^7fA weakfeed condition on a transmission or distribution system occurs when the available fault current is so low that relays become inoperative or their performance becomes marginal. Weakfeed conditions present many challenges to the correct operation of protective relays. With the increased installation of small distributed generators, more problems are expected to occur. Properly understanding the effect of weakfeed conditions on protective relays is critical to their correct application. In addition to weakfeed, another closely related difficult situation is also described in the paper -- outfeed conditions. An outfeed condition means that for an internal fault, current at one terminal flows from the protected line to the source while current is flowing to the fault. Outfeed conditions do not always correlate with weak sources and can occur more frequently in a system. The worst thing that can happen under outfeed conditions is failure to trip or delayed tripping for internal faults. The end results can be catastrophic damage to equipment or instability. Many excellent papers have been written describing the wide variety of relays and relaying systems that may be applied to these weakfeed circuits. None that we are aware of has examined the behavior of the different categories of relays when subjected to the low energy conditions that these systems provide. This paper will attempt to describe that facet of the problem. Some of the relaying systems that show particular strength in these situations will be described.
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