PP 14 Spring

MORE POWER. MORE PRODUCTS. MORE REASONS TO CHOOSE GENERAC.

To learn more, call toll-free 855-493-3863 or visit Generac.com/industrial.

At Generac, power is our sole focus. That means more innovation, whether you’re considering, specifying or installing a power system. From single generator sets up to 2 MW, to paralleled solutions up to 100 MW. With revolutionary products like Gemini® power systems that have two generators stacked in a single enclosure for amazing space saving. And the only Bi-Fuel™ generators that are EPA-compliant from the factory. Plus we off er tools like Power Design Pro™—among the most powerful electrical and mechanical design and sizing software on the market—and the continuing education we provide to countless facility managers, contractors and engineers each year. It’s easy to see why virtually every industry puts its power needs and trust in the hands of Generac Industrial Power.

input #400 at www.csemag.com/information

❮❮1

www.csemag.com/purepower

PU

RE

PO

WE

R // S

PR

ING

20

144 Protecting standby

generators for mission critical facilities The generator and standby power systems for mission critical facilities require a higher level of reliability and availability.

PUBLICATION SERVICES

Jim LanghenryCo-Founder and Publisher, CFE [email protected]

Steve RourkeCo-Founder, CFE [email protected]

Trudy KellyExecutive [email protected]

Kristen Nimmo Marketing [email protected]

Elena Moeller-YoungerMarketing [email protected]

Paul Brouch Director of [email protected]

Rick EllisAudience Management [email protected]

Michael RotzPrint Production [email protected]

CONTENT SPECIALISTS/EDITORIALAMARA ROZGUSEditor in Chief/Content [email protected]

JACK SMITHManaging [email protected]

AMANDA MCLEMANProject [email protected]

MICHAEL SMITHCreative [email protected]

PUBLICATION SALESMidwestMatt Waddell 312-961-6840 Fax [email protected]

ALPatrick Lynch 630-571-4070 x2210 Fax [email protected]

West, TX, OKTom Corcoran215-275-6420 Fax [email protected]

U.S., CanadaBrian Gross630-571-4070 x2217Fax [email protected]

NortheastRichard A. Groth Jr. 774-277-7266 Fax [email protected]

InternationalStuart Smith SSM Global Media Ltd. +44 208 464 5577Fax +44 208 464 [email protected]

Poland/Russia/Czech RepublicMichael Majchrzak+48 22 852 44 15Fax +48 22 899 29 [email protected]

1111 W. 22nd Street, Suite 250, Oak Brook, IL 60523phone: 630-571-4070 fax: 630-214-4504

Pure Power is published quarterly by CFE Media and is mailed as a supplement with

Consulting-Specifying Engineer and Plant Engineering magazines. Copyright 2014 by CFE Media

LLC. All rights reserved. Editorial of� ces are located at 1111 W. 22nd Street, Suite 250,

Oak Brook, IL 60523. Phone 630-571-4070.

cover story

ON THE COVER:This 12-engine, 14 MW generator plant serves a mission critical data center. The generators operate at 4,160 V in an N+2 con� guration, which allows for a failure of one generator while another is out for maintenance. Courtesy: Jacobs-KlingStubbins

FEATURES

Selecting energy-ef� cient transformers

Engineers should know the

design concepts for selecting

and sizing transformers to

help achieve energy ef� ciency.

Integrating powermonitoring systems

After determining the power

load pro� le 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.

Mitigating harmonicsin electrical systems

Although devices using power

electronics can produce distortion

in electrical distribution systems,

it’s up to the engineer to

apply effective solutions to

mitigate them.

16 ❮❮

12 ❮❮

23 ❮❮

Engineering is personal. So is the way you use information. CFE Media delivers a world of knowledge to you. Personally.

To do your job better each day, you need a trusted source of information: CFE Media – Content For Engineers.

CFE Media is home to three of the most trusted names in the business:

provides the latest knowledge on commercial

and institutional facility construction and management. Visit www.csemag.com

delivers a wide array of strategies and solutions to

help control system designers create a more effi cient process. Visit www.controleng.com

delivers plant-fl oor knowledge and expertise to help

manufacturers operate smarter, safer and more effi ciently.Visit www.plantengineering.com

We drive data center efficiency.

Rack-to-row-to-room-to-building architecture lowers cost.Improving both efficiency and system uptime requires a second look at today’s data centers! Featuring innovative and industry-leading physical infrastructure components, Schneider Electric™ data centers uniquely span traditional IT “white space” and facilities to improve interoperability, deliver true data center agility, and achieve cost-saving energy and operational efficiency. Our integrated architecture also lowers total cost of ownership, enables fast and easy design and deployment, and promises the highest availability.

It comprises best-of-breed components available from a single source and through a global supply and services chain. From our well-known APC InRow™ cooling units…to our innovative EcoBreeze™ facility cooling module with two economizer modes…to our unparalleled data center management software StruxureWare™ for Data Centers, Schneider Electric products canbe found literally in every data center domain.

We offer the most energy-efficient components — all uniquely engineered as a system. In the long run, the Schneider Electric rack-to-row-to-room-to-building approach reduces total data center life cycle cost up to 13 percent and 30 percent of data center physical infrastructure cost over 10 years!In fact, it’s the foundation of our Business-wise, Future-driven™ data centers.

©2014 Schneider Electric. All Rights Reserved. Schneider Electric, APC, Square D, InRow, EcoBreeze, StruxureWare, and Business-wise, Future-driven are trademarks owned by Schneider Electric Industries SAS or its affiliated companies. All other trademarks are property of their respective owners. www.schneider-electric.com • 998-1158241_GMA-US_Note3

Our innovative data center physical infrastructure with full-visibility management lowers operating costs.

> EcoBreeze with Two Economizer Modes Only the scalable EcoBreeze automatically switches

between air-to-air heat exchange and indirect evaporative cooling to maximize conditions year-round.

> Data Center Facility Power Module Our modular, step-and-repeat approach to facility power

lets you expand capacity in 500 kW increments as needed, cutting OpEx by up to 35 percent and CapEx from 10 to 20 percent.

> StruxureWare for Data Centers With building-to-server visibility, StruxureWare

for Data Centers enables you to make informed decisions about your physical infrastructure.

> Reference Designs Our standardized architectures for various data center

con� gurations, from 200 kW to 20 MW, reduce time, cost, complexity, and system risk.

> Data Center Life Cycle Services Including energy management services, professional

services from planning, build/retro� t, and operations help ensure highest system availability and ef� ciency.

Facility Power Module EcoBreeze with Two Economizer Modes

StruxureWare for Data Centers Reference Designs

Business-wise, Future-driven.

TM

Get on the road to data center efficiency with our FREE white paper efficiency kit and enter to win a Samsung Galaxy Note™ 3.Visit: www.SEreply.com Key Code: g702u


How important are generators in a standby power system for a mission critical facility? When the lights go out and you � nd

yourself counting the seconds until they come back on, that generator is the most important piece of equipment in the facil-ity. During utility power outages, mission critical facilities rely on generators to keep the facility operating (see Figure 1). If the generator fails to start or if there is a fault in the standby power distribution system, that facility will eventually stop operating.

This is not an option for mission critical facilities. Whether for public safety, national security, or busi-

ness continuity reasons, mission criti-cal facilities must remain operational. The reliability of the generator and the standby power system is crucial to the continued operation of the facil-ity. Therefore, it is important for design engineers and facility owners/operators to know what it means for a facility to be considered mission critical, as well as the differences between mission critical and emergency/legally required standby

power systems. It is also important that they understand the requirements for the design, installation, operation, and maintenance of standby power systems for mission critical facilities.

Cover Story❯❯ 4


PU

RE

PO

WE

R /

/ SP

RIN

G 2

01

4

The generator and standby power systems for mission critical facilities require a higher level

of reliability and availability.

Protecting standby generators for mission critical facilities

By Kenneth Kutsmeda, PE, LEED AP, Jacobs-KlingStubbins, Philadelphia

Figure 1: Mission critical

facilities rely on generators

for the power required to keep

operating. All graphics courtesy:

Jacobs-KlingStubbins

LEARNING OBJECTIVES� Know the power requirements for a mission critical facility.

� Understand how to protect mission critical facilities from disaster or power failure.

� Know the codes and standards that govern standby power in mission critical facilities.

