Transformer Tap Topology
The ArcFM UN supports two topology styles for connecting the transformer’s primary terminal to the conductors that supply the transformer with power. We refer to these two styles as the tap and in-line. The style that is used by any given transformer type is indicated by the type’s membership in either the E:Transformer - Tap or the E:Transformer - Inline network category, which are mutually exclusive.
E:Transformer - Tap Category
Many ArcFM users are familiar with the complex edge feature type in Esri’s Geometric Network (in ArcGIS version 10 and earlier), which made it possible for distribution transformers to tap power from any arbitrary location along the length of a Primary, or MV, conductor feature without having to artificially split the conductor feature at each transformer location to become two conductor features. This modeling capability allows the facilities database to better reflect the physical reality for overhead electric facilities. A single conductor feature in GIS represents the reach of a single, uninterrupted bundle of primary phase and neutral conductors and each physical conductor in the bundle possesses the same properties for the entire length of the reach. The phase designation (or neutral), material, size, ampacity, and more. This is much easier to visualize and manage in the GIS database, and closer to the perceived reality, than a model that would require many short conductor features. Each conductor would have the same attributes and own set of related ConductorInfo objects that are identical to the rest that are laid end to end from one transformer to the next.
The UN continues to support this tap model for connecting distribution transformers freely along the path of an uninterrupted length of primary conductor, but requires a tap junction to sit where power branches from the primary circuit into the transformer.
Required Configuration
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In the ArcFM UN, this is a junction feature that belongs to the E:Connection -Tap network category.
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Junction feature types that belong to the E:Connection - Tap category cannot be in Esri’s subnetwork tap category, since that category bestows unwanted tracing and propagation behaviors upon the tap features.
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The tap arrangement also requires a junction-junction (J:J) connectivity association. This association represents an explicit path in the electric network topology that travels between the transformer tap feature and the primary terminal of the transformer feature.
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The tap connectivity style requires that the transformer device feature is placed away from the transformer tap feature by a distance that is greater than double the configured xyTolerance of the UN dataset. This minimum required distance is typically small enough, about a millimeter, that the transformer symbol can appear to be sitting directly on the conductor feature, even when viewed on the largest of map scales. It is nonetheless a spatial constraint that must be strictly observed by editing tools.
Tap Transformer Diagram
Tap Transformer Usage Example: Uninterrupted Conductor Branch
