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.

03/12/2014


 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., ChicagoBruce W. Young, PE, senior associate, electrical department manager, Bala Consulting Engineers, King of Prussia, Pa.

Meet our power monitoring roundtable participants


Figure 1: Power metering doesn't have to be that complicated. This basic power meter with PQ analysis can be easily integrated into a main switchboard. All graphics courtesy: McGuire Engineers Inc.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.


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