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Esri Utility Network - Subnetworks and Load Swap

In this post, one more in the series of articles about the new Esri Utility Network, I use a Load Swap exercise to illustrate the concept of a Utility Network Subnetwork: a collection of Devices and Lines in a Domain Network having in common:

  1. One or several sources (or sink in some waste water applications).
  2. Being topologically connected.
  3. Sharing the same value(s) for a given characteristic.

Also, I illustrate how each Subnetwork has an associated line feature in the Utility Network SubnetLine feature class. Each line serves as a comprehensive visual representation of all the components of the associated Subnetwork. This allows for fast tracing and display capabilities. The exercise demonstrates how Subnetworks can be identified and modified.

Before we start the exercise, let me bring to your attention three key concepts introduced by the Utility Network: Domain Networks, Tiers, and Subnetworks.

Esri Utility Network: Domain Networks, Tiers, and Subnetworks

In an earlier article, Skye has presented the details of the Utility Network Model. For the exercise we will focus on three components of the model: Domain Networks, Tiers, and, above all, Subnetworks. The figure below shows the components of interest.

UNEA - EA Load Swap - Subset Model - Esri Utility Network

In the article Esri Utility Network - Topology, Tiers, & Subnetworks, Oh My! Skye elaborates further on the meaning of Domain Networks, Tiers, and Subnetworks. He also explains the role these components can play when modeling the specific needs of different utility companies. As a quick reference to the article, let me paraphrase by saying:

  1. A Domain is the collection of lines and devices and their assemblage and connection points; this represents a business unit, such as: Electric, Telecom, Gas, Water and Sewer.
  2. Domains may be logically partitioned into Tiers. Tiers are collections of domain features with a common characteristic. For instance, in an Electric Domain the operating voltage may be used to partition the network into High, Medium and Low Voltage Tiers.
  3. Within each Tier, a Subnetwork contains all connected features that share common sources, or sinks. For example, in a Medium Voltage Tier, all features with medium voltage, and topologically connected downstream from a particular source circuit breaker constitute an individual Subnetwork. (This concept is similar, but not identical to a feeder; as explained below.)

Some notes on Subnetworks

Contrary to Domains and Tiers, which represent logical partitions of the network, Subnetworks precisely define geographic partitions within the spatial extent of the network. In other words, the Subnetwork not only contains features of common characteristics, but it also specifies the geographic distribution and connectivity of its features.

SubnetLine Feature Class

Exploiting this property of Subnetworks, Esri has endowed the Domain Network with a line feature class, the SubnetLine. In the SubnetLine, each line "represents" one Subnetwork. In the example of the Medium Voltage Tier of an electric Domain, the SubnetLine class has a line for every Medium Voltage circuit. Representing the Subnetworks by line features allows Esri to utilize all tools available for line features to handle Subnetworks. For instance, they can utilize tools to visualize Subnetworks in layers with specified symbology, selecting individual subnetworks by selecting its line, finding Subnetworks by feature attributes, among others.

Topological Connectivity

On another note, let me clarify the statement that a Subnetwork contains all connected features sharing the same Tier-defining characteristic. Connectivity here means the Topological Connectivity native to Utility Network. This is regardless of their geometric coincidence or proximity. Using the example of the Medium Voltage Tier, a tie-switch is a point where two circuits coincide. Even though the two circuits are geometrically connected, in Utility Network the tie-switch has two different topological connections — one to each of the two underlying Subnetworks.

One Electric Feeder: Many Subnetworks

Finally, when dealing with Subnetworks, we must make sure we fully understand the concepts of connectivity, and particularly traceability within the network. For an example, think of a given Electric Distribution feeder. With all its features connected, we can trace the feeder from the load side of the head circuit breaker in the Substation to every single delivery point serviced by the feeder. Now then, when modeling the feeder in Utility Network with Medium and Low Voltage Tiers, as in the examples above, the connected and fully traceable feeder is implemented not by one, but instead by multiple Subnetworks. The model groups together all "primary" equipment as contained within one Subnetwork, while the "secondary" equipment is distributed among many individual Subnetworks. In other words, one Subnetwork represent the Medium Voltage circuit: from source circuit breaker to all service transformers. Then, each Low Voltage circuit, extending from each service transformer to all delivery points served by that transformer, constitute one of the many Low Voltage Subnetworks in this feeder.

With all the ideas in mind, let us run the Load Swap exercise to get a better understanding of Subnetworks in the Utility Network.

Subnetworks Example

The figure below shows a map of an area serviced by electric utility NRG, where two distinct circuits within the spatial extent of the network are energized by two different sources.

