X-Y-Z-Plot
An X-Y-Z plot shows the relationship between the values of two time series at the same points in time on the X and Y axis and makes another dimension visible via a color scale. Additionally, time series can be used as filters.
The values of a time series are displayed as points in the X-Y coordinate system and compared to the values of another time series at the same time. The virtual Z-axis is the color axis. Frequency points and density distribution can be optionally displayed.
Creating an X-Y-Z Plot Window
Create a new X-Y-Z plot window by right-clicking on an empty space in the Plot Manager window. The context menu opens, which you can use to create a 
New X-Y-Z Plot Window (see following figure).
In the Plot Manager, the new X-Y-Z plot window is created with the subfolders X, Y, Z (Colour), and Filter.
Drag and drop the desired time series from the Project Explorer or a Data Grid onto the X, Y, Z (Colour), and Filter folders in the Plot Manager. Only one time series each may be assigned to the X, Y, and Z (Colour) folders. Several time series can be placed in the Filter folder. Each time series may only be moved to one folder and not to several at the same time.
Example
As an example a Gas Turbine with Waste Heat Recovery Boiler is considered. The gas turbine burns fuel to produce electricity and steam. Three operating states are possible:
These operating states are shown in the following X-Y plot for comparison.
In order to analyze whether and how the relationship between Fuel Consumption and Electricity Generation depends on the outside Temperature, an X-Y-Z plot is created on whose X and Y axes the Fuel Consumption and Electricity Generation are entered as in the previous X-Y plot. The Z axis is occupied by the time series of the outdoor Temperature, whose times must coincide with those of the other time series.
The following plot with color gradients is created.
In the plot window on the right is the color bar, which shows the color gradient of the Z time series between the maximum and the minimum value.
For each of the three operating states it can be seen that the lowest values for electricity generation and fuel consumption occur at high temperatures (shown in red in the plot above), while the highest values occur at low temperatures (shown in blue in the plot). The example plot illustrates the temperature dependence of a gas turbine: as the outside temperature decreases, the maximum possible output of a gas turbine increases.
In order to limit the observation to a single operating state, e.g., full load, an additional filter is used. The operating state full load is defined by a certain steam mass flow. Therefore, the time series Steam Generation with the steam mass flow is inserted into the Filter folder of the X-Y-Z window in the Plot Manager (see following figure). It must also be defined for the same period as the other time series.
Configure Plot Window and Filter
In the Plot Manager, a configuration dialog can be opened via the context menu of the Plot Window or its subfolders to configure the Plot Window and the Filter.
The start and end times of the plot are defined under Common.
Minimum (min-value) and maximum values (max-value) can be defined for the Axes and the Filter. For the Z-Axis, the colors for the minimum (Colour for min-value) and maximum values (Colour for max-value) can also be defined.
Under Filter, select the time series to be used as a filter from the drop-down list. All time series that you have previously assigned to the Filter folder in the Plot Manager using drag and drop are available for selection.
In our example the time series Steam Generation is selected as filter. The minimum value is set at 110 t/h as the lower limit of the steam mass flow rate defined here for full load (see following figure).
According to the filter criterion, all times below the minimum value are filtered out. The result is the following plot.
Show Cluster Points and Density Spread
The Cluster Points and the Density distribution (Density Spread) can be displayed in the X-Y-Z plot (see the following two figures). They are accessed via the context menu of the plot in the Plot Window.
The settings for the display of the Cluster Points and the Density Spread are made in the Options dialog.
