THE BASICSOF

POWERQUALITY

IDEAL Test and Measurement

Table of Contents

What is Power Quality? 2

Sources of Poor Power Quality 3

Power Factor 4

Harmonics 8

Disturbances 12

IDEAL Power Clamps 14

IDEAL SureTest Circuit Analyzer 16

IDEAL Power Analyzer 18

Technical Definitions 20

Power Clamp Features & Ordering 22

SureTest Features & Ordering 23

Power Analyzer Features & Ordering 24

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Power Quality:An IntroductionThe Basics of Power Quality is a convenientguide to understanding the essential aspectsof monitoring and troubleshooting powerquality. Its easy-to-read format providesyou with a reference point on how to deal with the three key issues that makeup power quality: power factor, harmonicsand disturbances.

Just like our complete line of power qualitytesters and meters, this guide representsthe IDEAL Test & Measurement commitmentto helping the professional electrician.

IDEAL. The way every job should be.

Technical Support – Toll Free 877-201-9005www.testersandmeters.com

Sources of PoorPower QualityPower Quality problems can be tracked to three origins - supply, internal distribution and internal loads.

Supply This is the initial source ofpower from the utility companysuch as the main transformer of a commercial building. It’s where power coming intothe facility can be monitored.

Internal Distribution80% of all power quality problems occur in a company’sdistribution and grounding systems. Corroded connections,defective conduit, defective electrical devices, improperwiring and improper grounding are just some of theobstacles to be dealt with.

Internal LoadsEverything from variable speed drives and high-techdevices to unsophisticated loads such as heaters andlights contribute to the quality of electrical power in a circuit. Internal loads can cause poor power factor, harmonics and disturbances.

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A facility’s incoming poweris typically monitored at themain transformer, referredto as the supply.

Industrial machines containing variable speed drives can causea variety of costly power quality problems.

What Is Power Quality?The concept of power quality has often beenmisunderstood and oversimplified. But in this day and age of sophisticated electronics, monitoring power quality has become too important to ignore. Thewidespread use of high-tech devices has complicatedevery aspect of electrical power. Not only are thesedevices more sensitive to the effects of power quality,but they can also impact it negatively. Poor powerquality can result in lost productivity, lost and corruptdata, damaged equipment and poor power efficiency.When added up, U.S. companies waste an estimated$26 billion on electrical power-related issues each year.*

“Power Quality” is a broad term used to describe the measurement of electrical power performance. It can be broken down into three key areas. Each will be discussed in the following pages.

*Electrical Contractor Magazine, “Surveying Power QualityOptions,” March 2000.

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THREE KEY ASPECTS OF POWER QUALITY

• Power Factor • Harmonics • Disturbances

When power is “in-phase,” voltage and current travel congruently,meaning they reach maximum height and zero simultaneously. A large motor load can cause current to lag behind voltage. Thislagging effect, or phase shift, can cause a poor power factor.

Power FactorIn-Phase

Voltage

Current

Power FactorOut-of-Phase

Voltage

Current

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Power FactorPower Factor is the ratio of true power to apparent power in a circuit, or in otherwords, a circuit’s level of power efficiency. It is expressed as a ratio by using the equation below.

The most common reason to measure power factor is to determine the amount of power in a commercial orindustrial environment that is supplied but not utilized.When the power factor ratio is 1.00 it means that every watt of power arriving from the utility company is put to use. But unfortunately, motors and electronicequipment apply a load to the circuit which can result inout-of-phase power. (See illustration on next page)

A power factor of less than 0.90 is considered poor. It means that a considerable amount of incoming poweris being used inefficiently. To make matters worse, utilitycompanies apply a penalty charge when power factordrops to low levels. Maintaining a healthy power factoris an important part of maximizing power efficiency.

WVAWatts

Volts x Amps

To determine power factor,divide true power (watts) by apparent power (volt amps). If true power and apparentpower were equal, the resultwould be a power ratio of 1.00.

