Holbrook Substation Superconductor Cable System, Long Island, New York Final Report

Abstract

The LIPA Superconductor project broke ground on July 4, 2006, was first energized on April 22, 2008 (Earth Day) and was commissioned on June 25, 2008. Since commissioning, up until early March, 2009, there were numerous refrigeration events that impacted steady state operations. This led to the review of the alarms that were being generated and a rewrite of the program logic in order to decrease the hypersensitivity surrounding these alarms. The high temperature superconductor (HTS) cable was energized on March 5, 2009 and ran uninterrupted until a human error during a refrigeration system switchover knocked the cable out of the grid in early February 2010. The HTS cable was in the grid uninterrupted from March 5, 2009 to February 4, 2010. Although there have been refrigeration events (propagated mainly by voltage sags/surges) during this period, the system was able to automatically switch over from the primary to the backup refrigeration system without issue as required during this period. On February 4, 2010, when switching from the backup over to the primary refrigeration system, two rather than one liquid nitrogen pumps were started inadvertently by a human error (communication) causing an overpressure in the cable cooling line. This in turn activated the pressure relief valve located in the grounding substation. The cable was automatically taken out of the grid without any damage to the components or system as a result of signals sent from the AMSC control cabinet to the LIPA substation. The cable was switched back into the grid again on March 16, 2010 without incident and has been operational since that time. Since switching from the backup to the primary is not an automatic process, a recent improvement was added to the refrigeration operating system to allow remote commands to return the system from backup to primary cooling. This improvement makes the switching procedure quicker since travel to the site to perform this operation is no longer necessary and safer since it is now a programmed procedure versus the former written procedure that was still subject to human variation in the process.