ATC Dialog Options: Common Options

 

The Common Options sub-tab is found on the Options page of the Available Transfer Capability dialog.

 

 

The following parameters can be set on the Common Options page:

Seller Type, Buyer Type

For the ATC Solution Method of Single Linear Step (SL), transfer limits can be calculated for transfers between combinations of areas, zones, super areas, injection groups, buses, or to the system slack bus. For the iterated linear step ATC Solution Methods (IL and IL then full contingency solution), transfer limits can be calculated for transfers between areas, super areas or injection groups only. Use the seller type and buyer type options to indicate the type of the selling and purchasing entities.

Seller, Buyer

These dropdown boxes allow you to select the selling and buying entities. The contents of each depend on the Seller/Buyer Types selected. Clicking the Find Seller and Find Buyer buttons allows you to use Simulator’s Advanced Search Engine to locate the desired entities.

The Seller defines where power is injected into the system and the Buyer defines where power is taken out of the system. The transfer is simulated by increasing generation or decreasing load in the Seller and decreasing generation or increasing load in the Buyer. The ATC Analysis Methods - Solution Methods go into greater detail about how the impact of the transfer is actually determined. Depending on the type of Buyer or Seller, different rules apply:

Area, Zone, or Super Area

• Only on-line generators in the defined group that are on AGC control are allowed to participate in the transfer.
• Each generator participates in the transfer in proportion to its participation factor.

Injection Group

• Only on-line generators and loads defined with the injection group are allowed to participate in the transfer unless using one of the iterated methods and choosing to use Generator Economic Merit Order Dispatch for either the Seller or Buyer.
• When using the Single Linear Step method, on-line buses can be included as part of an injection group. Buses will be ignored for either of the iterated solution methods.
• Each element participates in the transfer in proportion to the participation factor defined with its participation point in the injection group.

Bus

• All of the power injection change needed for the transfer comes from that bus.
• It does not matter if there is a generator or load at that bus.

Slack

• When the slack is selected for the Seller, then all of the power injection change needed for the seller side of the transfer comes from the island slack bus for the island in which the Buyer belongs.
• When the slack is selected as the Buyer, then all of the power injection change needed for the buyer side of the transfer comes from the island slack bus for the island in which the Seller belongs.

For the Single Linear Step method, generator and load MW limits are not enforced regardless of the type of buyer and seller unless using the option to Allow Generator MW Limit Enforcement in Single Linear Step. Error messages will be displayed if the Seller and Buyer are not both completely contained within the same electrical island.

Reverse Buyer/Seller Button

Click this button to reverse the direction currently shown. The buyer becomes the seller, and the seller the buyer.

Linear Calculation Method

The ATC analysis tool can use either a Lossless DC or Lossless DC with Phase Shifters calculation method for obtaining the ATC results.

If you select the Lossless DC 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.

The Lossless DC with Phase Shifters method, a modification to the lossless dc approximation, takes into account phase shifter operation. It is especially useful when the ATC tool continually reports overloads on branches that obviously will not overload because of the operation of a phase shifting transformer. This method assumes that the phase shifter angles may change to any value to ensure that the line flow on those lines does not change.

The Linearized AC method is not yet available.

Enable Phase Shifters Post-Contingency

This option becomes enabled when you choose the Lossless DC with Phase Shifters linear calculation method. It allows you to choose whether or not phase shifter control should be enforced during post-contingency ATC calculations. When this option is checked, it is assumed that phase shifter angles may change to keep the line flow from changing after the contingency has been applied. Otherwise, it is assumed that phase shifters only maintain the flow in the pre-contingency state and the angles do not change in the post-contingency state. Base case (pre-contingency) transfer limiters will still be determined with phase shifters enforced, regardless of the setting of this option when the Lossless DC with Phase Shifters option is checked.

Assumed Location of Injection for Bus

This option is used when calculating PTDFs and one end of the transaction (either Seller or Buyer) is a Bus. Contingencies can outage generators or loads at the transaction bus, and interfaces can contain generator or load outages at the transaction bus. Use this option to modify the location of the injection point so that the generator or load being outaged is the injector rather than the Bus, which in turn will modify the resulting PTDF to reflect this outage. When the transactor is not a Bus, the outage of generators or loads that are contained in the transactor 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 generator or load outages at a Bus transactor.

Online Generator

This will take into account the outage of generators that occur at a Bus transactor. Regardless of how many generators there are at a particular bus, if any generator at the transactor bus is outaged, the PTDF will be adjusted to reflect this outage. The impact of load outages at a Bus transactor will not be reflected in the PTDF.

Online Load

This will take into account the outage of loads that occur at a Bus transactor. Regardless of how many loads there are at a particular bus, if any load at the transactor bus is outaged, the PTDF will be adjusted to reflect this outage. The impact of generator outages at a Bus transactor will not be reflected in the PTDF.

Online Gen or Load

This will take into account the outage of generators or loads that occur at a Bus transactor. Regardless of how many generators and loads there are at a particular bus, if any generator or load at the transactor bus is outaged, 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.

Limit Monitoring Settings Button

Click this button to open the Limit Monitoring Settings Dialog. Limiting Elements will only be reported for those elements that are selected to be monitored. Note that minimizing the number of monitored power system elements greatly improves solution speed as well as computer memory requirements for doing ATC Analysis.

Monitoring Exceptions can be used to include or exclude specific monitored elements on a contingency-by-contingency basis.

Save Results in PWB File

Check this box to save the ATC results in a PWB file. The settings are always saved.

Transfer Result Reporting Options

The options in this section of the ATC dialog are discussed in detail in the topic on Transfer Result Reporting Options.