Power Quality for Healthcare Facilities

Philip Keebler, EPRI

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 patient’s 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 ¼ 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.

CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .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

PQ TechWatchA product of the EPRI Power Quality Knowledge program

December 2007December 2007

Power Quality for Healthcare FacilitiesHealthcare Facilities

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ii Power Qual i ty for Heal thcare Fac i l i t ies

1 Power Qual i ty for Heal thcare Fac i l i t ies

INTRODUCTION

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 business—caring

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 open-

heart 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 blood-

pressure 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 equipment—a computed

tomography (CT) scanner in an emergency

room, for example—would be enough of a

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.

The Healthcare Environment

The 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

Healthcareproviders havelittle time to beconcerned withthe quality ofpower or to finda reliablesource of powerto operate theirequipment.


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

infrastructure—electrical 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 microprocessor-

based 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.

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

Complex Electronic Medical EquipmentUsed 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.

Healthcare staffcan contributeto improvingpatient careand theenvironmentthroughincreasing theirlevel ofawareness inrecognizingequipmentmalfunctionsthat may becaused bypower qualityproblems.

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 life-

sustaining devices listed in the act—such as

pacemakers, pulse generators, and

automatic defibrillators—that 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 Facilities

Although 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.

For equipmentwith lowimmunity,electricaldisturbancesare a primarycause ofdamage andmalfunctions.


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.

Medical equipment used in the United

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.

RECOGNIZING POWER QUALITYPROBLEMS

Symptoms and Their Causes

Disturbances can enter healthcare

equipment through any electrical port—the

AC power input, telecommunications, or

network—common in the facility’s electrical

environment. Most disturbances will enter

the AC power port and present themselves

to equipment’s 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 equipment’s

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

Integrated circuits, sensitive to electrical and electromagnetic disturbances, are used in

electronic medical equipment.

Circuit Boards from a Medical Imaging System

This medical imaging system creates dynamic power quality problems in healthcare

facilities with wiring and grounding errors.

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

Time (10 milliseconds/division)

Cu

rren

t (5

0 a

mp

s/d

ivis

ion

)

disturbance—undervoltage or overvoltage,

its duration, and the immunity of the

equipment to that disturbance—gradual 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 Imageand Digital Readout

Variations in DC voltages can cause problems with the

images and digital readouts from CT scanners.

The mostcommonequipmentmalfunctionsare causedby the inputsand outputs ofmicroprocessorserroneouslyswitching onand off becauseof voltage sags,swells,transients,andmomentarypowerinterruptions.

Incorrect Diagnostic Results

Electrical disturbances can alter the control

parameters stored in electronic medical

equipment and used to diagnose a patient’s

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 patient’s 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

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.

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 life-

threatening 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.

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 patient

to complete the operation, an unplanned

procedure that significantly increases the

patient risk, recovery time, and the cost of

patient care.


Incorrect Diagnostic Results

Electricaldisturbancescan causemicroprocessor-based medicalequipment tomalfunction.

An 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).

Loss of Stored Data

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.

Control or Alarm Malfunctions

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

A temporary overvoltage permanently damaged this power supply board from a

medical instrument.

Nurse Checking on the Status of a Patientafter 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.

An electricaldisturbance candamage anelectroniccomponent orcircuit board inmedicalequipmentcausing a lossof data storedin memory oreven destroyingthe memoryaltogether.


Sources of Electrical Disturbances

The 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.

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.

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.

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

Equipmentmalfunctionscan be avoidedif the level ofpower qualityis known andequipmentselected orinstalled to beimmune.


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.

Routine Electric Utility Activities

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

(MRI) systems, CT scanners, and linear

accelerators operate at high line voltages,

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

current—which 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.

Power-Factor Correction Capacitors at aSubstation Near a Healthcare Facility

Switching capacitors in and out of service can create

transients that impact sensitive instrument.

The powersupplyequipmentand wiring ina healthcarefacility mayfully complywith applicablestandards,codes, andrecommendedpractices andstill beinadequateto preventinterruptionof sensitiveelectronicequipment.


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 contactors—may 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

facility—which may account for more

increased patient risk than any other single

type of disturbance—can 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. Healthcare

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.

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).

Harmonic-Rich Current from an MRI System

This distorted current waveform was captured with a power quality monitor during a PQ

field investigation at a healthcare facility.

Time (25 milliseconds/division)

Cu

rren

t (2

0 a

mp

s/d

ivis

ion

)

Downed Power Pole Adjacent to aHealthcare Facility

This toppled power pole caused a power outage at the

healthcare facility nearby.

