18096508 Power Quality for Healthcare Facilities[1]

PQ TechWatchA product of the EPRI Power Quality Knowledge program

Power Quality for

Healthcare FacilitiesDecember 2007Philip Keebler, EPRI

CONTENTSIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . .1 The Healthcare Environment . . . . . . . . . . . .1 Power Quality in Healthcare Facilities . . . . .3 Recognizing Power Quality Problems . . . . . .4 Symptoms and Their Causes . . . . . . . . . . . .4 Sources of Electrical Disturbances . . . . . . .8 Improving Power Quality in the Healthcare Environment . . . . . . . . . . . . . . . .13 Meeting the Power Quality Challenges of the Healthcare Industry . . . . . . . . . . . . .13 Establishing Partnerships . . . . . . . . . . . . . .13 Creating a Power Quality Checklist for Procuring Equipment . . . . . . . . . . . . . . . . .14 Using Power-Conditioning Devices to Improve Equipment Compatibility . . . . . . .16 Understanding Facility Voltage Requirements, Grounding, and Dedicated Circuits . . . . . . . . . . . . . . . . . . .17 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . .24

EXECUTIVE SUMMARY

The healthcare environment is made up of perhaps the most unusual combination of electronic loads found in any facility. Healthcare facilities not only rely upon commercial loads (such as computers, servers, and lighting system) and industrial loads (such as food preparation equipment, laundry equipment, medical gas systems, but also rely on electronic medical loads (that is, medical equipment) to operate the facility and provide patient care services. As in other facilities, when an electrical disturbance such as a voltage sag, voltage transient, or voltage swell reaches the service entrance of the healthcare facility or medical location, computers in the accounting department may shut down, and motor starters and contactors providing power to the air-conditioning and ventilation system may change the environment within the facility. Unlike other places, however, a patients life could be threatened when an aortic balloon pump trips off-line during a cardiovascular surgery. The costs associated with downtime can be staggering, but no bounded cost can be placed on the irreversible result of loosing a patient. Building, electrical, and healthcare codes in the United States require that hospitals and other medical clinics have emergency power ready to activate upon the detection of a power quality problem and assume the load within 10 seconds of the detection. However, even though a generator may be used at a healthcare facility or medical location, it cannot be on-line to support critical medical equipment with an activated transfer switch in less than about 2 to 3 seconds at best. This duration of time might as well be forever in terms of the ability of electronic medical equipment to continue operating. In fact, an undervoltage as short as of a cycle (about 4 milliseconds) is often sufficient to confuse sensitive electronic devices. This PQ TechWatch will introduce the typical problems found in healthcare facilities, enlighten the reader on some new issues, and provide practical guidelines for avoiding those problems.

About the EPRI Power Quality Knowledge ProgramThe EPRI Power Quality Knowledge program provides a wealth of resources in well-designed, readable, and accessible formats. Paramount among these resources are documents covering a wide range of PQ topics, written not only for use by busy PQ professionals, but also to be shared with important end-use customers and internal utility managers. The programs website, www.mypq.net, is the most comprehensive electronic PQ resource available, providing 24-7 access to proven expertise via the PQ Hotline, hundreds of PQ case studies, over 200 PQ technical documents, PQ standards references, indexes, conference presentations, and a wealth of other resources. For more information, please visit www.mypq.net.

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Power Quality for Healthcare Facilities

Healthcare providers have little time to be concerned with the quality of power or to find a reliable source of power to operate their equipment.

INTRODUCTION

problem to cripple the emergency medical staff. A second CT machine may not be an option, and the nearest machine may be many miles away in another hospital. This mission-critical imaging system could be taken off-line by a minor voltage sag to 80% of nominal (i.e., a 20% sag), lasting for only three 60-hertz cycles (50 milliseconds). The U.S. power quality community has estimated that $10 billion is lost yearly when automated control systems in industrial plants are upset by voltage sag events. Such numbers have not been estimated specifically for healthcare facilities or providers, but one can assume that the cost of downtime will also include possibly placing one or more patients at risk.

Although the electricity provided to a healthcare facility or medical location is an absolute necessity for healthcare providers to operate their facilities, it is usually not given a lot of thought. The widespread growth of new and lingering illnesses and diseases, the call for increasingly critical emergency services, and the pressure to reduce healthcare costs force healthcare providers to keep their minds on their businesscaring for their patients, enlisting the best possible healthcare professionals, and purchasing and installing the best medical equipment that money can buy. Turning on a heart-lung bypass machine prior to a six-hour openheart surgery where the operating room lights are always on has become as routine as activating a medical gas supply of oxygen for a patient and then adjusting the flow rate so the patient receives the desired amount of oxygen. Healthcare providers have little time to be concerned with the quality of power or to find a reliable source of power to operate their equipment. They need quality power 24 hours per day, 365 days per year. Moreover, the time spent on power quality concerns is becoming shorter and shorter as bottom-line pressures continue to be applied. In most situations, instead of focusing on the power quality, they have learned ways to work around malfunctioning and failed medical equipment. When one bloodpressure monitor is broken (possibly from a voltage surge), a nurse or medical technician goes and finds another monitor. But, in smaller healthcare facilities where equipment may be limited, providers may find themselves with fewer pieces of redundant medical equipment and without resources including power to operate the facility. To healthcare providers, the malfunction or failure of one key piece of medical equipmenta computed tomography (CT) scanner in an emergency room, for examplewould be enough of a

The Healthcare EnvironmentThe healthcare environment in the United States is in continual transition in efforts to improve patient care. Aside from the practice of medicine, nursing, and other medical-related fields, two areas key to the success of these transitions are (1) improvements in the design, construction, and maintenance of healthcare facilities, and (2) the identification, selection, installation, and maintenance of medical equipment. Lessons learned in the area of power quality for healthcare demonstrate that efforts made beforehand to incorporate power quality into these two areas usually prevent significant interruptions in patient care services and escalations in the costs of medical equipment downtime. The healthcare environment encompasses everything associated with patient care and the healthcare facility from the time the patient enters the facility to the time the patient leaves the facility. This environment includes healthcare functions that occur outside and inside the facility. Healthcare facility designers, planners, architects, and engineers and facility operating engineers and maintenance support personnel should

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Healthcare staff can contribute to improving patient care and the environment through increasing their level of awareness in recognizing equipment malfunctions that may be caused by power quality problems.

focus upon those parts of the environment that contribute to shaping the quality of power and depend upon the quality of the power in providing patient care. Healthcare staff, including medical professionals, can also contribute to improving patient care and the environment through increasing their level of awareness in recognizing equipment malfunctions that may be caused by power quality problems. New electrotechnologies are continually introduced into this complex environment (see figure on right), placing new challenges upon the healthcare and facility staff, the quality of power delivered to the facility and to the equipment, and the electricity demand. These electrotechnologies may also consume additional floor space and weight load and place new burdens upon the facility infrastructureelectrical and mechanical systems. These new technologies include medical, functional, and facility equipment. Examples of new medical electrotechnologies include diagnostic imaging systems capable of resolving more patient detail, computer-based wireless clinical information systems, and advanced patient diagnostic and therapeutic equipment. Additionally, much of the medical equipment is mobile, requiring reliable, well-regulated electricity on tap throughout a facility. Examples of new functional technologies include microprocessorbased food preparation equipment and laundry equipment that use adjustable speed drives. Examples of facility equipment include energy management systems, electronic controls for facility HVAC systems and equipment, and medical gas systems.

