Fault Detection, Isolation & Restoration (FDIR)
The PRISM Fault detection, isolation and restoration (FDIR) application is designed for automated fault handling on distribution systems with radial or open loop configurations. The distribution system can consist of feeder sections with three phases, two phases or single phase. It provides the following fundamental control functions:
- Detect and isolate feeder faults (phase to phase and phase to ground faults).
- Automatically restore service to the feeder sections upstream of the fault (Primary Restoration).
- Provide a switching sequence that can be activated by the dispatcher to automatically restore service to the feeder sections downstream of the fault (Secondary Restoration).
- Provide a switching sequence that can be activated by the dispatcher to automatically connect the de energized feeder sections to available alternative sources if faults appear on the substation side of the feeder breaker.
- Provide a switching sequence that can be activated by the dispatcher to return the distribution system to its pre fault configuration when previously faulted feeder sections become available for service.
The feeder fault detection and isolation function of the FDIR software can be automatically initiated when a feeder breaker trip signal is received. If the breaker has reclosing relays, FDIR will not start execution until it detects subsequent failures of fast reclosing of the feeder breaker to clear the fault.
When the presence of a fault in the feeder is detected, FDIR will identify the fault location by logically analyzing the real time data from the RTUs on the faulted feeder, automatically isolate the faulted feeder section if the related line switches are in remote control mode. After ensuring the fault isolation, FDIR starts to make the primary restoration by re-energizing the feeder sections upstream of the fault. The total time for FDIR to complete all the necessary actions from the moment the fault is detected to the display of feeder re-energization data at the dispatcher console is normally less than 30 seconds.
The function of fault detection and isolation is executed in parallel by FDIR. While single faults occurring simultaneously on several different feeders, they can be handled in a parallel manner and each one can be completed in a few seconds. There is no hard limit on the number of single faults on different feeders occurring simultaneously for FDIR to process at the same time.
FDIR will begin to perform secondary restoration after completion of the fault isolations and primary restorations for all the faulted feeders with no new faults occurring within a dispatcher specified time interval. It will accomplish this by determining a switching sequence through reconfiguring of the associated and available tie switches to re-energize the feeder sections downstream of the faults. The switching sequence is developed with the objective of restoring as many of the de-energized feeder sections as possible with minimum number of switching actions within the allowed overload and voltage drop limits (either normal limits or emergency limits can be applied) of the impacted feeders and energy sources. Alarm messages will be provided if there exist non restorable feeder sections due to topology constraints or overload and voltage drop limits. The recommended switching sequence will not cause service interruption on other feeder sections whenever possible. The recommended switching sequence can be displayed in a tabular list along with their impacts on feeder loads. The resultant configuration of the impacted feeders, if the switching sequence would be implemented, can be graphically displayed with blinking symbols for the dispatcher to review.
Upon review, the dispatcher is able to reject or accept the sequence or modify one or more steps of the recommended switching procedures before it is initiated for FDIR to implement the switching procedures in either sequential or automatic or manual step by step mode. The dispatcher would also be able to abort and reverse the switching sequence at any time during or after the execution of the switching sequence. The implementation of switching sequence can also be automatically aborted, if desired, when a new feeder fault occurs during the execution.
The recommended switching sequence can be developed in a few seconds (generally less than 20 seconds), depending upon the numbers of involved tie switches and feeder sections related to the faults during the restoration. A recommended switching sequence will be automatically canceled if it is not implemented in a dispatcher specified time interval (e.g. 5 minutes). In this case, a pending flag will be set for each non restored feeder section such that a new switching plan can be developed for these sections by FDIR at any time under dispatcher's request.
FDIR also provides the capability to return the network to its pre-fault configuration under the dispatcher's request when the previously faulted feeders are available for service. Upon the dispatcher's request, FDIR will develop a recommended switching sequence to re configure the related feeder sections back to the default configuration. This switching sequence can be carried out automatically or in semi-automatic mode requiring operator approval at each step.