Integration Models for GIS Based Network Simulation and Analysis
Conversion
Finding the data needed for engineering analysis is the first step. Next, the data needs to be
converted. Unit and nameplate conversions are straightforward. Complications usually arise in
topology and connectivity conversion.
Engineering analysis is invoked on models of nodes and the node connecting branches. Nodes
are points of known or calculated voltage and branches are paths for current flow. Some GIS
packages do not use branch and node concepts. Others support different types of ?simple? and
?complex branches and nodes or junctions. Representations can be very different because the
GIS is a platform for spatial data and facilities representation and management. It is not a
platform designed for representing electrical analysis quantities.
Some GIS models allow branch (or edge) intersection at non-nodal points. Generating nodes
when necessary and forming the electrical topology is necessary to properly represent the
system. Some GIS models require nodes on all devices. However, some engineering analysis
tools do not require nodes on devices. In these cases, elimination of nodes may be necessary.
Mapping overhead and pad-mounted switch models between a GIS and an engineering analysis
model can be complex. Electrical topology is not usually managed within a GIS. A single node
in the GIS often represents a pad-mounted switch. Determining the electrical path and network
for these pad-mounted switches must be performed in a reliable manner.
Issues with feeder location, customer and load placement, line construction and many other
aspects must also be resolved. Furthermore, if engineering analysis results are desired from
within the GIS, results must be converted from the engineering model back to the GIS model
Validation
Most engineering simulation and analysis engines support robust data validation within the
context of their use. Unfortunately, errors and anomalies showing up in the analysis are difficult
to track back to problems in particular data coming from the GIS. For example, a line that is
30,000 feet long instead of 300 feet may result in bad voltages or failure to converge in load-flow
analysis within the simulation engine. There are many problems that could cause a failure to
converge problem. Associating the problem with an invalid line length could be time consuming.
Data validation rules that are in place during the data tracing and conversion phases are essential.
Having a length limit of 1000 feet would pinpoint the problem during the tracing and conversion
process. The problem would be flagged within the context of the GIS where the problem could
be directly investigated and possibly repaired.
Supplementation
A GIS typically supports data that is sufficient to specify the topology, connectivity, and
construction of a power system. Detailed modeling parameters about devices, loads, and
conductors are usually not stored within the GIS. This missing data must be supplied in order to
perform engineering analysis and simulation.
Data supplementation should occur during the model tracing and conversion phase so that a
complete data set is available for sophisticated data validation. Supplementation should be
implemented with a rule based system so that defaults for modeling parameters can be based on
line construction, phasing, location, or other GIS based constructs. Supplemental data may
include source impedances, settings, demands or other information.
Execution
The goal of GIS based simulation and analysis is to generate and publish valid results within the
context of the GIS. In some cases, the generation of analysis results is done from within an
engineering analysis package. In these cases, the engineer is in command of executing the proper
analysis. In other cases, it is desired to have engineering analysis invoked from the GIS. In those
cases, a method for commanding the engineering analysis from the GIS must be developed so
that the proper analysis is performed with the proper settings.