Complex Electronic Medical Equipment Used in Patient Care Areas

New technologies, such as electronic machines in the intensive care unit (top) and those used for laparoscopic imaging (bottom), are continually being introduced into the healthcare environment.

Today, the public and the government are making unprecedented demands upon the healthcare industry to provide high-quality, cost-effective patient care. Corporate restructuring and mergers are just two examples of how the healthcare industry is meeting a financial challenge that leaves little room for equipment malfunction. To ensure that the safe operation of medical equipment does not become a casualty of this new corporate mentality, the U.S. Congress passed the Safe Medical Device Act in 1990 (Public Law 101-69), which

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For equipment with low immunity, electrical disturbances are a primary cause of damage and malfunctions.

establishes a partnership in safety between the healthcare industry and manufacturers of medical equipment in the United States. This act is required to track all implantable medical devices and life-supporting or lifesustaining devices listed in the actsuch as pacemakers, pulse generators, and automatic defibrillatorsthat were distributed outside healthcare facilities after August 29, 1993. The electrical environment in U.S. healthcare facilities is regulated by the National Electrical Code (NEC). The purpose of this code is to provide minimum standards to safeguard life or limb, health, property, and public welfare by regulating and controlling the design, construction, installation, quality of materials, location, operation, and maintenance or use of electrical systems and equipment. This code regulates the design, construction, installation, alteration, repairs, relocation, replacement, addition to, use, or maintenance of electrical systems and equipment.

Power Quality in Healthcare FacilitiesAlthough inadequate and faulty wiring and grounding systems and equipment interactions can exacerbate power quality problems in healthcare facilities, electrical disturbances can damage low immunity equipment or cause malfunction. In facilities where wiring and grounding systems are error free and equipment immunity is known, electrical disturbances are less likely to cause power quality problems. Additional causes of power quality problems include the generation of disturbances from the normal operation of medical, functional, and facility equipment. For example, a contactor that controls power to part of the heating system in a facility can generate voltage transients that could impact the operation and reliability of electronic medical equipment powered by the same panel that powers the heating system. In this situation, using a contactor that contains a snubber to limit the voltage transients and powering the heating system from a separate feeder circuit than the one powering the medical equipment will help resolve the problem. Before the introduction of electronic medical equipment, common electrical disturbances were inconsequential to healthcare operations. Today, however, common electrical disturbances may cause high-tech medical equipment to malfunction, which is a problem given the intimate connection between this equipment and the patients that hospitals serve (see figure at left). Much of this equipment incorporates sensitive electronic power supplies and microprocessors (see figure on top of following page)possibly resulting in extended patient discomfort, misdiagnoses, increased equipment downtime and service costs, and even life-threatening situations. Moreover, equipment damage and malfunctions can jeopardize patient safety and increase the cost of healthcare.

Microprocessor-Based Electronic Medical Equipment

The healthcare environment is a unique one because of the intimate proximity of people to equipment.

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Medical equipment used in the United

Circuit Boards from a Medical Imaging System

States, such as diagnostic imaging systems, that present dynamic loads to the facility electrical systems can cause power quality problems internal to the facility. The figure at lower left is an example of a nonlinear current waveform captured by a power quality monitor connected to the input of a CT scanner during imaging system operation. From the figure, one can see that the current is very nonlinear and is characteristic of a high inrush current when the system is placed into the scan mode. If the healthcare facility contains wiring and ground errors with its earthing system, then dynamic loads such as those characteristic of diagnostic imaging system operation cause PQ disturbances that may impact other electronic devices in the hospital or even interfere with the operation of the dynamic load itself.

Integrated circuits, sensitive to electrical and electromagnetic disturbances, are used in electronic medical equipment.

Although patient safety is the number one reason for reducing the potential for equipment malfunctions, healthcare administrators must also consider the bottom line. Electrical disturbances can result in repeated diagnostic tests, wasted medical supplies, and expensive service and repair calls. These unexpected events are not covered by any healthcare insurance provider. The increasing use of healthcare insurance and the increased coverage limitations therefore compel healthcare facilities to minimize all equipment malfunctions.

RECOGNIZING POWER QUALITY PROBLEMS

Symptoms and Their CausesDisturbances can enter healthcare equipment through any electrical portthe AC power input, telecommunications, or networkcommon in the facilitys electrical environment. Most disturbances will enter the AC power port and present themselves to equipments power distribution unit or power supply. Because most medical equipment in a healthcare facility is networked to other equipment, variations in the facility grounding system provide paths for disturbances to enter the equipments telecommunications and network ports. The effects of electrical disturbances upon healthcare equipment can be noticeable or unnoticeable. Disturbances entering AC power input, telecommunications, or network ports may not cause immediate damage to electrical and electronic components or cause equipment to fail suddenly. Depending upon the type of

Non-linear (Harmonic-Rich) Load Current from a CT System

Current (50 amps/division)

Time (10 milliseconds/division)

This medical imaging system creates dynamic power quality problems in healthcare facilities with wiring and grounding errors.

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The most common equipment malfunctions are caused by the inputs and outputs of microprocessors erroneously switching on and off because of voltage sags, swells, transients, andmomentary power interruptions.

disturbanceundervoltage or overvoltage, its duration, and the immunity of the equipment to that disturbancegradual or fast occurring damage to electrical and electronic components may result. A disturbance such as a voltage surge entering the AC power input of medical equipment may not be sufficiently mitigated by internal overvoltage and overcurrent protection devices and may propagate through the power supply to other sensitive electronic subsystems and components. Voltage sags may cause post-sag inrush currents, which may cause permanent damage to overcurrent protection devices. A series of disturbances occurring over the period of a few hours or a few months, for example, may chip away at internal protection devices and electronic components, although damage to equipment may be virtually unnoticeable. Intermittent equipment malfunctions may be noticeable until eventual failure occurs. However, the most common equipment malfunctions are caused by the inputs and outputs of microprocessors switching between an on and off state resulting from voltage sags, voltage swells, voltage transients, and momentary power interruptions. For example, a voltage sag may cause the DC voltage (produced by the power supply) to the microprocessor of a blood-pressure monitor to decrease or suddenly change such that one or more of the microprocessor inputs or outputs drop from an on state to an off state. Or, a voltage transient incident upon the power supply may cause a change from an off state to an on state. In either case, data may be lost or scrambled, or the microprocessor may lock up or otherwise misoperate. Additionally, such changes in logical states can alter stored data, such as the control parameters of a defibrillator, ventilator, or an imaging system. Healthcare staffs have also reported power quality problems that are obviously not related to the malfunction of a microprocessor, such as 60-hertz artifacts on the signal recordings of biomedical equipment. The following are the most common symptoms of medical equipment

malfunction, including malfunctions not related to microprocessors.Distortion of Displayed Medical Information

Medical information displayed on cathode ray tubes (CRTs), liquid crystal displays (LCDs), printouts, and film may be distorted by disturbed DC voltages powering the display, a microprocessor malfunction, or faulty data from memory. For example, a waveform from an electrocardiogram printout may be disfigured, film from an X-ray may have a hot spot (a white area without any detail), or a video display on a physiological monitor may be distorted. Faulty data from memory or a microprocessor may also degrade the quality or resolution of an image captured by an imaging system such as a CT scanner (see figure below). Caregivers who encounter distorted information often report that they had to repeat tests or were unable to make timely, critical decisions because of the distortion.

Distorted Computed Tomography Image and Digital Readout

Variations in DC voltages can cause problems with the images and digital readouts from CT scanners.

