AEP Finds Design Efficiencies and Savings

To improve the efficiency and quality of its substation design, American Electric Power (AEP) began using the 3-D modeling capabilities of Bentley's Micro-Station V8i for its standard substation designs in 2004. In addition, the utility developed custom software to automatically generate bills of material (BOM) from its 3-D standard designs. The BOM file seamlessly integrates with the utility's material requisition and ordering software.

By implementing 3-D modeling, AEP experienced a 20% to 40% reduction in the time required to design a substation. The time savings were brought about by creating a single 3-D model to produce multiple 2-D views and the automated BOM simultaneously. Generally, greater time savings are achieved when more changes have to be made to a design. The ability to make changes to a single 3-D model as opposed to each individual 2-D model significantly reduces the overall project schedule.

Improved Quality

Designs in 3-D are easier to visualize because they are more closely related to the actual substation they represent. Errors are reduced when the design is completed on a single 3-D model compared to having to create multiple 2-D views. When a change is made to a 3-D design, it is made once. A 2-D design change requires thoroughly reviewing and changing multiple drawings. These multiple drawing changes must match exactly and be consistent with related details found on other drawings, thus providing more opportunity for human error. With 3-D modeling tools, it is possible to automate design clearance checks with minimal effort; 3-D designs help with visualizing and identifying possible clearance and interference violations.

Another advantage is the ability to analyze and optimize station shielding design by using the rolling sphere method. This method maximizes protection of substation equipment from direct lightning strikes. The rolling sphere presents a surface of coverage representing the desired shielding angle for the substation. Thus, any equipment not below the surface is not adequately protected. By simulating this in 3-D, the engineer can make changes to the shielding design and use the 3-D model to provide a visual check. There also are shielding software packages available that simplify the analysis. Having the station in a 3-D model allows the file to be imported into these tools with minimal modification.

The 3-D design models also generate BOM more accurately and efficiently. This enhances the ability to check materials because the 3-D model can be easily visualized, eliminating the inherent problem of 2-D designs that require material detail interpretations across multiple drawings.

Increased Efficiency and Reduced Costs

Using 3-D modeling techniques and tools increase the speed at which a substation can be designed. Time is saved in creating only one model instead of separate, independent plan, elevation and section 2-D views. When the designer makes a change to the 3-D model, the plan, elevation and section views are updated automatically. These tools also allow easy exploration of alternatives because the designer can look at the impact of several possibilities and select an optimum design.

Since design and modification are performed on one model, as opposed to multiple independent drawings, design time and design errors are reduced. This allows more time during the design phase to focus on the quality and optimization of the substation design, which minimizes costly construction rework. Since BOM generated from 3-D models are more accurate, the utility realizes cost savings from fewer construction delays due to issues with materials.

Standardization

With 3-D design, AEP creates design libraries of standardized substation equipment arrangements and equipment assemblies. Multiple design teams can use the completed designs as the building blocks for overall substation design. This method eliminates design duplication and minimizes the time needed to check design details as material catalogs are linked to 3-D model assembly objects. These standard library models are placed once in a 3-D model, as opposed to once in each 2-D view. This avoids working with multiple, disjointed drawings, which inevitably lengthens the time of the design process and increases the risk for errors.

By implementing 3-D design, AEP was able to break down a substation into building blocks instead of a large collection of individual components. The size and makeup of the building blocks can be designed in a way that fits the needs of a designer or engineer, and, as a result, allows their time to be allocated in a much more efficient manner. Another benefit is realized when a change needs to be made to one of these building blocks. Making a change to the 3-D model results in the 2-D views being automatically updated, thus eliminating human error and, again, saving time.

Ancillary Benefits

In addition to increased efficiency, reduced cost and standardization, 3-D design has a variety of other advantages. It paves the way for the future in that it will fit the next generation of designers' aptitudes and expectations. Less-experienced technical staff and client representatives can more easily understand and visualize complex designs. The implementation of these tools becomes more necessary in the coming years as a large percentage of experienced design and engineering staff approaches retirement and is replaced by less-experienced colleagues.

This technology also allows for the simple creation of 3-D portable document format files (PDFs). The PDFs provide for an effective method of sharing designs to all concerned without the need for computer-aided design (CAD) software or expertise.

Challenges

The move to 3-D design posed some challenges AEP had to overcome. These challenges included computing limitations that caused sluggish operation of MicroStation and extra attendant time associated with converting existing standards from 2-D to 3-D. Hardware upgrades enabled MicroStation to operate more efficiently, curtailing the computing issues.

However, the conversion of standards from 2-D to 3-D and the adjustment for vendors, designers, engineers and management was solved with patience and perseverance. The veteran staff was open to training in an unfamiliar and more advanced program, which can result in a difficult acclimation period. Vendors were subject to similar constraints, as they were required to provide detailed cut sheets of parts. Sustained commitment and patience from all parties allowed AEP to overcome these challenges and successfully integrate the new software into standards.

Legacy Projects

While AEP now requires all greenfield, or new, projects to be designed in 3-D, the base drawings for its brownfield, or existing, projects are in 2-D. Most substations were designed many years ago with either 2-D hand-drafted drawings or 2-D CAD drawings. While brownfield projects may not have an existing 3-D model, the process for using 3-D design is essentially the same as for greenfield projects. The only difference is the model for brownfield projects only consists of the improvements designed in 3-D.

