Secondary Voltage Analysis

When investigating meter voltage issues, the underlying issue could be related to secondary voltage drop.  While SmartMAP performs most load-flow calculations on the primary distribution system stopping at the secondary side of each distribution transformer it is capable of analyzing the secondary system as well.  The secondary system is omitted by default, because data on secondary lines is usually not as accurate as the primary distribution system.

Since the secondary system was omitted originally because of the likelihood of inaccurate data, the analysis of a specific location should usually include a field visit where conductor size and locations is verified as best as is reasonable to do.  The updated data can be provided to your GIS department, once added in GIS, it will be included in the SmartMAP System Model as well through the GIS-->SmartMAP sync process.

In our example below, the secondary voltage analysis is being performed because of high voltages recorded on the meters.  High voltages in a case like this, are usually the result of a transformer tap change in the past, to boost voltage to customers furthest from the transformer who were experiencing low voltage, but they often cause high voltages at meters closer to the transformer, especially when the load drops in different seasons.

figure 1 - many meters connected to this transformer and recorded voltage issues with multiple meters

The modeling process takes place in the SmartMAP Desktop application:

1. Open SmartMAP and load the Current System Model

2. Save a local copy of the model, so any changes can be made without affecting the System Model, which is the actual current state of the system.

3. Locate the meter/transformer where the analysis is to be performed, you can search for the location by going to Editing-->Find Asset, or using the shortcut CTRL+F

4. All of the secondary system is usually on a default '240V' meter layer (voltage doesn't really matter on a Meter Layer, since no analysis is run on it, so any value can be used here).  To run analysis, we will create a new secondary layer which will be included in analysis.  To do this, select the lighting bolt on the layers tab to create a new electrical layer

In this case, it will have a Nominal Voltage of 600V, and since we do want analysis performed on it, we will leave the Meter Layer box empty.

5. Right-click the transformer, and select 'Trace Secondary'

6. Select the Editing-->Change Layer button and move them to the new 600V layer you created.  Note: the primary lines feeding the transformer will get deleted in this step.

7. On the layers tab, select your primary voltage layer, then with the Add Node or Select tool selected, click (or right-click) the map in a location next to the transformer to add a node.  This new node will serve as the HV side of the transformer, while the existing one will be the LV side.  In the dialog box, click "Create Node", then "OK"

8. Next we will connect the new HV node by re-drawing the primary lines where disappeared when the 'Change Layer' tool was used.  To do this, select Editing-->Add Line, then draw the line(s) needed to connect the transformer.  SmartMAP will default to the conductor it is connected to, so usually you do not need to set it manually.  The blank fields are not required for this analysis, and can remain blank.

9. Change to the Select Tool (Editing-->Select), then click the transformer (LV) and cut the elements from it, they are no longer needed (CTRL+X)

10. Select both the HV & LV nodes for the transformer, hold the CTRL button to select multiple nodes (the SHIFT button can be selected to remove items from a selection), then press the Editing-->Add Power Transformer button

11. It will now prompt you for the details of the transformer.  The data entered here should be the detailed data which was confirmed during the field check:

Load flow will now include this section of the secondary system each time it runs.  Before running analysis, check the conductor size and placement against what was collected in your field visit.

Confirm the details of the conductor used by locating it in the References tab in the lower left corner of the screen:

Determine the load values you wish to use a single point-in-time may not give the results needed for this type of analysis.  Usually the goal is to upgrade such that a voltage drop issue will be resolved and boosting voltage at the transformer will no longer be necessary.  This means you want to model the secondary with the highest load conditions you may expect in the foreseeable future.  Before adding those loads, it is a good idea to Import System Loads for a recent date/time when system loading was fairly high.

For this, it can be helpful to use the↓ button in the Transformer Overview -->Connected Meters page in the Web application to download a .csv of all meters connected to the transformer when there are many meters connected. I then remove extra rows at the top, and add a "MaxLoad" column.  

For cases with fewer meters, it is usually quicker to just double-click a meter, and Add a Simple Load element to each, with the max load you want to model.  If doing this, check the "unmetered loads" box when adding the load, so you can easily retain those loads when loading different system load data.

If you added loads using the .csv, they can be imported into SmartMAP using the Import Loads process

After adding loads run Analysis -->Load flow to calculate the loading & voltages.  It can be helpful to set your map theme to "Node Voltages" & "Line Loading" which will color-code them accordingly.  The Legend/coding you use can be defined in SmartMAP Options