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.

1. 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 Quality for Healthcare Facilities

3. 1 Power Quality for Healthcare Facilities
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
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.

4. 2 Power Quality for Healthcare Facilities
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 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.
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.

5. 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.
3 Power Quality for Healthcare Facilities
Microprocessor-Based Electronic Medical Equipment
The healthcare environment is a unique one because of the intimate proximity of people
to equipment.
For equipment
with low
immunity,
electrical
disturbances
are a primary
cause of
damage and
malfunctions.

6. 4 Power Quality for Healthcare Facilities
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 QUALITY
PROBLEMS
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)
Current(50amps/division)

7. 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.
5 Power Quality for Healthcare Facilities
Distorted Computed Tomography Image
and Digital Readout
Variations in DC voltages can cause problems with the
images and digital readouts from CT scanners.
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.

8. 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.
6 Power Quality for Healthcare Facilities
Incorrect Diagnostic Results
Electrical
disturbances
can cause
microprocessor
-based medical
equipment to
malfunction.
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).

9. 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.
7 Power Quality for Healthcare Facilities
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 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.
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.

10. 8 Power Quality for Healthcare Facilities
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
Equipment
malfunctions
can be avoided
if the level of
power quality
is known and
equipment
selected or
installed to be
immune.

11. 9 Power Quality for Healthcare Facilities
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 a
Substation Near a Healthcare Facility
Switching capacitors in and out of service can create
transients that impact sensitive instrument.
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.

12. 10 Power Quality for Healthcare Facilities
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)
Current(20amps/division)
Downed Power Pole Adjacent to a
Healthcare Facility
This toppled power pole caused a power outage at the
healthcare facility nearby.
Voltage sags
originating
from outside a
facility can be
caused by
downed,
crossed, and
contacted
power lines.

13. 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.
11 Power Quality for Healthcare Facilities
Searching for a Neutral-to-Ground Bond
in the Emergency Generator at a
Healthcare 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 an
Arc Welder
Arc welders can introduce electrical disturbances into the branch circuits on which
medical equipment are operating.

14. 12 Power Quality for Healthcare Facilities
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?

15. 13 Power Quality for Healthcare Facilities
IMPROVING POWER QUALITY
IN THE HEALTHCARE
ENVIRONMENT
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 quality
in the
healthcare
environment
can be
improved
through
enhancing the
level of
awareness
among utilities,
healthcare
facility
designers, and
medical
equipment
manufacturers.

16. 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.
14 Power Quality for Healthcare Facilities
Building strong
relationships
between
healthcare
facilities,
equipment
vendors,
equipment
manufacturers,
and electric
supply
companies
offers many
benefits.

17. 15 Power Quality for Healthcare Facilities
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.

18. 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
16 Power Quality for Healthcare Facilities
General Summary of Available Power-Conditioning
Technologies

19. 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
17 Power Quality for Healthcare Facilities
Good
grounding is
essential for
good power
quality and
safety at any
healthcare
facility.

20. 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,
18 Power Quality for Healthcare Facilities
Regardless of
the earthing
system used,
providing a
solid low-
impedance
ground to
sensitive
equipment will
help minimize
power quality
problems.

21. 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
19 Power Quality for Healthcare Facilities
To avoid
equipment
malfunctions
during
renovation or
new
construction,
healthcare
facility
engineers
should
coordinate with
construction
foremen before
the electrical
system is
modified.

22. 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.
20 Power Quality for Healthcare Facilities
Continued on page 22

23. 21
EffectsofElectromagneticDisturbancesonPowerElectronicsTechnologiesUsedinElectronicMedicalEquipment
Cross-ReferenceofEuropeanStandardsApplicabletoElectromagneticCompatibilityofElectronicMedicalEquipment
PowerQualityforHealthcareFacilities
(Refertotablebelow)

24. 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.
22 Power Quality for Healthcare Facilities
Continued from page 20Healthcare
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.

25. 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.
23 Power Quality for Healthcare Facilities
U.S. and European
Electromagnetic
Compatibility
Standards Applicable
to Healthcare
Facilities and
Electronic Medical
Equipment

26. 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.
24 Power Quality for Healthcare Facilities
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