Trend data is useful for overall system analysis. Trend data can help to ensure that utility feeder and substation capacities meet demand. Trend data is also helpful for planning expansions to existing systems, such as adding new loads and backup systems. Trend data can include any periodically recorded measurements of power quality and flagged values. You log trend data over different time intervals, which can range from every 10 or 12 cycles to several minutes, hours, days, or years.