❮❮5


PU

RE

PO

WE

R // SPR

ING

20

14

Cover Story

WHAT IS MISSION CRITICAL?By definition, a mission critical facility is essential to the survival of a business or organization. Mission critical facility operations are significantly affected when the power system fails or is interrupted. Impor-tant aspects of a mission critical facility power system are availability, reliability, and security. Availability is important because the power system must func-tion when required—24 x 7. Reliability is important because the power system must not fail. If a failure occurs, the system must respond and recover quickly. Security is important because the power system must provide protection against an attack—either human or naturally caused.

Mission critical facilities can be divided into two categories: private and public safety. The private mission critical facility contains systems that must remain operational for business continuity reasons. The public safety facility contains systems that must remain operational to protect the safety of the public.

PRIVATE MISSION CRITICAL FACILITIESPrivate mission critical facilities include enterprise data centers, Internet companies, financial data cen-ters, and financial trading. In these types of facilities, the levels of availability and reliability are dictated by the business case. What level of risk can be tolerated? How much downtime for maintenance is acceptable? The answers to these questions will define the degree of redundancy and protection against failures that are built into the standby power system. Tier classifica-tions have been established to address these issues (see “Data center tier classifications” on page 8).

Tier 1 and Tier 2 facilities have higher risk toler-ance. They usually have certain windows of oppor-tunity for a shutdown to allow for maintenance and repair. These types of facilities typically have single distribution paths and do not require redundant com-ponents.

Tier 3 and Tier 4 facilities have a very low risk tol-erance and can’t allow for any downtime for perform-ing maintenance or repairs. These types of facilities require a high level of reliability and contain standby power systems with redundant (N+1, N+2, or 2N) gen-erators—more than required to carry the full load. The redundant generator allows for one of the generators to be taken offline for maintenance or due to a failure of one of the generators without affecting the opera-tion of the facility. Tier 3 and Tier 4 facilities usually contain UPS systems. During a power outage, the UPS provides ride-through power to the critical load until the generator starts and comes up to speed. Tier 3 and Tier 4 facilities also contain multiple paths for distrib-uting standby power to allow for maintenance of any

part of the system and to avoid any single points of failure that can shut down part or all of the facility.

Examples of typical generator and standby power distribution system configurations used in Tier 3 and Tier 4 data centers include:

N+1 generators and paralleling switchgear: In this design, the N+1 generators are paralleled onto a common bus (see Figure 2). Standby power is then distributed from that common bus to the load in multiple paths. This sys-tem con� guration is less complex than other systems and can be a cost-effective solution. However, it does create a potential single point of failure on the standby distribu-tion system. Often, the common bus is divided into two sections to prevent a fault on one section from taking down the entire standby power system. This system also allows load sharing without requiring the purchase of ad-ditional generators.

N+1 isolated redundant generators: In this design, there is a dedicated generator assigned to each power module (load block). The plus-one additional generator is isolated and can be used to back up any one of the primary generators (see Figure 3). This con� guration eliminates any common point of failure, but it does add a certain level of complexity to the standby power system.

2N dedicated redundant generators: In this design, there are two dedicated generators assigned to each power module (load block). Each one backs up its as-sociated generator and is capable of serving the entire power module load (see Figure 4). This con� guration eliminates any common point of failure and makes the standby power system less complex. However, it does have a higher cost.

Figure 2: This diagram shows an N+1 generator and paralleling switch-

gear con� guration.

Utility

Server load

Utility

Mechanical and house power


PUBLIC SAFETY MISSION CRITICAL FACILITIESPublic safety mission critical facilities include police and � re stations, emergency management centers, emergency call centers, hospitals, government facilities involved with national security, and � nancial facili-ties involved with national economic security. In these types of facilities, the levels of availability and reli-ability are required to protect the public safety, public health, and national security.

Unlike the private facilities where the attributes of the system are defined by the business itself, the at-tributes of public safety facilities are defined by codes. In 2008, the National Electrical Code (NEC) added Article 708: Critical Operations Power System (COPS) to address security issues for mission critical facili-ties. The article provides requirements for the installa-tion, operation, control, and maintenance of electrical equipment for designated critical operation areas that must remain operational during a natural- or human-caused disaster. The following requirements are included in NEC Article 708 to ensure the operation of the standby power system:

� Provide an alternate power supply.� Alternate power supply shall have on-site fuel capacity to operate for 72 hr.� The generator cannot depend on public utility gas for fuel.� Redundant equipment or, at minimum, the means to connect roll-up equipment is required. � Equipment must be located above the 100-yr flood plain.� Commissioning must be documented. � There must be a documented maintenance plan.

Unlike private facilities, these code requirements can’t be relaxed because they are vital to keeping standby power systems and facilities operational.

NEC GENERATOR CLASSIFICATIONSWhether it is a standby power system for emergency life safety, legally required, or mission critical, the goal is for the standby power system to provide power when there is a loss of utility power. However, each classi� ca-tion has different requirements.

Emergency systems (NEC Article 700): Emergency systems are those required and designated to be “emergency systems” by any governmental agency having jurisdiction. They are intended to automatical-ly supply illumination and power to designated areas and equipment essential to safety of human life. Emer-gency systems are generally installed in places where illumination is required for safe exiting and for panic control in large buildings. Emergency systems may also provide power to functions such as ventilation, fire detection and alarms, elevators, and fire pumps. Generators used to supply power for an emergency system are required to start automatically upon failure of the normal service and be available for load within 10 sec. A minimum of 2 hr of on-site fuel storage is also required.

Legally required standby systems (NEC Article 701): Legally required standby systems are those re-quired and designated to be “legally required” by any

Cover Story❯❯ 6P

UR

E P

OW

ER

//

SPR

ING

20

14

Figure 3: This diagram shows an N+1 isolated redundant generator

con� guration.

Figure 4: This diagram shows a 2N dedicated redundant generator con-

� guration.


2N generators

Server load

Server load

Utility

Utility Utility

Utility


E M E R S O N . C O N S I D E R I T S O L V E D.™

Emerson and ASCO are trademarks of Emerson Electric Co. or one of its affiliated companies. ©2013 Emerson Electric Co. CS104QR ASCO Power Technologies

Now you can see your critical powermanagement systems like never before.

www.EmersonNetworkPower.com/ASCO • (800) 800-ASCO • ascoapu.com

ASCO Power Switching & ControlsJust another reason why Emerson Network Power is a global leader inmaximizing availability, capacity and efficiency of critical infrastructure.

ASCO PowerQuest®. The vision to see what others can’t.PowerQuest delivers the answers you need about your Critical Power Management System (CPMS) — precisely when you need them. Finally, there’s one single gateway to reliably monitor all the critical power data points in your facilities.

• Communicate, monitor and control power transfer switches, generator paralleling switchgear, gensets, breakers, loadbanks, and more

• Review test schedules, event logs, power reports and trends

• Add and shed loads based on capacity and priority

• Analyze power quality issues with precise sequence of events recording

• Enjoy dynamic visualization over flexible, convenient and secure systems

ASCO’s PowerQuest. The singular solution to manage your critical power infrastructure.



UR

E P

OW

ER

//

SPR

ING

20

14

governmental agency having jurisdiction. They are intended to automatically supply select loads (other than emergency systems) in the event of failure of the normal source. Legally required standby systems are generally installed to serve loads such as heat-ing, refrigeration, ventilation, smoke removal, sewage disposal, and industrial processes that could create a hazard or hamper fire-fighting operations. Generators used to supply power for a legally required standby system are required to start automatically upon failure of the normal service and be available for load within 60 sec. Legally required standby also requires a mini-mum of 2 hr of on-site fuel storage.

The NEC requires that generators used for emer-gency and legally required systems shall not depend solely on a public source (gas line) for their fuel sup-

ply. However, the exception states, “where acceptable to the authority having jurisdiction, the use of other than on-site fuels shall be permitted where there is low probability of a simultaneous failure of both the off-site fuel delivery system and power from the out-side electrical utility company.”

Optional standby systems (NEC Article 702): Op-tional standby systems are those systems intended to supply select loads where life safety does not depend on the performance. Optional standby systems are generally installed to provide an alternate source of power for facilities such as industrial buildings, commercial buildings, and farms, and to serve loads such as heating and refrigeration systems that, when stopped during a power outage, could cause discom-fort or damage to the product or process. Generators

used to supply power for optional standby systems are not required to start auto-matically. However, they can be started manually. Optional standby systems have no time limitations and no on-site fuel storage requirements.

