In the field of power distribution, companies undertaking power grid automation projects often need to purchase equipment to protect the grid. Therefore, they want to understand the difference between auto reclosers and sectionalizers. This article, written by a manufacturer with many years of experience in producing automatic reclosers, explains the differences between these two devices.
The differences between an auto recloser and a sectionalizer lie in their function, operation, typical use, interaction, and fault response. Detailed analysis is provided below.
The automatic reclosing function attempts to automatically restore power. When a momentary short circuit is detected, it automatically interrupts the current, and after a preset delay, it recloses the circuit breaker to attempt to restore power. If the fault has cleared (e.g., a tree branch blown down by the wind, a lightning strike), power is restored. If the fault persists (a permanent fault), it will trip again and may attempt multiple “trip-reclose” cycles.
Example: A lightning strike causes a momentary ground fault on an overhead line. After the recloser trips, the arc extinguishes, and the insulation is restored. The recloser recloses, successfully restoring power to the entire line.
A fault isolator permanently isolates a faulty section after multiple faults occur. It does not have the capability to interrupt short-circuit current itself, but instead works in conjunction with an upstream recloser, “counting” the number of recloser trips. When the number of faults reaches a preset value, indicating a permanent fault, it automatically disconnects the circuit after the recloser trips again and the line loses voltage, thereby isolating the faulty section.
Example: A section of cable is dug up, causing a permanent fault. The upstream recloser trips and recloses, but the fault persists, causing it to trip again. This repeats. After the fault interrupter “counts” the second trip, it automatically opens the circuit when the system loses voltage, isolating the faulty cable section.
Automatic Recloser: Automatically performs disconnection and reconnection operations. It is a fully functional circuit breaker capable of interrupting fault currents and features logic control for multiple automatic reclosing attempts.
Fault Interrupter: Can only perform a permanent disconnection operation after a loss of voltage in the line and does not have the ability to reclose automatically. It is typically a load switch that, after isolating the fault, requires manual or remote control commands to reclose.
Automatic Recloser: Widely used in overhead power distribution lines, especially in areas prone to transient faults (such as lightning strikes, bird damage, and tree contact). It effectively reduces prolonged power outages caused by transient faults.
Fault Interrupter: Typically installed on branch lines or critical sectional points of radial or tree-shaped distribution networks. It is often used in series with reclosers to accurately isolate sections with permanent faults in complex networks, minimizing the scope of power outages and ensuring power supply to non-faulty areas.
Automatic Recloser: Can operate independently, performing basic fault clearing and restoration attempts. It can also act as an upstream protection device for the fault interrupter, providing operating logic (number of tripping attempts) for the interrupter.
Fault Interrupter: Must be used in conjunction with an upstream automatic recloser (or a circuit breaker with reclosing function). It cannot operate independently; its operating logic is entirely dependent on the recloser’s operating sequence.
Automatic Recloser: Its response logic is a “detection-trip-wait-reclose” cycle of attempts. A typical operating sequence might be “fast trip-fast reclose” (to clear transient faults), and if unsuccessful, multiple attempts of “fast trip-delayed reclose-fast trip-delayed reclose” may follow.
Fault Interrupter: Its response logic is “count-judge-isolate”. It continuously monitors line current and voltage. When a fault current exceeding the threshold is detected, followed by a loss of line voltage (indicating the upstream recloser has tripped), it increments a counter. When the count reaches a preset value (e.g., 2 times), and the line voltage is lost again (the recloser’s final trip), it immediately opens the circuit, isolating its section. Afterward, the upstream recloser can successfully reclose, restoring power to the non-faulty area.
| Feature | Auto Recloser | Sectionalizer |
| Function | Attempts to restore power | Isolates the faulted section |
| Operation | Reconnects automatically | Does not reconnect power |
| Typical Use | Overhead lines, temporary faults | Complex network sections |
| Interaction | Works alone or with sectionalizer | Works with auto recloser |
| Fault Response | Attempts multiple restores | Isolates after multiple faults |
The core of selecting Auto Recloser and Segmenter is functionality, application scenarios, and collaborative relationships. The following table summarizes the key purchasing points.
| Comparative Dimension | Auto Recloser | Sectionalizer |
| Main purchasing objectives | Quickly restore power supply and reduce power outages caused by transient faults such as lightning strikes and tree branches. | Accurately locate and isolate permanent fault sections to minimize power outages. |
| Key selection parameters | Recloser frequency and interval: Supports two or more recloses, with adjustable intervals. Rated voltage and current: match the line level (such as 10kV) and load. Protection function and setting value: It is necessary to have overcurrent, quick break and other protections, and cooperate with higher-level protection settings. | Fault counting frequency: It needs to be accurately matched with the tripping frequency of upstream reclosing. Voltage loss tripping function: It must be reliably tripped after the last trip of the reclosing and the loss of voltage in the line. Rated parameters: meet the requirements of the online road section. |
| Core Collaboration Considerations | As the main force of the protection system, it can provide a “trip signal” for downstream sectionalizers. | It must be purchased and debugged as a complete set with upstream reclosing, and its action logic completely depends on reclosing. |
| Prohibited and cautious scenarios | Prohibited for use in circuits that may endanger personal safety (such as handheld tools, medical equipment), flammable and explosive environments, and power supplies for precision equipment with extremely high requirements for power continuity (such as semiconductor manufacturing). | Usually not used alone; It is meaningless on a line without reclosing coordination. |
The typical buyers and application scenarios of the two devices are different.
| Buyer Type | More Emphasis On Purchasing Automatic Reclosing Scenarios | Scenarios That Require Cooperation In Purchasing (Automatic Recloser+Segmenter) |
| Power grid/supply company (core buyer) | 10kV overhead line: used for power grids, mountainous areas and other easily prone to instantaneous faults, installed independently. Distribution automation transformation: as a core equipment deployment for new technologies such as “secondary reclosing”. | Multi branch complex lines: Install on the main line and important branch lines, build a feeder automation system, and achieve automatic fault isolation and non fault section recovery. |
| Large industrial and mining enterprises | Entrance of enterprise dedicated overhead power supply line: serves as the main incoming line protection to resist transient interference from external power grids. | The complex and important distribution network within the factory area includes the installation of reclosers in the main incoming line and sectionalizers at branch points in the workshop and production line to protect critical loads. |
| Railway, new energy, etc | Electrified railway traction network and photovoltaic/wind farm transmission lines: respond to transient faults such as lightning strikes to ensure grid connection and operation. | Less application, usually considered by the grid side as a whole. |
Can I use a sectionalizer without automatic reclosing?
No, sectionalizers typically require automatic reclosing to effectively isolate faults.
What types of faults are best handled by automatic reclosing?
Automatic reclosing is best suited for handling transient faults, such as those caused by lightning strikes or falling tree branches.
How many times will the automatic recloser attempt to restore power?
Depending on the settings, the automatic recloser can attempt to restore power up to three times.
Are sectionalizers used in residential areas?
Sectionalizers are more commonly used in industrial and large power grid environments, where multiple automatic reclosers are typically employed.
Automatic reclosers act like “first responders,” attempting to restore power to the entire line through multiple attempts.
Sectionalizers, on the other hand, act like “surgeons,” precisely isolating and removing a section of the line after confirming that it is “beyond repair” (permanent fault), thus preserving the healthy parts. The combination of these two devices greatly improves the reliability of the power distribution network.
If a power distribution company wants to improve system reliability and reduce downtime, then purchasing automatic reclosing devices is a wise investment for the power grid.
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