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A technique to efficiently characterize the azimuth radiation patterns of monopole arrays based on evanescent reactive-near-field measurement in a compact anechoic box is presented. We describe a desktop-size measurement setup for determining the azimuth far-field pattern of an electronically steerable parasitic array radiator (ESPAR) at 2.5 GHz, and present a thorough statistical evaluation of the ESPAR antenna characterization technique. In addition, the sensitivity to probe position and the errors caused by possible fluctuations in the probe position are investigated. Furthermore, comparisons among patterns obtained by the proposed method, simulations and conventional far-field measurements are carried out, and a good agreement among them is obtained. We also provide a statistical evaluation of the proposed desktop-size measurement setup using forty ESPAR antennas and conclude that the proposed setup can be an inexpensive candidate to replace the conventional measuring system. Index Terms--Anechoic chamber, antenna arrays, antenna measurements, monopole arrays, probe antennas.

Maintaining dynamic security of a power system subjected to large disturbances is of utmost importance. Fast and accurate online detection of instability is essential in initiating certain emergency control measures. The techniques reported in the literature involve mainly the application of global phasor measurements and heuristic algorithms. In this paper, an accurate technique for the online detection of loss of synchronism based on voltage and current measurements in a line is presented. The technique makes use of the concept of potential energy in a line. The conditions for the system instability are derived from energy function analysis. However, no assumptions are made regarding the power-angle relationship in a line, nor are any data on the system equivalents necessary in implementing the detection scheme. Index Terms--Critical cutset, energy function, transient stability.