POWER QUALITY
Dr. Henry Wong
Chief Scientist
Anacle Systems Pte Ltd
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Challenge, Need…
 Determining the sources of poor power quality can prove to be a complex
task. There are hundreds of possible factors. Some disturbances may
originate within the electricity supply network while others may be located
within the users' systems. In addition, many of the sources of power quality
disturbances are interactive, making it difficult to accurately trace them and
to diagnose the root cause of the problem.
 Power quality also involves a large number of stakeholders, from electrical
utilities, electrical equipment manufacturers and suppliers, regulators,
consultants, educational institutions, right to the multitude of electricity users.
To properly resolve power quality issues, it is important that the stakeholders
not only have a common understanding of those issues, but also work in
coordinated and cooperative ways to find solutions.
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Recent Development And R&D
 The Power Quality interest group is currently financing several key projects:
• Power Quality impact assessment of distributed wind generation
• Techniques for locating voltage sag disturbances
• Utility incentives and penalties for power quality under performance based
Government regulation
• Assessing power quality disturbances using power quality monitoring
features of distribution network equipment.
 How to manage the huge volumes of data, often in different formats, that will
have to be processed, archived and displayed in order to provide useful
information to the end users.
 How to include recommended monitoring equipment configuration suitable for
recording and processing power quality information, including planning
and operating requirements, and the methods for assessing and displaying
the network power quality performance.
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What is Power Quality ?

Power quality is about deviations of voltage and/or current from
the ideal, but whether or not the deviation is important depends
on the purpose of the installation and the design of the
equipment.
Besides power interruptions, power quality issues encompass a
wide range of phenomena including harmonics, voltage
fluctuations, voltage dips, power frequency variations and voltage
imbalance. [Ref – SP Powergrid Ltd]

The concept of powering and grounding electronic equipment in a
manner that is suitable to the operation of that equipment and
compatible with the premise wiring system and other connected
equipment [Ref - IEEE Std 1159-2009, IEEE Recommended Practice for Monitoring Electric
Power Quality]
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What is Power Quality ?
 Electrical power is perfect for end users if voltage and current are
correctly balanced and describe a pure sinusoidal wave form. This
can be distorted by disturbances such as interruptions, dips or
surges, harmonic pollution, and interference.
Power quality can be degraded by any of these phenomena.. [Ref –
Leonardo Energy Power Quality]
 To describe the measurement of electrical power performance.
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General Info
 Poor Power Quality can result in lost productivity, lost and
corrupt data, damaged equipment and early failure of
equipment
 In U.S. - Power quality issues represent a large annual cost
to society, estimated to be in the tens of billions of dollars
[Ref – U.S. DOE – 2007]
 Power quality problems cost industry and commerce in the
EU about 10 billion per annum while expenditure on
preventative measures is less than 5 % of this. [Ref - European
Copper Institute – 2001]

2007 European Power Quality Survey shows that poor Power
Quality is seriously affecting business results in the industrial and
service sectors. It amounts to a total loss of €150 billion annually in
the EU-25. [Leonardo Energy Power Quality – 2007]
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European Power Quality Survey
[Ref - Leonardo Energy 2008]
 The following average costs by type of poor Power Quality event
were calculated from the survey results:
Surge or transient:
Long interruption:
Short interruption, service sectors:
Short interruption, industry:
Voltage dip:
Industry
Semiconductor production
Financial trading
Computer centre
Telecommunications
Steel works
Glass industry
€120,000 - 180,000
€ 90,000
€ 18,000 - 36,000
€ 7,000 - 14,000
€ 2,000 - 4,000
Typical financial loss per event
€ 3 800 000
€ 6 000 000 per hour
€ 750 000
€ 30 000 per minute
€ 350 000
€ 250 000
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Power Quality Culprits:
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Lightning
Utility Automatic Breaker Reclosure
Utility Capacitor Switching
Commercial High Rises w/o enough Distribution Transformers
Gen-sets not sized for Harmonic Loads
Applying PF Correction Capacitors w/o considering the effects of
Harmonics
Inrush Currents from High Torque Motor Loads Started Across-the-Line
Undersized Neutrals at the Panelboard
Running Power and Signal Cables Together.
Loose Conduit Connections and lack of Green Wire Grounding
Conductors
Shared Neutrals on Branch Circuits
Laser Printers and Copiers Sharing Branch Circuits with Sensitive Loads
Miswired Receptacles
Data Cables Connected to Different Ground References at Each End
[Ref - Engineering Exchange]
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Power Quality:
In More Broad Interpretations  Power Quality can also include load profiling.
 Power Quality can provide tools to measure
everything from voltage quality to power
factor and energy consumption and also provide
a
way to analyse the benefits of alternative
energy options like solar and wind
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Key Aspect of Power Quality
 Power Factor √
 Harmonic √
Main Focus Today
 Disturbances √
 Distortion
 Unbalance
 Frequency
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Sources of Poor Power Quality:

