  In this paper, we present a Fingerprint Linear Estimation Routine (FLiER) to
identify topology changes in power networks using readings from
sparsely-deployed phasor measurement units (PMUs). When a power line, load, or
generator trips in a network, or when a substation is reconfigured, the event
leaves a unique "voltage fingerprint" of bus voltage changes that we can
identify using only the portion of the network directly observed by the PMUs.
The naive brute-force approach to identify a failed line from such voltage
fingerprints, though simple and accurate, is slow. We derive an approximate
algorithm based on a local linearization and a novel filtering approach that is
faster and only slightly less accurate. We present experimental results using
the IEEE 57-bus, IEEE 118-bus, and Polish 1999-2000 winter peak networks.
