4 Things to Consider When Choosing a Sectionalizer

A sectionalizer is a device used to protect electrical equipment and distribution circuits from damage caused by faults in the system. It functions as a switch that is automatically activated when sensors detect an overcurrent or other faulty conditions. When a fault is detected, the sectionalizer opens the circuit to isolate the fault and prevent it from causing more damage. 

Sectionalizers work with backup devices such as reclosers, circuit breakers, fuse cut-outs, and line switches. Typically, sectionalizers are installed downstream of an automatic circuit recloser which serves as an active protection device. The recloser has sensors that can detect faults and interrupt them by tripping the circuit breakers. 

Sectionalizers are an important part of the railway infrastructure and can help to improve safety by preventing accidents on the train track or in the power station.

There are different kinds of sectionalizers based on capabilities, mode of operation, and other factors. Here are four things to consider while choosing a sectionalizer:

1.  Phase

One of the things to consider when choosing a sectionalizer is the phase construction. There are two types of sectionalizers based on the number of phases. There are single-phase sectionalizers and three-phase sectionalizers. 

Single-phase sectionalizers are used for protecting single-phase circuits like those in the branches or taps from a three-phase feeder. They are also used in single-phase connections for residential homes and domestic supplies. Single-phase connections use neutral and phase wires for distributing power. 

The voltage of a single-phase connection begins at 230v and has a frequency of around 50 Hertz. In single-phase power distribution, lightweight, and compact units are used. Also, the flow of power through wires is lower if the voltage is higher. 

On the other hand, three-phase sectionalizers typically open all three phases at the same time. They work to monitor temporary faults and permanent faults on a three-phase distribution system. 

Three-phase power connections include three separate electrical circuits. Each leg is separated by one-third of the time complete within one cycle and can reach maximum voltage. In addition, three-phase power supply systems can carry a higher voltage than single-phase connections. They are often used in large buildings like complexes where there is a need for multiple electricity feeders.

2. Voltage of the System

Another factor to consider when choosing a sectionalizer is the system voltage and current. Sectionalizers have different voltage ratings. The voltage and current rating of the sectionalizer should be greater than or equal to the maximum voltage and load current at the installation point. 

Typically, distribution lines in residential areas use sectionalizers with a voltage rating of 0-15kV. When choosing a train track sectionalizer, you should take note of the continuous current, the system voltage, and the number of counts for operation. Also, the short-circuit capacity must be equal to or higher than the fault level at the connection point.

3. Operating Systems to be Electronic

The operating system is another factor to consider when choosing a sectionalizer. Sectionalizers generally have two operating mechanisms: hydraulic and electronic operating mechanisms. 

Hydraulic-operated sectionalizers have operating coils in series with the line. Every time an overcurrent occurs, the operating coil drives a piston that begins a counting mechanism when the circuit opens. 

This works by the displacement of oil across the sectionalizer chambers when the circuit opens and the current is zero. Hydraulic operating sectionalizers are closed or opened manually using a hook stick. Some components of hydraulic operating sectionalizers include trip adjustment bars, actuating and counting mechanisms, and the operating handle. 

  • The trip adjustment bar can be adjusted to trip the system after one to three counts. 
  • The actuating coil and counting mechanism monitors the overcurrent interruptions and after a preselected number of counts opens the sectionalizer. 
  • The manual operating handle allows for the opening and closing of the sectionalizer.

Sectionalizers with electronic operating systems are more adaptable and easier to adjust than manual sectionalizing switches. 

Electronic-operated sectionalizers can come with a motor-operated disconnect switch or a manual switch for opening and closing. Here’s an example of an electronic-operating sectionalizer:

Manual sectionalizing switches are commonly used for rectifier disconnects, UPS systems, and other applications in electrified rail and catenary systems. 

On the other hand, motorized disconnect switches offer a safe and reliable means of disconnecting from a remote location. This is particularly useful for train track engineering which requires standby remote intervention when high-voltage is present.

The switches can also be designed to incorporate electrical interlocking to prevent operation when a voltage is present. In electronic-operated sectionalizers, CTs measure the load current. The secondary current is transferred to a control circuit that calculates the number of operations of the recloser. 

4. Coordination with Protection Devices

Lastly, when choosing a sectionalizer, you should consider the level of coordination with protection devices. You should consider coordination factors such as how it works with other protection devices that are installed upstream or downstream. 

Some of the protection devices you want to consider are fuses, breakers, and circuit switchers. 

With a power transformer, for instance, these protective devices aim to reduce the amount of time the transformer is exposed to faulty current. For sectionalizing low-side devices, you can use bank or station breakers. 

Also, when looking for how to seal electrical conduit from water, you’ll need protection devices like duct sealing systems. This will offer protection against the migration of water, gas, rodents, and fire. 

Ultimately, the goal of coordinating your sectionalizer with secondary protection devices is to ensure better system reliability and avoid issues like overcurrent.


Sectionalizers work with protection devices to automatically isolate faulty sections of a distribution unit. They serve as an effective and secure means of isolating faulty circuits. 

Since sectionalizers come in different capacities, operating modes, and functions, you should consider key factors like phase construction, system voltage, and operating system to be electronic. You should also consider how well the sectionalizer works with other protection devices. 

By keeping these things in mind, you’ll be able to choose a sectionalizer that works effectively.

Adam Hansen

Adam is a part time journalist, entrepreneur, investor and father.