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Electrical disturbances can cause microprocessor -based medical equipment to malfunction.

Incorrect Diagnostic Results

unacceptable levels of 60-hertz current), and miswired or damaged equipment that forces supply current through ground conductors. Electromagnetic fields from certain electrical distribution equipment, medical equipment, and facility equipment can also produce stray magnetic fields that can cause these artifacts. Artifacts in medical data may also be caused by current flowing in conductors that are not contained in conduits.

Electrical disturbances can alter the control parameters stored in electronic medical equipment and used to diagnose a patients condition. For example, the status of a CT system may be misreported via the digital readout as illustrated in the figure on the previous page. Moreover, biomedical equipment such as blood-pressure monitors may display diagnostic data, such as a digital readout or level indicator, that disagrees with the patients prevailing condition. Incorrect diagnostic results may also be caused by 60-hertz noise coupled to the patient or to the leads of diagnostic equipment such as electrocardiographs (EKGs) (see figure below) and electroencephalographs (EEGs). Such noise is commonly associated with stray currents caused by faulty grounds (i.e., miswired ground conductors carrying

Equipment Lockup

Electrical disturbances can cause microprocessor-based equipment to lock up and fail to capture data used by caregivers to make critical medical decisions. Infusion equipment used to administer a patient treatment may fail to regulate or count the proper dosage. The lockup of a medical imaging system wastes the valuable time of patients, imaging technicians, and medical staff and may extend patient discomfort when imaging scans must be repeated. Moreover, lockups of life-support equipment such as defibrillators pose lifethreatening risks to patients. Rebooting of medical equipment may take as long as two hours and in some cases cannot be accomplished if equipment software becomes damaged from electrical and electromagnetic disturbances.

Incorrect Diagnostic Results

Procedure Interruptions

Electrical disturbances may lock up microprocessor-based medical equipment, resulting in interrupted medical procedures. The consequences of these interruptions range from minor inconveniences to patient jeopardy. For example, if the video system fails during a routine laparoscopic surgery, the surgeon may have to incise the patientAn artifact-infested electrocardiograph (top) appears to match a textbook example of arrhythmia (bottom) (reproduced from Capuano, 1993). The waveform on the top had a rate of 300 beats per minute or 5 hertz and was accepted and diagnosed as arrhythmia, or atrial flutter (but actually was not).

to complete the operation, an unplanned procedure that significantly increases the patient risk, recovery time, and the cost of patient care.

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An electrical disturbance can damage an electronic component or circuit board in medical equipment causing a loss of data stored in memory or even destroying the memory altogether.

Loss of Stored Data

Control or Alarm Malfunctions

An electrical disturbance can damage an electronic component or circuit board in medical equipment causing a loss of data stored in memory or rendering the memory inaccessible. Such losses can occur in data stored in the memories of biomedical equipment and imaging systems, as well as billing and patient records stored in computer memory. If previously stored data suddenly becomes unavailable as a result of a disturbance incident upon an electronic data storage system, then patient tests may need to be repeated, delaying patient treatment. Power supply, mainframe, memory, interface, and other types of circuit boards may suffer damage from disturbances. Permanent damage to a power supply circuit board, like that shown in the figure below, may initiate the loss of stored data on a circuit board downstream of the power supply board.

The possible results of microprocessor malfunction include the loss of equipment control (see figure below) or the false sounding of an alarm. For example, the keypad on an infusion pump may not respond to finger touches of medical staff, the pump may not remain in the desired programmed state, or the equipment may sound an alarm contrary to the condition of the equipment or patient. Moreover, if an unstable patient condition develops and an equipment alarm does not sound, then the patient may be placed in a life-threatening situation. Some medical devices such as infusion pumps have a built-in battery backup that provides for internal backup power in the event of a sag or momentary interruption. The use of a backup battery system in a medical device does not protect the device from malfunctions caused by voltage transients and other disturbances.

Damage to a Power Supply Board

Nurse Checking on the Status of a Patient after Resetting a Medical Device

False alarms or, worse, alarm failures may result from any instrument malfunction, presenting a possible risk to patients and increased workload for healthcare professionals. A temporary overvoltage permanently damaged this power supply board from a medical instrument.

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Equipment malfunctions can be avoided if the level of power quality is known and equipment selected or installed to be immune.

Sources of Electrical DisturbancesThe most common causes of electrical disturbances that lead to power quality problems in healthcare facilities and medical clinics are low and unknown equipment immunity; faulty facility wiring and grounding; facility and equipment modifications; high-wattage equipment; routine electric utility activities; accidents, weather, and animals; and a transfer to an emergency generator or alternate feeder.

Faulty Facility Wiring and Grounding

In a fair number of cases, the cause of a power quality problem in healthcare facilities and medical clinics is simply a loose or corroded power or ground connection. Many medical equipment malfunctions attributed to poor power quality are caused by inadequate electrical wiring and grounding. Such problems frequently arise when new electronic medical or office equipment is connected to existing facility wiring; permanently installed medical equipment is moved from one location to another; or underlying non-PQ-related equipment malfunctions are not resolved and changes to wiring and grounding are made in efforts to enhance the quality of power to the equipment.

Low and Unknown Equipment Immunity

The immunity of most electronic medical equipment to electrical disturbances is low, unknown, or both. This is evidenced by the number of cases of medical equipment malfunction and damage that are caused by power quality problems. Many power quality problems can be avoided if the quality of power is known at the point of use within the healthcare facility and if equipment immunity is known and high enough to avoid equipment malfunction. When immunity is unknown, healthcare providers cannot determine if disturbances are likely to cause equipment malfunction and damage. As a result, healthcare providers cannot provide the utility with the data they need to warrant improvements to the power system and cannot determine the degree of mitigation that can be provided by improving the operation of facility electrical systems (that is, identifying wiring and grounding errors and resolving them) and by utilizing power quality mitigation equipment.

Wiring and grounding errors also enhance the negative effects of neutral-to-ground transients, which disrupt electronic medical equipment. Reversal of neutral and ground conductors; poor, missing, or redundant neutral-to-ground bonds; and poor, missing, or redundant equipment grounds are a few examples of faulty wiring and grounding that can lead to medical equipment malfunctions. Many facility engineers and electricians in healthcare facilities in the United States used to mistakenly believe that if electrical systems are wired and grounded according to Article 517 of the NEC (National Fire Protection Association [NFPA] 70), there should be no problems with the equipment. By increasing the level of awareness of the impacts of power quality and compatibility on healthcare facilities and medical equipment through EPRI research, facility

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The power supply equipment and wiring in a healthcare facility may fully comply with applicable standards, codes, and recommended practices and still be inadequate to prevent interruption of sensitive electronic equipment.

engineers, facility designers, and maintenance directors are realizing the importance of the integrity of their electrical systems in shaping the quality of power used for patient care. However, Article 517 focuses on electrical construction and installation criteria in healthcare facilities to reduce the risk of electrical shock and fire; it does not address power quality in the facility. The standard NFPA 99 entitled Handbook for Healthcare Facilities, also commonly used in the United States, focuses on the installation and performance of equipment in a healthcare facility, but also does not address power quality. The equipment and wiring in a healthcare facility may fully comply with applicable standards, codes, and recommended practices and still be inadequate to support sensitive electronic equipment commonly found in a healthcare facility.

Power-Factor Correction Capacitors at a Substation Near a Healthcare Facility

Switching capacitors in and out of service can create transients that impact sensitive instrument.

