  Communication network design for monitoring the state of an electric power
grid has received significant attention in recent years. In order to measure
stability of a power grid, it is imperative that measurement data collected by
the Phasor Measurement Units (PMUs) located at the Sub-Stations (SS) must
arrive at the Control Center (CC) within a specified delay threshold delta. In
earlier papers we formalized the design problem as the Rooted Delay Constrained
Minimum Spanning Tree (RDCMST) problem. However, RDCMST does not provide any
fault-tolerance capability, as failure of just one communication link would
prevent PMU data from reaching the CC. In this paper, we study the optimal cost
network design problem with fault tolerance capability. In our model the PMU
data from the SSs will have a path to reach the CC in spite of the failure of
at most R links within the delay threshold delta. If R = 1, each SS will have
two link disjoint paths of length at most delta to the CC. In other words, each
SS will be on a cycle with the CC. We refer to this problem as the Rooted Delay
Constrained Minimum Cost Cycle Cover (RDCMCCC) problem. We provide
computational complexity analysis, an Integer Linear Programming formulation to
find the optimal solution and a heuristic based on the sweeping technique. We
evaluate the performance of our heuristic with real substation location data of
Arizona.
