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1. What is power Quality?
Power Quality is the interaction of electronic equipments with its electrical environment, including generators, transformers, breakers and electrical wiring and grounding.The term Power Quality broadly refers to maintaining a near sinusoidal power distribution bus voltage at rated magnitude and frequency. In addition the energy supplied to a customer must be uninterrupted from the reliability point of view. |
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2. How is Power Quality measured?
Power Quality is measured by the consistency of the voltage supplied at your meter. The amount of voltage available may fluctuate or change due to controllable or uncontrollable circumstances. The measure of power quality depends up on the needs of the equipments that are being supplied. |
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3. Why is power quality such a problem today?
In recent years there has been an increased use of non linear loads which has resulted in an increased fraction of non sinusoidal voltages and currents in electrical network. Therefore power quality problems to day are more frequent and costly than ever before, despite the overall improvements in electricity reliability. |
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4. What terms are commonly used in the measurements and descriptions of power quality?
• Voltage sags/swells
• Voltage dips
• Voltage distortion
• Voltage unbalance
• Voltage interruption
• Voltage flicker
• Impulse or surge
• Harmonics |
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| 5. List out the power quality problems and causes? |
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| Broad Categories |
Specific Categories |
Characterization Methods |
Typical Causes |
| Transients |
Impulsive
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Peak magnitude, rise time and duration |
Lighting strike, Transformer
energisation and capacitor
switching |
Oscillatory
|
Peak magnitude, Frequency components |
Line or Capacitor or Load
Switching |
| Short duration voltage variation |
Sag
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Magnitude duration |
Ferro resonant transformers
Single
line to ground fault |
Swell
|
Magnitude duration |
Ferro resonant transformers
Single
line to ground fault |
Interruption
 |
Duration |
Temporary (self Clearing
faults) |
Long duration
voltage variation |
Under voltage
|
Magnitude duration |
Switching on loads, Capacitor de-energisation |
Over voltage
 |
Magnitude duration |
Switching off loads, Capacitor
energisation |
| Voltage Unbalance |
 |
Symmetrical components |
Single-phase load, Single phasing
condition |
| Waveform distortion |
Harmonics
 |
THD, Harmonic spectrum |
Adjustable speed drives and non
linear loads |
Notching
 |
THD, Harmonic spectrum |
Power Electronics converter |
| Voltage Flicker |
 |
Frequency of occurrences,
modulating
frequency |
Arc furnace, Arc Lamps |
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6.
What kind of equipments can be affected by power
quality problems?
Any type of electrical equipment can be affected by power quality problems. However
the most costly power quality problems involve more sensitive high tech equipments,
such as computer and data systems, which can be affected by their direct power
supply or through interactions with other electrical equipments.
7. Are power quality problems are always noticeable?
No – in
many cases disturbances can cause damage to circuits and other components.
Unfortunately many power quality problems go unsolved until a significant
monetary loss is actualized, and even then masked problems like failed
electrical or electronic equipments hide the underlying power quality
problems tat are the root cause of these failures.
8. What causes power quality problems?
Most
power quality problem causes can be divided into two categories – internal
and external.
Internal factors: faults o lightning strikes on transmission lines or
distribution feeders, equipment failures etc
External factors: Transformer
energisation. Capacitor or feeder switching, Power electronic loads,
Arc furnace and induction heating systems switching on or off of large
loads etc.
9. What are the types of electronic irregularities that cause power
quality problems?
• Outage or Interruptions:
An outage is a complete loss of voltage; it usually lasts for a few cycles
to several hours. Ice storms, lightening or winds are some of the more typical
causes of power failures. As different loads having different requirements,
there is no universal standard for power acceptability considering outages.
• Voltage sags or under voltage
A drop is service voltage below the proper nominal operating low voltage limit
for several seconds in duration is an under voltage condition. Voltage sag
may be caused by faults in the transmission system or by the switching loads
with the large amount of initial starting / inrush current.
• Voltage
swell or Over Voltage
It is a steady state voltage for several seconds or longer which is above
the upper source voltage limit. Over voltage usually occurs due to
improper adjustments of voltage regulators, capacitors etc. Line to
ground fault in a three phase system may cause voltage swell in the
un faulted phases.
• Surges or impulses:
Surge is a transient voltage or current that can have a high magnitude
for extremely shot duration. Causes include lightning, normal operation
of utility protection devices, equipment start up and shut down, welding
equipments. While lightning generates most impressive transients, switching
large motors and transformers or capacitor creates transients sufficient
o destroy today’s delicate microprocessor based equipments.
• Harmonics
The periodic steady state distortions of the standard sine wave due to
equipment generating a frequency other than the standard 50 cycles
per second.
Causes include electronic ballasts, non linear loads like switch mode
power supplies used in computers, variable frequency drives. In general
harmonics cause magnetic portions of the electrical system to over heat.
Such as transformers, line reactors, magnetic relays and power factor
capacitors
• Flicker
Flicker can be defined as the perceptible change in lamp output produced
by a sudden change in supply voltage. Some of the loads like arc furnace
load undergo rapid changes and generates variable voltage dip along the
distribution feeder. The disturbance may affect some of the loads like
incandescent lighting.
10. How is power quality problems diagnosed?
Electrical engineers and technical team use sophisticated monitoring and testing
to isolate the specific type of disturbances and pinpoint the root cause.
Examples of the testing that can be used include harmonic studies, load
studies, disturbance monitoring, wiring and grounding studies and power
factor measurements. |
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11.
