Organizing Your Gas Network for Understanding, Visualization, and Agility
Moving Beyond The Traditional Hierarchical Structure To “Where” The Industry Needs To Be
By Tom Coolidge and Tom DeWitte
Around the dawn of a new century 118 years ago, the gas industry evolved to a new stage of development. Up to that time, gas networks typically were relatively small, located close to where the manufactured gas was produced, and low pressure. The advent of high pressure distribution systems around 1900 signaled the start of the multi-pressure level gas system era. With this new era came a greater number of valves and regulators, and greater engineering, operational, and business complexity. The era of greater gas system complexity began. System complexity has been steadily growing through the ensuing years, with today’s gas networks being substantially bigger, more complex, and more geographically widespread than ever. All indications are that these trends will continue in the years ahead.
Today, answering questions about the asset components of your gas system, their characteristics, and how they operate often requires you to think about your network in different ways.
On the one hand, there is the issue of scope. Depending upon the question, you may need to think about all of your network. Or, perhaps answering the question only requires you to deal with part of it.
Which part? That may simply be an issue of geography. For instance, “Let’s look at assets in this political jurisdiction.” Or, it may be an issue of network connectivity or structure. An example of this is “Show me all the network components in this isolation zone.”
And, today’s question may not be the same as tomorrow’s. This makes the ability to easily define new sub-networks and combine different parts for a new purpose essential to business agility.
Traditional Network Hierarchy
Let’s look at long-standing gas industry practice.
Gas networks typically include multiple sub-networks, each operating at up to a different maximum pressure, with pipe sizes and maximum pressures reducing the closer gas gets to delivery points. For years, this led the gas industry to organize network data in a hierarchical tabular structure, where each successively lower sub-network is subordinate to that above it. Traditionally, this has been a series of tables organized into a parent-child relationship. A typical table organization might look like the following:
This common hierarchy has served the gas community well over the last several decades. But restricting this organization of the gas system to a tabular structure fails to address the common question of where these zones exist.
The GIS gas community has long been the masters of understanding “where”, but has long struggled with how to visualize an entire gas pipe system without having to wait an unacceptable length of time for the map to draw on the computer screen. This was a minimal issue when most end users viewed the GIS managed gas system via paper maps. But as more gas organizations have deployed web and mobile applications with interactive gas system maps, this issue has increased in priority.
So, what is a gas company to do
Turns out the solution to both of these common gas community issues is the new utility network’s subnetwork. This new capability deploys a similar hierarchy structure on top of the gas pipe system as has been traditionally used. But, since the utility network is a part of the ArcGIS Platform these traditional tables are geospatially enabled into polyline features.
I can see it
The utility network subnetwork capability aggregates the many individual pipe segments into a single multi-part polyline feature which is then stored as a single record in the Subnetline feature class. Similar to the traditional table management structure each subnetline feature class record represents and describes a single system, pressure, or isolation zone. These large but few features can be fetched from the database and drawn very rapidly on the computer screen. With utility network subnetworks’ users of the ArcGIS Platform can now see where their hierarchy zones are located and can do so with an interactive map which displays the entire gas system very rapidly.
How are Gas Subnetworks organized
The gas pipe system subnetworks are organized by tier groups and tiers. Each tier group can have its own unique tier hierarchy. There is no practical limit to the number of tiers within a tier group. The default hierarchy included with the UPDM 2017 edition data model divides the wellhead to customer meter gas system into three tier groups. Those tier groups are named; Gathering, Transmission, and Distribution. Each of these tier groups has been given the same tier hierarchy. That tier hierarchy is; System, Pressure, and Isolation. Each tier within each tier group has a unique definition to accurately model the subnetworks.
Do I have to manually maintain these subnetworks
The utility network automates the management of the individual subnetwork features within these tiers and tier groups. Mappers responsible for the maintenance of the as-built representation of the gas pipe system simply need to run a single Geoprocessing tool called “Update Subnetwork” to update the subnetworks with changes made to the gas pipe system. Since this is a geoprocessing tool, this update process can easily be incorporated into a nightly batch job further automating the management of subnetworks.
What else can I do with these Subnetworks
The tradition hierarchy tables used in the past, often had basic attributes such as zone name and some summary attributes such as operating pressure. In the legacy systems these were manually maintained descriptors of the different zones. In the utility network Subnetwork, these summary attributes are maintained by the ArcGIS platform and automatically recalculated every time the “Update Subnetwork” geoprocessing tool is run.
Default summary attributes are included in the UPDM 2017 edition data model. Below is a listing of the default summary attributes for the gas pipe system tiers.
The geospatial enablement of the traditional hierarchy tables adds a new dimension to the understanding of the zones by addressing the question of where are these zones located. The aggregation of the zones pipe segments into these geospatially enabled zones also solves the issue of being able to visualize the entire gas pipe system on the map display with the redraw performance that users have some to expect from the ArcGIS platform. The utility network Subnetwork capability resolves two long standing gas community issues by combining the organization and visualization of the gas hierarchy into a set of ArcGIS Platform managed features.
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