The FZW32-12/630-20 outdoor high-voltage vacuum load break switch is a three-phase switching device for 50 Hz, 12 kV distribution networks. Full type tests and long-running service experience confirm conformity with GB 3804 for 3.6 kV to 40.5 kV AC load break switches and with the applicable IEC recommendations.
Vacuum interrupters take over the breaking duty while the isolating knives leave a clearly visible open gap, so one unit performs both load switching and sectioning. With a spring or motor operating mechanism and a controller, the switch also serves as a sectionalizing device or an automatic line divider on urban and rural overhead feeders.
Model Designation
The type designation FZW32-12/T 630-20, also written FZW32-12/630-20, reads as follows:
- F: load break switch
- Z: vacuum
- W: outdoor type
- 32: design sequence number
- 12: rated voltage, kV
- T: spring operating mechanism
- 630: rated current, A
- 20: rated short-time withstand current, kA
The optional suffix behind the mechanism symbol denotes the control arrangement: manual spring operation, motorised operation, or a controller for automatic line division. Other current and withstand combinations are available on request.
Construction and Design
The three poles are mounted on a common steel frame, each pole combining a vacuum interrupter with an isolating knife on porcelain composite columns, so the unit is built for outdoor duty at pollution level IV. The isolating knives are driven by a spring-over-centre mechanism with three-pole ganged operation, which fixes the opening simultaneity of the interrupters at the factory. A quick-acting mechanism sets the interrupter travel speed independently of the operator, so arcing time does not depend on how fast the handle is moved.
Operating Function and Application
In service the switch makes and breaks rated load current, closed-loop transfer current, cable charging current and capacitor bank current; short-circuit current is cleared by back-up fuses or upstream protection. The visible isolating gap gives the maintenance crew a positive sectioning point on the pole. Typical duties are feeder sectioning and load transfer on 12 kV overhead lines, ring-network open and closed-loop operation, and fault isolation when a controller is added.
Technical Parameters
Service Conditions
- Ambient temperature: +40℃ maximum, -40℃ minimum
- Altitude: Not more than 1000 m; higher sites require a correspondingly higher insulation level
- Wind pressure: Not more than 700 Pa, equivalent to a wind speed of 34 m/s
- Seismic intensity: Not more than 8 degrees
- Pollution level: IV
- Maximum daily temperature difference: Not more than 25 K
- Relative humidity: Daily average not more than 95%, monthly average not more than 90%
- Site condition: No flammable gas, explosion risk, chemical corrosion or severe vibration
Technical Data
| No. | Item | Unit | Parameter |
|---|---|---|---|
| 1 | Rated voltage | kV | 12 |
| 2 | Rated frequency | Hz | 50 |
| 3 | Rated current | A | 630 |
| 4 | Rated active load breaking current | A | 630 |
| 5 | Rated closed-loop breaking current | A | 630 |
| 6 | 5% rated active load breaking current | A | 31.5 |
| 7 | Rated cable charging breaking current | A | 10 |
| 8 | Rated capacitor bank breaking current | A | 100 |
| 9 | 1 min power-frequency withstand voltage (vacuum gap / phase and earth / isolating gap) | kV | 42/48 |
| 10 | Lightning impulse withstand voltage (phase and earth / isolating gap) | kV | 75/85 |
| 11 | Rated short-time withstand current | kA | 20 |
| 12 | Rated short-circuit duration | s | 4 |
| 13 | Rated peak withstand current | kA | 50 |
| 14 | Rated short-circuit making current | kA | 50 |
| 15 | Mechanical life | operations | 10000 |
| 16 | Three-pole opening and closing simultaneity | ms | ≤ 5 |
Standards
- GB 3804 — AC high-voltage load break switches, 3.6 kV to 40.5 kV
- Applicable IEC recommendations for outdoor AC switching devices used on distribution networks
Installation & Wiring
Installation and Commissioning
- Choose the mounting mode. Horizontal pole mounting needs an overall width of 1300 mm with phase spacing of 750 mm and 320 mm; side mounting 1230 mm with 500 mm and 500 mm; pole-top mounting 1050 mm with 400 mm and 400 mm. The frame is levelled before the clamps are torqued.
