A feasibility analysis aimed at defining an alert system for Distribution MV Underground Cables

Abstract

In this work, a feasibility study of an alert system for predicting the failure of underground distribution cables in urban areas was assessed. In recent years, energy distribution utilities have observed a significant increase in the frequency of outages on underground cables, mostly concentrated in urban areas. The definition of an alert system for this type of outages required to have failures/outages provided by distribution power utilities. A first case study for the city of Milan was considered where power fault events were made available to us for the period 2012-2015. The availability of meteorological data was also of crucial importance, both in the atmosphere and on variables such as soil temperature and soil moisture in order to highlight the correlations with the outages. All these variables could be found as outputs of the forecast and meteorological reanalysis models currently in use in RSE. The influence of electricity demand on faults was also assessed by analyzing the Actual Load data published by TERNA, which can be considered a proxy for estimating the load for the urban area of Milan. Finally, other variables that could be correlated with the fault data were also considered, such as the skin temperature of a typical underground conductor with circulating current or other atmospheric variables for the identification of summer heat waves (e.g. the 2m air temperature). Once the correlations between the failures and the variables mentioned above have been assessed, a statistical model was finally developed on the city of Milan, to provide an estimate of the daily rate of failures with relative associated uncertainties. This model demonstrates a fairly good explained variance (about 50%) and shows how the variables that influence most the prediction of failures are associated with the Actual Load, air temperature and deeper soil moisture. This work is preparatory to the implementation of an alert system for predicting critical situations that may lead to widespread failures of underground power lines. To this end, however, a strong synergy with the distribution utilities is necessary to obtain other time series of faults also in other Italian urban areas.