Abstract: A method and an apparatus are presented which enable the identification of a capacitor fault in a given string of a capacitor bank, based on the computation of the string impedance by measuring the string AC current and voltages, where each string includes a plurality of capacitor elements connected in series. The method consists of measuring the string capacitive impedance and comparing this value with a previously measured capacitive impedance of the same string. If a difference between these two values is obtained, which exceeds a given threshold for a certain duration, a fault is recorded.

Abstract: A beam sampler comprises a substrate made of highly transparent fused silica or zinc selenide, both capable of sustaining high power laser beams. The substrate defines an outer surface through which the light beam being sampled propagates. A sinusoidal diffracting relief is etched on this outer surface directly into the light-propagating material of the substrate. When a light beam propagates through the outer surface of the substrate, the three-dimensional diffracting relief extracts from this light beam at least one pair of low power beam samples.