- Support hardware. Side mounting uses the lead wire terminal, pole, long and short support brackets, cable outlet and power supply cable; horizontal and pole-top mounting use the switch support component, support arm, terminal, shaped pull rod and end cable. A potential transformer supplies the electric operating mechanism where motorised operation is ordered.
- Mechanism checks. Charge the spring by hand, confirm close, open and trip actions, check the open-gap indication on all three poles and verify that the three-pole simultaneity stays within 5 ms.
- Before energization: carry out the 1 min power-frequency withstand test on the main circuit, bond the frame to the earth network and re-check terminal clearances against the approved outline drawing.
Applications
- Sectioning and load transfer on 12 kV overhead distribution lines
- Open and closed-loop switching in urban and rural ring-network supply
- Transformer and feeder control on branch lines with back-up fuse protection
- Automatic line division when combined with a controller and motor mechanism
Selection & FAQs
Selection Guide
- Fix the switching duty. The standard unit is 630 A with 20 kA for 4 s short-time withstand; confirm the prospective short-circuit level of the line so that back-up fuse coordination can be checked.
- Choose the breaking duties to be used. The switch is rated for 630 A load and closed-loop current, 10 A cable charging current and 100 A capacitor bank current; short-circuit currents are cleared by fuses or upstream devices.
- Select the operating arrangement. Manual spring operation for simple sectionalizing, motor mechanism plus controller where automatic line division and remote tripping are required.
- Match the mounting hardware to the pole. Horizontal, side and pole-top mounting need different bracket widths, so state the mode and pole diameter at order.
- Verify the site conditions. Altitude above 1000 m, wind speed beyond 34 m/s or a pollution level above IV require a technical agreement.
FAQs
Q1: What is the FZW32-12 used for?
It is an outdoor three-phase 12 kV, 50 Hz vacuum load break switch for urban and rural overhead distribution networks. It makes and breaks load current, sections the line for maintenance with a visible open gap, and with a motor mechanism and controller can act as a sectionalizing or automatic line-dividing device.
Q2: How do I read the model designation FZW32-12/T 630-20?
F = load break switch, Z = vacuum, W = outdoor type, 32 = design sequence number, 12 = rated voltage in kV, T = spring operating mechanism, 630 = rated current in A, and 20 = rated short-time withstand current in kA. The optional suffix after the mechanism symbol states the control arrangement.
Q3: Why does the switch have both vacuum interrupters and isolating knives?
The vacuum interrupter quenches the arc when load current is broken, while the isolating knives provide the air insulation of an open gap once the pole is apart. The combination gives load switching and sectioning in one pole-mounted unit, so the maintenance crew can see a positive break point without a separate disconnector.
Q4: Can the FZW32-12 interrupt short-circuit current?
No. It carries and withstands short-circuit current, rated 20 kA for 4 s with a 50 kA peak, but it is not a short-circuit breaking device. Faults are cleared by back-up fuses on the combination unit or by upstream protection; the capacitor bank and cable charging ratings of 100 A and 10 A are the only non-load breaking duties.
Q5: What space is needed on the pole for each mounting mode?
Horizontal pole mounting occupies 1300 mm overall width with phase spacing of 750 mm and 320 mm, side mounting 1230 mm with 500 mm and 500 mm, and pole-top mounting 1050 mm with 400 mm and 400 mm. The matching brackets, pole clamps, strain clamps and clevis fittings are ordered with the switch.
Q6: How does the FZW32-12 compare with the FZW-40.5, the FZW28Z-12 and the ZW32-24?
All are outdoor vacuum switching devices with a visible isolating gap, but they sit at different voltages and duties. The FZW-40.5 covers 40.5 kV lines at 1250 A, the FZW32-12 covers 12 kV feeders at 630 A with 20 kA short-time withstand, and the FZW28Z-12 is a compact pole-mounted sectionalizer for 12 kV distribution. The ZW32-24 is a vacuum circuit breaker, so it trips on short-circuit fault current itself, whereas the load break switches rely on fuses or upstream protection for faults.