Integration Models for GIS Based Network Simulation and Analysis
For example, information about fuse holders, fuse barrels and fuse links may be listed in the GIS.
The amp rating and time/current characteristics of the fuse may be the only piece required for
engineering analysis but information about the holder, barrel and link must be collected so that
the electrical connectivity between the fuse and its associated line section can be determined.
This is not a trivial exercise in many cases.
The GIS contains information that is not electrically relevant to analysis. The type of connectors
used on each elbow phase within a cabinet probably does not impact most types of electrical
analysis. The connectors could, however, be central in tracing the electrical connectivity of the
system. This is even the case with basic line or cable sections. Lines best represented in the
thousands of feet in analysis software may be broken up into segments of hundreds of feet in the
GIS. Poles, guys, arrestors, and other hardware may play a role in the GIS connectivity while
having no place in engineering analysis.
This leads to nodes. Nodes in a GIS are oftentimes spatial intersection points. Poles, guys, cross
arms may all share nodes. A 34 kV line and a 12 kV line intersecting on a pole may share a
"node" within the GIS. In the engineering analysis context, nodes represent electrical
connectivity points. Obviously 12 and 34kV lines cannot share an electrical node.
All of these issues are not necessarily problems. They are conflicts resulting from environments
focused on different aspects of the distribution system. The GIS is focused on tracking and
managing the facilities and assets making up the distribution system. The analysis software is
focused on a reasonable model for representing the electrical behavior of the system. The
electrical model is "reduced" from the tremendously granular GIS model so that every
component has some electrical analysis significance. Even an electrical system modeled at a
pole-to-pole level must undergo substantial reduction. The electrical model must also be
electrically connected. A pad-mounted switchgear may be made of dozens of components within
the GIS but it may be a simple tie within the electrical analysis model.
The data quality focus is different in a GIS and analysis environment. Serial numbers for
transformers may be tagged as critical data in the GIS while impedance data may not even be
required. Many parameters that have a significant impact on voltage and loading levels in
analysis may be loosely monitored in the GIS management process. These data issues and the
differences in "networks" drive the five parts of the model building process listed in the next
section.
Requirements for Generating Models From GIS
A GIS system is the key to a huge data system that is used by a diverse set of utility personnel
and drives many areas of the operation of the utility. As was mentioned above, engineering
analysis is most demanding of quality data. Furthermore, it hinges off of a small part of data that
is typically stored in a GIS and may require data that is not stored in a GIS. Any ?solution? that
results in engineering analysis directly or indirectly from GIS data must have implementations
addressing the following five areas.
Tracing
The GIS contains millions of pieces of data associated with a utilities service area. Engineering
analysis is typically needed for a feeder or substation. This data set is a very small fraction of the
GIS data set. However, finding a piece of the feeder and then following the connectivity rules of
the GIS to gather the complete feeder is complicated. Once the topology is found and
connectivity is traced, data necessary for engineering analysis must be found through the
normalization and referential integrity rules of the GIS.
Rules for topology, connectivity, normalization, and referential integrity are usually
implementation specific. These rules are often put into place in an effort concentrating on
mapping and facilities management. At the time of the rule implementation, engineering analysis
is often not a consideration. This leads to the navigation of what seems to be foreign and
convoluted rules when engineering analysis data extraction efforts are begun.
