See Also
- Bus real power load
- Bus reactive power load
- Generator real power output
- Real component of the bus shunt admittance
- Capacitive component of the bus shunt admittance
- Reactive component of the bus shunt admittance
Specification of Scale Amount to Scale By
The Scale tool allow specifying the new value or scale factor through a Number, Field Factor or Field Value with the object type to scale. When using the Field Factor or Field Value rather than the Number, the scaling will be done by individual object rather than the aggregation of all objects selected for scaling.
Scale by Bus
The button on the left labeled Bus enables selection of loads, generators and shunts by the bus to which the devices are attached. Selection of the buses can be done individually, by their area grouping, by their zone grouping, or by their super area grouping. Scaling is done on the buses chosen regardless of the area, zone, or super area specification. Options for areas, zones, and super areas are included only to aid in selecting and unselecting buses to be scaled. This is important to keep in mind if loads or generators are assigned to a different area or zone than their terminal bus.
The Buses Table lists the name and number of all buses in the system and whether or not each bus will participate in the scaling. Similarly, the Areas, Zones, and Super Area tables list the names and numbers of all areas, zones or super areas in the system and whether or not each area will participate in the scaling. Simulator initially assumes that no buses are to be scaled. The Power System Scaling Dialog furnishes a number of ways to select the subset of buses to be scaled:
- Use the Add to Scaling fields to enter either a range of areas, zones and/or buses to scale.
- Use the Remove from Scaling fields to enter either a range of areas, zones and/or buses to omit from the scaling.
- Use the Select buses using a network cut button to define a Network Cut to choose a custom set of buses within a portion of the system to be scaled or omitted from the scaling.
- Use the Buses,Areas, Zones and Super Areas tables to change the scaling status of individual buses. Simply double-click on the Scale field for a bus, area, zone or super area to toggle its value.
- Click the Set All to Yes button to scale the entire case. Click the Set All to No button to remove the entire case from scaling.
Changing the scaling for an area, zone or super area changes the scaling status for all buses in the grouping. For example, to scale all the buses in a single area, first click Set All to No. Then, click on the Scale field for the desired area in the Area Table. To scale all buses in an area except for a select few, repeat the above process, but then click on the Scale field for the buses not to scale.
As you select the buses to be scaled, the fields in the Totals for Selected Buses are updated to indicate the total load, generation, or shunt compensation that will be scaled.
Once you have selected the buses, you can either use the Scale By fields to enter a new scaling factor for each of the quantities or use the New Value fields to specify a new value directly. If you do not wish to scale a particular type of device, such as bus shunts, simply leave the Scale By field as unity.
To ensure that the reactive power is scaled proportionately to maintain the current load power factor, click the Constant P/Q Ratio option. To enforce generator limits when scaling generation, check the Enforce Gen MW Limits option. To scale generation and load to enforce ACE, check Scale Gen to Keep ACE Constant. When Simulator scales generation, all generator power outputs at the selected buses are scaled by the specified factor, regardless of area control. To scale only generators whose AGC field is set to YES, check Scale Only AGCable Generation and Load. To scale both in-service and out-of-service loads, check Scale Out-Of-Service Loads.
Finally, click Do Scaling to scale the load, generation, or shunt compensation.
Scale by Area
The button on the left side of the dialog labeled Area enables the selection of loads, generators and shunts based on the area designation of the device itself. Loads, generators and shunts can have a different area designation than the terminal bus to which the device is attached. In these cases, it is sometimes necessary to use the Scale by Area option to choose only the devices that are designated within a certain area, instead of all devices at a particular bus.
To specify the devices within certain areas to be scaled, toggle the Scale property of the areas desired in the Areas table, or use the Add to Scaling and Remove from Scaling fields to enter ranges of area numbers to be included or excluded from the scaling.
Scale by Zone
The button on the left side of the dialog labeled Zone enables the selection of loads, generators and shunts based on the zone designation of the device itself. This is identical to the concept described immediately above in the discussion on Scale by Area. As was the case with the area designation, loads, generators and shunts can have a different zone designation than the terminal bus to which the devices are attached.
To specify the devices within certain zones to be scaled, toggle the Scale property of the zones desired in the Areas table, or use the Add to Scaling and Remove from Scaling fields to enter ranges of zone numbers to be included or excluded from the scaling.
To ensure that the reactive power is scaled proportionately to maintain the current load power factor, click the Constant P/Q Ratio option. To enforce generator limits when scaling generation, check the Enforce Gen MW Limits option. When Simulator scales generation, all generator power outputs at the selected buses are scaled by the specified factor, regardless of area control.
Check the Scale Only AGCable Generation and Loadoption to scale only those generators and loads whose AGC field is set to YES. If the Ignore AGC flag to calculate participation but use AGC flag to scale individual loads or generatorsoption is checked, the Scale Only AGCAble Generation and Load is not enabled and will be ignored. If this option is checked, then all generators and loads, regardless of their AGC status, will be used to calculate the participation percentages for all participating elements. Only those generators and loads whose AGC field is set to YES will actually be scaled. Normally, if choosing to scale only AGCable generation and load, only those elements whose AGC status is YES will be used to calculate the participation percentages.
