Power quality issues are electrical conditions that cause equipment to operate poorly, trip unexpectedly, overheat, reset, fail early or behave unpredictably.

In a Canadian facility, poor power quality may show up as:

• Motors running hot
• Drives tripping
• PLCs resetting
• Lights flickering
• Breakers nuisance tripping
• Transformers overheating
• UPS systems switching repeatedly
• Sensitive electronics failing
• Production equipment stopping without a clear cause
• Higher energy costs
• Unexplained downtime

The difficult part is that power quality problems are often intermittent. A quick voltage reading with a multimeter may look normal, even though the problem happened five minutes earlier or only occurs when a large motor starts, a welder runs, a capacitor bank switches or a variable-frequency drive changes load.

That is why power quality troubleshooting usually requires recording voltage, current, frequency, harmonics and events over time. Fluke notes that power quality problems are often grouped into two broad areas: voltage anomalies and harmonic distortion issues, and that analyzers help monitor, compare and connect those problems to equipment operation history.

For Canadian industrial plants, commercial buildings, data centres, utilities, hospitals, mines, food-processing facilities, water-treatment plants and manufacturing sites, power quality testing helps move the conversation from guessing to evidence.

What Is Power Quality?

Power quality describes how closely the electrical supply matches the needs of the connected equipment.

A healthy system generally provides:

• Correct voltage level
• Stable frequency
• Balanced three-phase voltage
• Low harmonic distortion
• Limited transients
• Acceptable power factor
• Minimal flicker
• Reliable grounding and bonding
• Suitable protection from disturbances

Power quality does not mean the voltage is perfect at every moment. Real systems always have some variation. The question is whether the variation is large enough, frequent enough or long enough to disturb equipment.

CSA C235:19, reaffirmed in 2025, establishes steady-state voltage operating ranges at the point of connection for AC power systems in Canada and provides guidance for voltage performance and corrective measures.

This Canadian voltage context matters because a facility should not judge every voltage reading against a generic US assumption. The expected voltage level, allowable range and point of assessment should be understood for the Canadian installation.

Common Power Quality Issues

1. Voltage Sags or Dips

A voltage sag, also called a voltage dip, is a short reduction in voltage.

It may last for only a fraction of a second, but that can still be enough to disrupt sensitive equipment.

Common causes include:

• Large motor starting
• Transformer energization
• Short circuits
• Utility faults
• Welding loads
• Compressor starts
• Elevator starts
• Large HVAC loads
• Faults on nearby feeders

Common symptoms include:

• Lights dimming
• PLC resets
• Contactors dropping out
• Drives tripping
• Production equipment stopping
• Computer lockups
• Control relay issues
• UPS transfers

Fluke describes voltage dips or sags as one of the most common power quality issues and notes that recurring dips should be trended with a power quality analyzer or event recorder.

A sag is not always caused by the utility. It may be caused by an internal load, undersized conductors, poor distribution design, weak connections or equipment starting too close to sensitive loads.

2. Voltage Swells

A voltage swell is a short increase in voltage above the normal level.

Possible causes include:

• Sudden loss of a large load
• Single-line-to-ground faults
• Capacitor bank switching
• Incorrect tap settings
• Utility switching events
• Poor voltage regulation
• Neutral problems in some systems

Common symptoms include:

• Equipment alarms
• Drive trips
• Damaged power supplies
• Overvoltage shutdowns
• UPS transfers
• Lighting changes
• Sensitive electronics failure

Fluke notes that swells occur less often than dips, but they can still cause problems and require monitoring over time to understand their cause.

A single spot reading may miss swells because they can be short and irregular.

3. Interruptions

An interruption is a complete or near-complete loss of supply voltage.

Interruptions may be:

• Momentary
• Temporary
• Sustained

Possible causes include:

• Utility protective-device operation
• Faults on the distribution system
• Failed equipment
• Loose or damaged connections
• Breaker operation
• Transfer-switch operation
• Control-system faults
• Weather-related utility events

Symptoms include:

• Equipment shutdown
• Lost production
• Restart delays
• Data loss
• UPS operation
• Generator start
• Process interruptions
• Safety-system alarms

For troubleshooting, the important questions are:

• How long did the interruption last?
• Did it affect one phase or all phases?
• Did it happen upstream or inside the facility?
• Did protective equipment operate?
• Did the event align with a known load or utility event?
• Did the same event affect neighbouring equipment?