(MRI) systems, CT scanners, and linear accelerators operate at high line voltages,Routine Electric Utility Activities

require high steady-state current, and present dynamic loading (see figure on following page) to healthcare facility power systems. During startup, this type of equipment draws very high inrush current as high as 70 times the normal operating currentwhich can cause voltage sags and other electrical disturbances on adjacent circuits not properly sized for these loads. Problems occur when the circuits connected to such disturbance-causing equipment were not carefully planned for high-wattage equipment. Such problems most often arise after a facility has recently undergone a renovation or expansion or has recently moved existing medical equipment or installed new medical equipment. Also, installing high-wattage electronic equipment without upgrading the existing facility power system (i.e., switchgear, transformers, and electrical wiring and grounding) to accommodate the higher power consumption may result in overload, undervoltage, and even overvoltage conditions.

To correct the power factor of electricity, electric utilities routinely switch large capacitors (see figure on top right) onto the power lines. These switching activities may generate transient overvoltages, called capacitor-switching transients, which may enter a healthcare facility or medical location at the service entrance. These types of electrical disturbances are more likely to occur in the morning and evening, when industrial facilities are powering up and down. Other routine activities such as the operation of reclosures and breakers that occur to maintain and stabilize the power system and reduce the effects of electrical disturbances caused by natural events (e.g., lightning) can result in some residual disturbances.High-Wattage Medical Equipment with Dynamic Load

Large medical equipment such as X-ray machines, magnetic-resonance imaging

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Harmonic-Rich Current from an MRI System

facilities and medical clinics may find that equipment malfunctions are more prevalent on windy days when tree limbs may contact power lines. Voltage sags and interruptions may also be caused by lightning strikes, animals climbing atop the electrodes of a transformer or other utility equipment, and power-line conductor and insulator failures.

Current (20 amps/division)

Downed Power Pole Adjacent to a Healthcare Facility

Time (25 milliseconds/division)

This distorted current waveform was captured with a power quality monitor during a PQ field investigation at a healthcare facility.

Voltage sags originating from outside a facility can be caused by downed, crossed, and contacted power lines.

Mechanical equipment containing loads that are inductive (e.g., motors) and resistive (e.g., heating elements)such as heating, ventilation, air-conditioning, transportation, refrigeration, and pump equipment, which are controlled by starters and contactorsmay also create electrical disturbances. The startup, normal operation, and shutdown of this equipment can cause voltage sags, transient overvoltages, and electrical noise.

Accidents, Weather, and Animals

Voltage sags originating from outside a facilitywhich may account for more increased patient risk than any other single type of disturbancecan be caused by downed (like that shown in the figure on the right), crossed, and contacted power lines and are most likely to occur during inclement weather conditions and peak demand times. Cars crashing into utility poles and ice-laden, wind-blown, or overgrown limbs touching and landing on power lines may create a path from the power line to ground, creating electrical disturbances and power interruptions for some and voltage sags for many. Healthcare10

This toppled power pole caused a power outage at the healthcare facility nearby.

Facility electrical modifications

Renovating and annexing healthcare facilities and medical clinics are common in the global modern healthcare industry, as are the addition of transformers, subpanels, and circuits to an electrical system and the use of temporary circuits to power existing equipment. The rerouting of feeder and branch circuits can result in the commingling of loads (powering sensitive electronic medical equipment from the same bus as disturbance-generating loads).Power Quality for Healthcare Facilities

To provide power to some construction equipment, temporary electrical circuits may be connected to the wiring of existing structures, or construction equipment may be connected to the output of motorgenerator sets. The operation of construction equipment such as arc welders (see figure below) and line-powered motorized rotary equipment on the centers wiring system may introduce electrical disturbances into branch circuits powering sensitive electronic medical equipment.

manual transfer switch. (Ideally, in facility electrical designs where provisions for a second utility feed are included, the second feed should come from a different substation, but this is not always possible.) If the transfer switch is not properly installed, adjusted, and maintained to ensure a smooth transfer of power, the transfer may produce electrical disturbances that are severe enough to cause malfunction of electronic medical equipment. Inspection of generator wiring (see figure below) will reveal important wiring and grounding characteristics that are vital to the

Construction of a Shielded Room for an MRI Suite Using an Arc Welder

emergency power system. Engineers in healthcare facilities and medical clinics may also find that malfunction and damage to medical equipment may occur during routine generator testing (if generator testing is required by local, state, and international codes and laws). Most master generator control centers include an adjustable time delay to ensure that the generators are placed online or offline without creating electrical disturbances.

Searching for a Neutral-to-Ground Bond in the Emergency Generator at a Healthcare FacilityArc welders can introduce electrical disturbances into the branch circuits on which medical equipment are operating.

Transfer to and from Emergency Generator or Alternate Feeder

To ensure that power is always provided to feeder circuits that power subpanels and branch circuits connected to critical-care equipment, some electrical codes require that healthcare facilities have ready access to emergency power. Whether the source of emergency power is an on-site generator or a second utility feed, transferring from the normal power source to the emergency source is accomplished with an automatic orGenerator wiring should be inspected and maintained to avoid producing electrical disturbances during a power transfer.

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So You Think You Need Uninterruptible Power Supplies?In healthcare facilities where power quality problems occur frequently, healthcare providers may be eager to purchase and install power quality mitigation equipment to protect both small and large loads from electrical disturbances. In situations where small loads such as biomedical equipment do not contain internal battery backup systems, installing an appropriately sized uninterruptible power supply (UPS) will increase the immunity of these loads to common disturbances such as sags and momentary interruptions. UPSs for large medical loads ranging from 10 kVA to a few hundred kilovoltamperes, which can cost as much as $1 million, may be installed on an individual medical imaging system, can support multiple systems in a medical imaging department, or can be used for a group of critical equipment such as ventilators in an intensive care unit (ICU). In many situations where large UPSs are thought to be needed (and some are needed), healthcare providers discover that common disturbances are exacerbated by typical wiring and grounding errors within the healthcare facilitys electrical system. Prior to the decision to purchase and install a large UPS, a well-developed power quality investigation should be done within the facility to determine the extent to which wiring and grounding errors contribute to the root cause of malfunctions with small and large medical loads. In almost all situations, typical wiring and grounding errors internal to the facility can be linked to the severity of common disturbances entering the facility from everyday electrical events occurring on the utility power system and from events generated by the operation of large loads in neighboring customer facilities and/or generated by the operation of large loads within the healthcare facility. Purchasing and installing large UPS systems to protect individual imaging systems or several systems in a medical imaging suite can present additional problems for the healthcare provider. Healthcare facility designers do not make accommodations for such large pieces of power mitigation equipment. Healthcare providers, operating on extremely tight budgets, do not budget for the The types of portable electronic medical equipment that can be fitted with a low- to mid-power UPS are limited (to some less than 10 kVA machines. Because of the need to provide safe patient environments, most typical power quality solutions, such as constant voltage transformers and sagreducing technologies, cannot be implemented on medical equipment in the patient environment. Most medical equipment are designed to be portable and are placed on high-quality equipment carts without space provided for a UPS. Some devices such as blood-pressure monitors and infusion pumps must have power maintained to them as the patient is moved throughout Unlike industrial and manufacturing facility environments where industrial process systems can be made much more robust to voltage sag phenomenon with proper electrical and software design techniques, most medical equipment is not designed to offer this option. Medical equipment is designed for individual use in an array of equipment and for compact use. For example, the ten different types of medical equipment used in an ICU are not linked together with one downstream system depending upon the results from an upstream system. Instead, each piece of medical equipment is designed to carry out a specific task such as monitoring blood pressure, monitoring blood oxygen level, and providing breathing assistance to a patient. However, the typical solutions that can be applied in manufacturing environments to solve power quality problems with industrial equipment can also be applied to a healthcare facility. Healthcare providers are not willing to install a power mitigation device on each piece of medical equipment. However, they can be persuaded to have their maintenance staff sift through the details of a facilitys power distribution system through learning how to conduct power quality investigations. Moreover, healthcare providers may also be persuaded to improve their medical equipment procurement process by learning how to specify an acceptable level of immunity to voltage sags and momentary interruptions and voltage surges that is suitable to most healthcare facility electrical environments. But, before this concept can be widely applied, medical equipment manufacturers must succumb to determining the full immunity capability of their equipment to these common disturbances. installation and maintenance of these systems, even when new large medical equipment is specified and purchased. Large medical equipment such as diagnostic imaging systems can be fitted with a UPS at the installation site, but the barriers in doing so are significant. Imaging suites are tight on floor space, and the electrical system provided for these spaces was not designed to accommodate the installation of power mitigation equipment. Moreover, imaging system operators do not have time to routinely test a UPS or maintain the UPSs batteries. Even though electric utilities try to provide as many nines of reliable power to a healthcare facility as possible, healthcare providers must realize that their facilities are also fed from typical power distribution networks. Utilities will make every effort to ensure that a direct service feed (service entrance) to a hospital is properly maintained and that second feeds are provided from a second substation whenever possible. However, redesigning distribution systems or making other investments in the utilitys power delivery infrastructure may also be prohibitively costly. Given that the cost of the events and facility-level solutions can be very expensive, electric utilities and their healthcare customers search for ways to ease the financial burden of increasing the immunity of their healthcare customers to common electrical disturbances such as voltage sags, momentary interruptions, and surges. the facility. These devices are designed to operate on internal batteries, and thus continuous operation of this equipment is possible during a voltage sag or momentary interruption. One should note, however, that electronic medical equipment with an onboard battery recharger and an internal rechargeable battery may also malfunction during an electrical disturbance as the charger could be rendered inoperable as a result of a deep voltage sag; hence the need for characterizing this equipment for immunity to sags and interruptions.

