm a 12kV, 50Hz pole-mounted application and select 630A or 1250A after load, temperature-rise and future-capacity assessment.
- Choose 16kA, 20kA or 25kA breaking capacity above the calculated fault level and verify corresponding peak-making and three-second withstand ratings.
- Specify built-in CT ratios, protection cores, burdens and zero-sequence requirements to match relay pickup, metering and automation functions.
- Confirm mechanism control voltage, manual/motor operation, auxiliary contacts, controller protocol, power supply and local/remote operating logic.
- Check −40°C to +40°C outdoor conditions, altitude, wind/ice and seismic loads, pole strength, surge protection, grounding and 0.01MPa SF₆ pressure data.
Frequently Asked Questions
Q1: What short-circuit breaking capacities are available for this breaker?
Available capacities are 16, 20, or 25 kA. Select the rating based on your prospective fault level. Contact us with your load profile for an engineering recommendation.
Q2: Can this pole-mounted breaker operate in extreme cold climates?
Yes, subject to site verification. The ZW20A-12 operates in ambient temperatures from -40°C to +40°C. Ensure installation altitude does not exceed 1000 meters.
Q3: Which rated current options should I select for my project?
Choose between 630 A and 1250 A. The correct selection depends on your specific system load profile. Confirm your exact requirements with our engineering team.
Q4: Are standard factory tests performed before shipment?
Yes, standard routine tests are conducted per applicable IEC standards. Specific type tests or third-party certifications are subject to confirmation. Contact our sales team for the detailed test report.
Q5: How long is the standard delivery time for bulk orders?
Lead times vary based on order quantity and customization. Exact delivery schedules are subject to confirmation. Please contact us with your required quantity for an accurate quote.
Q6: Where is this outdoor vacuum circuit breaker typically installed?
It is designed for outdoor pole-mounted distribution networks. Ideal for 12kV systems without severe pollution or chemical corrosion. Confirm your specific installation environment with our technical support.