Emergency and legally required standby systems are generally designed to safely evacuate people and prevent hazards by keeping portions of the system operating for a period of time. Standby systems for a mission critical facility are designed to keep the entire facility operat-ing for the extent of the outage.

Table 1 provides additional differences between generators used for emergency/legally required systems and those used for mission critical facilities. Please note that these are observations and not requirements. Heath care facilities are special and can fall into both catego-ries depending on the type of care they provide. Generators used for heath care facilities do have additional requirements, which are stipulated in NEC Article 517.

STANDBY, PRIME VS. CONTINUOUSGenerator rating must also be considered when designing standby power systems for mission critical facilities. The International Organization for Standardization (ISO 8528-1 standard) generator ratings are:

Data center tier classi� cations

Both ANSI (ANSI TIA-942 Standard) and the Uptime Institute have established tierclassi� cations as guidelines for designing topologies that deliver data center availability and reliability. These resources further explain the differences between types of mission critical facilities. The following list explains the tier classi� cations:

TIER 1: BASIC� Susceptible to disruptions from planned and unplanned activity� Capacity design is need (N) with no redundant components� Infrastructure shutdown required for preventive maintenance and repair work.

TIER 2: REDUNDANT COMPONENTS� Less susceptible to disruptions from planned and unplanned activity� Capacity design is N with some redundant components� Single threaded distribution path� Infrastructure shutdown required for preventive maintenance and repair work.

TIER 3: CONCURRENT MAINTENANCE� Allows for planned infrastructure activity (maintenance, repair, expansion)

without disruption� Capacity design is N+1� Dual threaded distribution path� Errors in operation or failures can still cause a disruption.

TIER 4: FAULT TOLERANT� High reliability, availability, and serviceability� Allows for planned infrastructure activity (maintenance, repair, expansion)

without disruption� Capacity design is system + system (2N)� Dual threaded distribution path� System can sustain one unplanned failure with no impact to critical load.

Prime rating is the maximum power for which an engine-generator is capable of delivering continuously with a variable load for an unlimited number of hours.


❮❮9P

UR

E P

OW

ER

// SPRIN

G 2

01

4Cover Story

Emergency/standby: Emergency/standby rating is the maximum power for which an engine-generator is capable of delivering for up to 200 hr/yr. The al-lowable average power output over a 24-hr period is limited to 70% of the nameplate rating.

Prime: Prime rating is the maximum power for which an engine-generator is capable of delivering con-tinuously with a variable load for an unlimited number of hours. The allowable average power output over a 24-hr run period is limited to 70% of the prime rating.

Continuous: Continuous rating is the maximum power for which an engine-generator is capable of de-livering continuously for a constant load for an unlim-ited number of hours. Typically, continuous rating is used for exporting power to a utility.

An additional key difference between standby and prime is that the prime rating does allow for a 10% overload and the standby rating has no overload allow-ance. Because of power output and run time limita-tions, emergency/standby-rated generators are not gen-erally used for mission critical (Tier 3 and Tier 4) type applications. When sizing and specifying the genera-tors for mission critical facilities, engineers must evalu-ate the expected load pro� le of the facility, the number of redundant units operating, and the expectancy of the system to operate for longer than 24 hr.

Many generator manufacturers have recently de-veloped their own rating (mission critical standby or data center continuous), which basically falls between the ISO standby and prime ratings to correlate with the operation of data centers. Although the rating definitions vary among manufacturers, the result is an increased average power output and an increased limitation on the run hours. These ratings generally do not change the generator size or cost, but they may affect the system warranty.

EMISSION REQUIREMENTSThe U.S. Environmental Protection Agency (EPA) regu-lates emissions from diesel powered equipment based on engine horsepower rating. The generator ratings

range from Tier 1 to Tier 4 (different from the ANSI/TIA 942 Tier ratings). Since 2011, most nonemergency diesel generators have been required to comply with Tier 4 requirements, which include some type of af-tertreatment, such as selective catalytic reduction and particulate � lters.

The EPA does allow an exemption to the Tier 4 requirements if the diesel generators are used only for emergency applications such as during the loss of util-ity power. This exemption also allows the generator to be operated for up to 100 hr/yr for maintenance and exercise. The 100 hr/yr limit is an important number for mission critical facilities because those types of facilities tend to test and exercise the generators more often to ensure they will operate when called upon. In addition, if the engine generator is used to support the load when normal power is present (peak shaving, load curtailment, or storm avoidance), it is not exempt and must comply with the appropriate Tier requirements.

Figure 5: Generators for mission critical facilities are tested and com-

missioned before they are put into service. Part of that process is factory

acceptance testing, which includes load steps, transient response, and

heat runs.

Table 1: Typical differences between generator classi� cationsEmergency/legally required Mission critical

� Required to start within 10/60 sec � Required to start before UPS backup system expires

� On-site fuel storage = 2 to 8 hr � On-site fuel storage = 24 to 72 hr

� Redundancy not required � Redundancy required

� Shell enclosures � Walk-in enclosures

� Low voltage (208 V or 480 V) � Medium voltage (5 kV or 15 kV)

� Power distributed via ATS � Power distributed via breaker interlocks or multiple ATS

� Open transition transfer � Closed transition transfer



TESTING AND MAINTENANCEBecause facilities depend on generators and standby power systems to keep operating, all generator sys-tems should be fully tested and commissioned before they are put into service. For mission critical facili-ties, testing and commissioning involves a five-step process:

� Level 1—design review: Design plans are evaluated to confirm they meet the intended operation.� Level 2—factory acceptance testing: Key pieces of equipment are powered up and tested at the factory to ensure that they perform according to specified parameters.

� Level 3—installation inspec- tion and verification: Equip- ment is inspected and verified on site. � Level 4—component testing:

Individual components and systems are tested to verify operation. � Level 5—integrated systems testing: The complete system is tested with all components operating.

Some of the tests performed on generators during factory and component testing include load steps, transient response, and heat runs (see Figure 5).

Another important aspect of ensuring standby power system operation is implementing a preventive maintenance program. The National Electrical Test-ing Association recommends generator maintenance testing every 12 mo. Generator systems that require maintenance include lubrication, fuel, exhaust, cool-ing, and electrical/control systems. Additional standby power system maintenance recommendations include:

� Keep an inventory of spare parts� Properly train all operators� Exercise the generator regularly� Load test the generator� Analyze lube and fuel oil periodically� Arrange for annual or semiannual manufacturer

checks/service.

LESSONS LEARNEDDuring Hurricane Sandy, many mission critical facili-ties in the Northeast relied on their standby power sys-tems for multiple days to keep their facilities operating. Some of the lessons learned involve generator location, fuel supply, and, � lter changes.

Generator location: Locate generators and other standby power distribution equipment above the � ood

plain. In general, standby systems can’t keep the facil-ity operating if they are under water. Therefore, make sure the generators and any distribution equipment are located above the � ood plain to ensure they will operate when required. During Hurricane Sandy, some areas did see � ooding above the 100 yr � ood level, so consider locating the standby power equipment above the 500 or even the 1,000-yr � ood level.

Fuel supply: Maintain an adequate supply of on-site fuel storage. Although the water subsided in about a day, the debris and damage caused by the hurricane made it dif� cult to deliver fuel—even for those facilities that

had contracted emergency deliveries. On average, it was about three days before facilities could get fuel deliv-eries. A minimum of 72 hr of fuel storage is required by NEC Article 708 for critical operation of power supply systems.

Changing � lters: Provide means to change � lters while operating. In addition to the dif� culty of getting fuel delivered, the fuel that was delivered was often contaminated with water and debris. During the extended power outage caused by Hurricane Sandy, the demand

for fuel was very high. Fuel delivery companies were delivering everything they had, which meant sometimes getting fuel that was less than desirable (bottom of the tank). Many facility operators said that they were replac-ing � lters every couple of hours to keep the system from clogging. Recommend installing a dual-header fuel � lter system with a transfer valve that allows � lter replace-ment while the engine is running. In addition, consider adding a fuel polishing system to clean the fuel before it gets to the generator.

The goal of the generator and standby power system is to provide power when there is a loss of utility power. Mission critical facilities are required to remain opera-tional under all conditions. The generator and standby power systems for mission critical facilities require a higher level of reliability and availability.

