Latest Evolution of leading Automatic Circuit Recloser Firmware
The Solution to High Impedance Faults
Electrical switchgear engineers NOJA Power today announces the release of Relay Firmware 1.16, the latest version of its firmware platform for OSM series Automatic Circuit Reclosers (ACR or “auto-recloser”). With the release of Firmware 1.16, NOJA Power has included major new functionality to meet customer demand for simple control of the RC-15 control and communication cubicle’s built-in remote communication capabilities and advanced protection features. These new features include detection and protection functionality for broken conductors, higher resolution detection for Sensitive Earth Faults (SEF) and Admittance Protection for distribution networks that employ high-impedance earthing or active compensation earth-fault reduction techniques.
Firmware 1.16 is the first version of the product that has been specifically designed to integrate with the newly introduced RC-15 controller and its built-in communication capabilities. The RC-15 is NOJA Power’s latest supervisory control and data acquisition (SCADA)-ready controller and is based on the proven RC-10 cubicle––which is installed in thousands of locations across the world––but features Cellular, Wi-Fi and GPS capabilities.
Prior to Firmware 1.16, broken conductors were challenging to identify because these types of discontinuity often don’t result in an overcurrent fault. Firmware 1.16 provides a solution by employing the Negative Phase Sequence detection and protection that has been part of previous versions of the firmware, but instead of employing the functionality in isolation (conventionally used to measure imbalance across all phases of a feeder) Firmware 1.16 compares the ratio of Positive Phase Sequence current (I1) with Negative Phase Sequence current (I2) (ANSI 46BC). In a balanced three-phase system, the ratio approaches 0 percent; if one conductor is broken but not grounded, the ratio rises to 50 percent; two ungrounded broken conductors pushes the ratio up to 100 percent. Grounded broken conductors, or discontinuities in an underground cable system exhibit ratios of 25 to 50 percent. Firmware 1.16 enables utility engineers to set up protection schemes based on the measured I2/I1 ratio.
Firmware 1.16 also introduces higher resolution SEF in response to customer demand for NOJA Power ACRs capable of monitoring and protecting against earth fault currents in 100 mA steps down to a minimum of 200 mA. The OSM series ACRs’ matched current transformers plus the enhancements brought about by Firmware 1.16, allows the devices to form a 0.2-A SEF switchgear model for the protection of any medium-voltage distribution network subject to high-impedance faults (for example, Rf>5 kΩ). In addition, Firmware 1.16 allows the OSM series ACRs’ 0.2-A SEF switchgear model to be compatible with other smart grid protection devices such as Rapid Earth Fault Current Limiters and resonant grounded Petersen coil systems. (Such devices reduce earth fault current by injecting compensating currents to maintain faulty network operation and avoid tripping in order to keep network reliability indices high. In these systems very small earth fault currents need to be detected by protection devices to serve permanent or transient fault finding schemes.)
The introduction of Admittance Protection in Firmware 1.16 significantly increases the ACR’s capability to detect high impedance earth faults. The firmware introduces measurement of the neutral admittance characteristics of the feeder which increases the ACR’s protection sensitivity on compensated and high resistance networks. Such networks typically exhibit low resistive earth leakage currents—because they are designed to limit earth faults through techniques such as high impedance earthing or active compensation—making detection difficult. Increased neutral admittance indicates a worsening earth fault; by measuring the neutral admittance utility engineers can set an upper threshold above which protection is triggered.
Firmware 1.16 also introduces other components to enhance usability. Notable among these are the addition of blocking functionality for Neutral Displacement Overvoltage (OV3), Earth Fault (EF) and SEF. Blocking functionality enables utility engineers to configure various protection schemes. In addition, this functionality increases the interoperability of OSM series ACRs with other Intelligent Electronic Devices (IEDs), enhancing their suitability for substation automation applications. Finally, Firmware 1.16 allows the display to be configured to define where the alerts page (which enables engineers to see the critical status of the controller or any system fault occurrences) is displayed.
NOJA Power’s Control and Management Software (CMS) has also received an upgrade (to version 3.2.0) to facilitate seamless configuration of Firmware 1.16’s features. CMS is a configuration tool used with NOJA Power’s OSM range of ACRs and RC cubicles.
“NOJA Power’s Relay Firmware continues to lead the field in providing a simple to configure, highly usable auto-recloser operating system with the most comprehensive suite of advanced detection and protection features,” says Neil O’Sullivan, NOJA Power Group Managing Director. “The latest version of the firmware is a significant upgrade because it allows utilities to take full advantage of the RC-15’s communication capabilities and improves network safety because previously hard-to-detect broken conductor faults can now be routinely detected in protection regimes.”
Firmware 1.16 is available for NOJA Power’s RC-10 and RC-15 controllers for the company’s single-phase, three-phase and single triple OSM series ACRs. The ACRs provide a comprehensive suite of automation features. The units perform voltage measurement on all bushings, current measurement on all phases, bidirectional protection and extensive power quality and data logging capability. The OSM series has been fully type-tested by independent laboratory KEMA in the Netherlands to ensure long life and reliability under the harshest environmental conditions. Since their introduction, the OSM series ACRs have been installed by utilities in over 85 countries around the world.
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