Power Transfer Distribution Factors Dialog

 

The PTDF dialog enables you to control and view the results of power transfer distribution factor calculations. To access this dialog go to the Tools ribbon tab, and choose Sensitivities > Power Transfer Distribution Factors from the Run Mode ribbon group. This is only available in Run Mode.

Two PTDF dialogs can be open simultaneously, but when doing this Simulator forces one dialog to show Single directions, while the second dialog shows Multiple directions.

The dialog has the following options:

Linear Calculation Method

PTDFs may be calculated using either the full power flow Jacobian or only a portion of it. If you select the Linearized AC Approximation option, the sensitivity of the monitored element’s flow will be calculated as a function of both its real and reactive power components to the voltage magnitude and angle of its terminal buses. When using the AC method, losses are included in the calculation. Simulator assumes that the change in losses is taken care of by the Buyer.

If you instead select the Lossless DC Approximation option, branch flow sensitivity is calculated by estimating the real power that flows through the monitored element only from the difference in angles measured across its terminals. This method assumes that there are no losses.

The Lossless DC with Phase Shifters Approximation option is similar to the Lossless DC, except additional constraints are placed on the calculations that assume that the change in flow across active phase-shifting transformers is zero.

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 that sets these options.

Assumed Location of Injection for Bus

This option is used when calculating PTDFs when one end of the transaction is a Bus, interfaces contain contingency actions that open generators or loads, and these outages need to be reflected in the PTDFs for the interfaces. The location of the injection can be modified to assume that the generator or load that is being outaged is the injector rather than the Bus. When the transactor is not a Bus, the outage of generators or loads in the interface is handled automatically.

The following choices are available for modifying the PTDF results:

Always Bus

This is the default option. No change is made to PTDFs 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, if any generator at the transactor bus is outaged due to an interface contingency, the PTDF will be adjusted to reflect this outage. The impact of load outages will not be reflected in the PTDF.

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, if any load at the transactor bus is outaged due to an interface contingency, the PTDF will be adjusted to reflect this outage. The impact of generator outages will not be reflected in the PTDF.

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, if any generator or load at the transactor bus is outaged due to an interface contingency, the PTDF will be adjusted to reflect this outage.

When adjusting PTDFs 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 PTDF 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.

Directions

This option allows you to choose to define a single direction PTDF using the Seller and Buyer Type related fields, or to define multiple transfer directions between many different entities. If you choose to use multiple directions, the Seller and Buyer Type fields are replaced by the Direction Records display for viewing and defining directions.

For Single Direction: Seller Type, Buyer Type

Distribution factors can be calculated for power transfers between combinations of areas, zones, super areas, participation groups, or to the system slack bus. Use the seller type and buyer type options to indicate the type of the selling and buying entities. These fields are only present for single direction PTDFs. 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.

For Single Direction: Seller, Buyer

These drop-down boxes allow you to select the selling and buying entities. Their contents are filled when you select the seller and buyer types. These fields are only present for single direction PTDFs.

For Single Direction: Reverse Buyer/Seller

Click this button to re-calculate PTDFs for the direction that is the reverse of the direction currently shown. For example, if you have just calculated PTDFs for a transaction from area A to area B, press this button to calculate and display PTDFs for a transaction from area B to area A. This option is only present for single direction PTDFs.

Calculate PTDFs

Click on this button to update the PTDF values. The results table will reveal the latest calculations.

Automatically Recalculate

If checked, the PTDFs are automatically recalculated every time the power flow is solved.

Calculate MW-Distance

Click this button to open the MW * Distance Calculations form. This form allows you to calculate MW * Distance values for the transaction for which you calculated PTDFs. See MW-Distance Calculations for more information.

Increase in Losses

This is a read-only field that indicates the change in system losses caused by the transfer from the seller to the buyer. The change is expressed as a percentage of the transfer amount. This will only be non-zero when using the Linearized AC calculation method.

Use Area/Zone Filters

If this box is checked, then the results table at the bottom of the dialog will include only records associated with devices located in areas or zones included in the area/zone/owner filter set.

Only Show Above %

Restricts the result set to show only those PTDFs that exceed a specified value.

