Just an idea - I almost wonder if a Geometric Network may be a better way to go instead of using Network Analyst. However, I haven't used a Geometric Network, so don't know for sure. It might be worth checking out, though.
A geometric network is a set of connected edges and junctions, along with connectivity rules, that are used to represent and model the behavior of a common network infrastructure in the real world. Water distribution, electrical lines, gas pipelines, telephone services, and water flow in a stream are all examples of resource flows that can be modeled and analyzed using a geometric network. With a geometric network you can perform various network analyses such as finding loops or circuits within a network or trace upstream or downstream to find the source of flow within a network.
What are geometric networks?—Help | ArcGIS for Desktop
Trace Geometric Network—Help | ArcGIS for Desktop
Finding the upstream accumulation—Help | ArcGIS for Desktop
Also, let me tag a group that is involved in your field: https://community.esri.com/groups/electric-and-gas-user-group
Chris Donohue, GISP