PQ03
Using Test Equipment to Detect and Measure
Power Quality Issues
Power Quality
Related Presentations:
PQ01 – Harmonic Solutions for VFD’s
PQ02 - Power Quality and Monitoring with
iSense/iGrid/DySC & Surge/Sag/Transient Protection
2
Power Quality
•
•
•
•
Effects of bad power quality are not immediately obvious
Bad power quality can come from anywhere
Consequences could be severe (production loss)
Power quality problems are a root cause:
Malfunction
Shutdown
Excessive energy cost
Decreased lifetime of equipment
3
Measurement Safety
1. Safety
2. Power Quality Measurement
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PQ Issues
Measurement of Harmonics
The effect of distortion on simple test tools
Power Factor
Transients
Unbalance
Basic Measurements
4
Measurement Safety
•
Example:
DMM fitted with low energy fuse used
incorrectly on a high energy circuit
5
EN61010 LV Directive
• EN61010 is based on overvoltage transients, as
well as steady-state voltages.
• All instruments have to be tested by an
independent test house
• Each instrument must be marked with an
Overvoltage Category ( CAT I, II, III, IV )
• As well as a voltage level (300, 600, 1000 Volts)
6
Category Rating
 CAT IV “Origin of installation” Utility level and any outside
cable run, Electricity meters and primary connection
 CAT III Distribution wiring, including “mains” bus, feeders
and branch circuits, permanently installed loads.
 CAT II Receptacle outlet circuit, plug-in loads.
 CAT I Protected electronic circuits.
7
Voltage Rating per Category
Isolation and Safety Standards for Electronic Instruments,
Test Impulse Rating, Transient Voltage Tolerated
Nominal Voltage
(VAC)
CAT I
CAT II
CAT III
CAT IV
300
1500
2500
4000
6000
600
2500
4000
6000
8000
1000
4000
6000
8000
12,000
Source Impedance
30 Ω
12 Ω
2Ω
2Ω
8
IEC 1010 / EN61010
•
Regulations are not an option
•
Second edition EN61010 ( 2004 ) requires
independent testing
•
Remember Test leads are CAT rated ...
9
PQ Measurement
1. Safety
2. Power Quality Measurement
 PQ Issues
 Measurement of Harmonics
 The effect of distortion on simple test
tools
 Power Factor
 Transients
 Basic Measurements
10
Power Quality Culprits
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•
•
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Lightning
Non-Linear Loads – VFD’s, SMPS
Capacitor switching transients
Inrush Currents from Motors
Sags, Surges
Undersized Neutrals
Electrical Noise
Gen-Sets not sized for Harmonics
11
Medium
EPRI (Electrical Power
Research Institute)
Sag (0.5 cycles – 60s)
Unbalance (Fluctuating)
• Monitored 300 sites for 2+ years.
Undervoltage (>1 minute)
• 1993 study: 92% of all events
were voltage sags under 2
seconds
• 1995 study: 96% of all events
were voltage sags less than 2
seconds
Overvoltage (>1 minute)
Low
Noise (Constant)
Very Low
Frequency of Occurrence
High
The PQ Story
Transient (<50 ns – 5 ms)
Harmonics (Constant)
Swell (0.5 cycles – 60s)
Notching (Constant)
$
Grid
Related
Interruption (0.5 cycles – >1 hr)
$$
Facility
Related
$$$
$$$$
12
Harmonics Are …
Time Domain Analysis
Harmonics are …...
Deviations from the Ideal
Fundamental AC line voltage
and current waveforms
Non-linear loads
contain …..
Amplitude
AC
Drive
Input
Current
Input Current
Fundamental Current
time
Frequency Domain Analysis
Current Harmonics which
cause Voltage Harmonic
problems for other users
1 pu Current magnitude (RMS)
300 420
60 Hz
Frequency [Hz]
Frequency [h] Fundamental 5th 7th
Harmonics
660
780
780 780
11th
13th
17th 19th
13
Linear vs Non-Linear
Linear Load, sinusoidal waveform,
no harmonics
Non-linear Load, non-sinusoidal
waveform, harmonics present
14
Non-Linear Loads
Non-linear Commercial loads
generally come from:
Non-linear Industrial
loads generally come
from:
• Computers and CRT’s
• Welders
• Electronic Ballasts
• Arc furnaces
• And other single phase office
equipment
• UPS and DC power supplies
• AC & DC Drives
15
Adjustable Speed Drive
Bus = Fixed Vdc
Input =
Fixed V
Fixed freq
AC Drive
AC Line Input
AC Motor Output
Converter
AC to DC
480Vac
60Hz
Output =
Var Voltage
Var frequency
DC
Bus
Filter
~650Vdc
Inverter
DC to AC
0-460Vac
0-60Hz
16
Harmonic Measurement –
VFD Load w/ Line Reactor
Volt, Amp Measurement of Phase A
Harmonic Measurement of Current
Waveform
Harmonic Measurement –
VFD w/ Harmonic Filter
Volt, Amp Measurement of Phase A
Harmonic Measurement of Current
Effects of Harmonics
• Current Harmonics create Voltage Distortion
• One of the major effects is to increase the current in a system
• Component Overheating. Motors, Generators, Transformers,
wires will experience additional losses resulting in additional
heat.
• Power Factor Capacitor issues, resonance, additional loading.
• Voltage Flat Topping
• Increased Utility current requirement.