PF =

PowerFactor =

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Identify the ProblemThe first step in resolving a power factor issue is toidentify the origin and extent of the problem with apower clamp or power analyzer. A healthy power factor is in the mid to upper 0.90s. As mentioned earlier, a poor power factor usually results from a motor causinga phase-shift. Once the power factor is determined andthe motors are identified, correcting the problem is afairly simple process.

Implement a SolutionThe most common means of correcting a low powerfactor is to compensate the circuit with additionalcomponents. Most often, this compensation comes in the form of capacitor banks. While capacitor banksare a permanent solution, it is wise to continuemonitoring the circuit for any new problems.

Large motors make industrial operations especiallysusceptible to a poor power factor.

Troubleshooting Power FactorIn nearly all cases, it is more cost-efficient to take stepstoward improving power factor than it is to live withexcessive utility charges. While the effects of power factor cannot necessarily be eliminated, they can beminimized if properly diagnosed.

A power clamp, such as the IDEAL 61-802 pictured above, is thebest way to monitor a circuit’s power factor. With a single readingdirectly at the transformer, a power clamp can measure truepower, apparent power and power factor.

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HarmonicDistortion

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60Hz Sine WaveWith HarmonicsFundamental

Sine Wave

2nd Harmonic 3rd

Harmonic

Notice that the fundamental frequency requires twice as long asthe second harmonic and three times as long as the third harmonicto complete a single waveform.

Harmonic FactorizationBreaking down the total harmonic distortion into individualharmonics is an analysis called harmonic factorization.Typically, only the odd-numbered harmonics are analyzed.They are created by non-linear loads and have the greatestimpact on an electrical system. The two most importantcategories for commercial and industrial settings are thezero sequence, or triplen harmonics (3rd, 9th, 15th, etc.) andthe negative sequence harmonics (5th, 11th, 17th, etc.) Thetriplen harmonics are most commonly found in commercialsettings and are caused by computers and other electronicoffice equipment. Negative sequence harmonics arecommonly found in industrial environments and are causedby variable speed drives and other electronic equipment.

Total harmonic distortion (THD) is the percentage of distortion to thefundamental frequency. As a general rule, THD should not exceed 5%of voltage or 20% of current.

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HarmonicsWidespread use of electronic equipment intoday’s commercial and industrial environmentshas made harmonics an important but complex power quality issue.

Most simple electric devices like motors and incandescentlighting are linear loads, which means AC impedance isconstant regardless of the applied voltage. In this case, thefundamental AC sine wave, pictured below, is unaffected.

On the other hand, non-linear loads such as personalcomputers and copy machines strip off AC power andconvert it to DC power. This process adds harmonics tothe fundamental frequency.

By definition, a harmonic is a frequency which is aninteger of the fundamental 60Hz wave. For example, the second harmonic of the fundamental frequency is120Hz, the third harmonic is 180Hz and so on.

The addition of harmonics to a system results in distortion to the voltage and current waveforms. Theimpact to the electrical system depends on the totalamount of distortion present and on which harmonic the distortion is located.

60Hz Sine Wave

In the United States, the fundamental frequency of electricity is 60Hz. This illustration shows one cycle of that frequency.

Troubleshooting HarmonicsPreventing harmonics from causing damage to electricalcircuits and expensive equipment can be a difficult task.To effectively troubleshoot the problem, the total harmonicdistortion and harmonic factorization should be analyzed.Knowing the amount and characteristics of the harmonicswill aid in identifying a solution.

In our commercial example, harmonics are not usuallyremoved. Removal of harmonics requires the use of filtersor devices that minimize the effects on the circuit, andthese are not always cost-efficient solutions.

The alternative to removing harmonics is to minimize the effect they have on the system. Oversizing the neutral conductor or derating the existing transformersare possible solutions for a 3-phase, 4-wire systemaffected by triplen harmonics. While derating a motor ispossible, it is more common to use snubbers or filters toreduce the effects of harmonics in an industrial facility.

The IDEAL Power Analyzercan collect data concerningharmonic distortion as well as power quality issues like disturbances.

