The FZW28-12(F) load switch is also called watchdog. The users of 10kV overhead power distribution line through a T connection can cause the protective trip of the outgoing line switch in a transformer substation. Such problems happen when 1) faults occur at users’ incoming line, 2) or the protective motion time does not match that of the outgoing line switch of the substation, even though faults occur at the incoming line switch on user’s side.
If, unfortunately, the faults are permanent, then the substation can not be reconnected. Thus the accidents happened at the client’s end will paralyze the whole distribution line, causing serious society impacts.
However, our FZW28-12(F) load switch can avoid these accidents effectively. Installed at the responsibility demarcation point on the 10kV overhead distribution line, the watchdog can automatically disconnect the lines with single phase earthing fault or short circuit fault between phases, ensuring the safety of the power supply for normal clients.
Typical function
1. Automatically disconnecting single phase earthing line.
When a single phase earthing problem happened to a branch, the FZW28-12(F) load switch at the demarcation point will automatically disconnect the fault line, ensuring the normal power supply for users on the other braches of the feeder line, and the safe operation of the substation.
2. Automatically isolating the fault line with short circuit between phases.
When there is a short circuit problem at a branch line, the FZW28-12(F) load switch at the demarcation point will disconnect the fault line immediately after the trip of the outgoing line of substation. Then after the outgoing line of the substation is reconnected, the fault line will be isolated, while power supply for users on the other branches of the feeder line will be recovered.
3. Fast positioning of the fault line.
After the disconnection, the power supply for responsible users will be cut off. They can report the fault information to the electric power company, so the fault can be positioned and resolved soon.
4. Monitoring users’ load.
The FZW28-12(F) load switch at the demarcation point can transfer the monitoring data to the power control center for real-time monitoring of the load far away.
| The technical parameters of the controller | |||
| NO. | Item | Data | |
| 1 | Rated voltage | 12kV | |
| 2 | Gap insulating level | Power frequency withstand voltage (dry test/wet test, phase to phase and phase to earth, across open contacts) | 48kV |
| Lighting pulse peak testing voltage | 85kV | ||
| 3 | To earth and phase to phase insulating level | Power frequency withstand voltage (phase to phase and phase to earth) | 42kV |
| Lightning impulse test peak voltage | 75kV | ||
| 4 | Rated current | 630A | |
| 5 | Rated thermal stable current | 16kA | |
| 6 | Rated thermal stable time | 2S | |
| 7 | Rated short circuit peak making current | 40kA | |
| 8 | Rated peak withstand current | 40kA | |
| 9 | Rated cable charging breaking current | 20A | |
| 10 | Rated switching no-load transformer inductor current | ＜5A | |
| 11 | Closing time (built-in isolator motion time included) | 120ms ~180ms | |
| 12 | Opening time | 15ms ~40ms | |
| 13 | Mechanism endurance | 10000time | |
| 14 | Interlock current setting value range | ＜6ms | |
| 15 | Opening / closing synchronism | ＜5ms | |
| 16 | Loop circuit resistance | ＜700 μΩ | |
| 17 | Rated SF6 pressure | 0.002MPa | |
| The technical parameters of the controller | |||
| NO. | Item | Data | Note |
| 1 | Input working voltage | AC220V ±20% | |
| 2 | Input working frequency | 50Hz | |
| 3 | Overall power consumption | ＜10W | |
| 4 | Output voltage (opening operation) | DC48V | |
| 5 | Output control contact rating | DC48V, 8A | |
| 6 | Output power (opening operation) | DC48V, 8A | |
| 7 | sampling phase voltage input value | 0~264V | |
| 8 | sampling phase current input value | 0~20A | 5A or higher saturation current allowed |
| 9 | sampling zero sequence current input value | 0 ~20A | 5A or higher saturation current allowed |
| 10 | Phase to phase protective movement setting range | 0.5A ~5A | 20 grades (step length: 0.25A) |
| 11 | Phase to phase protective movement delay time | 0.3S | Adjustable by software |
| 12 | Zero sequence protection current setting range | 10mA ~200mA | 20 grades (step length: 10mA) |
| 13 | Zero sequence protective movement delay time | 0 ~2S | 5 grades (step length: 0.5S) |
| 14 | latching current setting value range | 6A | Adjustable by software |
| 15 | Low voltage latching setting value range | 66V | Adjustable by software |
| 16 | Setting value error allowance | ±5% | |
1. Close the circuit for energy storage
2. Manual closing lever
3. Opening and closing knob
4. Power
1.(rocket) Fastener
2. Cross arm
3. Utility pole
4. (rocket) Fastener
5. (rocket) Fastener
6. Demarcation switch
7. Demarcation switch controller
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