Power quality event logs are useful because they record the time, magnitude and duration of interruptions instead of relying on memory or operator reports.

4. Transients

Transients are fast voltage spikes or impulses.

They can be brief, but they may carry enough energy to damage sensitive equipment or degrade insulation over time.

Common causes include:

• Lightning
• Capacitor switching
• Utility switching
• Contactors opening
• Motor switching
• Welders
• Large inductive loads
• Poor grounding or bonding
• Fault clearing
• Static discharge

Common symptoms include:

• Damaged electronics
• Corrupted data
• Failed power supplies
• Control-system errors
• Communication faults
• Nuisance trips
• Premature equipment failure

Fluke describes transients as fast, high-energy pulses that can degrade equipment, corrupt data or cause complete system failure, especially in IT and process-control systems.

Surge protective devices may help, but they must be selected, installed and maintained correctly. A transient problem may also reveal grounding, bonding or wiring issues that need to be corrected.

5. Harmonics

Harmonics are unwanted voltage or current components at multiples of the fundamental frequency.

In Canada, the normal AC frequency is 60 Hz. Harmonics occur at multiples such as:

• 3rd harmonic: 180 Hz
• 5th harmonic: 300 Hz
• 7th harmonic: 420 Hz
• 11th harmonic: 660 Hz

Harmonics are commonly produced by non-linear loads such as:

• Variable-frequency drives
• UPS systems
• Rectifiers
• LED lighting drivers
• Switch-mode power supplies
• Welders
• Battery chargers
• Computers and servers
• Industrial power electronics

Symptoms may include:

• Transformer heating
• Neutral conductor overheating
• Nuisance breaker trips
• Capacitor bank failure
• Motor heating
• Equipment noise
• Communication interference
• Sensitive electronics malfunction
• Poor power factor
• Higher losses

The JM Test source article notes that high harmonic content can lead to overheating, nuisance tripping and premature failure, and that power quality meters can measure individual harmonic orders and total harmonic distortion.

Fluke also identifies VFDs, UPS systems, LED lighting and computers as non-linear loads that generate harmonics, which can distort waveforms and contribute to overheating, nuisance tripping and reduced equipment life.

6. Total Harmonic Distortion

Total harmonic distortion, or THD, is a summary value that indicates how much harmonic content is present compared with the fundamental waveform.

A high THD value can indicate that the waveform is significantly distorted.

Power quality analyzers can show:

• Voltage THD
• Current THD
• Individual harmonic orders
• Harmonic contribution by phase
• Harmonic trends over time
• Harmonic changes by load condition

IEEE 519 is commonly used as a harmonic-control reference for electrical systems with non-linear loads. The 2022 version provides guidance for harmonic control in electric power systems with nonlinear loads and sets limits for steady-state operating conditions.

For the Canadian article, IEEE 519 should be presented as a technical or project reference where applicable, not as a substitute for Canadian code or utility requirements.

7. Voltage Imbalance

Voltage imbalance occurs when the three phase-to-phase or phase-to-neutral voltages are not equal.

Even a small voltage imbalance can create larger current imbalance in motors.

Common causes include:

• Uneven single-phase loading
• Blown fuses
• Loose connections
• Poor transformer connections
• Unbalanced distribution loads
• Faulty capacitor banks
• Open or high-resistance conductors
• Utility-side imbalance
• Poorly distributed building loads

Symptoms include:

• Motor overheating
• Reduced motor efficiency
• Vibration
• Nuisance trips
• Transformer heating
• Reduced equipment life
• Drive alarms
• Uneven phase currents

The JM Test source article notes that even a few percentage points of imbalance can create excessive heating in motors and transformers, and that power analyzers display phase imbalance in real time.

Voltage imbalance should be checked phase to phase and under representative load conditions. A no-load reading may not reveal the problem.

8. Flicker

Flicker is a visible change in lighting intensity caused by voltage fluctuations.

Common causes include:

• Large motor starts
• Welders
• Arc furnaces
• Compressors
• Crushers
• Elevators
• Rapidly varying loads
• Loose connections
• Utility voltage fluctuations

Symptoms include:

• Visible light flicker
• Occupant complaints
• Eye strain
• Process issues
• Poor working conditions
• Customer complaints in commercial buildings

Flicker can be both a technical and human-comfort problem. A voltage change that does not damage equipment may still be unacceptable if it causes repeated visible lighting changes in a workplace.

