By Benjamin Ferguson, Vice President, Bluegrass GIS, Inc.

The city of Nashville is located along the Cumberland River in the Nashville basin of middle Tennessee. Surrounding Nashville are many rugged hills forested with the hardwood trees common in the southeast United States. Nashville, known as Music City USA, is the heart of the country music scene and is the home of the Grand Ole Opry, country music television and publishing, Gibson Guitars, and the Country Music Hall of Fame. While Nashville is famous for its country music, it is also a beautiful city of 1.2 million people that appeals to art lovers and history buffs. It boasts a full scale replica of the Greek Parthenon with a 43 foot tall statue of Athena. Civil War attractions and antebellum mansions abound, including the Hermitage, the home of Andrew Jackson, the seventh President of the United States.

Providing for Nashville's electrical needs is Nashville Electric Service (NES). NES is one of the 10 largest public electric utilities in the United States, serving more than 300,000 homes and businesses in middle Tennessee. The NES service area encompasses 700 square miles, which includes all of Davidson County and portions of six surrounding counties.

When Esri introduced the ArcGIS platform with its tight integration to ArcSDE, NES decided to move from its legacy system to this new platform. That meant migration of its ArcInfo 7 applications to ArcGIS applications and its ArcStorm database to an ArcSDE geodatabase. NES implementation requirements included maintaining (and improving) the link to its Outage Management System (OMS) and preserving the ease of use of its earlier Data Maintenance application, a customization of ArcInfo using ARC Macro Language (AML). Having worked closely with Bluegrass GIS, Inc. (Frankfort, Kentucky), an Esri Business Partner, during its initial GIS implementation, NES selected Bluegrass GIS to implement an enterprise-capable system based on ArcGIS.

Database Design

The data was migrated to ArcSDE, which provides a more robust editing environment and allows greater access within the utility. This was a good time for NES to modify its existing data model to take advantage of the new capabilities Esri offered with the geodatabase. The NES electric geodatabase data model was created by using the Unified Modeling Language (UML) in Visio and the wizards included in the ArcCatalog functionality of ArcGIS.

Important to the implementation was continued support for the OMS data model in use at NES. Close attention was paid to designing the GIS data model to streamline the migration of data from GIS to OMS. Since both of the systems rely on an Oracle relational database, Oracle SQL-stored procedures were created to facilitate the GIS to OMS table loading process, significantly reducing data loading times while improving data integrity.

New Maintenance Application

A new Data Maintenance application was created for NES using Microsoft's Visual Basic and Visual C++ in conjunction with Esri's ArcObjects and the ArcMap functionality of ArcGIS, giving users the tools they had come to expect in the old application.

Two primary application functions were to preserve the relationships between features for the OMS while editing and to implement an easy-to-use maintenance interface. Adding new data is frequently a multistep process. For example, adding a fuse for NES involves adding it, linking it to a pole feature, linking it to a node feature, linking it to a distribution line, rotating it, and finally editing the attribute values. That activity normally would require the user to use six different tools to add just one fuse. Tools were created to allow the user to work through the entire process with just one tool that "morphs" into the other tools as appropriate. Optional steps can be bypassed, and if the user doesn't complete the required steps, the whole process is rolled back, preventing the user from adding incomplete data.

NES put this system into production in March 2002. Since then, additional tools have been added to allow for global changes for circuit conversions from one voltage to another. Enhanced CAD and GPS tools have been added to aid in placing new data into the system. A point address tool has been enhanced to allow for repetitive placement of point addresses that increase automatically using a user-defined street number increment. The user specifies an increment value when the first address is placed. When each subsequent address is added, the street number is automatically calculated and assigned, with all other attributes being preserved.

With the core system in place, NES was able to implement ArcIMS to give staff immediate access to all of the GIS data. The ability to view current data for their electric network is a new capability in the enterprise. With the ease of use and availability on the NES Intranet, use quickly spread throughout the organization.

For more information, contact Arthur S. Bushing, Nashville Electric Service (e-mail: abushing@NESPOWER.com) or Benjamin Ferguson, Bluegrass GIS, Inc. (tel.: 502-722-1014, e-mail: aferguson@bluegrassgis.com, Web: www.bluegrassgis.com).