How do I know a certain problem is caused by power quality issues?
Determining the exact problems related to power quality issues requires sophisticated
electronic test equipments. The following questions are general indicators of
power quality problems.
• Are you experiencing premature failures of electronic equipments
or motors or drives?
• Do you have adjustable speed drives that frequently trip off-line?
• Do your computers lock up inexplicably?
• Does your computer monitor screens jitter?
• Do you have equipments problems during or shortly after lightning
storms?
• Is interruptible power supplies frequently go to battery?
• Are circuit breakers tripping without being overloaded?
• Are transformers caught extremely hot to the touch?
• Do equipments frequently malfunction at the same time of the day?
• Do automated systems fail for no apparent reason?
• Do certain electronic systems work in one location but not in another
location?
• Do light dim or flicker? |
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12. How is power quality problems fixed?
The solution to a power quality issue depend on the nature of the problem,
but may include the installation of power conditioning devices such as uninterruptible
power supplies, transient voltage surge suppressors or isolation transformers.
Other potential solutions include facility rewiring or replacement of damaged
or degraded equipment. |
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13. How do I perform a power quality audit of my
business?
The objective of a power quality audit is to find a solution to a problem.
This is accomplished by checking the wiring and grounding, which causes
a significant amount of most commercial and industrial problems, and
checking the quality of both the internal and external voltage. This
data is then used to determine an appropriate solution. In conducting
an audit, the power quality professional must find answers to four questions
viz;
• Does the facilities wiring and grounding meet code and more
importantly is it adequate to meet their power needs from a power quality
stand point?
• What is the quality of the ac voltage supplying the equipment?
• What is the impact of electric utilities power system?
• What solutions are indicated by the audit data?
The last question off course is the most important. The best out come of
any power quality audit is whether the problem was solved or not. |
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14. Is there a solution to the power quality problem?
Yes. HYKON UPQC can solve all the power quality problems |
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| Power Quality Issues |
Hykon Power Quality Products |
Benefits |
| Power factor, voltage sags/swells, voltage
interruptions, over voltage, under voltage |
UPQC - Unified Power Quality
Conditioner |
• Regulates load voltage
against sag/ swell and other voltage fluctuations.
• Individual phase compensation
of the load voltages to eliminate voltage unbalance
• Reactive current filtering by
STATCOM
• Maintains Grid Power Factor
near to unity and brings down Maximum Demand ( MD) • Uninterrupted production
and supply |
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15.
What is UPQC?
UPQC stands for Unified Power Quality Conditioner. UPQC is an active series /
shunt power line conditioner. It is used to compensate power quality issues
such as Voltage sags, swells, Voltage imbalance, flicker, harmonics and reactive
current. It is a combination of a STATCOM as well as a series compensating
stage connected before the load in series with the power network using a matching
transformer. |
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16. What is the basic function of
UPQC?
• Load voltage regulation be series voltage injection
• Dynamic current Injection for reactive power compensation
UPQC is
used to compensate voltage sags and current harmonics, control input power
factor near to unity as well as to regulate the load voltage. It can be installed
by the electric utilities to damp out harmonic propagation caused by resonance
with line impedance and passive shunt compensators. |
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17. What is the basic topology of UPQC?
UPQC consists of 1 x 3 phase and 3 x 1 phase Voltage source converters sharing
the same capacitive DC link. The 3 phase converter will act as an Active
Filter while the other is a series filter (Dynamic Voltage Regulator) The
basic block diagram of a UPQC is shown below: |
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18.
What is the role of Series Active Filter and Shunt Active Filter in
UPQC?
The Shunt Active Filter is primarily a Voltage Source Converter connected
to Point of Common Coupling (PCC) through series inductors.
The Series Filter (DVR) is primarily a Voltage Source Inverter connected
to Power network with LC filter and isolation transformer. The secondary
of the transformer is connected in series with Power Network. |
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19. Where UPQC can be installed?
• IT Parks
• Commercial Office Complexes
• Semiconductor industries
• Machine Tool plants
• Process Industries |
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20. Can I use a Power Conditioner instead of UPS?
Your question involves two different technologies used for differing
reasons. 95% of all power quality problems are caused by transient
noise, voltage surges, harmonics or frequently changing voltage conditions.
Unified Power Quality Conditioner provides solution for most of the
power quality problems.The primary function of any uninterruptible power
supply ( UPS) is to provide an alternate voltage source ( batteries)
to a critical load for some period of time should a complete power failure
occur. Complete power failure accounts less than 5% of all power quality
problems. For the other 955 of all the power quality problems unless
the UPS is the on-line version is of no help. |
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21. Does the UPQC need much on going
service and maintenance?
No. Depending up on the environment that the HYKON UPQC located only preventive
maintenance would be required and that involves ensuring that the door and
internal fans are fully operational and that all filters are free of dust
and not blocked.
22. Is the technology is developed by HYKON?
The technology is transferred from CDAC – which is a project supported
by Dept of IT, Ministry of Communication and Information Technology, Govt.
of India and manufactured at HYKON.
23. Whether the HYKON UPQC technology
field proven?
Yes. The 250 KVA proto model of UPQC is working in the Power Electronics Lab
of C DAC Thiruvananthapuram with light and fan loads of the centre connected
for the past one year.
24. My question is not on the list – how
can I get an answer to my question?
Please go to our FAQ form. We will answer your questions directly as quickly
as possible. |
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