Internal Distribution

80% of all power quality problems occur in a company’s distribution
and grounding/bonding systems. Corroded connections, defective
conduit, defective electrical devices, improper wiring, overloading
circuits and improper bonding are just some of the elements
involved.

Internal Loads

Everything from variable speed drives, microprocessor based
devices, and loads such as lighting and battery chargers contribute
to the resulting quality of electrical power in a circuit. Internal loads
can cause poor power factor, harmonics and power quality events
such as sags, swells, and transients.
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Power Quality –
Power Factor I
 The most common reason to measure power factor is to
determine the amount of Energy (Volt-Amperes) in a commercial
or industrial environment that is supplied but not converted to
useful work environment that is supplied but not converted to
useful work.
 Maintaining a healthy power factor is an important part of
controlling your energy costs.
 Poor power factor usually results from motors, lighting, or
microprocessor loads
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Power Quality –
Power Factor II
 Most common means of correcting a low power factor is to compensate the
circuit with capacitor banks to correct lagging inductive loads like
motors.
It is wise to continue Proactively monitoring the circuit for any new problems as
loads may in fact change over time.
Cannot just randomly add capacitors.
If a motor has a drive installed, the drive itself may be contributing to the poor
power factor, but it is not because of lagging displacement. The drive may be so
distorted that the return current waveform is causing poor power factor. This is
only corrected by use of a reactor, which can smooth out the current waveform
and lower distortion and improve power factor.
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Power Quality –
Harmonic Distortions I
 Widespread use of electronic equipment in today’s commercial and industrial
environments make harmonic distortion an important but complicated power
quality issue.
 Common problem areas caused by harmonic currents
 Overloading of neutrals
 Overheating of transformers
 Nuisance tripping of circuit breakers
 Over-stressing power factor correction capacitor
 Skin effect
 Problems caused by harmonic voltage
 Voltage Distortion
 Zero-crossing noise
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Power Quality –
Harmonic Distortions II
 Harmonic distortion may not necessarily need to be mitigated or
removed. Reactors can smooth out a lot of the current
distortion on
large motor drive loads, and filters and traps can
further reduce the
distortion on the voltage waveforms.
Depending on the sensitivity of
the devices powered and the general
stiffness of the voltage,
mitigation is not always necessary or costefficient. You cannot make a decision without measuring over
time.
 If heat is the only problem, then over-sizing the neutral conductor or
de-rating the existing transformers are possible solutions for a
3phase, 4-wire system affected by triplen harmonics. Zigzag
transformers also can be used to handle distorted currents..
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Power Quality –
Disturbances
“Disturbances” is used to describe any kind of fluctuation in power. The most
common types of disturbances are sags, swells, over-voltages, under-voltages,
transients and interruptions.
 Sags and Swells are the most common types of power quality disturbances,
resulting in downtime losses totalling millions of dollars each year
Sags (dips) are a decrease to between 10% and 90% of the normal voltage.
Swells are an increase to between 110% and !80% of normal voltage.
 Both can cause misoperation of equipment, can last for a duration of 0.5 cycles
to 1 min
 Sag causes equipment to drop off line
 Swell can damage insultion overtime
 Changing transformer tap settings, soft start on large loads and isolating
equipment are just a few solution for Sags and Swells
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Troubleshooting Power Quality Events
 Proactive Energy Management
 Recording over time is the only way to successfully
find a problem and diagnose it. The nature of
disturbances in industrial settings can be irregular.
By tracking a circuit over an extended period of
time with the Anacle Power Meter, data can be
saved and analyzed later on a computer. This
makes disturbances easier to pinpoint.
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Page 17
Starlight™
Appliance
Starlight™
Server
Power Socket
Series 200 PQM
Starlight™
Communicator
Starlight™
Communicator
Heavy
Equipment
Series 6000 PQM
Distribution Board
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Page 18
Thank You
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