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Commercial Environments In the 3-phase, 4-wire electrical system commonly foundin commercial buildings, current flows through eachphase conductor and returns in a common neutral con-ductor. In a balanced system, the neutral currents fromeach phase will mathematically cancel each other out. Anyimbalance in phase current will return on the neutral atthe fundamental frequency (60Hz). As this return current is typically small, it is generally not considered a problem.

The characteristics of the triplen harmonics (3rd, 9th,15th, etc.) disrupt this balance. Rather than cancelingeach other out on the neutral, the triplen harmonicsfrom all three phases are mathematically added togetherin the neutral conductor. This can result in a higher thanexpected current which can cause excessive heat in theneutral conductor and transformer.

Industrial EnvironmentsThe electrical loads within an industrial plant can begreatly affected by the negative sequence harmonics(5th, 11th, 17th, etc.). These harmonics counteract theenergy created by the electrical power system. Forexample, in a motor the negative sequence harmonicswill try to force the motor to turn in a reverse direction. The impact to the rotation of the motor depends on the magnitude of the current harmonics. A level of 20% distortion on the fifth harmonic means 20% of theenergy is working against the motor. This has a seriousimpact both to the torque produced by the motor andthe heat given off. This affects both production being runon the machine and the life of the motor.

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TransientsTransients are short-duration, high-amplitude pulsessuperimposed on a normal voltage waveform. They canvary widely from twice the normal voltage to severalthousand volts and last from less than a microsecondup to a few hundredths of a second.

Transients are caused by a rapid release of energystored in an inductive or capacitive source in the electricalsystem, or from an external source such as lightning.

Troubleshooting DisturbancesDisturbances may require a certain degree of monitoringin order to properly diagnose. The nature of disturbancesin industrial settings is often systematic but infrequent.By tracking a circuit over an extended period of timewith the IDEAL Power Analyzer, data can be saved andanalyzed later on a computer. This makes disturbanceseasier to pinpoint.

Unlike harmonics, reoccurring disturbances are oftenfairly easy to eliminate once they’ve been properly identified. For example, devices like surge protectors area simple way to protect against transients.

TransientVoltage

While the duration of transients is unnoticeable to a humanobserver, their effect on power quality is still considerable. A single lightning strike can result in a transient large enough to destroy electronic devices.

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DisturbancesThe term “disturbances” is actually used to describe any kind of fluctuation in power. The most common types of disturbances are sags, swells, overvoltages, undervoltages, transients and outages.

Sags, Undervoltages and OutagesSags are momentary decreases in voltage. This decreaseis typically 80% of the normal voltage with a durationbetween 0.5 seconds and one minute. A decrease involtage lasting longer than a period of one minute iscalled an undervoltage and a complete loss of power iscalled an outage. Sags occur when there is a momentaryloss of available electricity due to the starting of heavyloads such as a motor or heavy machinery.

Swells and Overvoltages Swells are the opposite of sags. They are momentaryincreases involtage up to 120% of normal with a durationbetween 0.5 seconds and one minute. This surge of energymay occur when a motor or heavy machinery is shutdown abruptly. An increase in voltage lasting longerthan a period of one minute is called an overvoltage.

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Sags &Swells

Though they are caused by different factors, sags and swellsoften follow each other as the system attempts to compensate.This further increases their potential to cause damage.

Large, easy-to-read dual display

True RMS

Data hold

2000A AC/DC current capability

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IDEAL 800 SeriesPower Clamps When testing power quality on high-voltagecircuits, a heavy-duty power clamp can help ensureaccuracy and safety. The 800 Series Power Clampsare True RMS clamps capable of measuring 2000AAC and DC currents for commercial and industrialjobs. They are designed to measure true power,apparent power, reactive power and power factor in a single reading, bypassing the need for manual calculations. Another key feature of these clamps is their ability to measure both single-phase andthree-phase circuits. Built to be rugged and versatile,the 800 Series is a necessity for commercial andindustrial power quality jobs.