9. Poor Power Factor

Power factor indicates how effectively electrical power is being used.

Poor power factor can increase current flow, losses and utility charges where demand or power factor penalties apply.

Common causes include:

• Lightly loaded motors
• Inductive loads
• Welders
• Transformers
• Poorly applied capacitor banks
• Large motor systems
• Harmonic distortion
• Non-linear loads

Symptoms may include:

• Higher utility costs
• Higher current draw
• Transformer loading issues
• Reduced system capacity
• Overheated conductors
• Capacitor bank problems

Fluke describes energy waste and poor power factor as power quality issues that can create utility bill penalties and strain electrical infrastructure.

Corrective action may include load management, capacitor banks, active power factor correction, harmonic filtering or equipment changes, depending on the root cause.

10. Frequency Deviations

Frequency deviation occurs when system frequency moves outside the expected range.

In grid-connected Canadian facilities, significant frequency deviations are less common than voltage issues, but they can still matter for:

• Generators
• Islanded systems
• Microgrids
• UPS systems
• Remote sites
• Industrial power systems
• Mining operations
• Renewable-energy systems

Symptoms may include:

• Generator alarms
• UPS alarms
• Clock timing issues
• Drive faults
• Control-system problems
• Motor speed variation in some equipment

Power quality tools often log frequency deviations along with sags, swells, interruptions and transients. The JM Test source article lists frequency deviations among the events that many power quality tools automatically record.

Power Quality Symptoms by Equipment Type

Motors

Poor power quality can cause:

• Overheating
• Reduced efficiency
• Vibration
• Noise
• Insulation stress
• Bearing issues
• Shortened life
• Nuisance overload trips

Likely issues include voltage imbalance, harmonics, sags and poor power factor.

Variable-Frequency Drives

VFD-related symptoms may include:

• Trips
• DC bus alarms
• Input overvoltage or undervoltage
• Harmonic current distortion
• Motor heating
• Communication faults
• Nuisance shutdowns

VFDs can be both affected by power quality problems and a source of harmonic distortion.

Transformers

Power quality issues can lead to:

• Excessive heating
• Audible noise
• Reduced efficiency
• Neutral heating
• Premature insulation ageing
• Capacity issues

Harmonics and imbalance are common concerns.

PLCs and Control Systems

Control-system symptoms may include:

• Random resets
• Lost data
• Communication faults
• I/O errors
• Relay chatter
• Unexplained machine stops

Short sags, transients or grounding issues may be the cause even when the system looks normal during a manual check.

Lighting

Lighting can show:

• Flicker
• Dimming
• Brightness changes
• Early driver failure
• Nuisance complaints

Lighting symptoms are often the first sign of voltage fluctuation or load-starting problems.

IT and Data Centre Equipment

Symptoms may include:

• UPS transfers
• Server resets
• Network faults
• Power supply failures
• Data corruption
• Cooling-system trips

Data centres are especially sensitive to sags, transients, harmonics, poor grounding and UPS-related disturbances.

How to Detect Power Quality Issues

1. Start With the Symptoms

Before connecting instruments, document what is happening.

Record:

• What equipment is affected
• When the issue occurs
• How often it happens
• Whether it matches a load cycle
• Whether one area or the whole facility is affected
• Whether utility events occurred
• Whether a protective device operated
• Whether lighting flicker was visible
• Whether motors or drives started at the same time

Good symptom notes help decide where to place the analyzer.

2. Review One-Line Diagrams

A one-line diagram helps identify:

• Power sources
• Transformers
• Distribution panels
• Motor control centres
• Major loads
• Sensitive loads
• Generators
• UPS systems
• Capacitor banks
• VFDs
• Grounding paths
• Measurement points

Fluke recommends using up-to-date one-line diagrams before troubleshooting power quality because they identify AC power sources, loads and ratings and serve as the electrical road map for the facility.

Without a one-line, measurements can be taken at the wrong point and lead to the wrong conclusion.

3. Use a Power Quality Analyzer

A power quality analyzer measures and records electrical parameters over time.

It may capture:

• Voltage
• Current
• Frequency
• Sags
• Swells
• Interruptions
• Transients
• Harmonics
• THD
• Flicker
• Power factor
• Unbalance
• Energy consumption
• Event timestamps

The JM Test source article explains that a power quality analyzer measures voltage, current, frequency and harmonic content over time, timestamps disturbances and allows symptoms to be correlated with events such as motor starts, load switching or utility disturbances.

