Through a partnership with PS2 Engineering, the University of California at Santa Barbara designed and implemented a campus distribution master plan, which incorporates the H&L Instruments Model 570 fiberoptic transceivers. The UCSB system uses a closed-loop, primary-voltage distribution-automation system with padmounted switch-gear and relays communicating through a multiplexed fiberoptic network. UCSB installed its own 66/12.47-kV double-ended substation and replaced the entire campus underground cable system with new 15-kV cables. The system is entirely owned and maintained by the university.
High speed communication is critical to supporting the 100 millisecond (six cycles) or less total clearing time provided by the primary network protection system. The same fiberoptic system also carries SCADA information back to the substation interface computer. The Model 570 fiberoptic communication system moves information between the switchgear locations with a delay of less than 2 milliseconds (one-eighth cycle).
To further ensure reliability, the fiber system uses a redundant ring topology, which allows for the immediate rerouting of information to the alternate direction around the loop in the event of a fiber break, a dig-in, or a failed unit. The fiber system can reconfigure from loop to radial operation in 4 milliseconds (one-quarter cycle) with no loss of data. The Model 570 fiberoptic system reconfigures so quickly that the relays may not even detect a fiber break if it were to occur. This SCADA system assures the integrity of the critical portion of the distribution system.
The switchgear relays on the main feeders provide both permissive over-reaching transfer trip (POTT) and directional comparison blocking (DCB) protection to the feeder circuits. This combination provides speed isolation and protection redundancy. Before the segment is isolated, the POTT requires the directional overcurrent relays on each end of acable segment to agree there is a fault between them.Read the full article ...