UNEA - EA Load Swap - Map Two Subnetworks  - Esri Utility Network

The red circuit has its source in Northside Substation, out of a circuit breaker monitored and controlled by Remote 003. A circuit breaker in the Southside Station, controlled by Remote 001, supplies power to the green circuit. Also, two tie-switches connecting both circuits are shown.

Subnetwork Details

Viewing Subnetwork Attributes

The two circuits have been implemented by two related Utility Network Subnetworks, both under the Medium Voltage Tier of the ElectricDistribution Domain modeling the network. The details of these, and all other Subnetworks in the Domain can be displayed in tabular form by clicking the View tool of the Subnetwork group, under the Data tab of the Utility Network ribbon.

UNEA - EA Load Swap - View Tool -  - Esri Utility Network

In tabular representation ArcGIS Pro shows the Subnetwork Controller, Tier and Domain names of each Subnetwork, as well as the Feature asset group of the device acting as controller - CircuitBreaker in this case. Among several other attributes, each Subnetwork also has a reference to its associated SubnetLine feature.

UNEA - EA Load Swap - Subnetworks Tabular View - Esri Utility Network

Displaying SubnetLine Features

The red and green multi-lines displayed in the map are, in fact, the SubnetLine features representing Subnetworks RMT003 and RMT001, respectively. As with any other Feature Class, the SubnetLine can be added to the map as a Layer, with some specified symbology; as shown in the Contents pane, under Drawing Order.

UNEA - EA Load Swap - Subnetworks Layer Symbology - Esri Utility Network

Also, the SubnetLine for a given Subnetwork can be found using the Select By Attribute tool of the Selection group in the Map tab. When the Geoprocessing form appears, ensure the Layer Name is set to Individual Circuits, that the Selection Type is set to New Selection, and use the Add Clause to find the SubnetLine for which its Subnetwork name is RMT003.

UNEA - EA Load Swap - Select Subnetworks by Attribute - Esri Utility Network

The result of this selection is shown below: a single feature highlighted in cyan.

UNEA - EA Load Swap - SubnetLineSelected - Esri Utility Network

The single feature can be manipulated like any other line feature, except that the SubnetLine Feature Class is presented to the user as read-only; fully managed by the Utility Network.

Subnetwork Controllers

The sources (or sinks) of the commodity for a given Tier in a particular Domain are modeled in Utility Network as Subnetwork Controllers. Zooming into Northside Station, and clicking on the source circuit breaker the following description pops up as highlighted in the figure below.

UNEA - EA Load Swap - Subnet Controller 003 - Esri Utility Network

The Circuit Breaker RTM003 has been configured with Subnetwork controller category and Device role type both set to Subnetwork Source. Also, during configuration of the sample Utility Network the circuit breaker was set to be the controller of Subnetwork RMT003.

Subnetworks are Tiered

Another detail worth mentioning in the figure is that we see the SubnetLine of Subnetwork RMT003 as geographically laying along the Medium Voltage features. Here, the underground primary is represented as blue dashes. But, even though the Low Voltage equipment is connected to the Medium Voltage via transformers, and the Low Voltage belong to the overall feeder, the SubnetLine does not extend over the Low Voltage. Recall from previous sections that Subnetworks are configured as belonging to particular tiers: Medium Voltage Tier in this example. So, Subnetworks cannot cross over equipment from different tiers. Consequently, their corresponding SubnetLines also remain within their associated Tiers. And even if we can trace these "secondaries" from the source circuit breaker, the "secondaries" (as Low Voltage equipment) do not belong to the RMT003 Medium Voltage Subnetwork.

NOTE: The symbology of the SubnetLine was set at an offset of its real geometry so that we could more clearly see the "primary" equipment it is associated with.

Tie-Switches: Connecting Subnetworks

Finally, let me draw your attention to one of the two tie-switches in the example. In the first close up (below) we can see how the switch is located in the proximity of the two SubnetLines.

UNEA - EA Load Swap - Tie-Switch - Esri Utility Network

An even closer look, and inspection of the switch's attributes shows the following characteristics:

UNEA - EA Load Swap - Tie-Switch Closeup - Esri Utility Network

  1. The device is actually modeled as belonging to the Tie Switch Asset Group.
  2. The Circuit Name attribute shows RTM001::RTM003; indicating that the switch is in fact connecting both Subnetworks.
  3. The Device Status attribute shows that, under normal conditions, the switch is open; thus maintaining both circuits isolated from each other.
  4. The switch is associated by containment to a Switch Gear, and the latter attached to a pad. The switch gear contains several other pieces of equipment, particularly a busbar that allows power flow between the two incoming underground primaries of the RMT003 Subnetwork.
  5. Topologically, the switch is connected to an Elbow at the end of the RTM001 underground primary, and to the connection point at the end of the busbar.

