Power Quality, Reliability and Management

What is a Power Quality Problem?

“Any occurrence manifested in voltage, current, or frequency deviations that results in failure or mis-operation of end-use equipment.”

Dictionary

What does that mean?

It’s dependant on your susceptibility.

Given the quality of supply do I have

to worry about problems with my equipment or systems?

Typical Financial Loss Per Event

Industry Typical Loss

Financial $6,000,000/event

Semi-conductor mfg. $3,800,000/event

Computer operations $750,000/event

Telecommunications $30,000/minute

Data processing $10,000/minute

Steel/heavy mfg. $300,000/event

Plastics $10,000-15,000/event

Source: The Cost of Power Quality, Copper Development Association, March, 2001

Sources Of Power Problems

Referenced at the utility PCC (point of common coupling)

• Utility• lightning, PF correction caps, faults, switching • impact from other customers

• Internal to the facility• individual load characteristics, motors, ASDs• computers, microprocessors• wiring• changing loads

Typically, 70% of all PQ events are generated within the facility

•Transients•RMS Variations

•Short Duration Variations•Long Duration Variations•Sustained

•Waveform Distortion•DC Offset•Harmonics•Interharmonics•Notching

•Voltage Fluctuations•Power Frequency Variations

Types Of Power Quality Disturbances (per IEEE 1159)

Types of Power Quality Problems

What is a Transient?

Momentary (& undesirable) high frequency sub-cycle “event”

• Usually measured in microseconds• May also be called a Spike, Surge or Impulse• Characteristics of a Transient:

• Rise time (dv/dt)• Ring frequency• Point-on-wave• Multiple zero crossings• Magnitude

Transients

-200

-100

0

100

200

UnipolarPositive

Negative

NotchingOscillatory

Multiple Zero Crossings

Bipolar

A transient power quality event has occurred on DataNode H09_5530. The event occurred at 10-16-2001 05:03:36 on phase A. Characteristics were Mag = 478.V (1.22pu), Max Deviation (Peak-to-Peak) = 271.V (0.69pu), Dur = 0.006 s (0.35 cyc.), Frequency = 1,568. Hz, Category = 3 Upstream Capacitor Switching

Possible Causes

• PF cap energization

• Lightning

• Loose connection

• Load or source switching

• RF burst

Possible Effects

• Data corruption

• Equipment damage

• Data transmission errors

• Intermittent equipment operation

• Reduced equipment life

• Irreproducible problems

Transients

What is an RMS Variation?(longer duration events)

A change in the RMS voltage. Typically 16 ms (1 cycle) or longer

• Reduction in voltage: Sag or Interruption

• Increase in voltage: Swell

RMS Voltage Variations

0

Sag Swell Interruption

100

-100

Motor Starting Timeplot Chart

09/13/96 09:49:00.50 - 09/13/96 09:49:04.00

Min Max Median CHA Vrms 206.11 222.25 219.19 CHA Irms 1.40 847.71 207.16

CHA Vrms CHA Irms 09:49:00.5 09:49:01.0 09:49:01.5 09:49:02.0 09:49:02.5 09:49:03.0 09:49:03.5 09:49:04.0

Volts

205.0

207.5

210.0

212.5

215.0

217.5

220.0

222.5 Amps

0

100

200

300

400

500

600

700

800

900

IEEE1159 Characterizations(RMS Variations)

• Instantaneous (0.5 - 30 cycles)• Sag (0.1 - 0.9 pu)• Swell (1.1 - 1.8 pu)

• Momentary (30 cycles - 3 sec)• Interruption (< 0.1 pu, 0.5 cycles - 3s)• Sag• Swell

• Temporary (3 sec - 1 minute)• Long Duration (beyond 1 minute)

What is Directivity?

Where the problem originated referenced to the point being monitored (where the instrument is)

• Typically referred to as “Upstream” or “Downstream”

• Upstream• Source side. Originated from the source of supply (can be utility)

• Downstream• Load side. Originated from a load

• Helps you identify where the problem is and what actions to take.

