Application Example: Diamondback paired with a Cobra Recloser
1. A fault occurs between Diamondback sectionalizer and Load 2
2. The Cobra recloser starts reclosing sequence: trips open, closes, trips open
3. The Diamondback sectionalizer opens after 2nd overcurrent trip
4. The Cobra Recloser closes and restores power on the line between the Cobra Recloser and Diamondback Sectionalizer
For tie applications, the Diamondback switch control senses a voltage loss on either the source or the load side to determine whether or not to close in from a normally open condition between two different sources. Once the voltage on one source has been lost for a pre-programmed period of time, the tie switch will close in restoring power to the de-energized line. Current transformers "tell" the controller that a fault exists when the main contacts are closed. For a normally open tie, the tie may close into a fault upon loss of voltage on one feeder. The control “knows” of the faulted condition and would not open unless it detects a loss of voltage on the faulted feeder side, signifying the upstream protective device has operated.
On a normally closed tie, the switch control would use similar logic, but no fault closing would be necessary prior to isolating the fault. Tie switches can also be applied to automatically bypass a feeder which has been locked out due to a failure, planned outage or a faulted line. If the switch closes into a fault, the tie switch would open once the upstream protective device has opened, de-energizing the line.
Loop schemes generally consist of two or more sources tied into a distribution system to ensure backup power is available when the primary feeder is lost. The scheme utilizes sectionalizing and tie switches to automatically isolate the fault and restore power to all areas unaffected by the fault quickly and reliably using the same principles and methods described previously.
For critical load applications such as hospitals, processing plants, military bases, etc., automatic transfer schemes are common. For overhead systems, this scheme requires two switches, voltage sensors and current transformers and a voltage-time controller. A loss of voltage on the primary source is sensed and initiates the controller to open the primary and close the alternate source switch to automatically restore power.
SCADA / Distribution Automation
Switches can perform the above functions either autonomously or through a SCADA system where the switch controls incorporate FTUs for interfacing with a master station. A variety of SCADA applications are available which employ either a master-slave or peer-to-peer communications architecture.
The distribution automation expertise and products of G&W and the high end software knowledge of Survalent Technology, our software company, have been combined to provide a state of the art solution – Lazer Automation. Three levels of Lazer solutions are available; Lazer I for peer-to-peer product applications, Lazer II for stand-alone controller based systems, and Lazer III for total system wide management and control.