Integrating power monitoring systems
After determining the power load profile of a commercial building, engineers need to ensure the system is monitored and integrated with the building's other engineered systems. Here a group of experts shed light on how to approach integrating power monitoring systems.
Meet our power monitoring roundtable participants
- Steven Shapiro, PE, mission critical practice lead, Morrison Hershfield Mission Critical, White Plains, N.Y.
- Douglas R. Strang Jr., PE, president, S & S Engineering, P.C., Batavia, N.Y.
- John Yoon, PE, LEED AP ID+C, senior electrical engineer, McGuire Engineers Inc., Chicago
- Bruce W. Young, PE, senior associate, electrical department manager, Bala Consulting Engineers, King of Prussia, Pa.
Q: When specifying power monitoring systems for your clients, how often do you recommend that they be integrated with a building’s other engineered systems?
Shapiro: The facilities we design are mostly mission critical/data center/telecommunication facilities. These sites are relatively large, with tens of thousands of monitoring points. We rarely, if ever, recommend that the electrical power monitoring system be integrated with a building’s other engineered systems. Data gathering speed, reliability, redundancy, and granularity are difficult to obtain with integrated systems.
Strang: While I believe in theory that every power monitoring system should be integrated with the building’s other engineered systems, in practice, we find this is seldom the case. In a competitive bidding environment with typical CSI classifications, you often find bidders assembling “packages” in a vacuum that achieve the lowest bid price. There should be collaboration between the electrical and mechanical disciplines to specify the power monitoring system and at a minimum bring the basic analog values for power, current, and voltage to the building or energy management system. A building management system (BMS)/energy management system that does not have real-time electrical load information is very limited in effectiveness.
Yoon: Depending on the project type, it can vary dramatically. For certain projects such as commercial interior build-outs in existing buildings, it is extremely unusual to even specify power monitoring unless the client is pursuing LEED EA credits for advanced energy metering. For other project types, such as data centers, the exact opposite is true where not specifying power monitoring is unusual.
Young: For our mission critical facilities, we always recommend that the power monitoring system be integrated into the BMS or building automations system (BAS). Additionally, we integrate with the critical facilities monitoring system. This can provide a snapshot of the overall power consumption, power quality, and demand levels. It can also help with integrating a demand response system if the owner chooses, as well as provide accurate power consumption levels for calculating power usage effectiveness.
Q: Provide an example of a success story in which a power monitoring system resolved a problem/challenge for your client. Provide specifics about the project.
Shapiro: In a recent project for a major financial client, we used the electrical power monitoring system (EPMS) during startup/commissioning of the facility to diagnose a failure of a medium-voltage circuit breaker during the closed transition procedure between the generator plant and the utility. The sequence of events and millisecond time stamping of the EPMS allowed us to trace back anomalies in the system operation forensically to the actual cause: failure of a medium-voltage circuit breaker to open the three phases of the breaker, causing single phasing of the closed transition of the plant and failure of a 2 MW generator in a multigenerator plant.
Strang: Our client was a college campus that was running out of capacity in one of its main substation transformers that distributed 4.16 kV to buildings across the campus. The existing transformer was overheating due to overloading, and was noticed only from the diligent maintenance staff’s annual oil testing. We designed a substation expansion with a new transformer and 5-kV switchgear that included a power monitoring system on the main switch and each outgoing feeder.
We often find that power monitoring is not included by many designers at the medium-voltage level, with the assumption that capacity is abundant at this level. This new powering monitoring system was networked back to a personal computer (PC) in the facilities office that would allow campus maintenance personnel to view loads in real time, as well as voltage, current, total harmonic distortion (THD), and power factor values. The new system allows the maintenance personnel to trend and alarm on any of these values and to better plan campus changes. Seeing the value of this system, the campus is now adding power monitors to the existing switchgear and connecting them to the same communication network.
Yoon: The biggest upside to power monitoring is the ability to understand a building’s load profile. In situations where our clients have had power quality/reliability issues, we’ve often recommended installation of standby generator power systems. While we are typically quite conservative with sizing equipment, having accurate trending of a building’s load profile over an extended period of time has allowed us to right-size generator equipment and reduce installation costs.
Young: On a local college campus, there was an increasing off-hours demand charge from the local utility that could not be explained. A power monitoring system, with time stamped demand readings, was installed on the loop to help determine the cause of the demand spike. There was a demand spike on early mornings, and the spike correlated to the approximate power consumption of a chiller that was programmed not to start for several hours, so the automation system was corrected to delay the chiller start time.
