Transmission and Distribution Tiers

The ArcFM Utility Network (UN) is focused on the representation of electric distribution facilities. While many utilities choose to include electric transmission and sub-transmission facilities in their electric Utility Network (UN) data model, we recommend you define the Transmission, Distribution, and Secondary Mesh lines into separate tiers for these facilities. The tier definition in the electric domain network should be configured as partitioned. For more information, see the Esri topic Utility Network Tiers.

When you subdivide a network into tiers:

• The data is organized into independent sections and improves the performance of network analysis tools, such as Update Subnetwork. It also allows the data to be managed in the same database.

• The boundary of the defined network segment keeps exported data in an accepted format for integrated systems, such as an Outage Management System (OMS).

  Example: One customer can have an OMS that may only require downstream data from a medium voltage substation. Another customer with GIS data that includes high voltage transmission can configure separate transmission and distribution voltage tiers to let the OMS use the Export Subnetwork tool in ArcGIS Pro to filter out transmission devices. This is preferable to developing and maintaining a custom Extract Transform Load (ETL) solution for each integrated system.

• The tier is based on the nominal voltage expected to be carried by the equipment in that segment. This is because different skills, business processes, and equipment (and integrated software) are required to build and maintain electric distribution systems at different voltage levels.

• A subnetwork controller is a device that delimits one tier to another at the boundary point. These boundaries are mainly at substations where the nominal voltage is changed. The subnetwork controllers are usually the last device in the substation (Switches or Fuses), not the Transformers where the nominal voltage is changed.

  Example: Substation models are different from the distribution network because equipment is rated to operate at high voltages. Transformers are connected using buses rather than cables and some protective devices may have specific categories assigned, like a subnetwork controller, that delimit the different tiers.

Required Configuration

• Transmission must be configured in its own tier.

Recommended Configuration

• Unbalanced: Distribution and Low Voltage Radial networks should be in the same tier, while Secondary Mesh networks should be in its own tier.

• Balanced: Distribution and Secondary Mesh networks should each be in their own tier.