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Calculates readingsfor both three-phase, three-wireand three-phase,four-wire circuits

Power measurements

An easy-to-read dual displayis a useful feature for viewingmeasurements like: powerfactor and kW, volts andamps, or frequency and volts.

See page 22 for features and ordering information.

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Large, easy-to-read LED display

Easy, one-button operation

Retractable ground prong

Circuit/HarmonicsAnalyzerIn the past, measuring total harmonic distortion (THD) was a task for bulky and expensiveequipment, but the SureTest Circuit Analyzer haschanged that. The SureTest is designed to troubleshootan electrical distribution system, analyzing both commoncircuit and power quality problems. It is the first hand-held circuit analyzer capable of applying a full 15-ampload without causing interruption to equipment on thecircuit. It identifies and locates loose connections, badsplices or receptacles, loose ground connections andhigh-resistance grounds.

The SureTest model ST-1THD is specifically designed forcommercial and industrial environments where electroniclighting and electronic equipment are present. TheSureTest captures True RMS measurements, analyzespower measurements such as watts and power factor,and measures harmonic distortion to the 31st harmonic.

Comfortable, ergonomic design

The SureTest Circuit Analyzer is used for a multitude of power quality measurements including total harmonic distortion (THD).

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See page 23 for features and ordering information.

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Large, easy-to-useLCD display

Lightweight,portable design 1 MB memory

Comes standardwith a full range ofaccessories forcomplete analysis

IDEAL Power Analyzer

There are a number of instrumentsdesigned for in-depth examination of commercial and industrial power quality issues like harmonics and disturbances. What sets the IDEAL Power Analyzer apart from the rest is its versatility andease-of-use. 1 MB of memory enables the saving ofparameters and allows for long periods of testing.Information can then be downloaded to a computer foranalysis. The Power Analyzer contains five base programswhich comprehensively test every power quality issuediscussed in this guide. The PowerVision analysis software creates a variety of tables and graphs to make in-depth analysis of power quality problems easier. It all adds up to the most complete, versatile and easy-to-use power quality tool anywhere.

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The versatility of the IDEALPower Analyzer enables fourtesting programs to runsimultaneously for extendeddurations of time.

Easy-to-usepush buttonoperation

See pages 24-25 for features and ordering information.

Power Factor - The ratio of true power (watts) to the apparentpower (voltamperes). It is an indication of the efficiency of anelectrical system.

Power Quality - A broad term used to describe the measurement of electrical power performance.

Sag - A reduction in AC voltage up to 20% below nominal levellasting for a duration from one half cycle up to a few seconds.

Swell - An increase in AC voltage up to 20% above nominallevel lasting for a duration from one half cycle up to a few seconds.

Transient - A release of positive or negative energy creating adisturbance within a single cycle of the AC waveform.

Total Harmonic Distortion (THD) - The percentage of distortion to the fundamental frequency caused by harmonicswithin the electrical system.

Triplen Harmonics - see zero sequence harmonics.

True Power - The power extended when one ampere of currentflows through a resistance of one ohm. Measured in Watts.

Voltage - A unit of measure of the electrical pressure in anelectrical system. Measured in Volts.

Voltamperes - Applied voltage multiplied by current. This isthe power utilized by a load or electrical system.

Watt - Often referred to as true power. It is the power expended when one ampere of current flows through a resistance of one ohm.

Zero Sequence Harmonics - Also called triplen harmonics,these are concurrent in direction with the fundamental frequency (3rd, 9th, 15th, etc.). They produce an amplitude that is triple any one phase when they combine on the neutralof a 3-phase, 4-wire electrical system.

2120

Technical DefinitionsAmpere - A unit of measure for the rate of current flow. Measured in Amps.

Apparent Power - Applied voltage multiplied bycurrent.This is the power utilized by a load or electrical system.Measured in Voltamperes (VA).

Frequency - The number of cycles per second that a waveform repeats itself. Measured in Hertz (Hz).

Harmonics - A frequency that is an integer (multiple) of the fundamental frequency caused by electronic equipment. Harmonics cause distortion to the voltage and current waveforms.

