PV/QV Quantities to Track
Specification of quantities to track during analysis is almost identical for both the PV and QV analysis (exceptions will be noted below). For PV analysis, the Quantities to Track tab is accessed from the PV Curves dialog, and for the QV analysis, this tab is accessed from the QV Curves dialog. Quantities to track are monitored and stored as the transfer increases for the PV analysis or the voltage set-point changes for the QV analysis. Any unselected system parameters will not be saved. The Quantities to Track page contains several sub-tabs that allow the monitoring of different types of objects including: buses, generators, injection groups, lines, transformers, shunts, interfaces, and the case as a whole. There is also a sub-tab for monitoring devices at limits.
Each of the object sub-tabs contains fields that can be tracked during the analysis. The default tracking for all of these fields is NO. To monitor a particular quantity, double-click the corresponding field entry to toggle it to YES, or in the case of some line quantities, the appropriate monitoring direction.
Quantities that are tracked can be plotted using the Plot page. They can also be stored to an auxiliary file with both the PV and QV tools. With the QV analysis a special file is created that stores the tracked quantities. For more information on this see the Extra Monitoring File section with the QV Curves Options: Output topic.
Buses
Voltage - per unit voltage
kV Voltage - actual voltage in kV
Angle - voltage angle in degrees
MW Load - total real power load
Mvar Load - total reactive power load
dV/dQ - sensitivity of voltage to change in reactive power injection at the same bus
VP Sensitivity - sensitivity of voltage change due to real power transfer. For PV analysis this is the sensitivity of the voltage at the bus due to the selected transfer from source to sink. This is a meaningless quantity for the QV analysis and should not be monitored.
VP sensitivities can also be calculated using the Flow and Voltage Sensitivities tool. With this tool there is an option to turn AVR control off for generators and continuous switched shunts that are at buses participating in the transfer. This same option is not available when calculating these sensitivities during the PV analysis because of the overhead of additional power flow solutions that would be required at each transfer step to implement this option. Leaving devices on AVR control will maintain the voltage setpoint at the regulated buses creating PV buses in the power flow Jacobian. At PV buses the sensitivity of voltage to a transfer will be zero.
Shunt Inj - total switched shunt reactive power (Mvar) output
For PV analysis if the intent is to trace PV curves, it makes sense to monitor at least one bus voltage. The process will not automatically monitor and store voltage quantities.
For QV analysis, per unit voltage will be monitored automatically for all buses selected to be included in the QV analysis.
If the Integrated Topology Processing add-on is available, an additional option will be available on the Buses tracking tab, the Modify Existing Bus Tracking to Track Only Single Bus Per Super Bus button. When using topology processing, only a single bus per super bus will be in the consolidated case. That means that the parameters for each bus in the super bus will be the same, i.e. same voltage magnitude and angle, etc. This button can be used to eliminate any excess tracking that would just take up computer memory by tracking essentially the same quantities at the same bus multiple times. To take advantage of this option and only track a single bus per super bus, first set up the bus tracking to track all of the necessary quantities. Then push the Modify... button. The field entries in the table will then be updated to only include a single bus per super bus. When determining the primary node (the primary node is the bus that will ultimately be tracked during the analysis) and super buses, the active defined contingencies will be used to determine how the case is consolidated. Because the consolidation can be different based on the contingency set, or lack thereof, it is best to just define the tracking to include all necessary buses and use this option to refine the list down to a single bus per super bus rather than manually trying to maintain such a list.
Generators
Gen MW - real power output
Gen Mvar - reactive power output
Mvar Reserve - reactive power reserves in the positive direction (Max Mvar - Mvar)
Injection Groups
This allows the monitoring of injection group parameters.
Mvar Reserve - total reactive power reserves in the positive direction for all generators in the group (Max Mvar - Mvar)
Gen MW - total real power output of all generators in the group
Gen Mvar - total reactive power output of all generators in the group
Load MW - total real power load for all loads in the group
Load Mvar - total reactive power load for all loads in the group
Lines
Note: all branches (whether transmission lines or transformers) appear on the Lines sub-tab.
Branch MW - real power flow on the branch in either the FROM-TO or TO-FROM direction
Branch Mvar - reactive power flow on the branch in either the FROM-TO or TO-FROM direction
Branch MVA - total power flow on the branch in either the FROM-TO or TO-FROM direction
Branch MW Loss - real power loss
Branch Mvar Loss - reactive power loss
Branch PTDF - Power Transfer Distribution Factor on the branch due to a defined real power transfer. This parameter only makes sense when doing the PV analysis. The PTDF is calculated for the transfer from the selected source to sink. This is a meaningless quantity for the QV analysis and should not be monitored.
Xfmr Tap - tap ratio if the branch is a transformer
For the flow (Branch MW, Branch Mvar, and Branch MVA) and Branch PTDF fields, double-clicking on a particular entry will toggle its value from NO to FROM-TO, and double-clicking again will toggle its value to TO-FROM. Double-clicking on a loss field or Xfmr Tap field will toggle the value between YES and NO.
