Overview
The ZW8-12/C intelligent type outdoor high-voltage vacuum circuit breaker is a three-phase AC device rated for 12kV / 50Hz distribution systems, designed for breaking and closing load currents in overhead feeder networks. It integrates overload protection, short-circuit protection, instantaneous trip protection, time-delayed protection, and automatic reclosing functions in a single self-powered pole-mounted unit.
An optional lightning arrester or disconnector combination (“combined intelligent switchgear”) is available on request. The built-in power supply enables local or remote operation without external DC/AC sources, and integrated CT/Pt interfaces support SCADA telemetry requirements.
Model Designation
Construction
The ZW8-12/C features a compact three-phase column structure with vacuum interrupters housed inside a stainless-steel sealed tank, mounted on a galvanized steel frame for pole or gantry installation. The external mechanism box contains the spring-storage mechanism, control board, and communication module.
Equipped with an integrated intelligent controller (FTU), the breaker provides overcurrent relay protection, instantaneous trip, time-delayed overcurrent, and auto-reclosing (1 to 3 operations). The controller supports remote/local switching, and the unit includes a manual operating handle for emergency use. The hermetically sealed vacuum interrupters ensure a long maintenance-free service life in harsh outdoor environments.
Technical Parameters
Service Conditions
- Ambient air temperature: -40 degC to +40 degC
- Altitude: <= 1000 meters (higher altitude on request with derating)
- Earthquake intensity: <= Grade 8
- Relative humidity: daily average <= 95%; monthly average <= 90%
- Site requirement: free from fire, explosion, severe pollution, chemical corrosion, or violent vibration
Technical Data
| No. | Item | Unit | Data |
|---|---|---|---|
| 1 | Rated Voltage | kV | 12 |
| 2 | Rated Insulation Level – 1min Power Frequency Withstand Voltage (Dry) | kV | 42 |
| Rated Insulation Level – 1min Power Frequency Withstand Voltage (Wet) | kV | 34 | |
| Rated Insulation Level – Lightning Impulse Withstand Voltage (Peak) | kV | 75 | |
| 3 | Rated Current | A | 400, 630 |
| 4 | Rated Short-Circuit Breaking Current | kA | 20, 16, 12.5 |
| 5 | Rated Operating Sequence | – | O-0.3s-CO-180s-CO |
| 6 | Number of Rated Short-Circuit Breaking Operations | times | 30 |
| 7 | Rated Short-Circuit Closing Current (Peak) | kA | 50 |
| 8 | Rated Peak Withstand Current | kA | 50 |
| 9 | Rated Short-Time Withstand Current | kA | 20, 16, 12.5 |
| 10 | Rated Short-Circuit Duration | s | 4 |
| 11 | Opening Time (Shunt Trip) – Highest Operating Voltage | ms | 15~50 |
| Opening Time (Shunt Trip) – Rated Operating Voltage | ms | 15~50 | |
| Opening Time (Shunt Trip) – Lowest Operating Voltage | ms | 30~60 | |
| 12 | Closing Time | ms | 25~50 |
| 13 | Total Opening Time | ms | ≤ 100 |
| 14 | Arcing Time | ms | ≤ 20 |
| 15 | Mechanical Life | times | 10000 |
| 16 | Closing Energy | J | 70 |
| 17 | Storage Motor Rated Input Power | W | ≤ 220 |
| 18 | Rated Operating Voltage & Auxiliary Circuit Rated Voltage | V | AC/DC 220, 110, 24 |
| 19 | Storage Time at Rated Voltage | s | < 8 |
| 20 | Overcurrent Trip Unit – Rated Current | A | 5 |
| Overcurrent Trip Unit – Trip Current Accuracy | % | ± 10 | |
| 21 | Overcurrent Setting Range | A | 1~9 |
| 22 | Instantaneous Trip Setting Range | – | 6~20 |
| 23 | Time Delay Range | ms | 80~500 |
| 24 | Remote Control Distance | m | 30 |
| 25 | Number of Auto-Reclosing Operations | times | 1~3 |
Installation & Wiring
Installation Diagram
The ZW8-12/C is designed for pole-mounted or gantry installation. The drawings below give the overall and installation dimensions for both the Electronic PT Type Circuit Breaker and the Recloser variants. Ensure proper phase-to-phase clearance, grounding, and mechanical load rating of the support structure during installation.
Overall and Installation Dimensions
| Dimension | Electronic PT Type Circuit Breaker | Recloser |
|---|---|---|
| Overall Width (mm) | 1030 | 830 |
| Overall Depth (mm) | 510 | 560 |
| Overall Height (mm) | 800 | 1050 |
| Installation Hole Spacing (mm) | 590 × 480 | 590 × 480 |
| Installation Holes | 4 × φ15 | 4 × φ15 |
Selection & FAQs
Selection Guide
- Confirm a 12kV, 50Hz three-phase overhead distribution application; select 400A or 630A rated current based on continuous feeder load.
- Choose 12.5kA, 16kA or 20kA breaking capacity above the prospective fault current at the installation point.
- Verify 75kV lightning impulse and 42kV (dry) / 34kV (wet) power-frequency withstand levels against system insulation coordination.
- Specify the FTU control voltage (AC/DC 220, 110 or 24V) and configure protection settings: overcurrent (1~9A), instantaneous trip multiplier (6~20x), time delay (80~500ms), and reclosing shots (1~3).
- Check −40°C to +40°C ambient range, altitude ≤1000m, seismic intensity ≤Grade 8; request custom derating for elevated sites.
Frequently Asked Questions
Q1: What protection functions does the ZW8-12/C intelligent breaker provide?
The integrated FTU controller provides overcurrent protection, short-circuit protection, instantaneous trip protection, time-delayed overcurrent protection, and automatic reclosing (1 to 3 shots). These settings are field-adjustable via the controller interface.
Q2: Can this breaker operate without an external power source?
Yes, the ZW8-12/C is self-powered. It uses an internal voltage transformer (Pt) to derive operating energy from the line, eliminating the need for a separate DC battery or AC supply at the pole.
Q3: What is the difference between ZW8-12 and ZW8-12/C?
The /C suffix indicates the addition of automatic reclosing functionality. Standard ZW8-12 provides basic breaking/closing; ZW8-12/C adds configurable 1–3 shot reclosing sequences for transient fault clearance on overhead feeders.
Q4: What remote control and monitoring options are available?
The unit supports local manual operation via handle, and remote electrical operation via the mechanism box terminals. CT and Pt interfaces are provided for SCADA telemetry integration. Remote control distance is up to 30m via the included wireless controller.
Q5: What are the rated insulation levels for this 12kV breaker?
1-minute power frequency withstand voltage: 42kV (dry) and 34kV (wet). Lightning impulse withstand voltage (peak): 75kV. These comply with GB and IEC standards for 12kV class equipment.
Q6: Can a lightning arrester or disconnector be combined with this breaker?
Yes. On request, the ZW8-12/C can be supplied with an integrated surge arrester or combined with a disconnector to form a “combined intelligent switchgear” assembly for enhanced lightning and isolation protection.
Q7: What is the mechanical and electrical service life?
Mechanical life is 10,000 operations. The breaker supports 30 rated short-circuit breaking operations before maintenance. Vacuum interrupters are sealed for life with no gas refills required.
Q8: Is the ZW8-12/C suitable for extreme cold environments?
Yes, it is rated for ambient temperatures from −40°C to +40°C, making it suitable for cold-climate overhead distribution networks in northern regions.