Harmonic Factorization - Analysis where the total harmonicdistortion is broken down into the individual harmonics.

Linear Loads - A load where the load impedance is constant.The relationship between the voltage and current drawn fromthe circuit are proportional. Examples of linear loads aremotors and incandescent lighting.

Negative Sequence Harmonics - Odd-numbered harmonicswith a phase sequence opposite to the fundamental frequency(5th, 11th, 17th, etc.). They have a reversal effect on motorswithin an industrial facility.

Non-Linear Loads - A load where the load impedance is not constant. The relationship between the voltage and current is unique to the type of load, resulting in harmonics on the circuit. Examples of non-linear loads are computers and variablespeed machines.

Odd-Numbered Harmonics - Odd-numbered integer of thefundamental frequency (60Hz). The 3rd harmonic of the fundamental frequency is 180Hz, the 5th is 300Hz, etc. Odd-numbered harmonics are typically created by non-linear loads.

Outage - The total loss of AC power for greater that oneminute. Outages typically last from 15 minutes to a few hours.

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Description Cat. No.ST-1 Circuit Analyzer 61-150ST-1P+ Circuit Analyzer 61-151ST-1D Circuit Analyzer (120VAC) 61-152ST-1THD Circuit/Harmonics Analyzer 61-156ST-1THDC Circuit/Harmonics Analyzer for use with Amp ClampST-1THDC Circuit/Harmonics Analyzer Kit,61-181 Clamp Adapter IncludedGround Continuity Adapter 61-175Isolated Ground Adapter 61-176Extension Cord 61-177Carrying Case 61-179500 Amp Clamp Adapter 61-181

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IDEAL SureTest®

Circuit Analyzer

Common Features• Identify and locate high resistance connections,

bad splices/receptacles, high resistance grounds• Verify proper wiring and GFCI operation• Test voltage drop under actual 15A load• Test line voltage

61-157

61-158

61-156 (ST-1THD)

• True RMS• Power factor• Harmonics• Event recording• Ground impedance• Load on branch• Dedicated circuits• Isolated grounds• False grounds

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IDEAL 800 SeriesPower Clamps

Common Features• 2000A AC/DC current capability• True RMS• Kilowatts• Data hold• Auto ranging• DC current zero function• Oveload protection• Lifetime limited warranty

61-800

• 2000AAC current capability• 2500ADC current capability• Temperature• Analog output (current ranges)• Relative mode• Min/max• Audible continuity

61-802

• 2000A AC/DC current capability

• kVA• kVAR• Power factor• Frequency• Dual display• Memory recall

Description Cat. No.800 Series Power Clamp 61-800800 Series Power Clamp 61-802

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Description Cat. No.800 Series Power Analyzer 61-805Disturbances Program 61-474Check-Meter Program 61-475Fast-Check Program 61-4762000/200AAC Clamp Adapter 61-453500AAC Clamp Adapter 61-455

Standard Equipment

1000AACClamp Adapters

Test Leads withAlligator Clips

Power Analyzer

RS232 Interface/Power Supply

IDEAL Power Analyzer

Features• Single- or three-phase measurements• True RMS• Data logging (1MB memory)• Auto ranging• Min/max/avg• Energy and Harmonics Program• PowerVision™ Software• Optional programs:

DisturbancesCheck-MeterFast-Check

• Lightweight, portable design• Easy-to-use push-button

operation• Password protected

on-screen setup• 160 x 160 pixel LCD • RS-232 interface• Customized data

collection• Real-time clock• Programmable trigger-

points and start/stop time• Auto display shutoff• Rechargeable Ni-Cad battery• Intelligent battery charging system

Power Measurements• Kilowatts (kW)• Voltamperes (VA)• Inductive reactive power (kvarL)• Capacitive reactive power (kvarC)• Power factor (PF)• Frequency (Hz)• Kilowatt hours (kWh)• Reactive power per hour (kvarhL, kvarhC)

Harmonics Measurements• Total harmonic distortion (%THD)• Harmonic factorization to 51st harmonic

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61-805

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Test & Measurement

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