Electrical switchgear engineers NOJA Power Switchgear announces the release of Relay 1.9, an upgraded firmware platform for its OSM series Automatic Circuit Reclosers (ACR).
Among other enhancements, the firmware now includes Negative Phase Sequence (NPS) protection and protection grading functionality during live line operation. In addition to Overcurrent (OC), Earth Fault (EF) and Sensitive Earth Fault (SEF) protection capabilities available previously in NOJA Power’s Relay firmware, the new firmware includes NPS protection to provide utilities with a full suite of protection capabilities for safeguarding three-phase electricity distribution systems.
The Relay 1.9 firmware employs the theory of symmetrical components to analyse the type, source and direction of faults and instructs the ACR to respond accordingly. Overcurrent magnitude and fault location can be determined from the positive phase sequence symmetrical component and earth faults and location from the zero phase sequence component. The provision of negative phase sequence in the new firmware now allows for the additional detection of broken conductors and their location even before power is lost from the system.
The parameters for NPS protection can be configured using NOJA Power’s Control and Management Software (CMS) and downloaded to an ACR or group of ACRs. Alternatively NPS protection can be configured via the ACR’s RC10 controller’s large backlit LCD display and keypad.
NPS protection is particularly useful for utilities striving to comply with the bushfire mitigation recommendations of the 2009 Victorian Bushfires Royal Commission. According to the Commission, although ACRs operated satisfactorily when detecting earth faults caused by broken conductors touching the ground, the energy dissipated from the conductor on contact with dry vegetation could still be sufficient to cause ignition.
NPS protection will now detect an isolated broken conductor, allowing the ACR to begin operation to lock out before the cable touches the ground, minimising the energy dissipated to vegetation.
NPS protection is also valuable to utilities with very long feeders. Such feeders typically exhibit high impedance that can mask faults far down a line because the high resistance results in upstream current changes too small to trigger protection devices. However, because NPS protection looks for phase imbalance rather than current anomalies, the high impedance of a long line becomes irrelevant and faults can be detected anywhere along the feeder’s length.
Relay 1.9 also includes enhanced live line capability. The OSM series ACRs’ live line configuration allows utilities to protect staff working on a live line while still providing consumers with power. Live line protection is activated via a single button push on the RC10 controller and now provides protection grading to customers down the feeder from the maintenance site as well as safeguarding work crews.
NOJA Power Managing Director Neil O’Sullivan observes that Relay 1.9 is the most comprehensive overhaul of their ACR firmware yet, with the firmware now more efficient and easier to use, while adding NPS protection and live line updates.
He explains NPS protection is a major enhancement because it completes the set of functionality required for utilities to detect and protect against all faults that can occur on medium-voltage distribution systems. As an Australian company, NOJA Power is particularly aware of the implications of this additional protection for bushfire mitigation. However, NPS protection brings many other advantages too, especially for utilities that employ very long feeders as well as work crews whose safety is assured with the inclusion of enhanced live line protection.
Units from NOJA Power's OSM series of medium-voltage (15, 27 and 38 kV) ACRs have been installed by utilities in over 80 countries around the world. The ACRs have been subjected to full type testing by independent test laboratories such as KEMA in the Netherlands to the latest standards.