Using BIM in electrical, power design
BIM can help facilitate efficiency gains in design, construction, and facility operations.
BIM technology for active building infrastructure is in the early stages of evolution for the AEC industry. While most large MEP firms have adopted BIM software and recognize BIM as an industry reality, the benefits currently realized are a fraction of BIM’s full potential as an efficient tool for design and engineering.
Context for the impact of BIM technology on electrical and power systems design is best established through a brief overview of legacy electrical power design that compares and contrasts the hand drafting and CAD environments with BIM delivery. The focus is how the migration to BIM technology platforms impacts, improves, and in some cases impedes design and engineering workflow.
Power and electrical system design in the legacy delivery models of hand drafting and CAD experienced limited gains in efficiency for the engineer as the migration from hand drafting to CAD did not create notable changes in electrical design processes or workflow. While there has always been debate around the gain—or lack of gain—of efficiency when comparing hand drafting and CAD, some argue that it is more efficient for engineers to do their own CAD rather than the redlining approach, while others maintain redlining for the CAD drafter is more cost effective. The efficiency gain statement made above is in the context of power systems and electrical design.
Initial capabilities of BIM
Creating panelboard schedules is a case-in-point for incremental efficiency gain in the move from hand drafting to CAD. For hand drafting, the schedules had to be filled out and calculated by hand. As CAD became more prevalent, firms and software companies started developing tools to incorporate a spreadsheet to perform the calculations. However, electrical loads had to be located by flipping through the various drawings, referencing equipment schedules, and manually annotating the various devices/equipment loads on the panel or distribution board schedule. The process was identical to hand drafting workflow with the exception of the summary calculations for the panel schedules.
Voltage drop and fault current calculations also improved moderately. When using software to perform the calculations, the information required by the particular program had to be gathered by review of the drawings, scaling of plans, and routing assumptions, then entering the information into a separate calculation program. Although the method of gathering the information was somewhat improved with CAD, the process was very similar.
Lighting is a similar example as most of the lighting design software packages required recreation of geometry external to the CAD drawings. The disparity of calculations; design process; and requirement to show information multiple ways, in multiple locations, and without any linking process created an error-prone environment. In addition, manual processes, such as counting light fixtures and receptacles for branch circuits, were time consuming and conducive to errors.
Essentially, the hand drafting to CAD transition simply changed the end product from hand drawn to computer-generated drawings. Both approaches relied on 2-D drawings that depicted the electrical systems and power infrastructure with a series of graphical symbols, numerous notes, and specifications that resulted in a limited illustration of the electrical installation. Regardless of the number of notes, details, and drawings, it was virtually impossible to articulate every aspect of the electrical installations or the power systems. Hence, there was significant room for contractor interpretation of the documents. In a competitive environment, the interpretation almost always gravitates to the cheapest solution to ensure the best chance of success for the bidding contractor.
Although the emergence of CAD created a notable increase in drafting speed, an argument can be made that CAD actually resulted in less accurate electrical designs due to the tremendous increase in the rate of change for design information. For hand drafting, the rate of change for the architectural and interior design was somewhat throttled by the media as background changes had to be modified by hand and then distributed to the rest of the design team. The migration to CAD enabled rapid change for the building, and the changes were often made without awareness of the implications to the time required for all of the disciplines to catch up and incorporate changes into their respective design documents. The rapid rate and domino effect of changes—particularly changes that occur just prior to major submissions—resulted in an environment that was sometimes more error prone than during the hand drafting era.
The inability to systematically link changes, track specific design revisions, capture cable lengths, and change something in one place limited the value of hand drafting and reduced the value of CAD as tools for the electrical design process. Information often had to be represented in multiple locations to clarify design intent and if, during an update, one location was missed, it created opportunities for conflict and cost impacts. CAD functionality such as x-refs enabled creation of overall plans per floor level with equipment layouts linked to partial or enlarged plans, which resulted in some improvement in accuracy of documents by allowing equipment drawn once to be linked to multiple views. Although coordination was simplified by performing x-ref overlays on the computer, as opposed to light table overlays one sheet at a time, lack of visibility into changes executed after the coordination overlay occurred frequently and compromised designs.
Also, in the past, there were limited consolidated platforms in which all of the pertinent project data, calculations, and design information could be housed. The platforms that were available focused primarily on storage, organization, distribution, and coordination of project documents. Historically, engineers and designers created their own repositories at their desk, on their computer, and/or on their company networks that were separate from the package issued externally for execution of the works.
The same has been true for the contractors and end user. Drawing sets, calculations, spreadsheets, three-ring binders, submittals, shop drawings, vendor installation drawings, start-up, and operation/maintenance manuals represent subsets of information required for proper design, engineering, installation, and operations over the building life cycle. Ultimately, the objective is to have one interactive data repository to ensure all pertinent building information is captured and can be easily accessed and fully used during the various phases of the building life cycle. A 3-D visual database in the form of a BIM model populated with intelligent objects can serve as the interactive repository.
As the BIM movement has progressed, there have been incremental improvements and benefits for power system and electrical design. Linked load information provides a significant benefit as updates in one location and the impact of the update permeate the entire documentation package. A specific example is when additional loads are incorporated into a design. The panel serving the load, the distribution serving the panel, the transformer, and all points up to the main distribution board are automatically updated to reflect the change. Imbedded clearance envelopes offer another advantage as equipment loaded in the BIM model with clear space defined can illustrate space requirements both visually and programmatically through clash detection (see Figure 1). If clearance spaces are violated by foreign infrastructure, the conflict is evident when reviewing the model and can also be identified as an unresolved conflict when clash detection is run on the model. The linking of loads and ability to have accurate counts of devices, fixtures, and equipment items is a clear advantage of BIM software that has improved design workflow. The ability to connect equipment together as a system, add conduits to define exact lengths, and imbed objects with cut-sheets and specifications are benefits of current BIM software. The more the software is used to automate repetitive time-consuming tasks, analyze multiple design iterations, and locate pertinent information, the more design efficiencies and return on investment (ROI) can be realized (see Figure 2).
