Overview
Capacitor Control Executive performs capacitor control functions for electric utility
companies. It implements those functions as dictated by the utility
industry, using resources provided by the NTMC
core components.
CCEX organizes its data as follows: CCEX maintains global management
parameters and a list of user defined substations.
Capacitor control can be done globally, on substation level, or on feeder level. In
the two latter cases one can have multiple capacitor control systems running in
parallel, using different management strategies.
Each substation maintains a list of user defined feeders. These are I/O points
used by CCEX for importing demand and reactive power data. Each feeder can be programmed to
add to the substation totals, or not to affect the substation totals.
Each feeder maintains a list of user defined capacitors. These are I/O points
used by CCEX for control of capacitor banks in the field.
CCEX also maintains a list of user defined schedules.
These are collections of capacitor parameters shared between capacitors.
Multiple capacitors can be assigned the same schedule. All those capacitors share
all parameters in that schedule.
Database
Each of the above items must be defined by the operator. This is a one time
process, most of which is done at the time of system installation. Subsequently
definitions usually get added or modified only when new devices are added to the
system, or when system changes are taken into account, such as changes in remote
unit model being used (new switch model, larger RTU, etc). Definition of each
item comes in several steps.
- First, a new database entry is made. This creates a record corresponding
to the item to be managed. For example, to import new demand and reactive
power numbers one
must define a new feeder database entry. At that time, the
item is said to be off-line.
- In case of capacitors
and feeders, a mapping onto appropriate I/O points
in RUEX needs to be made. A capacitor must be mapped onto an
appropriate control point in RUEX so the latter knows how to operate it when
requested to do so by CCEX. Similarly, each feeder must be mapped onto appropriate analog points in RUEX, so
CCEX knows where to find new demand and reactive power figures when they come in.
- Next, the new item has to be 'put on-line'. CCEX does not 'know' about the
new item until this step is performed. At that time CCEX verifies the type,
location, and integrity of the database entry. If all tests are passed CCEX creates a manager of appropriate type. (For those familiar with modern
software engineering jargon, CCEX creates an object of appropriate class.)
From that time on CCEX 'knows' about that item and maintains it by calling
functions exposed by the manager. At that point the item said to be on-line.
Please click here to see how to
implement this.
Data Processing
Data processing is done by both, RUEX and CCEX. The former does data
acquisition and calculations resulting in analog point values. Analog point
managers impose limits on acceptable value ranges. When numbers fall out of
those operator defined ranges, CCEX ignores the values and works with last
good known numbers. This is to prevent unwanted system oscillations caused by
occasional bad numbers which can come in because of hardware and / or software
problems. CCEX loads these analog point values into its feeders, then
adds them up, as configured by the operator, into substation totals, and
overall system total. Subsequent management cycle is done based on the
new numbers and other system settings.
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Data Recording
CCEX records the following demand values: system total, all substation totals, and all
individual feeder demands. The latter can be programmed
in RUEX as well, but this would only be duplication of data and is
unnecessary.
CCEX records the following reactive power values: system total, all
substation
totals, and all feeder numbers. The latter can be programmed
in RUEX as well, but this would only be duplication of data and is
unnecessary.
CCEX records the following power factor values: system total, all
substation
totals, and all feeder numbers. The latter numbers are computed by CCEX, and
do not come from RUEX.
CCEX records capacitor states by generating appropriate event log entries.
In addition, RUEX makes control point event log entries in its event log file.
Control point states are also recorded in standard data recording files by
RUEX. In addition to control point states, other information, such as manual /
auto, and which component issued control commands is recorded.
Capacitor control cycle logs can be generated on the global (system) level,
and / or substation level, and / or feeder level.
Please click here to see how to implement this.
Data Archiving
All data recording files and event logs fill up after a while, and must be
archived to a separate location, either on the same computer, or elsewhere on
the LAN. This is done manually by
the operator who executes archiving commands. Two kinds of information get
archived: data recorded from remote units, and event logs. CCEX does not
back up archived data recording files stored elsewhere on the computer (for
example, on a ZIP disk), or the LAN.
It is the user's responsibility to back those files up after each archiving
operation.
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Capacitor Control
This section describes how to implement capacitor control once database
setup has been completed. CCEX offers two algorithms, one managing VAr,
the other power factor. Management can be done on feeder, substation, or
global level. The latter options are usually useful in smaller systems,
with only one, or a handful of feeders.
Realizing that each installation is essentially unique, the software is structured
in such a way as to allow easy and rapid addition of custom algorithms,
dictated by the individual user needs. Likewise, other control variables,
other than those mentioned above, can be added. The new, custom algorithms can
easily be made to use any number of existing, or 'new' variables.
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Capacitor State Reinserting
Sometimes it is necessary to reinsert capacitor states, i.e. re-transmit control
codes to all capacitors in order to make certain that their states agree with
what is in NTMC database. CSR manager
simply transmits an OFF code to a capacitor if it thinks that the capacitor is supposed
to be OFF, and an ON code if the capacitor is supposed to be ON at the time.
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