Case Study – Major Financial Institution(Benefits of Learning Directivity)

• Problem – Utility Sag

• Damaged elevator controls

• No UPS alarms (2 static, 1 rotary)

• No reported problems with critical systems

02/19/2002 00:29:29.26

PM Module Input

Temporary Sag

Rms Voltage AB

Mag = 366.V (0.76pu), Dur = 3.300 s, Category = 2, Upstream Sag

02/19/2002 00:29:29.26

SYSA Input Temporary Sag

Rms Voltage AB

Mag = 353.V (0.73pu), Dur = 3.300 s, Category = 2, Upstream Sag

02/19/2002 00:29:29.26

SYSB Input Temporary Sag

Rms Voltage AB

Mag = 372.V (0.78pu), Dur = 3.300 s, Category = 2, Upstream Sag

Utility Sag

Utility Supply RMS Trend

Utility Supply Waveforms

Corresponding UPS Swell

Utility Supply

UPS Output

UPS Swell

Conclusion

• Utility sags damaged elevator controls • Corresponding UPS Swell coincident with utility

return to normal• Cause of swell being investigated by manufacturer• Possible effects of swells”

• Damaged power supplies and other devices

Without monitoring, the customer would be unaware of the UPS problem. The next time, the damage could be worse

PQ Rule #1

For a source generated Sag, the current usually decreases or goes to zero

August 14, 2003 Blackout:Long Duration Interruption

PQ Rule #2 For a load generated Sag, the current

usually increases significantly.Waveforms

Pre/Post-trigger at 09/13/1996 09:49:00.947File: C:\DranView\K_DEMO pq+ with inrush data.dnv

CHA Volts CHA Amps

09:49:00.90 09:49:00.95 09:49:01.00 09:49:01.04 09:49:01.09

Volts

-400

-300

-200

-100

0

100

200

300

400

Amps

-2000

-1500

-1000

-500

0

500

1000

1500

Possible Causes

• Sudden change in load current

• Fault on feeder

• Fault on parallel feeder

• Motor start

• Undersized distribution system

Possible Effects

• Process interruption

• Data loss

• Data transmission errors

• PLC or computer misoperation

• Damaged product

• Motor failure

RMS Voltage VariationsCauses and Effects

Common RMS Voltage Variations Visualization methods using power monitoring

instrumentation•Sampled data

•Recorded Waveforms•Magnitude vs. Time

•Timelines•Magnitude vs. Event Duration

•CBEMA (IEEE 446)•ITIC•3-D Mag-Dur

•Equipment susceptibility curves•Custom curves that represent that specific device

IEEE 446 - 1995 Limits (CBEMA)

Information Technology Industry Council(ITIC) Curve

Another Perspective – 3D Mag-Dur Histogram

(Laser Printer Heating Cycle)

Case Study

Voltage Timeline

Vl-n= 120 --> 108 45 seconds

SAG when heater turns on

V l-n

I load

Overlay Voltage & Current - Heater turning on

An integer multiple of the fundamental frequency

Fundamental (1st harmonic) = 60hz

2nd = 120hz

3rd = 180hz

4th = 240hz

5th = 300hz

…

What is a harmonic?

Linear Voltage / CurrentNo Harmonic Content

voltage

current

Non-Linear Voltage / CurrentHarmonic Content

voltage

current

When should I be concerned about Harmonics?

Harmonics are typically considered a problem when they are always present…Steady state distortion that is continuously occurring.

Although any waveform can have harmonics we are typically concerned with the cumulative effects of continual harmonic distortion on the power system

Waveforms

Waveform event at 03/22/1999 14:34:42.480File: C:\DranView\Q_DEMO Cycle by cycle harmonics.dnv

CHA Amps

14:34:42.20 14:34:42.21 14:34:42.22 14:34:42.23 14:34:42.24 14:34:42.25 14:34:42.26 14:34:42.27

Amps

-200

-150

-100

-50

0

50

100

150

200

How are harmonics measured?