4. Use Power Loggers for Longer Trends

A power logger may be better when the issue appears over days or weeks.

Use logging when:

• The problem is intermittent
• Utility disturbance is suspected
• Production patterns vary by shift
• Energy use needs to be analysed
• Demand peaks need to be studied
• Power factor penalties need review
• Load growth is being evaluated
• A spot test did not capture the issue

Fluke notes that event recorders can record dips, swells, interruptions, transients and frequency deviations over longer durations.

5. Review Waveforms

Waveform review helps identify the shape of the problem.

Common clues include:

• Flat-topped waveforms indicating harmonic distortion
• Notches or spikes indicating switching or transient activity
• Drooping amplitude indicating voltage sags
• Elevated amplitude indicating swells
• Distorted current waveforms indicating non-linear loads

The JM Test source article specifically identifies flat-topped waveforms with harmonic distortion, notches or spikes with switching or transient activity, and drooping or elevated amplitude with sags and swells.

Waveforms help avoid treating all voltage problems as the same issue.

6. Check Event Logs

Event logs help identify:

• Event time
• Event duration
• Event magnitude
• Affected phases
• Load condition
• Event frequency
• Whether the issue is internal or utility-side

JM Test notes that power quality tools commonly log sags, swells, interruptions, transients, frequency deviations and THD, which helps determine whether the root cause is internal or external.

This matters because the corrective action for an internal load-starting sag is very different from the corrective action for a utility-side disturbance.

7. Measure Harmonics and THD

When harmonics are suspected, measure:

• Voltage THD
• Current THD
• Individual harmonic orders
• Phase-by-phase harmonic content
• Harmonics at the point of common coupling
• Harmonic changes as loads switch on and off

Fluke recommends observing total harmonic distortion and using a power quality analyzer to measure harmonics at the point of common coupling when harmonic symptoms appear.

Common harmonic sources should be tested under representative operating conditions.

8. Verify Voltage Balance

For three-phase systems, measure phase-to-phase voltage and current under load.

Check:

• Phase A-B
• Phase B-C
• Phase C-A
• Phase currents
• Neutral current where applicable
• Load distribution
• Transformer and panel connections
• Single-phase load allocation

Voltage imbalance often becomes clearer when the system is operating under normal load rather than during light-load conditions.

Common Root Causes

Power quality problems may come from inside or outside the facility.

Internal Causes

Internal causes include:

• Large motor starts
• VFDs
• Welders
• UPS systems
• LED drivers
• Switch-mode power supplies
• Loose connections
• Poor grounding or bonding
• Overloaded transformers
• Unbalanced panels
• Capacitor switching
• Poorly applied filters
• Failing contactors
• Incorrect tap settings
• Undersized conductors
• Ageing distribution equipment

External Causes

External causes include:

• Utility switching
• Utility faults
• Lightning
• Voltage regulation issues
• Nearby industrial loads
• Distribution feeder disturbances
• Weather-related faults
• Grid events
• Neighbouring customer load changes

The goal of power quality testing is to identify the real source before spending money on the wrong fix.

Corrective Actions for Power Quality Issues

Corrective actions depend on the root cause.

Possible solutions include:

For Voltage Sags

• Stagger large motor starts
• Use soft starters or VFDs
• Correct overloaded circuits
• Improve distribution design
• Add voltage regulation
• Separate sensitive loads
• Review transformer capacity
• Coordinate with the utility where needed

For Swells

• Review capacitor bank operation
• Check tap settings
• Investigate load switching
• Check neutral or grounding issues
• Coordinate with the utility if the event is external

For Transients

• Install or improve surge protective devices
• Review grounding and bonding
• Identify switching sources
• Check capacitor bank switching
• Protect sensitive loads
• Review lightning protection where applicable

For Harmonics

• Identify non-linear loads
• Add harmonic filters
• Use line reactors or isolation transformers where appropriate
• Review VFD installation
• Separate sensitive loads
• Check neutral sizing
• Review IEEE 519 or project harmonic requirements where applicable

For Voltage Imbalance

• Redistribute single-phase loads
• Repair loose connections
• Check fuses and breakers
• Investigate transformer issues
• Review utility supply balance
• Correct failed capacitor stages

For Poor Power Factor

• Apply capacitor banks correctly
• Use active correction where needed
• Correct oversized or lightly loaded motors
• Review harmonic interaction
• Monitor demand and utility billing data

Corrective actions should be verified after installation. A fix is not complete until post-correction measurements confirm improvement.