Voltage sagsoriginatingfrom outside afacility can becaused bydowned,crossed, andcontactedpower lines.

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 motor-

generator sets. The operation of

construction equipment such as arc welders

(see figure below) and line-powered

motorized rotary equipment on the center’s

wiring system may introduce electrical

disturbances into branch circuits powering

sensitive electronic medical equipment.

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 or

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

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 Bondin the Emergency Generator at aHealthcare Facility

Generator wiring should be inspected and maintained to

avoid producing electrical disturbances during a power

transfer.

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

Arc welders can introduce electrical disturbances into the branch circuits on which

medical equipment are operating.


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 kilovolt-

amperes, 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

facility’s 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

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 UPS’s batteries.

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.

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 sag-

reducing 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

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.

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

utility’s 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.

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 facility’s 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.

So You Think You Need Uninterruptible Power Supplies?


IMPROVING POWER QUALITYIN THE HEALTHCAREENVIRONMENT

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 Industry

Although 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

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

problems.

Establishing Partnerships

Preventing 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 equipment-

compatibility 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 power-

conditioning equipment to mitigate these

problems, develop specifications (that

Power qualityin thehealthcareenvironmentcan beimprovedthroughenhancing thelevel ofawarenessamong utilities,healthcarefacilitydesigners, andmedicalequipmentmanufacturers.

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.

Creating a Power Quality Checklist for

Procuring Equipment

Healthcare 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, equipment-

procurement procedures should include the

following steps.

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

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 facility’s

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

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.


Building strongrelationshipsbetweenhealthcarefacilities,equipmentvendors,equipmentmanufacturers,and electricsupplycompaniesoffers manybenefits.


Purchasing Additional Equipment

Disclose to equipment suppliers the

power quality characteristics of the

electricity and wiring where the new

equipment will be installed.

Ask the manufacturer’s 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.

Installing Additional Equipment

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 single-

point 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.

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 Compatibility

Some 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 power-

conditioning 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-ConditioningTechnologies

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.

Understanding Facility Voltage

Requirements, Grounding, and

Dedicated Circuits

The 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

company’s transformer at the service

entrance, within the switchgear, throughout

the facility electrical system, and at the end-

use 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:

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 light-

assisted and light-dependent medical

procedures.

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


Goodgrounding isessential forgood powerquality andsafety at anyhealthcarefacility.

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.

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

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.

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 equipment—which is required by

the NFPA NEC and healthcare facility codes

and recommended by the IEEE Emerald,

Green, and White Books—will 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 circuit’s neutral and power

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,


Regardless ofthe earthingsystem used,providing asolid low-impedanceground tosensitiveequipment willhelp minimizepower qualityproblems.

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


To avoidequipmentmalfunctionsduringrenovation ornewconstruction,healthcarefacilityengineersshouldcoordinate withconstructionforemen beforethe electricalsystem ismodified.

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 22

21

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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 Equipment—Part 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 Equipment—Part 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

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 B—Non-patient-connected

equipment, or equipment with

grounded patient connection.

Type BF—Equipment with a floating

patient connection.

Type CF—Equipment with a floating

connection for direct cardiac application.

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 93-

42-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.


Continued from page 20Healthcarefacilitystandardsaddressimportantaspects of theelectricalsystem in ahealthcarefacility fromplanning,voltageselection,loading,harmonics,disturbances,mitigationtechniques,emergencypower systems,renovation,telecommunications, andlighting.

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 EuropeanElectromagneticCompatibilityStandards Applicableto HealthcareFacilities andElectronic MedicalEquipment

CONCLUSION

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

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.


BIBLIOGRAPHY

Capuano, 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. 475–483.

Dorr, Douglas S., and Douglas C. Folts, “UPS Response to Power Disturbances,” Medical Electronics Magazine, December 1994, pp. 48–56.

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 Facilities—IEEE 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. 14–21.

Loznen, Steli P., “Product-Safety Requirements for Medical Electrical Equipment,” Compliance Engineering Magazine, March/April 1995,

pp. 17–29.

Russell, Michael J., “Cardiovascular Imaging Equipment Requires Emergency Power,” Power Quality Magazine, January–March 1992,

pp. 8–19.

Waterman, Craig, “Medical Facility Power Quality Problems Can Be Deadly,” Power Quality Magazine, Premier II 1990, pp. 82–90.

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).

Documents

Power Quality for Healthcare Facilities