GRID Healthcare

Utilities spend a great deal of time and money performing inspections of their distribution system facilities to identify weak links in the system that will ultimately lead to a failure and possible customer impact if gone unaddressed. While methods for inspection are fairly comprehensive on some parts of the distribution grid (for example a utility’s pole inspection and replacement program where physical attributes (ie strength of the pole) are the most critical aspect of the unit’s usefulness or on distribution reclosers where a maintenance program targets replacement on a periodic basis), the criteria for addressing life expectancy on wire and cable or on pole top and padmounted transformers today does not include a comprehensive history of the loading that the wire/cable or transformer was subjected to during it’s life, which is a critical attribute in calculating the unit’s remaining usefulness. Similar to substation transformers where lengthy histories of gas and oil sampling, current loading and through fault conditions are available and often used to determine remaining strength and life expectancy of the unit, the use of customer metering data now available through the implementation of AMI systems to generate a system loading profile makes monitoring of the current loading on a certain line segment or a distribution pole top or padmounted transformer possible.

The results of this type of analysis can identify areas of immediate concern (ie overloaded line segments that have gone unnoticed in the past due to the lack of visibility into the distribution grid) and the utility can make a determination on whether the condition identified is a risk which requires replacement to avoid an imminent failure or whether the risk being taken is acceptable. This type of proactive failure prevention may be of high value to a utility in their discussion of reliability with their respective commissions.

These values of loading histories can also be stored within the database features of GRIDmaster and, over time, a history of the unit’s loading be monitored to aid in the determination of the remaining usefulness of the unit in question. While one years worth of data won’t make for a conclusive picture on the performance history of a unit, this data becomes extremely valuable over the life cycle of the unit. Starting to collect the information for future use (beyond immediate issues found) is a valuable step in managing the distribution system assets.