www.eaton.com IM02601004E Page 856 Functions on the Web Server PagesDEMANDDemand is the power consumption at the receiving terminal averaged over a specific interval oftime or in response to a signal at a designated discrete input. The Power Xpert Meter is capableof measuring demand by two internally triggered methods; Fixed or Sliding in intervals of 1 to 60minutes. These measurements are configured to calculate the Total Current, kW Forward/Reverse,Net and Sum; kVar Lead/Lag, Net and Sum and kVA.FIXED AND SLIDING DEMANDFixed demand (Total Current), which is an average system current over time can be set to averagecurrent over a range of 1 to 60 minutes. This is known as a fixed window. For example, setting thecurrent demand window to 15 sets the meter to determine the average current over the past 15minutes and update the value every 15 minutes.Power demand can be fixed, as described above, or sliding. For example, a 15 minute average canbe obtained that is updated every 3 minutes. To accomplish this, the subinterval is set to 3 minutesand the number of intervals is set to 5 (i.e. 3 minutes times 5 intervals equals 15 minutes).NOTE: The demand interval is the number of minutes in the average calculation. The subinterval isthe number of minutes between updates.Separate demand values are computed on a monthly basis. At the end of every calendar month,peak demand values with date and time stamps are saved as last months values. Peak demand isreset and new peak demand calculations begin for next month.In the absence of an External Synchronization, the Power Xpert Meter starts demand windowsaccording to the real-time clock at the top of the hour and top of the minute. In the typical case of a15-minute window, the intervals would start at the top of the hour, at 15 minutes past the hour, half-past the hour, and 45 minutes past the hour.Demand reset can be executed using any available user interface or it can be scheduled in thecalendar. When the demand reset occurs a snapshot of all peak demand values and energy valuesare saved as last demand reset values and demand reset count, with date and time.Snapshots of peak demand values with date and time stamps and energy values are saved in a fileeach time the demand reset is executed. This self-read process can also be initiated by using thecalendar schedule. The latest five snapshots are available in a file.