Individual Harmonics 2, 3, 4, 5, 6…50+ Fourier Transform, FFT, DFT

Total Harmonic Distortion (THD) Ratio, expressed as % of sum of all harmonics to:

Fundamental (THD) Total RMS Load Current (I TDD only)

Interharmonics Content between integer harmonics Required for new IEC standards (IEC 61000-4-30)

Harmonic SpectrumEvent waveform/detail

Total RMS: 24882.56 VoltsDC Level : 880.46 Volts

Fundamental(H1) RMS: 24725.89 VoltsTotal Harmonic Distortion (H02-H50): 10.60 % of FNDEven contribution (H02-H50): 7.97 % of FNDOdd contribution (H03-H49): 6.99 % of FND

CHA Volts

Thd H05 H10 H15 H20 H25 H30

% of FND

0.0

2.5

5.0

7.5

10.0

12.5

PQ Rule #3 Even harmonics typically do not appear in a properly

operating power system.Symmetry

Positive & Negative halves the same: Only odd harmonics. If they are different: Even & Odd harmonics

What are Triplen Harmonics?

Harmonics who’s order is a multiple of 3 3, 6, 9, …

Why should I be concerned about Triplen Harmonics?

• Triplen Harmonics add in the neutral.

Additive Triplen Harmonics

Possible Effects

• Overload of neutral conductors

• Overload of power sources

• Low power factor

• Reduced ride-through

Possible Causes

• Rectified inputs of power supplies

• Non-symmetrical current

• Intermittent electrical noise from loose connections

Harmonics (sustained)

(Laser Printer Heating Cycle)

Continued…

Case Study

Current Waveform - heater on

HARMONIC DISTORTION - heater on

Ithd = 5%

Harmonics V l-n

Harmonics I load

Vthd = 2.8%

Current With Printer Idle

Harmonic Distortion - Idle

Ithd = 140%

Harmonics V l-n

Harmonics I load

Vthd = 3.1%

Review of What We Just Saw

Nearly Sinusoidal Current– Low Voltage Harmonic Distortion (4%)

Voltage and Current In-phase– Power Factor Near One

Flat-topping of Voltage when Idle Corresponds with Current Pulse

Other PQ Concerns(defined in IEEE 1159)

• Frequency• Frequency different from the ideal 50/60hz• Frequency not synchronized with the grid

• Unbalance• Deviation from the average 3 phase voltage (IEEE)

• Voltage Fluctuations (Flicker)• Small changes to the magnitude of the voltage• Visual perception. Effects on lights

How Many Can You Find?

Monitoring Approaches and Tools

Handheld/Portable

(Reactive) Vs. Permanently

Installed (Proactive)

Reactive Monitoring

After the fact - Reactive Forensic approach Problem Solving, Hopefully you’ll find it! Portable instrumentation typically used

Proactive Monitoring

Permanently installed monitoring systems

Anticipate the future, On-Line when trouble occurs

Monitor system dynamics

Preventive Maintenance, Trending, identify equipment deterioration

Power Quality and Flow

Monitoring Solutions FromDranetz-BMI

Portable/HandheldPermanently Installed

Get the right tool for the job!

CapabilitiesCapabilities

Handheld Family

PowerXplorer PX5PowerXplorer PX5

PowerGuide 4400PowerGuide 4400

New Products!

• 8 Channels• 4 Differential Voltage, AC/DC • 4 Current, AC/DC

• 256 Samples Per Cycle• 50/60HZ, 16/20HZ (railroad)• Harmonics to the 63rd

• Flicker• Low Freq Transients (up to 5KHZ)• Medium Freq Transients (5-

10KHZ)• Ethernet, USB, serial commun.

PowerGuide 4400

Color touch screen

Unique annunciator

PowerGuide 4400• Applications

• Inrush

• Fault Recorder

• Motor Testing

• Power Studies

• System Commissioning/compatibility

• Telecommunications

• General Troubleshooting

• Compliance

PowerXplorer PX-5• Advanced Power Quality Analysis• Includes all PowerGuide 4400 Features• High Speed (658/8800 like) Digitized

Transients• Advanced Power Analysis

• IEEE1459 • PX5-400 – 400HZ Option

PowerXplorer PX-5• Applications

• All PowerGuide 4400 Plus…• Medical Diagnostic Equipment• Advanced PQ Surveys• 400HZ Aircraft, Naval, Military • Utility Surveys• Any 658 or 8800 application

Data to ...

... Information to ...

... Answers

Advanced Visualization

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Questions?Questions?

Dranetz-BMI 1000 New Durham Rd.Edison, NJ 088181800-372-6832www.dranetz-bmi.com