Sectionalizer performance in distribution network

What Is a Sectionalizer?

A sectionalizer is a switch that operates similarly to a recloser, commonly used in radial networks, sometimes with looped configurations. Its primary role is to control a specific section of the network. When a fault occurs in the distribution network, a protective switch issues a command to disconnect the circuit.

The issue arises when faults are often transient, such as those caused by tree branches or birds, where a permanent disconnection of the network isn’t necessary. This is where a “recloser” comes in—after a fault triggers a disconnection, the recloser attempts to restore power, assuming the fault was temporary. If a persistent fault is detected, the recloser, after several open-close cycles, ultimately issues a permanent circuit disconnection.

However, a drawback of the recloser is that when it permanently disconnects, it cuts power to all downstream branches, even though the fault might be limited to a small section. To address this, a “sectionalizer” is used as a complement to the recloser. Positioned at various points downstream of the recloser, the sectionalizer identifies the faulted section and isolates only that part, minimizing the impact.

Using single-phase circuit breakers in three-phase systems is particularly effective for ground fault isolation. Overall, employing single-phase protective devices can reduce the number of outages by half, assuming single-phase customers are evenly distributed across phases.

Service reliability for three-phase customers downstream of a single-phase breaker typically improves. These customers often have multiple single-phase loads, and the loads on unaffected phases remain operational during single-phase outages. Three-phase equipment might continue functioning during a single-phase outage (though motors could overheat due to voltage imbalance).

Source: Bargh News