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Power quality in the healthcare environment can be improved through enhancing the level of awareness among utilities, healthcare facility designers, and medical equipment manufacturers.

IMPROVING POWER QUALITY IN THE HEALTHCARE ENVIRONMENT

disturbances and that generates fewer electrical disturbances, effectively use power-conditioning technologies for existing medical equipment in accordance with standards and recommended practices, carefully plan new construction or renovation of existing healthcare facilities with regard to power quality concerns, maintain existing wiring and medical equipment in healthcare facilities, and learn from past power quality

Power quality in the healthcare environment can be improved through enhancing the level of awareness among the stakeholders: utilities, healthcare facility and medical staff, healthcare facility designers, and medical equipment manufacturers. Power quality problems in this mission-critical environment present a series of challenges among stakeholders. Meeting these challenges helps to prevent these problems before they become monumental to healthcare providers.

Meeting the Power Quality Challenges of the Healthcare IndustryAlthough healthcare staffs rely upon advanced medical procedures using advanced medical equipment to provide immediate patient care, they must sometimes plug equipment into antiquated and unreliable electrical systems. Moreover, some equipment manufacturers design equipment without fully considering and understanding the electrical environment of a healthcare facility. Because of its obligation to human care, the healthcare industry must demand high standards of performance from facility designers, equipment manufacturers, equipment service companies, facility and equipment support staff, and electric supply companies. To meet the challenges of the healthcare industry, these people must meet on common ground to establish new partnerships to improve power quality in the healthcare environment, improve the procurement process for new medical equipment, encourage equipment manufacturers to design medical equipment that is more immune to electrical

problems.

Establishing PartnershipsPreventing or resolving power quality problems should be a cooperative effort between healthcare facilities, equipment vendors, equipment manufacturers, and electric supply companies. Electric supply companies have always offered assistance to customers in emergencies and have sometimes promoted new energy-efficient technologies to improve productivity and reliability as well. As problems associated with new technologies were revealed, many electric supply companies established power quality programs that invested in power quality research to assist utility customers and manufacturers with equipmentcompatibility problems. Electric supply companies especially recognize the necessity of identifying or providing power quality engineering services to their healthcare customers. These services enable healthcare staff to learn how to identify wiring and grounding problems that exacerbate power quality problems, select the proper powerconditioning equipment to mitigate these problems, develop specifications (that

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Building strong relationships between healthcare facilities, equipment vendors, equipment manufacturers, and electric supply companies offers many benefits.

include power quality specifications) for purchasing medical equipment problems, establish correct installation guidelines, and plan center renovations or the construction of new healthcare facilities and medical clinics to help avoid problems. Building strong relationships between healthcare facilities, equipment vendors, equipment manufacturers, and electric supply companies offers many benefits. These benefits include learning how to avoid wiring and grounding errors, reducing or eliminating controllable electrical disturbances, managing common uncontrollable electrical disturbances, encouraging equipment manufacturers to design and build robust equipment immune to most electrical disturbances, significantly reducing the potential for lawsuits by healthcare patients involved in events possibly initiated by equipment malfunctions, and avoiding citations and penalties from international regulatory agencies.

and clinics where significant and costly power quality problems have occurred find it cost-effective to purchase a monitor and learn to use it. Consider tapping the expertise of your local utility company or independent consultants. Determine the characteristics of your facilitys electrical system: Can it tightly regulate equipment voltage? Is voltage to equipment continuous? Does high-wattage equipment create electrical disturbances in the facility wiring? Your local utility company may also provide site-specific characteristics such as expected voltage regulation and statistical analysis of electrical disturbances. Evaluate the immunity performance requirements of existing equipment. How susceptible is each type of medical equipment to common electrical disturbances such as voltage sags and transient overvoltages? Set your expectations for the

Creating a Power Quality Checklist for Procuring EquipmentHealthcare facilities and medical clinics routinely procure and install medical, functional, and facility equipment. To reduce power-quality-related problems between equipment and the intended electrical environment, equipmentprocurement procedures should include the following steps.

performance of new equipment, and then ask your utility company for help in specifying design features that enhance compatibility between the equipment and its intended electrical environment. Identify and repair all wiring and grounding problems. Identify all areas where critical electronic medical equipment may be used and the special power requirements of such equipment. With assistance from your local utility company or independent consultants, identify appropriate power-conditioning devices for critical electronic equipment.

Planning for Additional Equipment

Begin a sound in-house power quality program with the purchase of a PQ monitor to conduct an on-site survey to identify potential power quality problems and diagnose problems with sensitive electronic medical equipment. Some facilities

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Purchasing Additional Equipment

Installing Additional Equipment

Disclose to equipment suppliers the power quality characteristics of the electricity and wiring where the new equipment will be installed. Ask the manufacturers representative about known power quality problems with the equipment and if the equipment has been tested for compatibility with the utility power system. If there is reason to believe that compatibility may be an issue, ask to see the power quality test report. For all new equipment, specify the voltage range (required voltage regulation), frequency, and voltage sag immunity (i.e., ride-through) performance. Purchase equipment with an input voltage rating matched to the voltage at the installation site when possible. Purchase high-quality matching transformers with new equipment when the voltage ratings of the equipment do not match the available voltage at the installation site. If a power-conditioning device is needed, make sure that it is designed for compatibility with electronic medical equipment. Medical equipment such as imaging systems with dynamic load behavior may not function properly when connected to some power conditioners. Make sure that all medical and power-conditioning equipment complies with applicable international codes, standards, and recommended practices. To reduce susceptibility to common electrical disturbances, select the highest input voltage rating for equipment known to be sensitive to common electrical disturbances.