ABOUT THE AUTHOR

Kenneth Kutsmeda is an engineering design principal at Jacobs-KlingStubbins in Philadelphia. For more than 18 years, he has been responsible for engineering, designing, and commissioning power distribution systems for mission critical facilities. His project experience includes data cen-ters, specialized research and development buildings, and large-scale technology facilities containing medium-voltage distribution.

The generator and standby power systems for mission critical facilities require a higher level of reliability

and availability.


UR

E P

OW

ER

//

SPR

ING

20

14

Most power control systems are designed for automatic operation only.

Russelectric systems come equipped with controls that provide for complete manual operation including synchronizing and paralleling of generators in the event that automatic controls malfunction.

Don’t settle for less than the best power control systems… Insist on Russelectric.

www.russelectric.com1-800-225-5250 An Employee-Owned CompanyAn Equal Opportunity Employer

Made in USA

The best power control systems provide for full manual operation


Transformers are perhaps among the most overlooked components within an electrical distribution system. However, they play a key role in our

everyday lives. Every house is fed by a single transformer. In our of� ces, a single trans-former may serve the computers for the entire � oor. In hospitals, the operating rooms and intensive care units are typically fed from two separate transformers.

If a transformer fails or is improperly sized, catastrophic outages, which are not quick and easy to � x, could occur. Also, transformers don’t shut off; they continue to use current and generate heat 24 hr a day, seven days a week.

TRANSFORMER SELECTIONTransformers are available in many different � avors. High- and medium-voltage transformers (primary volt-

age greater than 600 V) are available as dry type units, but are more commonly liquid � lled or liquid immersed. That liquid is commonly petroleum-based oil, but many companies are starting to offer similar products based on biodegradable seed oil. Commercial buildings operate on low-voltage (primary voltage less than 600 V) predominately, and typically use dry type transformers to step down the voltage from 480 V to 208 Y/120 V or 240/120 V.

This article focuses primarily on dry type transform-ers. However, many of the concepts presented apply to higher voltage transformers as well.

To select a dry type transformer, you need to answer three simple questions:

1. What is the purpose of the transformer?2. How do I want the transformer to perform?3. What options should I select?Generally, there are three purposes of a transformer:

Change the voltage, isolate power systems, and har-monic accommodation. Voltage can be decreased or increased. These transformers are available in either delta- or wye-connected primary or secondary, de-pending on the distribution voltage and system re-quirements. They may be single- or 3-phase, and are available in a variety of sizes (see Figure 1). Isolation transformers can be used in health care facilities to minimize the risk of stray currents in the electrical system, or even on a single load that has very sensitive electrical requirements.

How the transformer performs boils down to temper-ature and ef� ciency. Transformers are listed with a rate of temperature rise, typically 80 C, 115 C, or 150 C. This temperature rating is the rise above ambient (see Figure 2). The surface temperature of a transformer with an 80 C rise is signi� cantly less than one at a 150 C rise.

How engineers approach energy ef� ciency is evolv-ing. Every other year, the U.S. Dept. of Energy (DOE) revises many of the energy standards that regulate

Transformer Ef� ciency❯❯ 12


PU

RE

PO

WE

R /

/ SP

RIN

G 2

01

4

Engineers should know the design concepts for selecting and sizing transformers to help achieve energy ef� ciency.

Selecting energy-ef� cient transformers

By James Ferris, PE, and Aaron Johnson, TLC Engineering for Architecture, Orlando, Fla.

Figure 1: Transformers are available in a variety of sizes and distribution

voltages, and can be installed indoors or outdoors. All graphics courtesy:

TLC Engineering for Architecture

LEARNING OBJECTIVES� Understand the different types and uses of transformers.

� Know how to select and size transformers.

� Understand the concepts of transformer protection.

❮❮13


PU

RE

PO

WE

R // SPR

ING

20

14

Transformer Ef� ciency

our industry. Transformers manufactured today, and since 2007, are required to meet the criteria de� ned under NEMA TP-1 2002. In April 2013, a new rule was adopted that implements new transformer standards, effective Jan. 2016. NEMA TP-1 2002 introduced two signi� cant changes to energy ef� ciency considerations: Minimum ef� ciency was de� ned for each transformer size, and the point where that ef� ciency was measured changed from full load to 35% of transformer capac-ity. As a part of the origin of NEMA TP-1, research was performed to determine that most low-voltage distribu-tion transformers are, on average, only 35% loaded. Many manufacturers currently offer a NEMA premium ef� ciency transformer, which was created prior to the implementation of the April 2013 � nal rule (see Table 1). Please refer to the NEMA class I ef� ciency chart for further information on the past, present, and future rat-ings of transformers.

The decision of which transformer to provide be-comes a decision of which options to specify. Questions that engineers should ask include:

� Are the transformer windings aluminum or copper?� What kind of enclosure do you need for your

application?� Is it outdoors, or is a NEMA 1 enclosure acceptable?� What are the speci� c requirements of the manufac-

turer in terms of required space around the transformer?

Some manufacturers require a 3-in. clearance around transformers, while some require a 6-in. clearance. Un-fortunately, sometimes 3 in. can make a big difference in designing electrical rooms.

TRANSFORMER EFFICIENCYConsider a facility that has an older 225 kVA transformer that was installed around 1973. It has a 480 V primary and a 208/120 V secondary, and it meets the required clearances. When the issue of replacing the transformer arises, considerations include:

� The unit is 40 years old, but for this example, assume it has been fully checked for hot spots and is still in good operating condition.� The unit is speci� ed at 150-C rise, which means at full load, the surface temperature of the transformer can get quite hot.� The unit is more than 112.5 kVA, which per National Electrical Code (NEC), Article 450, requires the room to have a minimum � re rating of 1 hr.� The unit is less ef� cient than the currently available

Figure 2: This graph shows transformer rate of temperature rise above am-

bient, typically listed with 80 C, 115 C, or 150 C temperature rise ratings.

Table 1: NEMA Class I ef� ciency levelsDry type, 3-phase, low voltage

kVABase ef� ciency(TP-1-2002)

DOE Final Rule 10 CFR 431Effective Jan. 2016

NEMA premium ef� ciency(EL-3,CSL-3)

15 97.0% 97.89% 97.90%

30 97.5% 98.23% 98.25%

45 97.7% 98.40% 98.39%

75 98.0% 98.60% 98.60%

112.5 98.2% 98.74% 98.74%

150 98.3% 98.83% 98.81%

225 98.5% 98.94% 98.95%

300 98.6% 99.02% 99.02%

500 98.7% 99.14% 99.09%

750 98.8% 99.23% 99.16%

1,000 98.9% 99.28% 99.23%



transformer models, but the question is: Does the energy savings alone justify the replacement of this transformer?

Transformers have losses, and those loses are given off into the room in the form of heat. If you want to know what the transformer losses are, you can either obtain information from the manufacturer’s cut sheet or perform a series of no-load and loaded tests on the

actual transformer. For this example, a data sheet from a transformer from that era was used for com-parison. Table 2 compares a standard TP-1 efficient model and a transformer available from that era. Note that transformer losses reviewed between 1973 and 2003 appear to have similar efficiency and loss charac-teristics. It was not until the introduction of TP-1 that transformers were re-evaluated and efficiencies saw a big adjustment.

For the 225 kVA example, today’s unit is more ef� cient by 728 W. Keep in mind the different components associ-ated with this energy loss. The energy loss is given off into the room in the form of heat, and that heat is then cooled by the HVAC system, which itself has losses. The owner pays for the energy required from the transformer—plus the losses of the transformer. The owner also pays the util-ity company for the energy required to drive the fans, chill-ers, and pumps for the additional capacity. In effect, the owner pays for these losses twice. As part of this exercise, and working in conjunction with our HVAC brethren, we were able to expand this chart to compare how many more cfm are needed to keep the electrical room at 75 F based on 55 F supply air temperature (see Table 3).

The ef� ciency of replacing a 225 kVA transformer with a new 225 kVA unit can result in a reduction of approxi-mately 113 cfm in air conditioning. This isn’t a big differ-ence, won’t have a huge impact on the utility bills, and won’t pay for the new transformer in savings. So let’s add a new wrinkle to the case study. When the U.S. Environ-mental Protection Agency did the TP-1 study, it found that most transformers are only 35% loaded, and in most cases this is true. If we put a 30-day load reading on this trans-former, we can determine the existing load per the NEC, and have the � exibility of sizing the transformer at exist-ing load +25%. A 225 kVA transformer at 35% + 25% per NEC would result in a 98 kVA required transformer size.

