By Terri Humel
Change comes fast to the electric power industry–especially when that change improves processes and lowers costs. In recent years, many utilities have embraced 3-D computer aided drafting (CAD) technology to design electric substations. Being able to visualize substation assemblies and subassemblies in 3-D has made it easier to design and avoid potentially expensive clashes between parts.
As the 3-D revolution continues to take hold in the industry, Nashville Electric Service (NES) decided to embrace an even more game-changing approach to substation design: digital prototyping. At NES, design engineers create intelligent, digital models–or prototypes–of substations assembled from a library of 3-D parts. Vaughan Charles, engineering supervisor for NES' substation group, explained how digital models has enhanced the design process: "For us, 3-D visualization is just the beginning. We create designs that serve as digital models of actual substations, with parts, calculations and bills of materials (BOMs) coming together quickly and more automatically."
Disconnected Processes Slow Designers
Taking advantage of the efficient, hydroelectric power provided by the Tennessee Valley Authority, NES began delivering power to 52,000 customers in 1939. Today, NES serves more than 355,000 customers in a 700-square-mile service area. As NES has grown, its commitment to providing reliable power and value to customers hasn't changed. The publicly owned, nonprofit company continually strives to enhance operational efficiencies. In 2007, NES decided to address issues that hampered substation design productivity.
The substation engineering department at NES relied on AutoCAD software for many years. Whether for new substations or retrofits to existing facilities, the NES team used 3-D part designs–called blocks–to create substation assemblies. As designers encountered new parts, they drafted a 3-D block and added it to an ever-growing library of parts. The 3-D process allowed the designers to work quickly and easily visualize designs.
Inefficiencies in other aspects of the process slowed substation projects. Substation designers relied on manual processes and disconnected tools for many tasks. To generate BOMs, for example, they had two options. They could count individual parts and enter the results in a spreadsheet manually, or they could extract parts lists using a cumbersome, multistep process. Both options were equally time-consuming and required frequent double checking for accuracy.
"We liked designing with 3-D because it enhanced our ability to visualize assemblies and communicate design intent," said Denise Jackson-Holder, senior associate engineer with NES. "But we wanted to go beyond 3-D to work with designs that included more embedded intelligence. Looking at our overall design process, we saw a number of opportunities to accelerate tasks and improve productivity."
Choosing the Right Technology
Believing it had maximized the advantages of 3-D, the company decided to explore other alternatives for enhancing the substation design process. Working with an outside consultant, NES evaluated several technology options. In the end, the consultant made a recommendation that enabled NES to build on its existing AutoCAD expertise: Autodesk Inventor software. Autodesk Inventor software allows mechanical engineers to design, visualize and simulate 3-D digital models to determine how a design will work under real-world conditions before it is built, helping reduce cost and speed the design process.
"Autodesk Inventor stood out for a number of reasons," Charles said. "It allowed us to build the insights we've gained through the years into every design–automatically. On a more practical level, compatibilities with our CAD software would allow us to leverage the huge library of 3-D parts we developed, helping speed up implementation."
From 3-D to Intelligent Models
To implement the model-based substation design process, NES began by bringing its 3-D parts library into the new solution, enhancing the blocks with additional specification and material information supported by the model-based process. NES also redrew steel structural pieces used in substations to ensure a higher degree of precision. At the same time, NES embedded its engineering standards within the solution and integrated it with its procurement process.
After a brief trial and training period, NES launched the new substation design process. "Whether we're designing a new substation or retrofitting an existing one, the goal is to create an accurate, digital model of the substation as a whole," Jackson-Holder said. "Embedded standards and automated calculations facilitate parts selection. It's as though another experienced designer is helping guide the process and perform calculations as the design evolves."
"Working from a model enables unprecedented efficiencies," Charles said. "That's why it's our goal to have an accurate digital model of each of the more than 60 primary substations in our network. We'll be able to respond to operational needs faster and more proactively. So will the maintenance and construction crews we support. It adds up to more value and reliability for our customers."
While the new model-based process has increased the pace of many design tasks, designers are particularly pleased with improvements to BOM generation. The new software automatically tracks part types and material quantities during design. Using a single command, designers can export accurate BOMs directly to their spreadsheet-based purchasing workflow. When designs change, they simply repeat the process to generate an accurate parts list. Business rules within the application help prevent over- and under-ordering of materials.
"Compared to the prior process, we're able to generate BOMs as much as 80 percent faster," Jackson-Holder said. "It's also much easier to create accurate BOMs. Before, we wasted quite a bit of time on multiple rounds of quality checks to ensure the correct materials made it to job sites."
Insights Enable Better Decisions
NES expects to study the overall impact of changes to its substation design process in the future, but individual designers are already realizing significant productivity gains. "We recently compared the time-to-completion for a project from before our implementation with a recent, similar project," Jackson-Holder said. "The newer design was done in three weeks, and the earlier project took six weeks. No two projects are ever exactly alike, but the time savings reflects the productivity gains we're seeing."
Charles explained that the faster design process is also helping support better decisions. "Today, we have more time to explore what-if scenarios. This helps us see how choices might impact constructability or long-term maintenance," Charles said. "The model isn't just a drawing. It's like having a digital prototype of a substation on the desktop. A person can walk through a project with other engineers, or even the construction crew, to find options that contribute to better real-world performance."
About the author:
Terri Humel is the principal associate engineer in the Substation Design section at Nashville Electric Service. She is responsible for construction drawings for foundations, structures, facilities and equipment mountings for primary substations (69 kv and 161 kv). She has an associates' degree in mechanical engineering, is a longtime user of Autodesk software and has been using Autodesk Inventor for nearly two years.