NOJA Power

Technical Article

Published 05/2023

Connecting Grid Scale Solar with NOJA Power OSM Reclosers

A NOJA Power OSM Recloser with RC-10 control

As solar generation asset costs continue to decrease, more and more grid scale solar projects become economically viable and are reaching project development stages. Many of these solar projects connect to the electricity distribution grid, between 11 to 38 kV.

Connecting these projects to the distribution grid requires a few key features for protection, control and automation. Many solar project developers are turning to the NOJA Power OSM Recloser system as an all-inclusive connection asset. Here we cover a few of the key features of the OSM Recloser that makes renewable connection projects cost effective, reliable and safe.

A NOJA Power OSM Recloser with RC-10 control outside a solar farm, Goondiwindi Australia © NOJA Power 2023
A NOJA Power OSM Recloser with RC-10 control outside a solar farm, Goondiwindi Australia © NOJA Power 2023

Frequency Protection

Most distributed generation sites are subject to strict frequency controls through local standards. These standards typically stipulate performance parameters for frequency of generation, and to handle islanding events.

NOJA Power’s OSM Recloser system with RC series control is equipped with Overfrequency, Underfrequency and Rate of Change of Frequency functionality as standard. The latest version of firmware for the RC control also includes multistage frequency capability, granting engineers the capability to customise device response based on severity of frequency excursion.

With the proliferation of renewable generation connections, frequency protection is applied in the majority of cases. The integrated frequency protection capability of the OSM Recloser makes it a reliable option for connecting these generation assets.

Power Quality Monitoring

Generators are subject to monitoring of power quality. While modern inverters can provide an overview of power quality elements, such as harmonics, power factor and voltage quality, many utilities require an additional layer of monitoring to be added to the connection point of grid scale solar.

NOJA Power’s OSM Recloser with the RC control has integrated power quality monitoring. The RC-10/15 generation product provides harmonic analysis up to the 15th harmonic, while the RC-20 generation with its increased sample rate provides a profile up to the 63rd harmonic.

This information is all available via SCADA from the controller, which allows solar developers to meet most power quality monitoring obligations through a single asset. Rather than an expensive additional power quality monitoring installation, the OSM Recloser with RC control can accomplish both protection and monitoring capabilities in a single device.

 A Grid Scale Solar substation with NOJA Power OSM Reclosers as the connection circuit breakers  © NOJA Power
A Grid Scale Solar substation with NOJA Power OSM Reclosers as the connection circuit breakers


Grid synchronisation and interlocks are essential considerations for distributed generation. Many connection regulations call for specific grid energisation states prior to re-connection.

The NOJA Power OSM Recloser system has ANSI 25 synchocheck capability integrated. This allows electrical engineers to configure acceptable grid parameters that allow the breaker to close.

This interlock capacity is standard in all NOJA Power OSM Recloser systems, providing added safety in grid scale connections.

“ With the net carbon zero by 2050 target on the agenda in almost all of our electricity distribution utility customers globally the challenge of connecting large scale solar generation to the grid is at the forefront of current work,” says NOJA Power Group Managing Director Neil O'Sullivan.

“We have developed solutions in all our RC-10, RC-15 and RC-20 controllers for all of the connection challenges. In particular, power quality monitoring is often one of the expensive challenges but with our RC-20 product it is bult into the controller at no additional charge which also makes our solution very economical, either in the OSM Recloser or the Ground Mount Kiosk solution.”


Aside from the standard protection capabilities of NOJA Power’s OSM Recloser, the suite of protection and monitoring capabilities allow the system to act as a single integrated point of connection for grid scale solar. For more information, visit or contact your local NOJA Power distributor.

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