Harmonics Troubleshooting
For troubleshooting:
• Check the harmonics present
• Check for the levels of the harmonics
• Look for recognizable patterns
Distortion Effect
Effect of distortion on test tools
Both Clamp Meter’s are calibrated and functioning
correctly
59.2 A
40.5 A
True RMS Measurement
True RMS / Harmonics
A True RMS meter calculates the effective
heating value of the distorted waveform.
This will include all harmonics.
“RMS” stands for root-mean-square.
Crest Factor
Crest Factor = Peak Value / RMS Value
For a Sinewave, Crest Factor = 1.414
Peak
RMS
Peak value = 2.9 X RMS Value.
Crest Factor = 2.9
RMS vs Average Sensing
• True-RMS versus Average Sensing
Crest Factor = Peak Value / RMS Value
Sinewave = 1.414
Square wave = 1
More on Crest Factor
C.F. = 1.43
C.F. = 2.39
C.F. = 4.68
• Professional Multimeters usually
rated at CF <3
• High Quality units rated at CF of 6
• Power Quality Analyzer CF >11
Two Power Factors
Power Factor Measurement

Screen Shots from a Fluke 43 Single Phase and a Fluke 434 Three Phase analyzer
Power Factor, no Harmonics
• System with no Harmonic content
Reactive power (VAr), Q
Apparent power (VA), S
True Power (W), P
Cos φ (DPF) : True power/Apparent Power (fundamental)
DPF = Displacement Power Factor
What about the Power Factor?
What is the Power Factor
of a Non-Linear load?
REACTIVE
Current
S
y-axis
P2  Q2  D2
Iharm
PF = Watts/VA
or phase angle between
voltage and current
D
Ireact
Q
Itotal
S
Ifund
S1
Ireal
P
z-axis
HARMONIC
Current
x-axis
REAL
Current
(in phase with
line-to-neutral
voltage, VLN)
Linear Load Power Factor
Non-Linear Load Power Factor
No Current Distortion
Includes the Effect of Current Distortion
Power Factor with Harmonics
Total Power Factor = 𝑷𝑭 = 𝑷/𝑺, (includes Harmonics)
Cos φ (DPF) = 𝑷𝑭𝟏 = 𝑷/𝑺𝟏 = cos (angle between 𝑷 and 𝐒1 )
DPF = Displacement Power Factor (fundamental)
Distortion Power Factor = 𝑷𝑭𝑫 = 𝑺𝟏 /𝑺
Power Factor Measurement
Two Power Factors !

Screen Shots from a Fluke 43 Single Phase and a Fluke 434 Three Phase analyser
What are Transients?
• High energy, short term deviations or changes
from desired voltage level
• Unwanted electrical energy in AC power lines or
communication lines (a potential seeking a
pathway to ground)
• High voltages spikes
31
How are Transients Generated?
Any switching that creates a spark
From outside the facility
20%
Lightning strike
Utility grid switching
Within the facility
80%
Motors
Large starters
Power factor correction capacitor banks
Air circuit breakers
Any inductive load as it switches on and off
80% Transients are created from inside the facility
32
PFC Capacitor Switching - LV
Power Factor Correction Capacitor Switching Transient
Peak Value approx. 1100 V.
“Noisy” Voltage Waveform
PQ Measurements & Equipment
Measurements
1. Volts, Amps &
Frequency
2. Power
3. Harmonics
4. Transients
5. Sags & Swells
6. Unbalance
7. Flicker
8. Inrush
9. Temperature
1) Volts, Amps & Frequency
Using a Power Quality
Analyzer
View all of the main
parameters at point of
connection
Graphical as well as
numeric display can help
highlight potential
problems
Scope
Vector
Trend
2) Power & PF Measurement
• Typical power
measurement information
• Shows the sides of the
triangle
3) Harmonic Measurement
4) Transient Measurement
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•
•
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Cause….. interference
Difficult to capture
Modern power quality analyzers purpose built for the job
Envelope trigger
Accurate real time stamping is essential
+X%
240V
- X%
5) Sags & Swells
• Recording of upstream and downstream sags & swells can
indicate loads causing problems
Upstream Sag
Downstream Sag
6) Unbalance
•
The phase diagram gives a
quick indication of phase
relationships and balance
•
In this example voltage
unbalance is very small, but
current unbalance is nearly
19%.
7) Flicker Measurements
than
1 meansthan
that most
peoplethat
will
• Agreater
reading
greater
1 means
perceive
flickerwill
in anperceive
incandescent
most
people
flicker in an
incandescent bulb
• Measurement
– Pst (1 min): Short-term flicker over 1
minute
– Pst: Short-term flicker over 10
minutes
– Plt: Long-term flicker over 2 hours
8) Inrush
• Inrush Current Measurement
– Momentary peak of current
during switch on.
– Current clamps can capture
peak reading
– Analyzers can give time
measurement
Screen Shot of a PQA showing start-up current
generated by a cooling system
Three Phase Inrush Measurement
Temperature
• Many power quality problems initially result in an
increase in temperature of components,
connectors, cables and machinery
• Infra red non contact measurement is the ideal
way to locate this type of problem
Fluke Equipment on Show Floor
To view Fluke Test Equipment visit Booth 303
Power Quality
Related Presentations:
PQ01 – Harmonic Solutions for VFD’s
PQ02 - Power Quality and Monitoring with
iSense/iGrid/DySC & Surge/Sag/Transient Protection
Fluke Meters Booth 604
Rockwell Power Quality Solutions area SA1
46
Questions?
For questions or additional information please contact:
Mark Skoyen
Werner Electric
715-855-0584
mskoyen@wernerelec.com