Extended Feeder Manager requires that you designate certain point feature classes (your choice) as SubSources. There are two ways to do this. The first option is significantly faster than the second option.

Option 1: Update SubSources and Trace All Feeders

First you will need to disable the Feeder Manager autoupdaters. In ArcCatalog, right-click the electric geometric network and select Feeder Manager | Settings. In the Feeder Manager Settings dialog, clear the checkbox labeled "Tracing Autoupdaters Enabled." Click Save, then close the Feeder Manager Settings dialog. DO NOT clear the checkbox labeled "Weight Autoupdater Enabled."

Next, set all existing Feeder Manager sources as SubSource. The autoupdaters assigned in Step 6: Assign Autoupdaters will write all of these sources to the CircuitSourceID table and define them as UltimateSources as necessary.

Open ArcMap and begin an editing session.
Use the Locator tool to select all existing Feeder Manager sources (e.g., CircuitBreakers).
Select the feature class (e.g., DynamicProtectiveDevice for CircuitBreakers) in the Display tab of the TOC. Right-click and select Open Attribute Table.
Click Selected in the Show field.
Right-click the SubSource column and select Field Calculator. Set the SubSource value to 1 (Yes). This is not required on ultimate source features.
Close the Selected Attributes window.
Repeat steps 3-7 for all features that may be designated as SubSources.
Save Edits.
When you've finished updating the SubSource column for all features that may be SubSources, close ArcMap. Do not open ArcCatalog through ArcMap, instead re-open ArcCatalog.
Enable the Feeder Manager autoupdaters. Right-click the electric geometric network and select Feeder Manager | Settings. Select the checkbox for "Tracing Autoupdaters Enabled." Click Save, then close the Feeder Manager Settings dialog.
Next, run Trace All Feeders to execute all Feeder Manager autoupdaters and populate the ParentCircuitSourceID fields for all features in the network. In ArcCatalog, right-click the electric geometric network and select Feeder Manager | Trace All Feeders.

Option 2: Update SubSources

You may set sources and subsources with the Feeder Manager autoupdaters enabled. If you wish to use this option, perform only steps 2-10 from Option 1. Note that this will take more time as all appropriate autoupdaters will fire with each edit.

Option 3: Define an Ultimate Source Upstream of Current Circuit Source

If you wish to define an ultimate source upstream of an existing circuit source, follow the steps below.

In ArcMap, select the circuit source(s) downstream of the ultimate source feature(s).
Delete the CircuitSource relationship on each selected feature. This removes them from the CircuitSource table.
Select the features to be designated as ultimate sources.
Create a relationship with the CircuitSource table on each ultimate source feature.