sectionalization

Sectionalization is a method used in electrical power distribution to limit the extent of outages by dividing a network into smaller, electrically separated sections bounded by protective devices. The technique is applied on feeders and at distribution substations to contain faults and to speed restoration, thereby improving service reliability for customers.

In a typical arrangement, sectionalizing devices such as sectionalizers or manually or remotely operated switches are installed at strategic points on a feeder, often near the ends of the section or at tie points. They operate in coordination with fuses, circuit breakers, and reclosers. When a fault occurs within a section, the upstream protective device will clear the fault. If subsequent fault events occur within the same section, the sectionalizer, after a prescribed count or time delay, opens to isolate that section from the rest of the feeder. Once the fault is cleared, the protected section can be re-energized, and the device may reset automatically or require a reset.

Benefits of sectionalization include reducing outage size and customer minutes of interruption, improving restoration times, and enabling selective isolation without affecting healthy portions of the network. It complements automatic reclosing by preventing a prolonged outage in unaffected areas and by containing faults.

Limitations include the need for careful protection coordination and timing settings, added equipment and maintenance costs, and potential reduced effectiveness for certain fault types or in networks with few sectionalizing points. Effective design and testing are essential to ensure proper isolation and reliable operation.