Visualize Actual Power Flows, Visualize PTDFs

Click to toggle the onelines between showing the actual power flows and the PTDF flows. Selecting this button changes the Flow Visualization field for all the visible onelines. You can also change this field manually using the Oneline Display Options Dialog. When choosing to visualize PTDFs, the animated flow arrows will represent PTDF values, and any transmission line pie charts will also be changed to show PTDFs.

Tables of Results

The tables of results occupy the bottom of the PTDF dialog. They are a set of case-information displays and thus share many characteristics common to all other case information displays. The tables will show results for lines/transformers, interfaces, areas, zones, generators, and phase shifters. The tables feature a local menu from which you can print, copy, or modify its records as well as view the information dialog of its associated element. You can also sort the area records by clicking on the heading of the field by which you want to sort.

Lines/Transformers

Shows the transaction distribution factors for the lines and transformers. The following fields are shown:

From Number, From Name, To Number, To Name, Circuit

Identifiers for the transmission line or transformer.

% PTDF From

Distribution factor associated with the MW flow at the "from bus" end of the line or transformer, specified as a percentage of the transaction amount.

% PTDF To

Distribution factor associated with the MW flow at the "to bus" end of the line or transformer, specified as a percentage of the transaction amount.

% Losses

Shows the percentage of the PTDF assigned as losses.

Nom KV (Max) and Nom KV (Min)

Displays the maximum and minimum nominal voltages for the line. This is useful for identifying transformers and which end of the PTDF relates to which nominal voltage.

Interfaces

Shows the transaction distribution factors for the interface records. The following fields are shown:

Name

Alphanumeric identifier for the interface.

Number

Numeric identifier for the interface.

% PTDF

Distribution factor associated with the MW flow through the interface, specified as a percentage of the transaction amount. A positive value indicates the transaction would result in an increase in the flow through the interface.

Interface MW Flow

Amount of real power flowing on the interface.

Has Contingency

Signifies if an interface contains a contingent element.

When an interface has a contingency element of a generator or load, the PTDF will include the impact of this outage if the outaged element is part of the Seller or Buyer. See the Assumed Location for Injection for Bus option to specify how to include this impact if the Seller or Buyer is a Bus.

Areas and Zones

Shows the impact the transaction has on the losses for the area or zone. The following fields are shown:

Area/Zone Number and Name

Number and name identifiers for the area or the zone

Losses %

Change in the losses in the area or zone, specified as a percentage of the transaction amount. A positive number indicates that the transaction would result in increased losses in the area or zone, while a negative number indicates that the transaction would result in decreased losses.

Gen Chg %

Total change in all of the generators in area or zone, specified as a percentage of the transaction amount. For areas, this field should show 100% in the selling area, and 100% minus the change in system losses in the buying area.

Generators

Shows the marginal participation of each generator in the transaction. The following fields are shown:

Number of Bus, Name of Bus, ID

Generator’s terminal bus number and alphanumeric identifier, and the id for the generator.

Area Num of Gen, Area Name of Gen

Name and number of the generator’s area.

Gen Chg %

Assumed participation of the generator in the transaction, specified as a percentage of the transaction amount. This value is directly proportional to the participation factor for the generator, provided the generator is available for AGC and is free to move in the specified direction (i.e., is not at a MW limit). The generator’s participation factor and AGC status are modified on the Generator Dialog, which can be displayed by right-clicking anywhere in the record’s row in the table and selecting the Show Dialog option.

Phase Shifters

Shows the transaction distribution factors for the phase shifters. This applies when using the Lossless DC with Phase Shifters calculation method. The following fields are shown:

From Number, From Name, To Number, To Name, Circuit

Identifiers for the phase shifter.

Status

Indicates whether or not the phase shifter is in-service.

Phase (Deg)

The current phase angle of the transformer.

XF Auto

Indicates if the phase shifter is currently enabled for automatic control.

Deg per MW

This field indicates the amount of angle change, in degrees, that would be required to keep the flow across the transformer constant for a one MW transfer between the seller and the buyer.

Tap Min, Tap Max

The minimum and maximum tap positions for the phase shifter.