Use high-performance wiring and proper grounding techniques specified in the International Electrical Code (IEC), the Institute of Electrical and Electronics Engineers (IEEE) Standard 602-1996 (White Book; Recommended Practice for Electric Systems in Healthcare Facilities), and the IEEE Standard 1100-1992 (Emerald Book; Powering and Grounding Sensitive Electronic Equipment). For circuits connected to sensitive electronic equipment, use singlepoint grounding, locate equipment as electrically close to the source as possible, and make sure that the sizing of phase, neutral, and ground conductors follow international and local codes and manufacturer installation requirements. When adding grounding conductors to an existing facility, run the grounding conductors parallel to the existing power conductors to reduce stray electromagnetic fields. When installing high-wattage medical equipment in an existing facility, monitor the input voltage at the proposed installation site for electrical disturbances for at least a 30-day period before completing the installation.

Maintaining Equipment

Regularly review equipment performance and continue the relationship between healthcare facility staff, utility company representatives, equipment vendors, equipment manufacturers, and medical equipment service companies.

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Document all facility power outages, noticeable disturbances (i.e., light flicker), and equipment problems. Include patient schedules, the location of equipment, the symptoms, suspected causes, time and date of occurrence, and any other related events. Checking disturbance logs against utility company records and facility activities can help reveal the source of electrical disturbances. These logs can also be used to specify future equipment purchases and determine correct installation methods.

Using Power-Conditioning Devices to Improve Equipment CompatibilitySome power quality problems in healthcare facilities and medical clinics can be solved with appropriate power-conditioning devices. Some of these technologies are listed in the table on the left and include isolation transformers, surge-protective devices, voltage regulators, and UPSs. However, power-conditioning devices are not always the answer to a power quality problem. In some cases, installing power quality mitigation equipment can worsen a medical equipment malfunction, especially in cases where medical equipment loads are very dynamic in nature, like that of diagnostic medical imaging equipment. In addition, low-kilovolt-ampere powerconditioning devices and ice-cube relays, power supplies, and contactors routinely used in industrial facilities can be used in the physical plants (i.e., where HVAC, steam, air, vacuum, and other mechanical systems are located) but cannot be used with medical equipment to solve power quality problems. In other cases, installing such equipment is not necessary and can have no effect on the problem. For example, power-conditioning devices will not protect equipment against radiated emissions or electrostatic discharge, which has been reported as one of the electromagnetic-related causes of equipment malfunction. In some cases, the potential for this problem can be virtually eliminated by maintaining correct humidity levels or installing building materials that reduce the buildup of static charge. In other cases where wiring and grounding problems exacerbate equipment malfunctions caused by voltage transients, installation of a UPS can provide enhanced immunity to voltage sags and momentary interruptions and some mitigation of transients. However, if equipment damage is

General Summary of Available Power-Conditioning Technologies

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Good grounding is essential for good power quality and safety at any healthcare facility.

caused by a wiring and grounding problem and voltage transients developed at the point of use (where the equipment is connected to the center electrical system), then installing an upstream UPS will not resolve the problem. Consult the equipment manufacturer and local utility company to determine whether a power-conditioning device can be used effectively.

medical equipment such as imaging and radiology equipment and medical air pumps, and mechanical equipment such as adjustable speed drives, chillers, fans, pumps, and HVAC equipment.

Other support equipment, such as biomedical and laboratory equipment and low-power kitchen and laundry equipment, are powered at 120 volts. However, effective January 1, 2008, the tolerance levels for the electric supply voltage with a range of 10% will again be unified for European healthcare facilities and medical clinics. Thus, European manufacturers of medical equipment used in the United States, who have integrated design changes into their equipment to help ensure reliable operation in Europe, may find that United States users file fewer complaints regarding medical equipment malfunctions. Healthcare facilities and medical clinics in the United States may experience fewer malfunctions caused by long-term steady-state undervoltage conditions and possibly minor voltage sags. In areas such as medical laboratories where microscopes are used and surgical suites where eye surgery and other surgical procedures are performed, high power quality lighting that is immune to more types of voltage fluctuations and other electrical disturbances may operate with less flicker to lamps, thus improving lightassisted and light-dependent medical procedures.

Understanding Facility Voltage Requirements, Grounding, and Dedicated CircuitsThe voltage level provided to the service entrance of a healthcare facility will impact the voltage that is provided to all loads in the facility, especially the medical equipment loads. Because the healthcare provider must provide healthcare services to patients in real-world power quality environments, grounding the facility infrastructure, the secondary of the utility companys transformer at the service entrance, within the switchgear, throughout the facility electrical system, and at the enduse level where the equipment is connected and used is also critical. Moreover, many end-use loads in healthcare facilities require the use of a dedicated feeder or branch circuit, which helps to maintain voltage and current quality to critical equipment. The voltage levels selected for new equipment will depend upon the available utility voltage, the size of the healthcare facility or medical location, voltage levels used within, type of equipment, building layout, voltage regulation requirements, and cost. Typically, power to a healthcare facility or medical location is supplied by the utility company at a medium voltage level for large facilities and clinics and at 480 volts (with a 5% range), three-phase. These voltages may be used to power:

Voltage Matching

Once the nominal voltages of equipment have been selected, the voltage source for all medical equipment to be installed in the facility should be carefully checked to assure proper voltage levels. New equipment

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should be ordered to match one of the planned voltage sources. Otherwise consider using buck/boost transformers, autotransformers, or standard two-winding isolation transformers to match the voltage requirement of the equipment to the voltage source. Variacs should never be used to match a source voltage to an equipment voltage.

However, the focus of the discussion in this section of this report is not on patient safety, but on wiring and grounding (i.e., earthing systems) as they relate to power quality in U.S. healthcare facilities and medical clinics. Moreover, the compatibility between medical equipment and the electrical environment in these facilities and clinics is dependent upon the type of earthing system that powers and grounds the medical equipment. Regardless of the earthing system used, providing a solid low-impedance ground to sensitive equipmentwhich is required by the NFPA NEC and healthcare facility codes and recommended by the IEEE Emerald, Green, and White Bookswill help minimize power quality problems. Because patients are often moved from one location in the healthcare facility to another, grounded receptacles should be available at all possible equipment locations. Power cords should never be modified to accommodate an ungrounded receptacle by removing the grounding connector. Nor should grounding adapters be used on equipment requiring a ground. In some older healthcare facilities, grounding conductors may be present but may not be running parallel to the power conductors. In the course of enhancing the grounding system in these facilities, the grounding conductors should be run parallel to the circuits neutral and power

Regardless of the earthing system used, providing a solid lowimpedance ground to sensitive equipment will help minimize power quality problems.

Equipment from International Manufacturers

Equipment purchased from international sources originally designed to operate in countries with different nominal voltage levels requires careful consideration of the design of the facility distribution system so that the correct voltage can be supplied to the equipment. Equipment designed for nonstandard U.S. voltages may require matching transformers. The addition of a transformer may make equipment more sensitive to common electrical disturbances. Also, equipment designed for 60-hertz operation must be able to operate properly at 60 hertz. The voltage tolerance of overseas equipment may also be a concern and should be checked. Equipment purchased from European manufacturers not recognizing the standard U.S. nominal voltage may require a special transformer to be powered from U.S. voltage sources.