In summary, two Subnetworks may be connected by devices, such as a tie-switch in electric parlance, or a valve in the gas and/or water domains. The devices establish the connection between the Subnetworks via the Connectivity Association established between the device and pieces of equipment of both Subnetworks. With a "normal" device status of open (for an electric switch) or closed (for a valve) the device maintains the two connected Subnetworks isolated.

Load Swap Example

Suppose that for some reason the sample electric utility, NRG, determines that RMT001 is overloaded, and that its energy delivery needs to be decreased. Yet, NRG cannot leave consumers without power... Joe Queen, NRG engineer, comes to the rescue. Joe has resolved this type of situation multiple times. He uses a switching operation commonly called a Load Swap: A section of the overloaded circuit is isolated by say a sectionalizer, and then energized from an underloaded circuit connected via a tie switch.

Joe attended one of SSP's Utility Network Jumpstart sessions, and learned about the new model and how to use it with ArcGIS Pro. So... he follows these steps.

Section Isolation

Using the Select By Attributes tool of the Selection group under the Map tab, Joe looks for Distribution Device\Switches\Switch with Asset ID 92957. Once selected, he zooms in to analyze the state of the network in that area. (See figure below.)

UNEA - EA Load Swap - Sectionalizer 92957 - Esri Utility Network

The Device Status attribute indicates that, under normal operating conditions, the switch is Closed. In order to isolate the "north-western" area of the Subnetwork RMT001, Joe toggles the Device Status value to Opened. Since the Auto Apply box is checked, the change of status is applied immediately. And because such a change modifies the connectivity of the Utility Network, Joe must validate the new state of the network by clicking the Validate tool of the Network Topology group under the Data tab of the Utility Network ribbon. Once validated, he saves his edit.

The change of status, by itself, does not affect the state of the Utility Network. For the isolation to take effect, Joe must run the Update Subnetwork tool of the Tools group under the Analysis tab, and configuring the Geoprocessing tool as indicated in the figure below.

UNEA - EA Load Swap - Isolation - Esri Utility Network

The Update Subnetworks tool is run for the ElectricDistribution Domain for the Medium Voltage Tier, specifically for Subnetwork RMT001; since this is the Subnetwork that originally contained the sectionalizer. Notice how after updating RMT001 the desired section of the network has been isolated; i.e., it does not belong to any Subnetwork.

Note how automatically, the SubnetLine feature associated to Subnetwork RMT001 (green) readjusts its geometry to within the energized area of the circuit.

Restoring Power From RMT003

Joe selects now the tie-switch previously identified, which has an Asset ID of 94691. The switch is Opened under normal conditions. But now Joe must toggle it to Closed, to represent the dynamic state in the field that supports the Load Swap.

UNEA - EA Load Swap - Energizing - Esri Utility Network

As with the isolation step, closing a previously Opened switch does affect the topology of the network, and the operation must be validated. (Although not mandatory, Joe has the habit of saving edits after validating.)

Once more, and in order to propagate the changes in the network that derive from closing the tie-switch, Joe must run the Update Subnetwork tool; this time applied to the RMT003 Subnetwork.

UNEA - EA Load Swap - Power Restored - Annotated - Esri Utility Network

The update completes successfully, and Joe observes that the SubnetLine associated with Subnetwork RMT003 redraws to include the previously isolated area. The Load Swap exercise has been completed... Power has been restored to the whole network, and Subnetwork RMT001 has shed some of the energizing responsibilities to its "neighboring" RMT003 Subnetwork.


The Utility Network Model introduces the concept of a Subnetwork as:

  1. The equipment in a Domain
  2. Sharing a common, tier-specific characteristic
  3. Topologically connected
  4. And where one or several Subnetwork devices act as sources (or sinks) in the propagation of the commodity.

The properties of the Subnetwork have been illustrated in this article with examples from the Electric Distribution domain. In particular, we have explained how the geographic distribution of the Subnetwork is implemented by the Utility Network via a new line feature class: the SubnetLine.

Finally, a Load Swap exercise has demonstrated how Subnetworks, and related concepts, can be used and managed from ArcGIS Pro.

But... Let us not stop here... There is much more to learn about the Utility Network. All of us at SSP, as a trusted Esri Partner, are excited to continue disseminating information about the Utility Network, and start building productivity tools for when you transition to the new model. So... stay tuned, as more articles are on their way.

Author Information

  • Joaquin Madrid

    Joaquin Madrid

    Joaquin Madrid comes to SSP from having worked in the GIS and Smart Grid fields for the last 12 years, and specializes in Electric Utilities systems integration. In this role, Joaquin manages the technical direction for SSP implementation’s team and provide leadership in the adaptation of new technologies for the long-term future growth of SSP Innovations.

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