Doc# E107706 2 - 13
2: Meter Overview
Electro Industries/GaugeTech
The Leader In Power Monitoring and Smart Grid Solutions
Electro Industries/GaugeTech
The Leader In Power Monitoring and Smart Grid Solutions
(arithmetic mean), with as many previous subinterval averages as programmed, to
produce the Rolling Window Demand.
Example
: With settings of 3 five-minute subintervals, subinterval averages are com-
puted every 5 minutes (12:00, 12:05, 12:15, etc.) for power readings over the
previous five-minute interval (11:55-12:00, 12:00-12:05, 12:05-12:10, 12:10-
12:15, etc.). In addition, every 5 minutes the subinterval averages are averaged in
groups of 3 (12:00. 12:05, 12:10, 12:15. etc.) to produce a fifteen (5x3) minute
average every 5 minutes (rolling (sliding) every 5 minutes) (11:55-12:10, 12:00-
12:15, etc.).
Thermal Demand:
Traditional analog Watt-hour (Wh) meters use heat-sensitive elements to measure
temperature rises produced by an increase in current flowing through the meter. A
pointer moves in proportion to the temperature change, providing a record of
demand. The pointer remains at peak level until a subsequent increase in demand
moves it again, or until it is manually reset. The Nexus® 1250/1252 mimics
traditional meters to provide Thermal Demand readings.
Each second, as a new power level is computed, a recurrence relation formula is
applied. This formula recomputes the thermal demand by averaging a small portion of
the new power value with a large portion of the previous thermal demand value. The
proportioning of new to previous is programmable, set by an averaging interval. The
averaging interval represents a 90% change in thermal demand to a step change in
power.
Predictive Window Demand:
Predictive Window Demand enables the user to forecast average demand for future
time intervals. The Nexus® uses the delta rate of change of a Rolling Window
Demand interval to predict average demand for an approaching time period. The user
can set a relay or alarm to signal when the Predictive Window reaches a specific level,
thereby avoiding unacceptable demand levels. The Nexus® 1250/1252 calculates
Predictive Window Demand using the following formula:
Example
: Using the previous settings of 3 five-minute intervals and a new setting of
120% prediction factor, the working of the Predictive Window Demand could be
described as follows:
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