Q: Of the power monitoring systems you have encountered, what percentage has been integrated into a BAS, BMS, or other engineered systems?
Shapiro: We have seen integrated systems in smaller facilities. The functionality of these systems as electrical power monitoring systems with power quality monitoring capability is limited. Usually dedicated power quality applications are required to view and analyze the information from power quality meters directly.
Strang: We are finding that more power monitoring systems are being incorporated into BMSs. However, of those we encounter, I would be surprised if more than 25% were truly seamlessly integrated. In most cases, only a real-time kW value or maybe current and voltage are brought over as individual data points.
Yoon: For the most part, we’ve specified power monitoring as stand-alone systems. While the ideal building would have a fully integrated BMS capable of real time, system-level power monitoring and demand response, actual implementation is rare.
The challenge has been overcoming our clients’ skepticism regarding return on investment (ROI) versus perceived complexity and cost. While the Midwest historically had much lower electrical costs in comparison to the east and west coasts, there just hasn’t been enough motivation here to overcome these perceptions. For every motivated triple net lease, single tenant building, or owner occupied building, there are a multitude of buildings where energy cost just isn’t as much as a consideration. In multi-tenant buildings where base building electrical costs are simply passed through to the tenants as part of the annual operations costs, you’re incredibly dependent on having a proactive building management and operations staff to help convince a building’s ownership that making a capital investment in a power monitoring system makes sense.
Young: Almost all LEED buildings that have the measurement and verification credit, integrate the power monitoring system into the BAS/BMS. This provides the building management with a dashboard of the overall power consumption, but it also can provide the building occupants with information as to the potential energy savings being realized.
Q: What metrics can you provide to indicate quantifiable reasons for or against integrating power monitoring systems?
Shapiro: Data gathering speed and the granularity of the information in the event of an electrical failure is critical. Integrated systems are typically more of a basic type of system and lack the ability to achieve the sequence of events down to the synchronized millisecond, which is essential for failure analysis. Dedicated local area network (LAN) infrastructure as well as dedicated servers and dedicated human-machine-interfaces (HMIs) allow for the speed, clear graphics, data presentation, and analytical tools required to achieve the tasks required for the facilities we design and commission.
Strang: I have heard various percentages used over the years, such as a power monitoring system can save you 10% of your utility bill. Based on experience, I would say that savings should be easily achievable with a power monitoring system. The catch phrase is “you can’t reduce what you can’t measure.” I firmly believe many of the benefits of a power monitoring system are more intangible and harder to quantify. For example, trending of current or voltage waveforms with a high resolution power monitor (i.e., 256 samples/cycle or greater) can provide insight into transformer internal arcing, incipient ground faults, or harmonic overheating of neutrals. The value of predictive maintenance saving a large power outage could be very high depending on the criticality of the load.
Young: The cost of the power monitoring system integration into the BMS is often one of the deciding factors. Another metric is if integrating the systems significantly increases the complexity and maintainability of either system.
Q: How often are power monitoring systems integrated with demand response scenarios?
Shapiro: Facilities we design and commission typically are not part of demand response scenarios due to the critical nature of the facility.
Strang: We typically do not see power monitoring systems integrated with demand response scenarios unless they are dedicated systems for that purpose. I think there is a big future, though, for this application and we will see more of it. There are many demand response vendors with programs that can only benefit the end user by signing up to curtail load and be paid to do so.
Yoon: In most cases, we see power monitoring only being used by buildings to optimize their load profiles, to identify operational issues, and to control monthly electrical demand charges. Very infrequently will we see power monitoring integrated with a demand response program, even though it seems like it should be a logical extension. The primary hurdle to overcome is the perception of the risk associated with demand response. Most clients think of demand response as a singular program where they are going to be asked to curtail electrical usage when they need it the most. This serves to highlight a very clear gap in understanding of the available programs. It’s very uncommon to come across clients who can explain the basic differences between emergency demand response, economic demand response, and real-time pricing. If we could better explain that there are multiple different versions of demand response with various different potentials for risk and reward that can be tailored to meet the needs of the client, the acceptance of these programs would dramatically increase.