Canadian Safety and Code Considerations

Power quality measurements are often made on energized electrical equipment.

That means the work may involve shock and arc-flash hazards.

Canadian teams should follow:

• Employer electrical safety procedures
• Lockout and hazardous-energy control where applicable
• Shock and arc-flash risk assessments
• CSA Z462 workplace electrical safety guidance
• Qualified-worker requirements
• Correct PPE
• Properly rated meters, analyzers and leads
• Site-specific safe work procedures

CSA Z462:24 specifies requirements and guidance for electrical safety management systems, safe work procedures, PPE selection and qualified electrical worker criteria for people exposed to hazards associated with energized electrical equipment.

The analyzer’s voltage and category rating must match the measurement location. A tool that is suitable for a control panel may not be suitable for service entrance equipment or high-energy distribution gear.

When to Perform a Power Quality Study

A power quality study may be needed when:

• Equipment trips without a clear cause
• Motors or transformers overheat
• Breakers nuisance trip
• Production equipment resets
• UPS systems transfer frequently
• Lights flicker
• Sensitive electronics fail early
• Energy costs seem abnormal
• Power factor penalties appear on utility bills
• Harmonic distortion is suspected
• New large loads are being added
• VFDs or capacitor banks are being installed
• A facility is expanding
• A data centre or critical system needs validation
• Utility-side disturbance is suspected

A study is most useful when it captures normal operation, peak operation and the conditions under which symptoms occur.

Choosing Power Quality Test Equipment

Digital Multimeter

Useful for quick checks such as:

• Voltage
• Current
• Frequency
• Continuity
• Basic troubleshooting

Limitations:

• May miss short events
• Usually does not capture trends
• May not show harmonics or waveform shape
• May not record event timing

Recording Digital Multimeter

Useful when the problem is intermittent but basic.

It can help capture min/max or trend data, but it is not a full power quality analyzer.

Power Logger

Useful for:

• Load studies
• Energy use
• Demand
• Power factor
• Long-term voltage trends
• Current trends
• Facility expansion planning

Power Quality Analyzer

Useful for:

• Sags
• Swells
• Interruptions
• Transients
• Harmonics
• Flicker
• Unbalance
• Event capture
• Waveform review
• Compliance-style reporting

Fluke states that power quality analyzers are necessary tools for troubleshooting power quality problems and that other tools such as data loggers, thermal imagers, infrared thermometers and recording digital multimeters can also support the work.

Thermal Imager

Useful for finding:

• Overheated connections
• Overloaded conductors
• Transformer heating
• Harmonic-related heating
• Unbalanced load effects
• Failing equipment

Thermal imaging does not replace electrical measurements, but it can help identify where the electrical issue is causing heat.

Practical Power Quality Checklist

Before beginning a power quality investigation, confirm:

• What symptoms are being reported?
• Which equipment is affected?
• When do the symptoms happen?
• Are the symptoms tied to a shift, load, weather event or utility event?
• Are one-line diagrams available?
• Where should measurements be taken?
• What voltage level and system type are involved?
• Is the equipment single-phase or three-phase?
• Is the analyzer rated for the measurement point?
• What duration should be recorded?
• Are harmonics suspected?
• Are transients suspected?
• Are sags or swells suspected?
• Is a utility-side issue possible?
• Are qualified workers available?
• What PPE and safety controls are required?
• How will results be reviewed and documented?

Practical Takeaway

Power quality issues are often the hidden cause behind nuisance trips, equipment resets, overheating, flicker, premature failures and unexplained downtime.

The most common issues include:

• Voltage sags
• Voltage swells
• Interruptions
• Transients
• Harmonics
• Voltage imbalance
• Flicker
• Poor power factor
• Frequency deviations

The right troubleshooting process starts with symptoms, one-line diagrams and safe measurement planning. A power quality analyzer or logger can then record the actual voltage, current, frequency, waveform, harmonic and event data over time.

For Canadian facilities, measurements should be interpreted with Canadian voltage context, site-specific electrical safety procedures, CSA Z462-informed safe work practices and the actual project or utility requirements.

JM Test Systems Canada can support electrical teams with power quality analyzers, power loggers, recording meters, thermal imagers, electrical safety equipment, rentals and calibration support. Confirm Canadian availability, accessories, calibration documentation and support before publishing firm service claims.