NOJA Power

Technical Article

Published 05/2024

NOJA Power Sectionalizer - A Direct Replacement for Aging Sectionalizer Assets

NOJA Power OSM Recloser in North Cyprus

Sectionalizers are a common distribution network asset used to subdivide a distribution network into smaller segments or “zones”. By subdividing a network into smaller zones, fewer customers are impacted by any fault or planned outage.

Many legacy designed sectionalizers used SF6 insulation or exposed air terminals, presenting either an environmental or reliability challenge respectively. Fortunately, modern units such as NOJA Power’s OSM Recloser can be used to fulfil the Sectionalizer application on the distribution grid.

In this article, we review the key items on how to use a NOJA Power OSM Recloser as a direct replacement for aging sectionalizer assets.

What is a Sectionalizer?

A sectionaliser is a switch which automatically opens when a fault causes an upstream circuit breaker to open.

When the upstream circuit breaker recloses, the power supply reaches the sectionalizer, but doesn’t go through it. This way, the sectionalizer divides up the distribution network into more zones.

Figure 1 shows this principle in action. A fault downstream of both the Recloser R1 and Sectionalizer S1 causes R1 to trip. When R1 trips, S1 has seen both the fault, and the interruption. It then opens before R1 re-energizes the line.

When R1 closes, S1 has “sectionalized” the fault.

Figure 1 – Basic Sectionalizer behaviour in response to a fault
Figure 1 – Basic Sectionalizer behaviour in response to a fault

Why use Sectionalizing?

Returning to the case in figure 1, the diagram doesn’t detail how many customers are connected. Usually, distribution network customers are connected via distribution transformers all along the line between R1, S1, and then from S1 to the end of the line.

For example, If we assume 1000 customers downstream from R1, we could position S1 so that it serves 500 of those customers.

Under the case scenario in figure 1, if no sectionalizers were deployed, a fault would cause loss of revenue from 1000 customers. Now with a Sectionalizer, a fault only causes losses from 500 customers.

Adding more sectionalizers reduces the economic loss of the utility business, while improving reliability for the greatest number of customers.

How to use a NOJA Power OSM Recloser as a Sectionalizer

All NOJA Power OSM Reclosers can be programmed to work as a Sectionalizer.

To configure Sectionalizing functionality in a NOJA Power Recloser, select the “Sectionalizer” function button in the protection group settings. This enables the addition of two new elements to the Recloser Map. They are “Count” and “Sectionalize”.

The “Count” function instructs the recloser to watch for current readings which exceed a threshold, called a pickup value, followed immediately by a loss of current. This combination is considered a “count”. This is what a Sectionalizer sees on the network as the upstream protection device interrupts the fault.

The ”Sectionalize” function does the same as the “Count”, except it causes the NOJA Power OSM Recloser to “Open” after seeing the current exceed the threshold, followed by the loss of current.

This seems counterintuitive, as a Recloser does have the ability to break fault current. However, the NOJA Power OSM Reclosers’ ability to directly emulate a sectionalizer means that the legacy device’s settings can be implemented in the NOJA Power Recloser when a replacement is being commissioned. This removes additional engineering cost and makes the changeover simple.

Figure 2 – 3 Count Sectionalize behaviour programmed in the configuration software for NOJA Power’s OSM
Figure 2 – 3 Count Sectionalize behaviour programmed in the configuration software for NOJA Power’s OSM

Advantages of using an OSM Recloser as a Sectionalizer over older technology

Firstly, using an OSM Recloser to replace sectionalizers in the network gives utilities a way to upgrade their networks. The OSM Recloser can fulfil a sectionalizer role in a replacement program, and later be converted to a direct protection asset. This allows for progressive network upgrade without great cost.

Secondly, it allows for equipment standardisation. Since the product is identical to the pole mount recloser, the common spares, training, and general arrangements offer substantial operational cost savings for electricity distribution businesses.

The OSM Recloser is also an environmentally friendly alternative to SF6 based sectionalizers in use today.

“Our OSM reclosers are both reclosers and sectionalizers and can be configured as either using our complete range of RC controls,” says NOJA Power Group Managing Director Neil O'Sullivan.

“Some customers start by configuring our devices as sectionalizers when first installed and as they mature the protection on their feeder change settings to make them reclosers over the course of their installed life.”

For more information, visit or contact your local NOJA Power Distributor.

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