Shift Factors Dialog

(In Version 21 and earlier this was called the TLR Sensitivities or Generation Shift Factors)

The Shift Factors dialog allows you to calculate Shift Factor Sensitivities for the load flow case at its solved load flow point. To access this dialog go to the Tools ribbon tab, and choose Sensitivities > Shift Factors from the Run Mode ribbon group. This is only available in Run Mode.

Two Shift Factor dialogs can be opened at the same time, but when doing this Simulator forces one dialog to show the Line/XFMR or Interface device type, while the second dialog shows Multiple Elements device type.

The following describes the sections of the dialog:

Device Type

Select whether you want to calculate the sensitivities for a transmission Line/XFMR, Interface, or for Multiple Elements. To calculate sensitivities for an interface, you must have the interface defined in the case.

When you choose an individual line/transformer or interface, you need to specify the device by selecting it from the list of devices. In this case you specify the From Bus, To Bus, and circuit identifier for a branch, or the interface name or number. When you select the Multiple Elements option, the device selection area of the dialog changes to allow you to select a Multiple Device Type. The dialog results display changes accordingly in order to accommodate Shift Factor sensitivities for multiple elements.

Interfaces can have contingency actions that outage generators or loads. These outages will be reflected in the shift factor calculations automatically if either end of the transaction is an object type other than Bus. To include the impact of these outages when a bus is part of the transaction, use the Assumed Location of Injection for Bus options.

Line/XFMR or Interface Only: Choose device

Specify the From Bus, To Bus, and circuit identifier for a branch, or the interface name, number, and monitored flow direction.

For multiple elements, specify the multiple device type. Choices are: selected lines/transformers, selected interfaces, overloaded lines/transformers in the base case, overloaded interfaces in the base, overloaded lines/transformers during the set of contingencies, and overloaded interfaces during the set of contingencies.

Multiple Elements Choosing Which Devices

See the Multiple Device Type topic for details on selecting which devices to study when selecting multiple elements.

Transactor Type

Specify if the sensitivities will be calculated for the transactor being the buyer or the seller. Sensitivities are calculated between each bus in the system individually and the transactor with this field determining the direction of the transfer.

Transactor Object

Specify what the transactor will be. The choices are Area, Zone, Super Area, Slack, Injection Group, and Bus. When choosing Area, Zone, or Super Area, this really means all generators in the Area, Zone or Super Area weighted by the generator participation factor.

If using the Integrated Topology Processing add-on, an Only show the primary bus for each superbus checkbox will be available on the Buses tab. Checking this box will limit the buses shown on that tab and the list of Bus transactors to only those that are primary buses. This provides a quick means of removing the clutter of redundant data. The primary buses and superbuses are determined from the base case topology.

PTDF Calculation Method

Choose the solution method to use for calculating the sensitivities similar as done on the Power Transfer Distribution Factors dialog.

Note: The Lossless DC methods will be affected by the DC Power Flow Model settings in Power Flow Solution: DC Options. Click on the DC Model Options button to open the dialog, which sets these options.

Assumed Location of Injection for Bus

This option is used when calculating shift factors for interfaces that contain contingency actions that open generators or loads and these outages need to be reflected in the shift factor values. Shift factor calculations are done by default with one end of the transfer being a bus. The shift factors that are reported for generators and loads show the same shift factors as their terminal buses. This means for example if an interface contingency opens a generator, the shift factor for that generator could be a non-zero value because the outage is not reflected in the shift factor calculation. For that outage to be reflected in the shift factor, the assumed location of the injection must be modified.

In addition to the shift factors being calculated on a per-bus basis, the Transactor Object can be a Bus. These same options are applied when calculating the impact of the transactor bus object on the shift factor.

The following choices are available for modifying the shift factor results:

Always Bus

This is the default option. No change is made to shift factors because of outages that occur in interfaces.

Online Generator

This will take into account the outage of generators that occur with interfaces. Regardless of how many generators there are at a particular bus, there is only a single shift factor value that is applicable to the bus and all generators at that bus. If any generator at the shift factor bus is outaged due to an interface contingency, the shift factor will be adjusted to reflect this outage assuming that the shift factor is effected by this generator only. The impact of load outages will not be reflected in the shift factor.

Online Load

This will take into account the outage of loads that occur with interfaces. Regardless of how many loads there are at a particular bus, there is only a single shift factor value that is applicable to the bus and all loads at that bus. If any load at the shift factor bus is outaged due to an interface contingency, the shift factor will be adjusted to reflect this outage assuming that the shift factor is effected by this load only. The impact of generator outages will not be reflected in the shift factor.

Online Gen or Load

This will take into account the outage of generators or loads that occur with interfaces. Regardless of how many generators and loads there are at a particular bus, there is only a single shift factor value that is applicable to the bus and all generators and loads at that bus. If any generator or load at the shift factor bus is outaged due to an interface contingency, the shift factor will be adjusted to reflect this outage assuming that the shift factor is effected by the outaged generator or load only.

When adjusting shift factors for generator or load outages, make-up power is used to determine how those outages are balanced. The make-up power specified with contingency analysis is used. One might expect the shift factor to go to zero for the outage of the element used for the assumed injection location for a bus, but this might not be the case depending on the make-up power.

