A New Approach to Predicting Power Failures in Underground Electrical Systems

• Targeted inspections for the most vulnerable manholes: We created periodic inspections at regularly scheduled intervals for the most vulnerable k manholes. Specifically, every 50 days, we inspected the top 10% of vulnerable manholes for that day, all at once. While this targeting policy is effective in terms of reducing the overall hazard rate, it is plausible that some manholes may be inspected over and over whereas others can go un-inspected for extended periods of time, which violates current government safety regulations. Hence we require regular inspections for all manholes, discussed just below. • Targeted inspections for all manholes: We ensure that all manholes are regularly maintained even if they have not had a serious event (or not selected by the first component) for a long time. At each day, inspections are scheduled for a small subset of manholes that have not been inspected for a long time (200 days). We schedule inspections for (up to) 1% of manholes for each day using this policy. • Ad hoc inspections: Con Edison’s ad hoc inspections program allows workers that are in a manhole (for instance to install new service or make repairs) to fill in an inspections form while they are on the premises. We model these ad hoc inspections as being uniformly randomly distributed, where at each day, we randomly select 0.2% of the manholes and inspect them.