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[User
Guide]
Load Management Executive
is responsible for executing NTMC load management functions. This
means running one or more of the following algorithms: peak shaving, average
demand extrapolation, load rotation, and load state reinserting. The module also
does demand recording, and maintains load activity logs. The sections below
summarize these activities.
Data Organization
Demand readings are tracked by Demand
Points - objects which get associated with appropriate analog
points in RUEX. Load
Points manage load shedding and load restoration. These objects get
associated with appropriate control
points in RUEX. A collection of Demand Points and Load Points
is called a Metering Point.
LMEX can have several Metering Points. Load management can be done by
each Metering Point independently, or globally.
Average Demand Extrapolation
LMEX runs this to improve on the standard peak shaving algorithm. Instead of
attempting to bring current demand below a preset threshold it tries to estimate
the average demand between the current and the next polls, taking into account
the shed portion of the current cycle, and the overall demand trend at the time.
The algorithm tries to keep that average demand below the preset threshold.
Active Cycle Demand Correction
When the program sends out load control codes it affects the next polling
cycle demand reading. To correct for that LMEX keeps track not only how much
power it shed, but also how long it took to do that. Using this information it
calculates the appropriate demand reading correction for the next cycle.
Two-way Load ManagementTM
Ideally one would like to know which of the load points are actually active at
any one time. Not knowing this information means slower response (and,
therefore, revenue loss) when it comes to bringing demand down quickly from a
high level to below a preset threshold. By Two-way Load ManagementTM we
mean knowing just that information. By using appropriate load management RTUs LMEX
is able to send out control codes, and know right away, what the load numbers
are in each case. The customers not running show up as zero load, and LMEX
immediately adapts by sending out more
control codes, repeating all this until the desired load drop is accomplished,
without having to poll in the mean time.
LMEX accomplishes this by communicating with RTUs with special Two-way
Load ManagementTM functionality. When such an RTU is polled it
not only reports the value of its pulse counter (energy consumed to that time),
but also the change in value of that pulse counter in the last minute or so
(demand at that time). This can be used to pre-poll all loads just before load
management is supposed to start. Only one poll is needed, not two, to ascertain
who is running at that time - this speeds up load shedding if one is to follow.
In addition, during load shedding, when such an RTU receives a control code
to turn of the load, the RTU not only confirms the operation, but also reports
instantaneous demand at the time of disconnect. The master uses this information
to greatly speed up the load shed.
Load Rotation
When load is controlled for extended periods of time it may be desirable to
periodically substitute those which are off with others. LMEX can manage groups
of load points and rotate the ones being controlled within those groups. The
percentage of demand controlled within any of those groups can be assigned by
the operator, or by LMEX dynamically based on demand situation at the time.
Water heaters are one example where this kind of load management can be done
without too much inconvenience to the customers.
More
discussion of above algorithms can be found here.
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