This paper presents a method for the detection of series arc faults in electrical circuits, which has been developed starting from an experimental characterization of the arc fault phenomenon and an arcing current study in several test conditions. Starting from this, the authors have found that is it possible to suitably detect arc faults by means of a high-resolution low-frequency harmonic analysis of current signal, based on chirp zeta transform, and a proper set of indicators. The proposed method effectiveness is shown by means of experimental tests, which were carried in both arcing and nonarcing conditions and in the presence of different loads, chosen according to the UL 1699 standard requirements.

The current transformer (CT) performance under distorted waveform conditions is usually characterized by means of the frequency-response test. In this paper, a new way to characterize CTs, closer to real operation conditions, is proposed. The harmonic phase-angle and ratio errors are measured using a nonsinusoidal current composed of fundamental and one harmonic with adjustable phase shift. The new method was tested by determining the performance of two metering class CTs commonly used by the Italian power company. The errors measured using the proposed approach are larger than the ones obtained with the frequency response. This result suggests that the frequency-response approach for the evaluation of CT performance under distorted waveform conditions is not a reliable method.

This paper deals with the issue of measurement device placement for load flow analysis in medium-voltage (MV) distribution networks. The study is carried out using an innovative measurement algorithm for load flow analysis developed by the authors. It is based on low-voltage (LV) load power measurements applied on a backward/forward algorithm for the load flow resolution. The final aim is to identify the most suitable number and placement of the LV measurement points in order to limit the uncertainty on the power flow estimation to a target value. The proposed approach is based on the uncertainty evaluation of the estimated power flows; a sensitivity analysis is performed in order to assess the uncertainty contribution of each LV power measurement to the estimated power flow upstream of each MV feeder of the distribution network. The LV measurement device placement is presented and discussed in a real case study, i.e., the distribution network of the Ustica Island.