The choice of Scale Starting Point impacts the reference point from which the scaling starts. Scale from Present Value scales by adding an incremental change to the present MW values based on the difference between the New Value and Original Value. Scale from Zero sets all participating elements to zero injection (0 MW load or generation) and then scales to the New Value from that starting point. When using the Scale from Zero option, only a single injection group can be scaled at a time. The following example explains the difference between these two options:
Suppose that Load 1 is 800 MW and Load 2 is 700 MW. These two loads are the only elements in an injection group and they both have a participation factor of 0.5. The desired New Value is 1600 MW. Choosing Scale from Present Value will result in Load1 being 850 MW and Load 2 being 750 MW. The incremental change in the total load is 100 MW and both loads pick up half of this change. Choosing Scale from Zero will result in Load 1 being 800 MW and Load 2 being 800 MW. Both loads have been scaled to 0 MW initially and they each pick up half of the desired 1600 MW total load.
The Scale Load Field options provide a way of scaling load that is out-of-service. Selecting Actual MW (MW Column) will scale only those loads that are in-service. (The MW column in the load case information display reflects the total in-service load at a bus.) Selecting Modeled MW (ignore load and bus status) will scale all load regardless of the load and bus status.
Injection Group Scaling Options Modified in version 19, build on Aug. 10, 2016
Several different injection group scaling methods are available for injection groups:
Proportional
The MW output for generators and loads in the injection group will be adjusted in proportion to their specified participation factors. These factors will be normalized for all generators and loads participating in the dispatch. Mvar load will be adjusted according to the Constant P/Q Ratio or specified Mvar injection options.
Merit Order
This will scale generators and loads in the order of highest to lowest normalized participation factor. This means that each generator and load participating in the injection group will be moved to either its maximum or minimum limit, depending on the direction of the scaling, before the output of the next element in the list is changed, until the total scale amount is achieved. If this option is checked, generator MW limits will be enforced regardless of the status of the Enforce Gen MW Limits option. Load limits will always be enforced, but loads that have both their minimum and maximum MW limits set to zero will not be allowed to increase. They can only decrease to 0 MW.
Economic Merit Order
This method involves dispatching generators so that they are dispatched within an economic range. Details about how economic merit order dispatch is performed can be found under the Generator Economic Merit Order Dispatch topic.
If using this option and an injection group contains ONLY loads, the MW portion of loads will be adjusted in proportion to their participation factors and economic merit order dispatch will not be used. Mvar load will be adjusted if maintaining a Constant P/Q Ratio. Otherwise, no Mvar adjustments will be made.
Merit Order Close Added in version 19, build on Aug. 4, 2016
This method will dispatch generators in a merit order determined by their specified participation factors. Economic generator limits will be enforced during this process regardless of how the Enforce Gen MW limits option is set. Details about this method can be found under the Generator Merit Order Close Dispatch topic.
If using this option and an injection group contains ONLY loads, the loads will be adjusted in proportion to their participation factors and merit order close dispatch will not be used. Mvar load will be adjusted if maintaining a Constant P/Q Ratio. Otherwise, no Mvar adjustments will be made.
Click Do Scaling to scale the selected injection groups.
Injection groups have their own set of options that can override the options on this dialog if they are in use. See the Injection Group Specific Scaling Options topic for more information.
You can scale the generation and load values by ownership by first clicking on the Owners button. The Buses Table will be replaced with a new table listing the Owners in the case. To choose the owners to scale, double-click the Scale field to toggle the value between No and Yes. As Scale fields are toggled to Yes, the Generator and Load MW and Mvar fields will update to display the totals for the selected owner. When all of the desired owners have been selected, either the Scale By or the New Value fields can be modified for a desired new value for the selected owners.
To ensure that the reactive power is scaled proportionately to maintain the current load power factor, click the Constant P/Q Ratio option. To enforce generator limits when scaling generation, check the Enforce Gen MW Limits option. To scale generation and load to enforce ACE, check Scale Gen to Keep ACE Constant. When Simulator scales generation, all generator power outputs at the selected buses are scaled by the specified factor, regardless of area control. To scale only generators whose AGC field is set to YES, check Scale Only AGCable Generation. To scale both in-service and out-of-service loads, check Scale Out-Of-Service Loads.
Finally, click Do Scaling to scale the load and generation for the selected owners.
Note: When scaling generators with multiple owners, the scaling will be done on the entire output of these generators, regardless of the fact that not all of the owners have been set to scale. If this is not a desired behavior, you can define multiple generators at the bus, each with 100% ownership.
Note: When scaling loads using the Scale Only AGCAble Generation and Load option, only the AGCable loads will scale, but the non-agcable loads will figure into the total. The user sets the scaling factor/total load that is desired and internally Simulator determines the new scaling factor for the AGCAble load only so that the AGCAble load is adjusted. When the AGCable load is then added to the non-agcable load, the result will be the desired scaling factor/total load.