As it is, we depend on education and advocacy from groups like the Building Owners and Managers Association (BOMA) to spread the message among building owners and operators. We see relatively little from the utility company side to promote these programs. This is a shame given that there’s relatively minimal risk associated with many programs. For example, emergency curtailment calls by the regional transmission organizations for the Midwest are extremely rare. It’s basically leaving easy money on the table.
Young: Almost all power monitoring systems are integrated when the owner contracts for demand response. The building system monitors and records the demand reduction as well as the time frame for the reduction. This can provide a separate, independent record of not only the level of reduction, but the time of the reduction.
Q: How large does a power load profile of a commercial building need to be to justify a power monitoring system? To justify integrating the power monitoring system into a BAS or with other engineered systems?
Shapiro: A power monitoring system should be recommended for all commercial buildings regardless of the size. The nature of the system depends on the size and tenants of the building. Power usage at the service as well as throughout the major portions of the distribution facility allow for proper operation of the facility as well as a functional method of understanding the possible maintenance requirements and load growth possibilities without subjecting operating personnel to the risk of arc flash by actually opening electrical equipment to measure loads.
Strang: I don’t think a particular load profile would be the determining factor for justifying a power monitoring system, or for integrating it with an overall BMS. I suppose if you were looking at only ROI of the power monitoring system based on energy savings, you could prognosticate typical payback numbers. I think the criticality of the load would be the biggest factor in implementing the power monitoring system. A strip plaza could have a larger load than a small data center, but the small data center may serve critical 24×7 customers (i.e., a bank) where the data from a power monitoring system would provide much more value.
Yoon: It goes beyond the size of the load profile. To say that a building falls into a specific utility rate class doesn’t justify it by itself. Concepts of load profile variability and value of business continuity also factor into it.
Q: How have power monitoring systems helped ensure a building’s power quality is stable?
Shapiro: Power monitoring systems have given operating personnel a tool to diagnose internal as well as external power quality issues. Having power quality monitoring at the facility on a continuous basis allows for immediate identification of power quality issues before they can cause operational problems. As equipment is added to the distribution system or changes are made to the distribution system, the power quality is monitored and anomalies can be identified. The monitoring provides evidence of power quality before and after changes to help identify the causes of power quality issues, help remedy them, and ensure power quality stability.
Strang: Power electronics have come a long way. A 256 sample/cycle analog-to-digital converter is nothing today. Many of the power monitors today can easily achieve this resolution and much higher. This monitoring resolution allows capturing of sub-cycle events and THD that, years ago, required more expensive portable equipment. So, in addition to seeing general trends to ensure power stability, now we can easily see sub-cycle aberrations that can be indicative of equipment that hasn’t quite failed yet but may fail very soon. A power monitoring system can also be very valuable in analyzing what events are produced internally vs. from the utility. For example, a motor starting the same time every day could be easily identified and turned off to see the effect.
Yoon: We have seen situations where utility side power quality issues such as brownouts and single phasing have caused or contributed to equipment failures. However, we’ve typically seen power monitoring systems used simply to record such disturbances and not necessarily to automatically take equipment offline.
Q: When working with a building’s operations and maintenance (O&M) staff to set up training, systems manuals, etc., what guidelines do you provide for system testing and/or maintenance of the power monitoring system?
Shapiro: EPMS system testing and maintenance goes hand-in-hand with the electrical system testing and maintenance program. As the electrical systems are operated and tested, the EPMS is used to document the positions of circuit breakers, facility load changes, power quality impact of load shifts, etc. As long as the proper signals are received by the EPMS through the electrical equipment and LAN systems, the actual maintenance of the EPMS system and interfaces is limited to the meters and LAN infrastructure, which is minimal.
Strang: When implementing a power monitoring system, testing, commissioning, and training are definitely requirements. We have seen projects where a power monitoring system was installed as part of the original contract, with all of the capabilities intended to be brought back to a PC for remote monitoring and trending. However, the communication cables were never terminated. All the capability was there and the owner was completely unaware. Typically, we specify that the system be completely tested and commissioned by the installer in cooperation with the vendor, and after complete functionality is achieved, a vendor’s representative (of the equipment manufacturer) provides at least 8 hr of training to the O&M staff. Obviously, the actual duration should be adjusted based on the number of staff and complexity of the project, but the goal is for the staff to be comfortable with basic operations before this new system is dropped in their laps. The system will have no value if no one knows how to use it. Lastly, be careful to specify a system that will not hold the customer hostage for minor assistance and changes.