In many cases, the existing drawings for these stations are either nonexistent or not adequately accurate. One solution for capturing actual station details and filling in missing information is to compare any available 2-D drawings with measurements obtained on a site visit. Unfortunately, this method can become time-consuming, especially on larger stations or existing station assemblies that do not allow for a safe means to capture all required details.

In such cases, light detection and ranging (LiDAR) technology can capture existing substation details. LiDAR projects light beams on various points in the substation, measuring distances from a known point to calculate and map object point locations. This information is then used to create 3-D renderings of the substation, which can be used to create 3-D CAD models of the existing substation.

While AEP has not yet used LiDAR technology to generate 3-D models of its substations, it uses a field verification and measurement approach for select station projects and portions of the station where the interface details become critical to the design. Interfacing areas considered critical to the design include existing equipment connecting to new expansion equipment. In cases where station expansion and rehabilitation are extensive enough that very little existing hardware and equipment will remain, 3-D models are created using both verified 2-D drawing details and field measurements.

Greenfield Projects

AEP contractor Burns & McDonnell has used 3-D to design several substations. It was one of the first companies AEP worked with to use 3-D for greenfield substation designs. For these types of projects, AEP's 3-D standard yard assembly arrangement models were incorporated in the 3-D station design model with necessary modifications to meet each project's specific design requirements.

Most of the design effort was concentrated on the overall arrangement of the yard and details unique to a particular station's design. By employing AEP's standardized 3-D design library of station yard and equipment assemblies as well as equipment and design details, Burns & McDonnell also experienced reduced design time, which significantly reduced AEP's cost. Design quality improved with fewer design errors and the accuracy of materials ordered.

Future Potential

In the future, 3-D models can create opportunities that further enhance substation design, construction and maintenance. With a more realistic output, analysis improves because 3-D models are more detailed and complete than their 2-D counterparts. A 3-D model allows for the availability of more accurate information for an existing substation.

Web-based software or a mobile device app could allow zooming into the station model, selecting an existing component and immediately finding out details such as equipment specifications, service information, serial number and maintenance logs, which can be used for such tasks as ordering replacement parts and determining preventive maintenance. This information could be easily accessed anytime, anywhere, by authorized personnel. The vast possibilities make future work on existing substations more cost effective through means such as automation and more effective asset management and maintenance programs.

By implementing 3-D modeling into its substation standards, AEP has changed how its substations are designed and constructed in a way that promotes long-term cost savings, faster schedules and improved quality.

Ron Wellman ([email protected]) is the supervisor of station design standards at American Electric Power, which he joined in 1988. His responsibilities have included designing subtransmission/distribution lines and stations, and he is now overseeing the development of new standards as well as maintaining the current standards. He holds a BSEE degree from the West Virginia Institute of Technology, and he is a registered professional engineer in Ohio, Pennsylvania and Texas.

Hugo Bonjour ([email protected]) is project manager/associate electric engineer for American Electric Power. He is responsible for management and oversight of substation projects and business development on intercompany interface. He has more than 16 years of experience as a project manager for the industrial automation, facilities and transmission and distribution industries. He holds a BS degree in aerospace engineering from the University of Texas at Arlington.

Companies mentioned:

American Electric Power | www.aep.com

Bentley | www.bentley.com

Burns & McDonnell | www.burnsmcd.com

Brownfield Projects

The most frequent application of brownfield 3-D design modeling is in cases where available locations to add equipment in an existing station are limited. In these situations, there also is potential for clearance violations because of space constraints.

Marfa Alamito Creek Station

In its original configuration, the Marfa Alamito Creek Station was a 138/69-kV substation with a 69-kV dual-lattice steel box bay, one 138/69-kV autotransformer, four 69-kV lines, one 138-kV line and one control building. Burns & McDonnell expanded the substation to include a second 69-kV, dual-tube steel box bay; a second 138/69-kV autotransformer; and a 138-kV, six-position ring bus. Limited real estate available for the expansion created several design challenges.

Since most of the equipment would be replaced along with the existing control building, only a small portion of the substation drawing remained 2-D, which included the original 69-kV lattice structure and the remaining equipment that was reused. For the new equipment and expansion of the station, the design team employed several of American Electric Power's 3-D standard assemblies as a starting point, then customized and incorporated elements of the standard to create a new design that made it possible to fit all the equipment, structures and new control building in a tight space.

By designing the station expansion in 3-D, Burns & McDonnell tested several alternatives in a fraction of the time compared with traditional 2-D techniques.

Rotan Substation

In the case of the Rotan Substation upgrade, Burns & McDonnell discovered possible clearance issues because of space constraints with the installation of a 69-kV capacitive voltage transformer (CVT) and wave trap assembly between an existing structure and a fence. To mitigate this risk, a 3-D model was created of the new equipment (the CVT and wave trap assembly) and relevant adjacent equipment and hardware (the existing structure and fence).

With the 3-D model, several clearance violations were identified. The appropriate equipment parts were easily moved in the model to find the optimum design solution, meeting clearances. From the 3-D model, it was determined the only viable solution was to elevate the CVT and wave trap assembly close to the disconnect switches using 138-kV steel support and changing the switch spacing to meet clearance requirements.

Lakeside Substation

On the Lakeside Substation project, with 3-D CAD modeling software, Burns & McDonnell overcame several design challenges with the installation of a new transformer, a strain bus that required a take-off angle and hanging a CVT under one of the line terminals. Here, too, the ability to easily move equipment in the 3-D model allowed relatively easy resolution of potential issues.