❯❯ 14P

UR

E P

OW

ER

//

SPR

ING

20

14

Figure 3: This time-current curve of the example 112.5 kVA transformer

shows that the primary and secondary breakers, damage curve, and inrush

current are selectively coordinated.

Table 2: Transformer full load ef� ciency and losses1973 example 2013 example

Size (kVA) Ef� ciency Total loss (W) % Ef� ciency Total loss (W)

15 95.3% 740 96.8% 551

30 96% 1,250 97.2% 904

45 96.6% 1,620 97.9% 1,027

75 96.8% 2,570 97.7% 1,782

112.5 97.5% 1,400 97.9% 2,521

150 97.6% 1,830 98.3% 2,760

225 98% 4,775 98.3% 4,047

300 98.3% 5,400 98.9% 5,338

500 98.4% 8,300 98.9% 5,858Note: Comparison of energy losses at full load between current TP-1 2002 compliant transformers and transformer produced in 1973.Note: Table shows the full load ef� ciencies of one of today’s transformers, and not the ef� ciency at 35% as required by TP-1.



The next size transformer available is 112.5 kVA. Chang-ing our comparison from a 225 kVA existing to a 112.5 kVA new transformer means that we can reduce the air� ow required to cool the room by more than 300 cfm. Losses for the new transformer are 53% of the losses of the existing transformer. This is beginning to look like a viable option for the owner to consider.

TRANSFORMER PROTECTIONFor the remainder of this article, assume we selected a dry type transformer rated 112.5 kVA with a 480-V primary and a 208 Y/120 V secondary. Because the unit is installed indoors, it requires a NEMA 1 enclosure. We’ve selected aluminum windings because space is of no concern, and it’s more cost effective for our size of transformer.

Overcurrent protection shall be selected and sized on the primary and secondary in accordance with the NEC table 450.3(B), which indicates that the secondary must be sized no greater than 125% of the full load of the trans-former (312 FLA). We select a 400-A breaker because it is the next available size. The primary can be selected at up to 250% of the transformer rating (135 A), so we can select anything from a 175-A breaker to a 300-A breaker. We typically keep the primary at 125% as well because it helps simplify selective coordination, considering that these breakers can be set to overlap each other. For our example, we will select a 175-A primary breaker and a 300-A secondary breaker. When we de� ne the breaker settings and sizes, we need to review them against two distinct points: the transformer damage curve and trans-former inrush.

Transformer damage curve: The transformer damage curve is an ANSI standard curve that all transformers are measured against. It indicates the level of current over time the transformer can withstand and typically is

shown as a sloped line on time-current curves. We must ensure that the overcurrent protection will trip before this current is reached.

Transformer inrush: Every transformer has windings, which means it is inductive. Because transformers are in-ductive, they experience an inrush of current when power is applied. Because a transformer operates on magnetic principles, there can be differences in transformer start-ing current, depending on the phase angle of the voltage when the transformer is � rst energized. The starting cur-rent can vary from full load current to 20 times the trans-former’s full load rating, and can essentially appear as a fault. Manufacturers can provide the maximum inrush current for each of their units, and it should be considered when selecting the size of the primary overcurrent protec-tion. In our coordination study, the breaker will not trip from transformer inrush current (see Figure 3).

TRANSFORMER SELECTION, SIZING, AND PROTECTIONTransformers discussed in this article are dry type, but the theory remains the same for larger transform-ers of different types. However, some of the protection schemes are more advanced and different materials are used in transformer construction. Now that you are armed with additional information, it’s time to go out in the world and check those lonely transformers that are protecting so much.

ABOUT THE AUTHORS

James Ferris is an electrical project engineer with TLC Engi-neering for Architecture. He specializes in power distribution for health care facilities.Aaron Johnson is a mechanical project engineer and project manager at TLC, where his focus is on HVAC design.

❮❮15P

UR

E P

OW

ER

// SPRIN

G 2

01

4

Table 3: Transformer ef� ciency and HVAC impact1973 (full load) 2013 (full load)

Size(kVA)

Ef� ciencyTotal loss

(W)Heat loss (Btu/hr)

Air� ow(cfm)

% Ef� ciencyTotal loss

(W)Heat loss (Btu/hr)

Air� ow(cfm)

15 95.3% 740 2,526 115 96.8% 551 1,881 85

30 96% 1,250 4,266 194 97.2% 904 3,085 140

45 96.6% 1,620 5,529 251 97.9% 1,027 3,505 159

75 96.8% 2,570 8,771 399 97.7% 1,782 6,082 276

112.5 97.5% 1,400 4,778 217 97.9% 2,521 8,604 391

150 97.6% 1,830 6,246 284 98.3% 2,760 9,420 428

225 98% 4,775 16,297 741 98.3% 4,047 13,812 628

300 98.3% 5,400 18,430 838 98.9% 5,338 18,219 828

500 98.4% 8,300 28,328 1,288 98.9% 5,858 19,993 909

Power Monitoring Roundtable❯❯ 16

Q: When specifying power monitoring systems for your clients, how often do you recommend that they beintegrated with a building’s other engineered systems?

Steven 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 electri-cal power monitoring system be integrated with a building’s other engineered systems. Data gathering speed, reliability, redundancy, and granularity are dif� cult to obtain with integrated systems.

Douglas R. Strang Jr.: While I believe in theory that ev-ery power monitoring system should be integrated with the building’s other engineered systems, in practice, we � nd this is seldom the case. In a competitive bidding environment with typical CSI classi� cations, you often � nd bidders assembling “packages” in a vacuum that achieve the lowest bid price. There should be collabora-tion between the electrical and mechanical disciplines to specify the power monitoring system and at a mini-mum 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 electri-cal load information is very limited in effectiveness.

John Yoon: Depending on the project type, it can vary dramati-cally. 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.

Bruce W. Young: For our mis-sion critical facilities, we always recommend that the power monitoring system be integrated into the BMS or building automa-

tions system (BAS). Additionally, we integrate with the critical facilities monitoring system. This can provide a snapshot of the overall power consumption, power qual-ity, 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 calcu-lating 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 speci� cs about the project.

Shapiro: In a recent project for a major � nancial client, we used the electrical power monitoring system (EPMS) during startup/commissioning of the facility to diagnose


PU

RE

PO

WE

R /

/ SP

RIN

G 2

01

4

After determining the power load pro� le 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.

Integratingpower monitoring systems

By Jack Smith, Managing Editor; and Amara Rozgus, Editor in Chief

Figure 1: Power metering doesn’t have to be that compli-

cated. This is basic power meter with PQ analysis can be

easily integrated into a main switchboard. All graphics

courtesy: McGuire Engineers Inc.

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 run-ning out of capacity in one of its main substation trans-formers 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 � nd 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 of� ce that would allow campus maintenance personnel to view loads in real time, as well as voltage, current, total har-monic 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 communi-cation network.

Yoon: The biggest upside to power monitoring is the ability to understand a building’s load pro� le. In situ-ations where our clients have had power quality/reli-ability issues, we’ve often recommended installation of standby generator power systems. While we are typi-cally quite conservative with sizing equipment, having accurate trending of a building’s load pro� le 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 increas-ing 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 consump-

tion 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 fa-cilities. The functionality of these systems as electrical power monitoring systems with power quality monitor-ing capability is limited. Usually dedicated power qual-ity applications are required to view and analyze the information from power quality meters directly.

Strang: We are � nding 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) ver-

Power Monitoring Roundtable ❮❮17


PU

RE

PO

WE

R // SPR

ING

20

14

Meet our power monitoring roundtable participants

Steven Shapiro, PE,

mission critical practice lead,

Morrison Hersh� eld 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 man-

ager, Bala Consulting Engineers,

King of Prussia, Pa.

