Result Analysis Mode (Added in Version 22)
When performing results analysis on defined Transient Stability Result Analaysis Time Windows, PowerWorld will calculate the modes and the contribution of each mode to each signal as described later on this page. The list of modes that are calculated are found under the Result Analyzer - Damping\Modes portion of the Transient Stability dialog.
When looking at all the modes, the display is filtered to show only the contingency chosen from the contingency drop-down shown in the red box below. In addition to make filtering by particular time windows easier, there is a display listing all time windows in the blue box below. By checking or unchecking particular time windows the list of signals is filtered. Each row in the table represents one mode that has been calculated for a particular Time Window and Transient Contingnecy. We call each of these rows a "TSResultAnalysisMode". As you click on a row in the table of modes, a second case information display to the bottom left is updated to show you information about all the Signals and the contribution the selected mode to this signal. In addition as you click on rows in the upper table the bottom right portion of the dialog will update a display showing a compass plot of all the contributions of this mode to all signals that were studied.
Remember from the theory of Modal Analysis that this contribution is a complex number with both a magnitude and angle. In the example image below you can see that there are groups of buses that have 180 degrees of separate between them which tells you that one group of signals is oscillating against the other group of signals. On the right you may also specify two options for the compass plot of the mode contributions
Sort Signals By
Specify whether the Magnitude or Rank is used to sort and display the contribution. The Compass plot will then be normalized based on the largest contribution of those being shown.
Signals to Show
A colors dot will be shown to represents each signal and the legend below the compass plot will list the signals that have the largest magnitude of contribution. Set this value to either All to show all signals, or set it to Top Count and specify an integer to choose to only show a specified number of colored dots on the compass plot.
The columns shown with the contributions from each mode are as follows.
Time Window Name
Name of the Time Window for which the mode was calculated.
CTG Name
Name of the Transient Contingency from which the transient results were obtained
Frequency (Freq)
Frequency of the mode in Hz
Damping % (Damp)
The damping ratio percentage. This is 100 times the damping ratio and is equal to
Lambda (Lambda)
Exponential term for the mode which represents the damping. Negative Lambda indicates positive damping
Number (Number)
Number of the mode. Number as just assigned by the calculation tool in no particular order
If you right-click on a particular Mode and choose Show Dialog you will see information about only one mode. This shows information about the Time Window at the top of the dialog as well as the Contingency, Mode Number, Frequency, Damping Ratio %, and Lambda. After this is a list of contributions of the mode to all the signals is shown. The contributions are called TSResultAnalysisModeMagAngle objects. On the bottom right of the dialog there will be a compass plot showing the contributions from this mode across signals which was described earlier in this help topic.
The columns in the table of contributions are as follows
Magnitude (Mag)
Magnitude at Start Time for selected mode's contribution to the signal represents in the row
Magnitude End (MagEnd)
Magnitude at End Time for selected mode's contribution to the signal represents in the row
Angle
Angle in desgrees for selected mode's contribution to the signal represents in the row
Rank
This is the rank contribution of this mode to this signal based on the magnitude. It's based on the large of either Mag or MagEnd and is then normalized across all modes for this particular signal such that the summation of Rank values is 100.
Signal Field
The field that the signal result represents
Signal Object, and many other object related fields for Area, Zone, etc.
The object that the signal result represents