Glossary of Terms

MPM - Main Processing Module

OSM - Outdoor Switch Module

The Outdoor Switch Module is an outdoor, pole-mounted, medium voltage recloser. It features full-directional protection, current and voltage measurement on all six bushings, no SF6 or oil insulants and is light weight. Full SCADA and communications features are standard along with programmable digital I/O.


A recloser is a circuit breaker incorporating a multishot, autoclosing relay, installed on a medium voltage feeder. They are designed to trip when a fault is detected, then automatically reclose after a set amount of time in an attempt to clear transient faults on the feeder. They can save considerable time when restoring power.

Rogowski Sensor

A Rogowski sensor is an air-cored CT design made out of a helix coil. They are immune to core saturation at high fault currents, produce safe voltages (millivolts) have an increased accuracy over a wider range and are very lightweight.

RTU - Remote Terminal Unit

Remote control and monitoring unit used in SCADA systems.

SCADA - Supervisory Control And Data Acquisition

SCADA systems are used to monitor and control a population of remote devices from a central control room. A communications protocol is required to receive and transmit alarms and other data. NOJA Power reclosers are SCADA ready with RS232, USB, Ethernet, Wi-Fi and 4G connectivity and a number of protocols including DNP3, 2179, IEC 60870-5-101 and 104 and IEC 61850.

SEF - Sensitive Earth Fault

Sensitive Earth Fault is a form of Earth Fault protection capable of detecting low fault currents. The OSM recloser can detect SEF from 0.2 - 80A.

SF6 - Sulfur hexafluoride

Colourless, odourless gas used to insulate electrical switchgear. Identified by the KYOTO protocol as one of the 6 greenhouse gasses. SF6 gas has a an environmental impact 23,800 times CO2 (Carbon Dioxide) and has an atmospheric lifetime of up to 3200 years.