NOJA Power

Technical Article

Published 03/2024

Understanding Negative Phase Sequence Protection

NOJA Power OSM Recloser

Negative Phase Sequence Protection is among the most applied protection techniques in the NOJA Power OSM Recloser system with the RC Series Control.

Unlike Overcurrent and Earth Fault Protection, Negative Phase Sequence (NPS) protection can be used to detect broken conductor scenarios on the overhead distribution network.

Choosing not to use NPS protection can introduce a risk that floating broken lines remain undetected, posing both a safety and reliability risk.

Fortunately, the NPS protection feature is available in every version of NOJA Power RC Series Recloser Control.

A NOJA Power OSM Recloser with RC-20 Recloser Control © NOJA Power 2024
A NOJA Power OSM Recloser with RC-20 Recloser Control © NOJA Power 2024

Where to Learn More:

For those who learn best by video, this NOJA Power Webinar covers the fundamentals of NPS and Broken Conductor Protection:

Watch Video

Alternatively, if you prefer written documentation, a summary of broken conductor protection is available here.

Finally, Negative Phase Sequence protection is also used on Two Wire Single Phase lines. A summary of this application is available here.


Negative Phase Sequence Protection delivers visibility to fault categories missed by conventional Overcurrent and Earth Fault protection. Fortunately, a NPS protection feature is available as standard in all current NOJA Power OSM Reclosers with RC Series controls.

“Negative phase sequence protection is included standard in our complete range of RC-10, RC-15 and RC-20 recloser control cubicles,” says NOJA Power Group Managing Director Neil O'Sullivan.

“A lot of customers don’t know it is available for their product and I would encourage everyone to consider implementing it as it will improve the safety and quality of supply on all feeders in your network.”

For more information visit

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