Power Monitoring Roundtable


sus perceived complexity and cost. While the Midwest historically had much lower electrical costs in compari-son 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 build-ing, 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 build-ing 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 mea-surement and veri� cation 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 quanti� able 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 milli-second, which is essential for failure analysis. Dedi-cated 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 � rmly believe many of the bene� ts 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 inte-gration into the BMS is often one of the deciding factors. Another metric is if integrating the systems signi� cantly 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

❯❯ 18P

UR

E P

OW

ER

//

SPR

ING

20

14

Figure 2: A double-ended switchboard with manual tie-breakers and power monitoring on both utility feeders allows last minute checks of the utility

status prior to transfer.

Honoring Engineering Leadership

Submit your firm’s data to be considered for the

Consulting-Specifying Engineer 2014 MEP Giants

program and be among the top mechanical, electrical,

plumbing, (MEP) and fire protection engineering firms in

the United States.

Your firm’s information will be included in our printed

and online MEP Giants poster, featured in the

Consulting-Specifying Engineer August 2014 issue.

The in-depth analysis of these firms reveals what’s

going on in the industry, and how it has changed over

the past few years. Special emphasis will be placed on

commissioning firms in a separate report each October.

Nominations for the 2014 MEP Giants are now open!

Go to www.csemag.com/giants to download

the official 2014 MEP Giants submission form.

Nomination Deadline:

To participate in the 2014 MEP Giants, submit your firm’s information by Friday, April 11, 2014.

SPONSORED BY:

PRESENTED BY:

Power Monitoring Roundtable❯❯ 20


PU

RE

PO

WE

R /

/ SP

RIN

G 2

01

4

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 bene� t the end user by signing up to curtail load and be paid to do so.

Yoon: In most cases, we see power monitoring only be-ing used by buildings to optimize their load pro� les, to identify operational issues, and to control monthly elec-trical 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 de-mand 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 poten-tials 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 Asso-ciation (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 as-sociated with many programs. For example, emergency curtailment calls by the regional transmission organiza-tions for the Midwest are extremely rare. It’s basically leaving easy money on the table.

Young: Almost all power monitoring systems are inte-grated 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 pro� le 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 recom-mended 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 distribu-tion facility allow for proper operation of the facility as well as a functional method of understanding the

possible maintenance re-quirements and load growth possibilities without subject-ing operating personnel to the risk of arc � ash by actually opening electrical equipment to measure loads.

Strang: I don’t think a particu-lar load pro� le 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 critical-ity 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 24x7 custom-ers (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 pro� le. To say that a building falls into a speci� c utility rate class doesn’t justify it by itself. Concepts of load pro� le 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 oper-ating 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 identi� cation of power quality issues before they can cause operational problems. As equip-ment is added to the distribution system or changes are

Figure 3: The photo shows branch circuit level power monitoring

integrated into the wiring gutter of a typical electrical panelboard.

Power Monitoring Roundtable

made to the distribution system, the power quality is monitored and anomalies can be identi� ed. The moni-toring provides evidence of power quality before and after changes to help identify the causes of power qual-ity 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 noth-ing today. Many of the power monitors today can easily achieve this resolution and much higher. This monitor-ing 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 eas-ily identi� ed 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. How-ever, we’ve typically seen power monitoring systems used simply to record such disturbances and not neces-sarily to automatically take equipment of� ine.

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 op-erated and tested, the EPMS is used to document the po-sitions 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 sys-tem, testing, commissioning, and training are de� nitely

requirements. We have seen projects where a power monitoring system was installed as part of the origi-nal contract, with all of the capabilities intended to be brought back to a PC for remote monitoring and trend-ing. 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 represen-tative (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 sys-tem 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 de� ne 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 speci� cations are written requiring a 1% calibration between the power monitor-ing system and calibrated test equipment. A mainte-nance contract is usually required from respective ven-dors, as well as 8 hr on-site staff training on all systems.

Q: Describe a mission critical facility in which you speci� ed a system to monitor complex standby, back-up, or emergency power.

Shapiro: The � nancial 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 equip-ment in the rack on the computer � oor. The system has a dedicated LAN infrastructure with redundant serv-ers and looped communication systems to eliminate

❮❮21


PU

RE

PO

WE

R // SPR

ING

20

14

“When implementing a power monitoring system, testing, commissioning, and training are de� nitely requirements.”-Douglas R. Strang Jr., S & S Engineering

Power Monitoring Roundtable❯❯ 22P

UR

E P

OW

ER

//

SPR

ING

20

14

the risk associated with a loss of communication in a single communications path. All monitoring sys-tems have dedicated power redundancy to isolate the system from the impact of an electrical distribution failure and ensure continuous monitoring. A dedi-cated 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 reli-ability and security.

Strang: Unfortunately, we have not had the opportunity to specify a dedicated power monitoring system for such a mission criti-cal 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 of� ce building complex with on-site power generation installed to back up the data cen-ter, and as an additional bene� t, provide power to the complex. With the power monitoring system installed, the owner is able, based on the power consumption re-corded prior to an outage, to continue to provide power to the of� ce 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 meter-ing 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 ef-fective to retrofit into a facility.

Strang: Looking two to � ve 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 veri� ca-tion, and the general green movement, power monitor-ing systems will become a standard in system design,

rather than an amenity only afforded by higher end facilities. Capturing the power � ow 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 associ-ated with power monitoring and participate in demand response program energy markets. It should be a win-win: the utility compa-nies 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 is-sue. 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 link-ing a building’s energy usage to economic contribu-tions 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.


“I believe the HMI will become easier to use and better interfaces will be developed for use with portable and mobile devices.”-Steven Shapiro, Morrison Hershfield Mission Critical

❮❮23


PU

RE

PO

WE

R // SPR

ING

20

14

Harmonic Mitigation

In North America, alternating current (ac) electrical power is generated and distributed in the form of a sinusoidal voltage waveform with a fundamental frequency of 60 cycles/sec, or 60 Hz. In the context

of electrical power distribution, harmonics are voltage and current waveforms superimposed on the funda-mental, with frequencies that are multiples of the fun-damental. These higher frequencies distort the intended ideal sinusoid into a periodic, but very different shaped waveform.

Many modern power electronic devices have har-monic correction integrated into the equipment, such as 12- and 18-pulse VFDs and active front-end VFDs. However, many nonlinear electronic loads, such as 6-pulse VFDs, are still in operation. These nonlinear

loads generate signi� cant magnitudes of � fth-order and seventh-order harmonics in the input current, resulting in a distorted current waveform (see Figure 1).

The characteristics of the harmonic currents pro-duced by a recti� er depend on the number of pulses, and are determined by the following equation:

h = kp ± 1

Where:

h is the harmonic number, an integral multiple of the fundamental

k is any positive integerp is the pulse number of the recti� er

Thus, the waveform of a typical 6-pulse VFD recti-� er includes harmonics of the 5th, 7th, 11th, 13th, etc., orders, with amplitude decreasing in inverse proportion to the order number, as a rule of thumb. In a 3-phase circuit, harmonics divisible by 3 are canceled in each phase. And because the conversion equipment’s cur-rent pulses are symmetrical in each half wave, the even order harmonics are canceled. While of concern, harmonic currents drawn by nonlinear loads result in true systemic problems when the voltage drop they

Although devices using power electronics can produce distortion in electrical distribution systems,

it’s up to the engineer to apply effective solutions to mitigate them.

Mitigating harmonicsin electrical systems

By Nicholas Rich, PE, LEED AP, Interface Engineering, Seattle

Figure 1: This diagram shows time-domain waveforms for the fundamental

frequency, 5th- and 7th-order harmonics, and resultant distorted compos-

ite waveform. All graphics courtesy: Interface Engineering

LEARNING OBJECTIVES� Understand current and voltage harmonics in electrical systems, and their negative effects on the facility electrical system.

� Know how electronic power equipment such as VFDs creates harmonics.

� Understand characteristic and noncharacteristic harmonics.

� Understand IEEE 519 guidelines for the reduction of electrical harmonics.

� Learn design techniques for mitigating harmonics with recommended applications.


cause over electrical sources and conductors results in harmonics in the voltage delivered to potentially all of the building electrical system loads—even those not related to the nonlinear loads. These resulting harmon-ics in the building voltage can have several detrimental effects on connected electrical equipment, such as con-ductors, transformers, motors, and other VFDs.

Conductors: Conductors can overheat and experience energy losses due to the skin effect, where higher fre-quency currents are forced to travel through a smaller cross-sectional area of the conductor, bunched toward the surface of the conductor.

Transformers: Transformers can experience increased eddy current and hysteresis losses due to higher frequen-cy currents circulating in the transformer core.