Yoon: One of the biggest gaps that we’ve experienced in the design process is how to define the look and feel of the HMI and the commissioning of the overall system. Every integrator does things just a bit differently.
Young: For system testing, the specifications are written requiring a 1% calibration between the power monitoring system and calibrated test equipment. A maintenance contract is usually required from respective vendors, as well as 8 hr on-site staff training on all systems.
Q: Describe a mission critical facility in which you specified a system to monitor complex standby, back-up, or emergency power.
Shapiro: The financial client I referred to previously was designed to have 32 MVA, 2N medium-voltage utility services, an N+2 standby-generator plant, more than 16 MVA of UPS power, and 100,000 sq ft of computer room. All of these systems require the EPMS to interface with power quality monitoring at the utility, generator plants, UPS systems, and at the computer room distribution. Synchronized millisecond time stamping is required for all the major distribution systems with live electrical one-line diagrams and live load information down to the branch circuit breaker serving the computer equipment in the rack on the computer floor. The system has a dedicated LAN infrastructure with redundant servers and looped communication systems to eliminate the risk associated with a loss of communication in a single communications path. All monitoring systems have dedicated power redundancy to isolate the system from the impact of an electrical distribution failure and ensure continuous monitoring. A dedicated monitoring station is located in the operating engineers’ office with summary system alarms cross connected to the BMS. The system can be accessed through connection at any internal facility network connection. The system is not accessible outside of the facility via modem or Internet connection to ensure system reliability and security.
Strang: Unfortunately, we have not had the opportunity to specify a dedicated power monitoring system for such a mission critical facility. The power monitoring capability was built into the UPS equipment, which was out of our scope of work.
Young: One of our projects was a rather large data center and office building complex with on-site power generation installed to back up the data center, and as an additional benefit, provide power to the complex. With the power monitoring system installed, the owner is able, based on the power consumption recorded prior to an outage, to continue to provide power to the office complex in addition to the data center.
Q: Looking 2 to 5 years into the future, how do you think power monitoring systems will change?
Shapiro: I believe the HMI will become easier to use and better interfaces will be developed for use with portable and mobile devices. Power quality resolution and event capture will be enhanced, more devices will have communications, and power quality metering ability will be standard. These improvements will reduce the cost of the EPMS overall, make the EPMS easier to install, and even enable them to be cost effective to retrofit into a facility.
Strang: Looking two to five years into the future, I can see power monitoring systems having roughly the same features as now, except more cost effective due to competition and proliferation. We may see them more integrated with other systems (i.e., EMS/BMS) as a standard. I think with energy conservation and verification, and the general green movement, power monitoring systems will become a standard in system design, rather than an amenity only afforded by higher end facilities. Capturing the power flow of renewable source integration in distributed generation applications will also drive the need for power monitoring systems.
Yoon: We’ve traditionally focused on customer-financed and installed power monitoring solutions. If it was low cost/no cost, it would end up on every project, but it isn’t. However, with utility-company smart-meter initiatives starting to materialize, many of our clients view that as an opportunity to defer/avoid the direct capital investment associated with power monitoring and participate in demand response program energy markets. It should be a win-win: the utility companies should be able to have more reliable power grids and building owners should be able to reduce operating costs.
The primary challenge is more of a legal than a technical issue. Who owns the smart meter energy usage information that is collected, how it can be used, and should it be made public? For example, in major municipalities, we’re starting to see the adoption of benchmarking ordinances with mandatory reporting of building energy usage through Energy Star. While there are not yet formal penalties, such as cash fines to penalize poor scores, these mandatory public disclosure requirements still concern many building owners. The standard metric of energy use intensity doesn’t necessarily reflect efficiency of the individual building systems, but rather overall energy usage for a given square footage of building area. Whether right or wrong, many new Class A buildings have been given a proverbial black eye through lower than expected Energy Star scores compared to what we would normally consider antiquated and obsolete buildings. This would seem to put agendas of energy efficiency and economic development at odds. Some have suggested that this gap can be bridged by linking a building’s energy usage to economic contributions of the businesses within that building. It should be interesting seeing how our engineered solutions evolve to fit into this new world.
Young: More Internet protocol-based systems will be installed to minimize initial installation costs and to not only allow integration into BMSs, but also allow occupants to see a dashboard of energy consumption for their building.