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#180466 - 08/26/08 09:47 PM Power demand math  
cgw  Offline
Member
Joined: Jul 2004
Posts: 133
Rochester NY
I'm looking for the math that a demand meter would use to calculate the power demand. Specifically the average demand over a 15 minute period (see NEC 220.87).


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#180477 - 08/27/08 10:11 AM Re: Power demand math [Re: cgw]  
JBD  Offline
Member
Joined: Jul 2001
Posts: 599
WI, USA
There are many ways to accomplish this. Mechanical demand meters use a different technique than do electronic meters. Utilities use a different algorithm than do most power management devices (sliding window, fixed interval etc.)

The underlying concept is to decide on a number of sampling intervals per demand interval. At the end of each sampling interval add the new KW reading to the total KW of the previous intervals. At the end of the demand interval, divide the total KW by the number of sampling intervals.



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