Electrical switchgear engineers NOJA Power today announces the release of Relay 1.12, an upgraded firmware platform for its OSM series Automatic Circuit Reclosers (ACR or “auto-recloser”). Among other enhancements, the firmware now includes sectionalizer functionality, dynamic directional protection, live load blocking, additional logic channels and remote battery test.
The addition of sectionalizer functionality to the Relay 1.12 firmware platform enables utilities to configure the ACR as a conventional recloser, a sectionalizer or to function as either device depending on the type of fault. The ACR is able to perform all three functions in either direction of the electricity feeder. To access the new functionality utilities need only to upgrade to the new version of the software - no hardware changes are required.
An ACR has a number of key advantages over a conventional sectionalizer, including limiting the duration of outages in the event of a fault, operating thousands of times under fault current loads, and replacing the greenhouse gas sulphur hexafluoride (SF6) with a solid dielectric. (See “About sectionalizers” below.)
Further enhancements to the firmware platform include dynamic directional protection and live load blocking. Dynamic directional protection enables the ACR to react to a change in the direction of a fault even part way through a reclose operation. Previously the ACR would commit to a complete reclose operation even if the fault changed direction during the operation. Dynamic directional protection is useful, for example, when an overcurrent occurs due to load switching. Previously the energy dumped due to the load switching in the first cycle would cause the ACR to commit to a complete reclose operation; but with dynamic directional protection, the ACR detects the energy being returned in the next cycle as a change of fault direction and terminate the reclose operation.
Live load blocking is an advantage in situations such as when a subscriber load is lost causing a reclose operation, and the subscriber’s back up generator starts up. The ACR now remains open if it detects voltage on the subscriber side during the reclose operation to eliminate the risk of damage due to switching back in unsynchronised generation capacity.
Relay 1.12 also includes remote battery testing of NOJA Power’s RC10 control and communications cubicle’s uninterruptable power supply (UPS). (The RC10 is a SCADA-ready controller for the OSM series.) Previously a periodic on-site visit was required to check the battery. Now a remotely triggered battery test determines whether the battery is healthy or requires replacement.
Other new features of Relay 1.12 include an expansion from eight to 32 for both logic channels and customisable variables (the additional channels meet the demands of customers who need the extra facilities to develop custom-SCADA points or -automation) and support for the floating data point format of the IEC 60870-5-104/101 Transmission Protocol (adding to the current normalised and scaled data point format support).
NOJA Power’s Control and Management Software (CMS) has also received an upgrade to facilitate seamless configuration of Relay 1.12’s features. CMS is a configuration tool used with NOJA Power’s OSM range of ACRs and RC10 controllers.
“Conventional sectionalizers lack the flexibility demanded of distribution automation by today’s smart grids,” says Neil O’Sullivan, NOJA Power’s Managing Director. “By building sectionalizer functionality into the supervisory software of our auto-reclosers, we now offer utilities the option of using an auto-recloser to replace a conventional sectionalizer. The auto-recloser can later convert to a recloser role when the grid topology demands by just a simple configuration change from the RC10 controller. The auto-recloser is a more capable device than a sectionalizer. A NOJA Power auto-recloser is, for example, able to close onto a fault current of 2 kA thousands of times. That’s not possible with a sectionalizer without causing permanent damage to the device.
“Relay 1.12 eliminates the need for utilities to purchase and maintain two types of switchgear, simplifying smart grid implementation,” adds O’Sullivan.
NOJA Power’s OSM series ACRs benefit from the use of a vacuum interrupt and solid dielectric insulator instead of the environmentally unfriendly oil or sulphur hexafluoride (SF6) gas used in sectionalizers and older products. Another key feature of the OSM series is its stainless steel enclosure that forms the only solid dielectric unit with controlled arc venting on the market. The controlled arc venting design is in accordance with the requirements of IEC62271-200 Clause 6.106 and Annex A, and the efficacy of this important safety feature has been tested and verified by independent test laboratories. The OSM series has also been fully type-tested by independent laboratory KEMA in the Netherlands to ensure long life and reliability under the harshest environmental conditions. (See “About the NOJA Power OSM series” below.)
A sectionalizer can be used to reconfigure a distribution network under normal operation, but can’t switch under fault conditions. In a typical configuration, utilities site a sectionalizer downstream from an auto-recloser. If there is a fault, the auto-recloser will trip and reclose a set number of times (typically three) to attempt to clear the fault. The sectionalizer counts the reclose cycles and opens during the dead time of the final cycle to isolate the section of line in the event of an uncleared fault. Isolation by the sectionalizer maximizes the extent of live line that can be kept open.
Sectionalizers have a number of disadvantages compared to NOJA Power OSM series ACRs. First, they must be used in conjunction with an ACR which adds complexity to the grid which leads to longer outages compared with ACRs alone. Second, sectionalizers are load break/load make devices with limited or no fault make capability. The likely effect of closing a sectionalizer onto a fault current is permanent damage necessitating replacement. In contrast, a NOJA Power OSM series ACR is rated for 30,000 full load operations and can be closed onto a 2-kA fault current more than 2000 times without damage. Finally, sectionalizers use environmentally unfriendly oil or sulphur hexafluoride (SF6) for arc quenching and insulation compared with the OSM series ACR’s vacuum interrupt and solid dielectric insulator.