Transformers
Note: all branches (whether transmission lines or transformers) appear on the Lines sub-tab. See Lines above for setting up common branch quantities. Only branches containing transformers will appear on the Transformers sub-tab.
Type - set the transformer type (Fixed, LTC, Mvar, or Phase)
Reg Val - regulated value for the transformer control
Tap Pos - tap position
Reg Err - deviation of the regulated value from the regulation Min/Max range
All fields specified above except for the Type field are used to determine which quantities should be monitored and stored during the analysis. The Type field can be accessed here in order to change the type of transformer. The type will not be monitored during the analysis.
Shunts
This allows the monitoring of switched shunt parameters.
Actual Q - actual reactive power output
Actual P - actual real power output
Nom Q - nominal reactive power output
Nom P - nominal real power output
Reg Err - deviation of the regulated value from the regulation Min/Max range. This can either be in per unit voltage or Mvar depending on the type of regulation that the shunt is doing.
Reg Val - value of regulated quantity at the regulated bus. This can either be in per unit voltage or Mvar depending on the type of regulation that the shunt is doing.
Interfaces
MW Flow - real power flow
Mvar Flow - reactive power flow
MVA Flow - total power flow
MW Loss - real power losses
Mvar Loss - reactive power losses
Interface PTDF - Power Transfer Distribution Factor on the interface due to a defined real power transfer. This parameter only makes sense when doing the PV analysis. The PTDF is calculated for the transfer from the selected source to sink. This is a meaningless quantity for the QV analysis and should not be monitored.
Case
These options allow the tracking of case quantities to provide a better picture of what is going on in the case as a whole without requiring the individual tracking of quantities that make up the case total. These quantities are determined in the same manner as those found in the Case Totals section of the Case Summary dialog.
Available quantities for tracking include:
Load MW/Mvar - total real or reactive power load for the entire case
Generation MW/Mvar - total real or reactive power generation for the entire case
Shunts MW/Mvar - total real or reactive shunt injection from switched shunts, bus shunts, and line shunts. A positive value will indicate shunt load where a negative value will indicate shunt compensation such as capacitance.
Losses MW/Mvar - total real or reactive power losses for the entire case
ATC Extra Monitors
This option is only available when using the PV Curves tool. The following will appear at the bottom of the Quantities to Track tab accessed from the PV Curves dialog.
ATC Extra Monitors are typically used with the ATC add-on tool to monitor special branches or interfaces in addition to ones monitored by setting the Limit Monitoring Settings. This would be done for example if trying to determine an interface flow limit so that interface can be used as a proxy for limiting the transfer between a source and a sink. This same functionality is desirable when using the PV analysis. Both the ATC and PV analyses are similar in that they study the impacts of real power transfers. The ATC analysis is concerned with thermal limitations while the PV analysis looks at voltage stability limitations. Use of the ATC Extra Monitors with the PV analysis could be additionally useful for developing a proxy interface to help prevent voltage stability problems.
Click the Define ATC Extra Monitors button to view a list of existing ATC Extra Monitors or create new ones. To include monitoring of these elements at part of the PV analysis, check the Include ATC Extra Monitors box.
When monitoring ATC Extra Monitors with the PV analysis, the real power (MW) flow on the specified branches and/or interfaces will be monitored at each base case transfer level. No monitoring is done with contingencies implemented.
ATC Extra Monitors can be added to the Overview table, available on the PV Results tab, via the Display/Column Options... dialog. When displayed in this table, the value reported with the extra monitor is the flow on the extra monitor at the Max Shift level of transfer for the given scenario. Values for ATC Extra Monitors will only be displayed in the Overview table for critical scenarios.
Values for ATC Extra Monitors can also be displayed in the Overview table for transfer levels at which inadequate voltages are found. These values will only be available if using the option found on the Limit Violations tab to Store inadequate voltages. Fields for reporting these values are found in the Inadequate Voltage folder in the list of available fields for the Overview table. The value reported for each extra monitor is the flow on the extra monitor at the Inadequate Voltage Nominal Shift transfer level.
Access to the ATC Extra Monitor values stored at transfer levels other than the Max Shift transfer for critical scenarios and values stored for non-critical scenarios is available through SUBDATA sections of the PWPVResultListContainer data type that is saved when saving PV results to an auxiliary file or in the output file saved when choosing to save results to file from the PV output tab.
Devices at Limits
The Devices at Limitssub-tab allows the selection of various options to track devices that hit or back off limits during the PV analysis. Devices at limits can only be tracked for PV analysis and will not be tracked for QV analysis. Generators and switched shunts at var limits, LTC transformers at tap limits, and lines and interfaces at thermal limits can all be tracked.
To track the limits of any of these devices, check the appropriate checkbox. Next to each checkbox there is a dropdown box for selecting an advanced filter to apply to the tracking. A new filter can be defined for a particular device by clicking the Define button next to that device. The filter will limit the number of devices that get tracked. It is a good idea to define a filter for tracking devices so that all elements in the case will not be tracked. Keep in mind that tracking any quantities will take up space in the computer memory. If too many devices are tracked, it is possible to run out of memory.
With these options, device limits are only tracked in the base case at valid transfer levels. No device limit tracking is done with contingencies implemented.