Ensuring Proper Grounding and Wiring

conductors, which will minimize stray electromagnetic fields due to the presence of any unwanted ground currents. Similar to the requirements of electrical systems for providing quality voltage and current to large loads such as chillers and printing presses found in commercial and industrial facilities, large loads in healthcare facilities must be circuited such that their operation does not affect other loads. Powering disturbance-generating loads such as HVAC equipment (e.g., motor contactors,

Power quality investigations carried out in the United States are revealing that the integrity of wiring and grounding systems in healthcare facilities and medical clinics has an even greater impact on the immunity of medical equipment to common electrical disturbances. Since the term leakage current was coined for the medical equipment industry, much of the focus on the integrity of grounding systems in healthcare facilities has been on patient safety.

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To avoid equipment malfunctions during renovation or new construction, healthcare facility engineers should coordinate with construction foremen before the electrical system is modified.

motor starters, chillers, heating systems, etc.) from the same voltage bus that powers critical medical loads (e.g., X-ray equipment and medical imaging systems) is a prescription for incompatibility problems between building and facility loads, and critical medical loads. Large diagnostic medical imaging systems, such as MRI systems, CT scanners, and various X-ray machines require dedicated power, neutral, and ground conductors also, because they usually draw fluctuating dynamic currents. Providing dedicated conductors for power, neutral, and ground is not only concerned with individual circuits (i.e., the fact that the circuits are separate runs from switchgear and electrical panels) but also the size (i.e., wire gauge) of the conductors with respect to the required length and the allowable voltage drop from the supply to the load. Many power quality investigations result in findings that identify dedicated circuits to X-ray equipment and imaging systems that are sized too small in wire gauge. The size of the grounding conductor is also important and should be specified according to the requirements of the X-ray or medical imaging system manufacturer. When this equipment is installed, the facility electrician should also determine what other sensitive or disturbance-causing equipment may be powered by the common source. In some cases, the solution may require providing a dedicated circuit to certain sensitive medical equipment to isolate it from other disturbance-causing equipment. To avoid equipment malfunctions during renovation or new construction, healthcare facility engineers should talk to the designated construction contact before the electrical system is modified. This precaution will help ensure that good power quality is maintained on circuits deemed essential to patient safety, critical care, and other equipment necessary for the effective operation of the healthcare facility during the construction and renovation process.

The IEEE Standard 602 (White Book), and IEEE Standard 1100 (Emerald Book) are also both excellent technical resources that address power quality in healthcare facilities and medical clinics and offer guidance on powering and grounding sensitive electronic equipment during facility construction.

Medical Equipment Power Supplies

In healthcare facilities and medical clinics, the failure of the facility power may pose life-threatening consequences to patients. Examples of these concerns are the failure of a power supply in a ventilator, a lighting system in an operating room, and the branch circuit to a life support system in an ICU. The restoration time for medical power supplies to restore power to the medical equipment is not specified in the United States for medical microprocessor-based equipment. Designers of medical power supplies must be conscious of the amount of leakage current they allow to flow out of the supply under certain conditions, and the allowed levels are governed by the Association for the Advancement of Medical Instrumentation (AAMI). Lower leakage currents equate to higher levels of conducted emissions, thus increasing the likelihood of a medical device creating an electromagnetic interference (EMI) problem. Careful balance between EMI filter design and leakage current helps to ensure success in both areas. However, as medical devices become more digital in the next 20 years, this balance will become more difficult to achieve.

Standards

The healthcare and medical equipment industries are heavily regulated to protect patients. Both the United States and Europe have developed and published standards, recommended practices, and guidelines related to power quality and electromagnetic compatibility in the areas

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of healthcare facility design, medical equipment design (i.e., product standards), and emergency preparedness. Standards, recommended practices, and guidelines have also been developed that define disturbances and test methods for power quality and electromagnetic compatibility. The United States has made significant contributions in power quality standards and healthcare facility design standards. Europe has made significant contributions in the area of immunity standards (i.e., emissions and immunity) regarding product design and safety. The top table on the following page presents a summary of power-line and electromagnetic disturbances, power electronics technologies, emissions and immunity standards, and equipment performance standards relating to electronic medical equipment. Medical equipment designers and manufacturers in the United States have become more cognizant of these standards. The emissions and immunity standards listed in the bottom table on the following page are the Basic Electromagnetic Compatibility (EMC) standards prepared by the European-based International Electrotechnical Committee (IEC). In the past few years, they have been referred to as IEC 61000-X-X standards. After the European Union (EU) recently adopted them as European Norms (EN) standards, they were referred to as EN 61000-X-X standards. The requirements listed in these standards serve as the basis for all present and future power quality and EMC requirements for all products traded internationally, including electronic medical equipment. The Basic EMC standards consist of the following six parts: EN 61000-1-X: General EMC standards EN 61000-2-X: Compatibility levels of environments

EN 61000-3-X: Emissions, limits EN 61000-4-X: Emissions, measurement techniques EN 61000-5-X: Immunity, testing techniques EN 61000-6-X: Installation and mitigation guidelines

Other healthcare codes, standards, and recommended practices are promulgated by the NFPA, the IEEE, the American National Standards Institute (ANSI), the Federal Communications Commission (FCC), the IEC, and the International Special Committee on Radio Frequency (CISPR).

Healthcare Facility Standards

Standards, recommended practices, and guidelines have also been developed in several areas related to the design of healthcare facilities and medical clinics. The NFPA 99 (Standard for Healthcare Facilities), the facility code standard developed and used in the United States; the NFPA Standard 70 (The National Electric Code), the electrical code standard developed in the United States; and the IEEE Standard 602-1996, White Book (Recommended Practice for Electric Systems in Healthcare Facilities), the electrical system design practice developed and used in the United States, provide guidance to designers of healthcare facilities and medical clinics. Facility designers in the United States also commonly refer to the well-known IEEE Standard 1100-2006, Emerald Book (Powering and Grounding Sensitive Electronic Equipment), for guidance on powering and grounding electronic medical equipment.

Continued on page 2220


Effects of Electromagnetic Disturbances on Power Electronics Technologies Used in Electronic Medical Equipment

(Refer to table below)

Cross-Reference of European Standards Applicable to Electromagnetic Compatibility of Electronic Medical Equipment

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Healthcare facility standards address important aspects of the electrical system in a healthcare facility from planning, voltage selection, loading, harmonics, disturbances, mitigation techniques, emergency power systems, renovation, telecommunica tions, and lighting.

Continued from page 20

strength, and isolation transformer construction to enable its use in electronic medical equipment. The Y capacitors required in the input filter of a standard switch-mode power supply for information technology equipment would almost certainly cause the power supply to fail on the grounds of excessive leakage current. Briefly, the more-stringent requirements that are of particular relevance to power supplies used in electronic medical equipment are (1) service entrance to secondary creepage and clearance distances for double or reinforced insulation for equipment operating from 250 volts AC maximum must be 8 and 5 millimeters, respectively; (2) primary to secondary dielectric withstand test must be 4,000 volts AC; (3) earth leakage current maximum is 0.5 milliamp for normal operation and 1 milliamp maximum for a single fault condition. These values are for type B, type BF, and type CF equipment categories: Type BNon-patient-connected equipment, or equipment with grounded patient connection. Type BFEquipment with a floating patient connection. Type CFEquipment with a floating connection for direct cardiac application.