Motors: Motors can experience higher iron and eddy current losses. Mechanical oscillations induced by cur-

rent harmonics into the motor shaft can cause premature failure and increased audible noise during operation.

Other VFDs and electronic power supplies: Distor-tion to the increasing voltage waveform in other VFDs and electronic (switch mode) power supplies can cause failure of commutation circuits in dc drives and ac drives with silicon controlled recti� ers (SCRs).

ESTABLISHING MITIGATION CRITERIAThe critical question is: When do harmonics in electri-cal systems become a signi� cant enough problem that they must be mitigated? Operational problems from electrical harmonics tend to manifest themselves when two conditions are met:

1. Generally, facilities with the fraction of nonlinear loads to total electrical capacity that exceeds 15%.2. A � nite power source at the service or within the facility power distribution system with relatively high source impedance, resulting in greater volt-

age distortion resulting from the harmonic current � ow.

IEEE 519-1992, Recom-mended Practices and Requirements for Harmonic Control in Power Systems, was written in part by the IEEE Power Engineering Society to help de� ne the limits on what harmonics will appear in the voltage the utility supplies to its customers, and the limits on current harmonics that facility loads inject into the utility. Following this standard for power systems of 69 kV and below, the harmonic voltage distortion at the facility’s electrical service connection point, or point of common coupling (PCC), is limited to 5.0% to-tal harmonic distortion with each individual harmonic limited to 3%.

In this standard, the highest constraint is for facilities with the ratio of maximum short-circuit current (I

SC) to maximum demand load current (IL) of less than 20, with the following limits placed on

Harmonic Mitigation❯❯ 24P

UR

E P

OW

ER

//

SPR

ING

20

14

Figure 3: This diagram shows the connection and polarity arrangement of a typical delta-wye zig-zag type

transformer.

Figure 2: This diagram shows the connection and polarity arrangement of a typical delta-wye transformer.


the individual harmonic order: (Ref. Table 10.3, IEEE Std. 519)

� For odd harmonics below the 11th order: 4.0%� For odd harmonics of the 11th to the 17th order: 2.0% � For odd harmonics of the 17th to the 23rd order: 1.5% � For odd harmonics of the 23rd to the 35th order: 0.6%� For odd harmonics of higher order: 0.3%� For even harmonics, the limit is 25% of the next higher odd harmonic.� The total demand distortion (TDD) is 5.0%.

There are various harmonic mitigation methods available to address harmonics in the distribution sys-tem. They are all valid solutions depending on circum-stances, each with their own bene� ts and detriments. The primary solutions are harmonic mitigating trans-formers; active harmonic � lters; and line reactors, dc bus chokes, and passive � lters.

HARMONIC MITIGATING TRANSFORMERSIn a standard delta-wye transformer, zero-sequence currents flow through the secondary wye winding and are coupled into the primary delta winding where they are trapped (see Figure 2). These zero-sequence currents can cause excessive heating and voltage distortion. Harmonic mitigating transformers can be implemented in pairs to mitigate 5th, 7th, and higher-order harmonic currents by taking advantage of the transformer phase shifts relative to each other, to cancel a significant amount of the harmonic current at these higher frequencies.

One type of harmonic mitigating transformer uses a zig-zag configuration. The zig-zag transformer is configured by winding half of the secondary turns of one phase of the transformer on one leg of the 3-phase transformer, with the other half of the secondary turns on an adjacent phase (see Figure 3).

Note that harmonic mitigating transformers are not a panacea for the elimination of harmonics in an elec-trical system. Mitigation of 5th, 7th, and higher order harmonic currents requires the installation of mul-tiple transformers with a 30-deg relative phase shift between the two, connected to a common bus in an electrical distribution system. Also, when mitigating these higher level harmonic currents by this means, balance of loads between the transformers is required. As shown in Figure 4, one transformer is a delta-zigzag configuration harmonic mitigating transformer

with a 0-deg phase shift, and the second transformer is a delta-wye with a 30-deg phase shift.

Voltage distortion is normally greatest at the point where the equipment is connected to the distribution system. Therefore, to attain maximum benefit, har-monic mitigating transformers should be installed as close as practical to the load that they feed.

Installation of a non-phase-shift harmonic mitigat-ing transformer provides an effective treatment of tri-plen (3rd, 9th, 15th, and so on) harmonic currents that are generated by loads connected to the transformer. Triplen harmonic currents are treated in the secondary windings of the transformer due to the transformer’s low zero-sequence impedance.

When a standard or K-rated delta-wye transformer is installed in an electrical distribution system, the addition of a non-phase-shift harmonic mitigating transformer offers an economical solution for treating higher order harmonic currents. The 30-deg phase-shift created between the standard or K-rated delta-wye transformer and harmonic mitigating transformer provides treatment of 5th, 7th, 17th, and 19th order harmonic currents to the extent of the balance of the load between the two transformers. In this configura-tion, the harmonic currents are canceled in the com-mon electrical bus that feeds the transformers. Close

❮❮25P

UR

E P

OW

ER

// SPRIN

G 2

01

4Harmonic Mitigation

Source

LoadAHF

L

Isource

Ia

Iload

Figure 5: This diagram shows a conceptual arrangement of an active har-

monic � lter as a parallel device.

Figure 4: This diagram shows a parallel connection of a harmonic mitigating transformer and a typi-

cal delta-wye transformer.

HM transformer

Electrical bus

Standarddelta-wye transformer

Electrical panels feeding single-phase and/or 3-phase nonlinear loads

Harmonic Mitigation❯❯ 26


PU

RE

PO

WE

R /

/ SP

RIN

G 2

01

4

coordination between the construction and location of the two transformers must be executed, as the imped-ance values of the transformers should be identical to receive the maximum mitigation of these higher-order harmonic currents.

ACTIVE HARMONIC FILTER (AHF)The concept of an active � lter is to produce harmonic components of the fundamental current waveform that are out of phase with—and thus cancel the harmonic components generated from—the nonlinear loads. Figure 5 conceptually illustrates how the harmonic cur-rent generated by the AHF is injected into the system to cancel harmonics from a VFD load. The AHF is installed as a parallel device and is scalable, making it a highly effective device that cancels multiple order harmonics in the distribution system. This method addresses harmonics from a systemic point of view and can save significant cost/space in many applica-tions, with performance levels that can meet a TDD 5% target.

The active harmonic � lter uses a current transducer to actively monitor the load current in real time to react to changes in load. Some AHFs are designed to also inherently synchronize the line current with the voltage to approach unity displacement power factor. The system typically performs fast Fourier transforms to calculate the amount of harmonics present for each harmonic order in the load current to determine the

amplitude of the � rst 30 to 50 orders. The system logic processor � lters out the fundamental frequency, and then directs the power converter to inject the phase-inverse of only the harmonic currents back into the circuit for cancellation of the harmonic content.

The bene� ts of AHFs include:� Dynamic adjustment for virtual real-time correction of the nonlinear current� Synchronization of the current and voltage waveforms� Adjustment using a feedback loop to prevent leading power factor.

AHF equipment is available for implementation at the PCC of the facility to the utility, for connection to a distribution bus within 3-phase power distribution systems inside facilities, and within distribution and control equipment, such as motor control centers (see Figure 6).

SOLUTIONS AT THE NONLINEAR LOADAs an alternative to the systemic approach to harmonic mitigation, some components may be more economi-cally viable for facilities where the potential for injec-tion of excessive current harmonics is limited to a few speci� c loads.

A line reactor is the simplest solution for reducing harmonic current caused by nonlinear loads, typically converter-based devices such as VFDs. Inductors or isola-

Rules of thumbFor facilities with multiple, distributed nonlinear loads, system-based solutions are typically more effective.

System-based harmonic mitigation solutions

Bene� ts Disadvantages

Harmonic mitigating transformers � Low system losses� Mitigation of 5th, 7th, and higher order harmonic currents

� Higher order harmonic cancelation requires multiple transformers and the loads must balance

Active harmonic � lters � Mitigation of 5th, 7th, and higher order harmonic currents� Reduction to 5% or less� Power factor correction available

� Higher maintenance requirements� Losses can be higher than for passive � lters

For facilities with few, discrete, or concentrated non-linear loads, an at-the-load solution will likely be more cost effective for harmonic mitigation needs.