Shift Factor Sensitivities

Specify if the next set of calculated shift factor sensitivities should replace the currently calculated values, or be appended to the current values. The normal option is to Clear before Calculate. When choosing to Append on Calculate, then as new calculations are performed, the results will only replace the existing sensitivity value stored if the new value is larger than the old value. (Note: in this situation, negative values are considered smaller than positive values).

Disconnected Device Options

To calculate a shift factor, the terminal buses of generators and loads must be connected. These options allow shift factors to be calculated for buses containing generators or loads if the bus can be connected through a series switching device. The shift factor will then be used from the energized terminal of the switching device instead of reporting 0 for the sensitivity. This makes it possible for calculating shift factors that can be used to determine the impact of closing in generators or loads. The possible choices are the following:

Close Breaker

Any bus that is disconnected and has either generation or load will attempt to find a breaker, Branch Device Type = Breaker, that can be closed to energize the bus. The network of branches between the breaker that needs to be closed and the bus that is being connected must be in series. The resulting shift factor is the value from the connected side of the identified breaker.

This option will only be enabled if the power flow has at least one branch with Branch Device Type of Breaker.

Close Load Break Disconnect

Any bus that is disconnected and has either generation or load will attempt to find a load break disconnect, Branch Device Type = Load Break Disconnect, that can be closed to energize the bus. The network of branches between the switching device that needs to be closed and the bus that is being connected must be in series. The resulting shift factor is the value from the connected side of the identified switching device.

This option will only be enabled if the power flow has at least one branch with Branch Device Type of Load Break Disconnect.

DC Model Options

Click this button to open the DC Options page. Here you can adjust the DC options you want used if you are computing the PTDFs with a Lossless DC approximation.

Include only AGCAble Generators

If checked, then only generators available for automatic generation control (AGC = YES) will be included in the calculations for the Transactor object. This impacts Transactor object types of Area, Zone, Super Area, and Injection Group. For Injection Groups, loads can also participate as part of the Transactor. If this option is used, loads in the injection group must also have their AGC field set to YES.

Calculate Shift Factor Sensitivities

Click this button to calculate the sensitivities. The calculation processes through each bus and determines the sensitivity of the MW flow of the selected device with respect to a change of real power at each bus. When the Transactor Type is Buyer, then the assumption is that power is injected at each bus and absorbed at the Transactor Object. When the Transactor Type is Seller, then the assumption is that power is injected at each transactor object and absorbed at each bus.

Set Sensitivities At Out-Of-Service Buses Equal to Closest

After shift factors have been calculated, click this button to set the sensitivities of out-of-service buses. If this option is not used, the sensitivities of out-of-service buses will be 0. When this button is clicked a dialog will open with additional options. The Use Closest checkbox is checked by default and the default algorithm will be used. The default method finds the closest energized buses and uses the average of the sensitivities at these buses. When Use Closest is not checked, Distance Measure options become available. The Distance Measure options are the same options that are used with the Determine Path Distances to Buses tool.

Line/XFMR or Interface Only: Bus, Generator, Load, Injection Group, and Area Sensitivities

The Bus Sensitivities show the values calculated at each bus. Generator sensitivities show the same information but have only a list of generators with the P Sensitivity column showing the sensitivity calculated at the terminal bus. The Load sensitivities are similar to the generator sensitivities in that they show the same information as the bus sensitivities but only show the list of loads with the P Sensitivity column giving the sensitivity calculated at the terminal bus. The Injection Group sensitivities represent averages of the bus sensitivities weighted by the participation factors of each generator, load, or switched shunt in the group. All participation factors are included in this calculation regardless of the AGC status of any included generators. The Area Sensitivities calculated represent a weighted average of the generator buses in the area with the weighting done by generator participation factor.

Multiple Elements Only: Multiple Bus, Generators, Loads, and Injection Group Sensitivities

The Multiple Bus Sensitivities show the values calculated at each bus for each device examined during the analysis. Multiple Generator and Load Sensitivities show the same information but have only a list of either generators or loads with the P Sensitivity column showing the sensitivity calculated at the terminal bus. The Multiple Injection Group Sensitivities represent averages of multiple bus sensitivities weighted by the participation factor of each generator, load, or switched shunt in the group. All participation factors are included in this calculation regardless of the AGC status of any included generator.

The results of the multiple element analysis can be accessed using script commands or SimAuto by using the variable SensdValuedPinjMult with the appropriate data object: Bus, Gen, Load, or InjectionGroup. There will be as many variables with the SensdValuedPinjMultname and appropriate location number as there are elements that were studied. The location numbers start at 0. The results are assigned in the order that the elements are included in the list of branches or interfaces to be studied. For example, if the list of branches includes five branches defined in the case in the following order: 1 to 2, 2 to 4, 4 to 3, 3 to 1, 2 to 3, and branches 2 to 4 and 4 to 3 are selected for inclusion in the multiple element TLR calculation, SensdValuedPinjMult:0 will correspond to branch 2 to 4 and SensdValuedPinjMult:1 will correspond to branch 4 to 3 for all sets of results. When selecting devices to study based on them being overloaded or contingency-overloaded, the results will appear in the order that the overloaded elements are defined with the case. To determine which elements are overloaded in the base case, use the Percent field with Branch data objects and the Percent field with Interface data objects. If these fields are greater than 100 percent then the element is overloaded. The CTGVIOL variable can be used with the Branch or Interface data type to determine if an element is overloaded due to a contingency. This field will be non-zero for any element that has overloads due to contingencies.