Healthcare facility standards address every aspect of the electrical system in a healthcare facility from planning; voltage selection; loading (e.g., historical load densities and profiles, demands, and factors); harmonics; disturbances; mitigation techniques; emergency power systems; renovation; telecommunications; and lighting. Guidance is given on how to avoid overloading, undervoltaging, overvoltaging, and equipment damage and shutdown caused by power problems.

Medical Equipment Safety Standards

In the EU, technical safety problems of electronic medical equipment are addressed by the EN 60601 series of standards which follow IEC 601 (now referred to as IEC 60601-1-2), Medical Electrical Equipment. In the United States, UL 544, Medical and Dental Equipment, covers medical and dental equipment, but in 1994 UL 2601-1, Medical Electrical EquipmentPart 1: General Requirements for Safety, came into effect. This standard is harmonized with IEC 60601-1-2, to be used at present in parallel with UL 544, Medical Equipment, and the U.S. safety standard for medical equipment, but it became the sole mandatory standard in 2004. In Canada, CSA 22.2-601.1, Medical Electrical EquipmentPart 1: General Requirements for Safety, has been in use since 1990, again, alongside the existing standard CSA 22.2-125, Electromedical Equipment, and it became the sole applicable standard in the year 2000. The bulk of the electrical safety requirements detailed in IEC 60601-1-2 are based on IEC 950, Safety of Information Technology Equipment Including Electrical Business Equipment. However, an IEC 950 (EN 60950) approved power supply would need to pass the additional test and inspection requirements of EN60601-1 for separation, leakage current, dielectric

Patient leakage current for the above categories is 0.1 milliamp (0.5 milliamp for a single fault condition) for type B and BF and 0.01 milliamp (0.05 milliamp for a single fault condition) for type CF. In the EU, electronic medical equipment is subject to the Medical Device Directives 9342-EEC, which was implemented on January 1, 1995. These New Approach Directives gave a three-year transitional period (up to January 1, 1998) until CE marking (mandatory marking to indicate conformity with the health and safety requirements set out in the European Directives) was required.

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Two New Approach Directives, 90/385/EEC Active Implantable Medical Devices (AIMD) and 93/42/EEC Medical Devices Directive (MDD) exempt those specific product categories from the EMC Directive. They contain their own specific EMC requirements. Probably only the MDD will be of interest to power supply designers and users. The EMC standards cited are IEC60061-1-2, adopted by European Committee for Electrotechnical Standardization (CENELEC) and published as EN60601-1-2. Emission standards required follow CISPR 11 (EN55011), Limits and Methods of Measurement of Electromagnetic Disturbance Characteristics of Industrial, Scientific, and Medical (ISM) Radio Frequency Equipment, normally class B, with a 12-dB relaxation for radiated emissions in X-ray rooms, for example. Immunity standards again rely heavily on IEC 801 as follows: IEC 801-2, Electrostatic Discharge: 3 kV contact, 8 kV air IEC 801-3, Radiated Radio-Frequency Interference (RFI): 3 V/m from 26 to 1000 MHz, 80% amplitude modulation, 1 V/m in X-ray rooms

IEC 801-4, Electric Fast Transients: 1 kV at service entrance plug, 2 kV for hardwired service entrance, 0.5 kV on connecting leads greater than 3 m long IEC 801-5, Service Entrance Surges: 1 kV differential, 2 kV common mode After June 14, 2000, electronic medical equipment was allowed to be sold within the EU as compliant with either the EMC or MD Directives. An important point to note for all products subject to the AIMD, and many products under the MDD (except class I), is that they cannot be self-certified. Approvals must be carried out by Notified Test Organizations. Class I equipment is defined as equipment for which electric shock protection is achieved by basic insulation and protective earth. All conductive parts that could assume hazardous voltages in the event of failure of basic insulation must be connected to a valid protective earth conductor. The table below lists some additional medical equipment performance standards.

U.S. and European Electromagnetic Compatibility Standards Applicable to Healthcare Facilities and Electronic Medical Equipment

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CONCLUSION

power quality problems. The information provided in the PQ TechWatch Hardening Manufacturing Processes Against Voltage Sags (EPRI, 200) can also be applied to the physical plant of healthcare facilities and medical clinics in efforts to harden mechanical equipment against voltage sags and momentary interruptions. Most voltage sag-sensitive components typically found in a healthcare facility or medical location cannot be placed on a power conditioner at the patient level. Diagnostic medical imaging systems are ultrasensitive to voltage disturbances, and many times these systems are not compatible with a UPS or cannot be placed on a power conditioner due to cost and space limitations in imaging suites. The cost of resolving underlying wiring and grounding errors and separating disturbance-causing loads from sensitive medical equipment is typically much less than the cost of placing an entire department or facility on conditioned power.

Important information has been provided here about how healthcare facilities and medical clinics view power quality problems, how such problems can be recognized by facility and medical staffs, definitions of the sources of electrical disturbances that can impact healthcare facilities and medical clinics, and how power quality challenges might be met in a complex environment where patient safety must prevail above power quality. Recognizing and correcting wiring and grounding errors and the commingling of loads are paramount in resolving power quality problems in healthcare facilities and medical clinics, and establishing partnerships between electric supply companies, facility designers, medical equipment manufacturers, and the facility and medical staffs is also critical. This approach is based on common practices employed in U.S. healthcare facilities to understand, identify, solve, and prevent

BIBLIOGRAPHYCapuano, Mike, Patrick Misale, and Dan Davidson, Case Study: Patient-Coupled Device Interaction Produces Arrhythmia-Like Artifact on Electrocardiographs, Biomedical Instrumentation & Technology, November/December 1993, pp. 475483. Dorr, Douglas S., and Douglas C. Folts, UPS Response to Power Disturbances, Medical Electronics Magazine, December 1994, pp. 4856. IEC 601-1-02, Medical Electrical Equipment, Part 1: General Requirements for Safety. 2. Collateral Standard: Electromagnetic Compatibility

Requirements and Tests, 2nd edition (Geneva: International Electrotechnical Commission, June 1996).IEEE Standard 1602-1996, Recommended Practice for Electric Systems in Health Care FacilitiesIEEE White Book (Piscataway, NJ: Institute of Electrical and Electronics Engineers, 1996). Keebler, Philip F., Power Quality for Diagnostic Medical Imaging Systems, EPRI, November 2006. Keebler, Philip F., Power Quality for Healthcare, BR-109172 (White Plains, NY: EPRI Healthcare Initiative, 1997). Keebler, Philip F., Solving Power Quality Problems in Medical Imaging Systems, PB-106393 (Knoxville, TN: EPRI Power Electronics Applications Center, 1996) Lamarre, Leslie, Power Prescriptions for the Health Care Industry, EPRI Journal, June 1994, pp. 1421. Loznen, Steli P., Product-Safety Requirements for Medical Electrical Equipment, Compliance Engineering Magazine, March/April 1995, pp. 1729. Russell, Michael J., Cardiovascular Imaging Equipment Requires Emergency Power, Power Quality Magazine, JanuaryMarch 1992, pp. 819. Waterman, Craig, Medical Facility Power Quality Problems Can Be Deadly, Power Quality Magazine, Premier II 1990, pp. 8290. Whitfield, John, The Electricians Guide to the 16th Edition of the IEE Wiring Regulations BS 7671 and Part P of the Building Regulations (Wendens Ambo, Essex: EPA Press, March 2005).

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Documents

18096508 Power Quality for Healthcare Facilities[1]