Bene� ts Disadvantages

Line reactors, dc bus chokes, and passive � lters

� Relatively low cost with low residual harmonics� Reliable, relative to active � lters

� Requires series-connected � lter� Requires use with nonlinear loads only� Induces low, leading-power-factor at light loads� Increases system losses� Primarily designed to cancel one harmonic order; some for cancellation of higher orders� Harmonic reduction 15% to 25%

12 Burt Drive, Deer Park, NY 11729 USA(631) 586-5125 // (800) 851-1508

www.mcgsurge.com

The new MCG 500 Series are industrial grade, high-performance surge protectors for multiple AC applications including smart home, dedicated equipment, branch/local panel protection and outdoor applications up to 240VAC, 1ph.

At the heart of the unit is a fresh new design of MCG’s signature protection module which packs five high current, thermally protected protection components for a total surge capacity of 100,000 Amps. Parallel and series connected units can be ordered with or without the compact NEMA 4X indoor/outdoor enclosure with clear front door.

Finding a comprehensive protector at an attractive price point can be a daunting task. Call us. Five minutes on the phone can solve your surge protection problems.

MCG SURGE PROTECTION

A REAL SURGE PROTECTOR.

Proudly Made in the USA since 1967

THE CLEAR CHOICE IN SURGE PROTECTION

input #405 at www.csemag.com/informationwww.csemag.com/purepower

Figure 7: This diagram shows conceptual schematics of a tuned harmonic � lter and a broadband � lter.

VFD

VFD

VFD

MCB

Starter

Starter

Starter

SPD

AHF

Figure 6: This diagram shows a typical implementation of an active harmonic � lter in a motor control

center.

tion transformers, installed in series with and ahead of the load, can reduce the harmonic current content up to 50%, depending on the amount of imped-ance added to the line, to approach TDD levels of 30% to 40%. The most com-mon values of ac line reactors are 3% and 5%. Typically, line reactors are less expensive than transformers.

In lieu of inserting line reactors in series with a VFD, a dc choke can be added to the drive’s dc bus, reducing approximately the same degree of har-monics as the ac reactor. The advantage of applying dc chokes is that they are typically physically smaller and are often mounted inside the VFD. Many VFDs can be ordered from the manufacturer with dc chokes already installed.

PASSIVE FILTERSPassive � lters are comprised of static, linear components such as inductors, capacitors, and resistors arranged in predetermined fashion to either atten-uate the � ow of harmonic currents through them or to shunt the harmonic component into the � lter circuit. There are several types of passive � lters, but the most effective type is the low-pass broadband � lter, which offers

Harmonic Mitigation❯❯ 28P

UR

E P

OW

ER

//

SPR

ING

20

14

great performance and versatility with lower risk of resonance with the line.

Figure 7 shows a typical tuned harmonic filter and a broadband filter circuit. In the tuned filter, the inductor (Lp) and capacitor (C) provide a low impedance path for a single (tuned) frequency. An induc-tor on the line side (Ls) is required to detune the filter from the electrical system and other filters’ resonance points. This type of filter is very application specific. It can mitigate only a single frequency, and it injects leading reactive current (kVAR) at all times. But it is economical if you need to deal with only a dominant harmonic in the facility. It normally can reach a TDD target of 20%.

BROADBAND FILTERSA broadband � lter is designed to mitigate multiple or-ders of harmonic frequencies. Notice the similarity and the difference of the circuit from the tuned � lter. Both inductors (L) could have impedances greater than 8%, which means there could be a 16% voltage drop across the � lter. Its physical dimension is normally very large, and it generates signi� cantly high heat losses, typi-

cally greater than 4%. A well-designed broadband � lter can meet a TDD tar-get of around 10%.

LOW-PASS FILTERSLow-pass harmonic filters have gained popularity due to their abil-ity to attenuate multiple harmonic frequencies to achieve low levels of residual harmonic distortion. The typical low-pass filter configuration

includes one or more series elements plus a set of tuned shunt elements. The series elements increase the input circuit’s effective impedance to reduce over-all harmonics and detune the shunt circuit resonance. The shunt elements are tuned to attenuate most of the remaining circuit’s harmonics, primarily the 5th and 7th order harmonics. This type of filter is most commonly applied in series with and ahead of 6-pulse rectifier loads. Note that the harmonic distortion is reduced at the input stage of this filter. However, the load side will have significant current and voltage dis-tortion, and thus it is recommended that only nonlin-ear loads be connected. Further, due to the series reac-tance, low-pass filters produce a voltage drop under loaded conditions, while voltage boosting will occur under no-load conditions, so some low pass harmonic filters may not be suitable for use with SCRs.

Engineers have many options available for miti-gating harmonic current distortion. There is also the option of taking no action. However, this runs the risk of reduced equipment life, failure of sensitive micro-processor-controlled equipment, downtime, safety risks, and potentially even utility penalties. The best economical and technical solution is not the same for all cases, and a thorough cost/benefit consideration of the application is necessary to evaluate and select the optimized solution to a facility’s harmonics problems.

Whichever method is selected for a specific applica-tion, as a general rule, the greatest benefit is realized when harmonic mitigation solutions are placed close to the loads generating excessive harmonic currents (see “Rules of thumb”). With this topology, the electri-cal system can be more effectively used for real work, and the probability of creating resonance and harmon-ic related is significantly reduced.

ABOUT THE AUTHOR

Nicholas Rich is principal and senior electrical engineer at Interface Engineering. He has more than 25 years of experi-ence in designing electrical power distribution, lighting, and communications systems.

AD INDEX

ASCO Power Technologies - pg 7 402800-800-2726 www.ascoapu.com

Caterpillar - Northeast - pg C-3 406 www.NECatDealers.com/power

CFE Media, Engineering Is Personal - pg 2 630-571-4070 www.csemag.com

Generac Industrial Power - pg C-2 400800-436-3722 www.Generac.com/industrial

Kohler - pg C-4 407800-544-2444 www.KOHLERPOWER.COM/INDUSTRIAL

MCG Surge Protection - pg 27 405 800-851-1508 www.mcgsurge.com

MEP GIANTS 2014 Sponsored by Eaton - pg 19 630-571-4070 www.csemag.com/giants

Russelectric Inc. - pg 11 403 800-225-5250 www.russelectric.com

Schneider Electric - pg 3 401 847-397-2600 www.schneider-electric.com

A broadband � lter is designed to

mitigate multiple orders of harmonic

frequencies.

© 2013 Caterpillar All rights reserved. CAT, CATERPILLAR, their respective logos, “Caterpillar Yellow,” the “Power Edge” trade dress as well as corporate and product identity used herein, are trademarks of Caterpillar and may not be used without permission. www.cat.com www.caterpillar.com

Whether you’re powering a sporting event, or supporting recovery efforts following a hurricane, your Cat® dealer has the equipment to help you solve the challenge. As part of the Caterpillar® dealer network, your local Cat dealer has access to a vast rental fleet of power generation and temperature control equipment specifically designed to meet the requirements of commercial, industrial, institutional and manufacturing applications, capable of supporting even the most critical operating systems.

Whether you’re dealing with an emergency, or planning ahead for scheduled downtime, Cat Standby Power equipment can be on its way in minutes. Visit us online today at www.NECatDealers.com/power

Alban CATwww.albancat.comBaltimore, MD800-492-6994

SiNCE 1927

Giles & Ransome Inc. www.ransome.comBensalem, PA877-RANSOME

SiNCE 1916SiNCE 1948

Cleveland Brothers www.clevelandbrothers.comMurrysville, PA888-232-5948

Milton CATwww.miltoncat.comMilford, MA866-385-8538

SiNCE 1960

H.O. Penn Machinerywww.hopenn.comPoughkeepsie, NY845-437-4051

SiNCE 1923

ONE NAME YOU CAN COUNT ON

PLANNED EVENT

UNPLANNED EVENT


TOTAL SYSTEM INTEGRATIONgenerators | transfer switches | switchgear | controls

this is a Kohler® power system. and it’s built to perform. how do

we know? we engineered it ourselves. generators, transfer switches,

switchgear, controllers – you name it, we make it. every part is designed

to work with the entire system.

so when the grid goes down, you’ll be glad you spec’d Kohler.

spec your job at KOhLERPOwER.cOM/INduSTRIAL Power Systemsinput #407 at www.csemag.com/information

Documents

PP 14 Spring