One of the most significant challenges for full integration as a consistent delivery mechanism for MEP systems has been the lack of accurate, relevant, and standardized BIM content. In order to move forward with BIM implementation, most firms initiated content creation and developed their own content libraries. Our experience with content creation was both time-consuming and costly. In addition, for more complex products that may be subject to frequent manufacturer updates, versioning of the content and maintenance of the libraries becomes difficult. Autodesk Seek and other Internet-based repositories have attempted to fill the content void by creating and hosting models of manufacturers’ products in BIM format. The online libraries are accessed by the specifying community for BIM content downloads. For simple commodity products, this approach can be effective. The challenge is with highly configurable and customizable items that have multiple options and variations that must be identified to accurately reflect the object in the BIM model.
However, the majority of the usefulness of BIM content hosted online is limited to spatial coordination assuming accurate geometry. The challenge with lack of standardization for the parameters associated with the specific object creates difficulties when attempting to mine the BIM model for information pertinent to specific calculations or design analysis. For example, assume third-party software is used in emergency power analysis for generator sizing and the desire is to compare three manufacturers. If the content is dissimilar in terms of parameters, the mapping of information from the model to the analysis software becomes very problematic.
From a workflow standpoint, electrical content created to express each variation of the equipment as a unique BIM model creates significant work to address design modifications, whereas flexible and configurable content can increase efficiencies through simplification of the change process. To illustrate this point, assume Revit content for generators on a project is comprised of separate BIM families for each kW rating and the initial requirement for the design was a 1,000 kW generator; however, design changes resulted in a requirement for a 1,500 kW unit. The 1,000 kW unit was loaded into the project, connected to the electrical system, and physically connected with conduits. The design change in this scenario results in the need to delete the 1,000 kW model, load in the new 1,500 kW model, and revise all of the pertinent connections. If a configurable generator family that includes several kW generator ratings is in a single content family, the designer can simply revise the kW parameter to update the engine and associated connections.
The lack of an integrated single-line diagram tool is a limitation of the current BIM software. It is an environment where feeder length, conductor size, impedance, AIC ratings, available fault current, overcurrent device operating parameters, time current curves, physical locations, and similar parameters are captured in the model. However, the engineers’ ability to mine the model and use the information for analysis and calculations is impeded by lack of appropriate tools and limited contextual relevance for BIM content with regard to information required for engineering analysis. Again, lack of standardized BIM content creates another set of challenges as the quality of intelligent objects varies extensively from manufacturer to manufacturer and from engineering firm to engineering firm.
An additional challenge in incorporating BIM for power systems analysis is the complexity of the software for the BIM platform. The various BIM software programs are exceedingly complex and not well aligned with the way engineering work is developed and deployed as the overall facility design progresses. In CAD, engineers could either engage or not engage in CAD and still maintain control of the design process. With BIM, the specifications, layout, spatial coordination, and infrastructure routing are integral with model development as the engineering and design are much more closely coupled with the tool used to create the BIM model. The dilemma for engineers, and people trying to run a profitable ongoing business concern, is how much time, energy, and money can be reasonably invested in learning highly complex software. Proficiency in engineering expertise is a full-time undertaking. Less complex software and simple engineering tools would serve the industry better as they would allow more senior engineering engagement with the BIM workflow.
The future of BIM
Proliferation of BIM is a positive development for the AEC industry with the end goal of facilitating a more streamlined and efficient built environment. A picture is worth a thousand words and, according to studies conducted by NIST, BIM or the 3-D intelligent visual database environment is worth about $16B of savings on an annual basis due to improved coordination and reduction of interoperability issues. The challenge for industry will be creation of intuitive tools and resources that are complementary to engineering workflow and actually enhance an engineer’s ability to articulate his or her specific subject matter expertise. To be effective and widely adopted, BIM tools must be intuitive for the user and align with the way engineers engineer. Software that is written and formatted for software experts to understand and use does not serve the industry well. The tool becomes such a large focus of learning and mastery that it detracts from the engineering community’s ability to practice its disciplines.
However, there is tremendous potential for BIM to streamline power system design particularly as the commercial enterprises driving the technology refine the various software tools and resources to take full advantage of the model data for system analysis (see Figure 3). The current ROI is questionable specific to electrical design. However, the industry is only beginning to scratch the surface with respect to potential benefits the technology can yield. From a business standpoint, BIM for electrical systems can be performed without excessive cost challenges provided the level of development for the model is clearly communicated to the client and also limited to what is relevant in the context of the overall model and anticipated use of the design model for the construction phase.
The positive impact BIM has in terms of reduced costs paired with the potential for substantial increased life cycle efficiencies for facilities are compelling arguments to keep moving forward with adoption and refinement of the technology. As it continues to develop, BIM will help facilitate efficiency gains in design, construction, and facility operations, ultimately yielding a more efficient built environment which, as an industry, we have a responsibility to provide for our children and future generations.
Dwayne G. Miller is an electrical engineer PE and an RCDD with 23 years of engineering experience. He serves as CEO of jba consulting engineers and committed his firm to embracing and driving BIM technology in 2006. In addition, he serves as CEO of BIMAdvent, which is a software company focused on tools and resources to further industry adoption of BIM technology. JBA and BIMAdvent are separate companies that collaborate on development of BIM technologies that drive workflow efficiencies.
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