Appeal No. 2002-0496 Page 2
Application No. 09/182,542
When a section of cable fails, it causes a blackout. To return power to
customers, a repair crew must find the failed section of cable and reconnect the
transformers on either side thereof with a working section of cable. Conventionally,
explain the appellants, a faulted circuit indicator ("FCI") is installed on the cable at each
transformer enclosure to assist the repair crew as follows. Power is supplied to the
cable from one end only, viz., the "feed point." The other end is left open, viz., the
"open point". When a cable fails, a large over current passes through the cable from
the feed point into the fault. The over current trips each FCI located between the feed
point and the fault. The FCIs in the transformer enclosures between the open point and
the fault do not trip because no over current flows through these cable sections. The
repair crew examines each FCI until it locates the last tripped FCI and the first
"untripped" FCI; the failed cable section lies therebetween. (Id. at 1-2.)
Unfortunately, the larger the URD, the larger the number of FCIs needed to
monitor the system. The appellants also add that "traditional FCIs . . . are expensive to
install, time consuming to operate and somewhat unreliable." (Id. at 2.)
Accordingly, the appellants' use a fault distance indicator ("FDI") to determine
the location of a fault on each half of a URD loop. For each half, an FDI is placed at the
junction between two of sections of cable. After a fault occurs in a half, the associated
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