2. POWER QUALITY
• Power Quality is a term used to broadly encompass the
entire scope of interaction among electrical
suppliers, the environment, the systems and products
energized, and the users of those systems and
products. It is more than the delivery of "clean" electric
power that complies with industry standards. It
involves the maintainability of that power, the
design, selection, and the installation of every piece of
hardware and software in the electrical energy system.
Stretching from the generation plant to the utility
customer, power quality is a measure of how the
elements affect the system as a whole.
3. POWER QUALITY PROBLEMS
• ‘Any power problem that results in failure or
misoperation of customer
equipment, manifests itself as an economic
burden to the user, or produces negative
impacts on the environment.
4. TYPES OF PROBLEMS
• Harmonic Distortion
• Voltage Transients
• Voltage Sags or Dips
• Voltage Surges
5. Power Quality Problems:
• VOLTAGE SAGS :
Voltage sags are under-voltages on the
power system and commonly caused by
power failures, downed lines, utility recloser
operations, and storms. They can be corrected
by using backup power sources such as
UPSs, generators or similiar voltage
restoration technologies
6. VOLTAGE SWELLS:
• Steady state voltage rise for several seconds
• Caused by line to ground fault in a three phase
system
7. VOLTAGE TRANSIENTS:
• Classified into two categories,
namely,
Impulsive Transient
Oscillatory Transient
• These terms reflect the wave shape of a
current or voltage transient.
8. • HARMONICS DISTORTION:
Harmonics result from distortions to the
voltage and/or current sine waves. Harmonics
are commonly caused by ASDs, industrial
processes, certain electronic loads, and wiring
connections. Harmonic problems often can be
corrected by filtering or resizing power system
components.
9. • Power Quality Solutions:
The need for solutions to power quality
problems grows with every passing second. Currently many
projects are under way and they are loooking at how to
collect data to find and analyze power quality problems.
Presently, the analysis ;of power quality problems is often
difficult due to the fact that the source of a problem can be
a few feet away in the form of a loose connection, or a
hundred miles away in the form of a power system fault. If
we look back at the stated power quality problems of
sags, surges, harmonics, and wiring and grounding, one can
see that each one has possible solutions to correcting these
problems.
10. METHODS OF SOLUTIONS
The solutions for power quality may be obtained
by the following methods:
• Using HYBRID FILTERS
• Using TRANSFORMER METHODS
• Using COIL CLOCKS
• Using POWER FACTOR CORRECTION
• Using UNIFIED SWITCHED CAPACITOR
COMPENSATOR
11. 1.HYBRID FILTERS
• Hybrid filters constructed of active and passive filters
• with different structures are used for removing the
• disadvantages of passive filters such as probability of
• resonances and non dynamic responses and also high
• costs of active filters, while using both the advantages of
• both of them with lower costs. Different structures of
• hybrid filters can be utilized in power systems such as
• shunt passive filter and series active power filter with
• nonlinear loads, shunt active and passive filter with
• nonlinear load, series active and passive filter parallel
• with nonlinear load, etc. shown in Fig. 1.
12. 2. TRANSFORMER METHODS
In this method we can control varous power
quality problems such as
• Large inrush currents
• Reduction of electromagnetic field emission
• Reduction of electromagnetic noise
13. a)LARGE INRUSH CURRENTS
• Currently virtually all power transformers are built with high permeability
GOSS cores. An unwanted
• feature of using high permeability core materials is that the inrush
currents are largely increased. This is
• even more problematic when the transformers are toroidal shaped made
of tape wound GOSS. To solve
• the inrush problems, transformer manufacturers resort to gaps in the
core. Gapping is an expensive
• production methodology and is difficult to control and test. In
addition, gapped transformers become
• acoustically noisy.
• With our proprietary technology (gapless) we can produce toroidal
transformers that have reduced inrush
• currents without resorting to gaps or external components. The
magnitude of the inrush currents has
• become another specification to meet rather than a problem.
14. b).REDUCTION OF ELECTROMAGNETIC
FIELD EMISSION
• We have been able to further reduce
• the amount of stray fields emitted by a toroidal transformer by a
factor of 2 to 5 when compared to the
• standard practice. The following design parameters play important
roles in reducing the stray fields:
• a) The design flux density.
• b) The permeability of the material.
• c) The core geometry (flat, tall, squared cross sectional area, etc.)
• d) Winding sequence.
• e) Winding style (precision, random, casual, bank, sector, etc.)
• f) Single, bifilar, or multi-filar windings.
• g) Use shielding core bands.
15. c).REDUCTION OF
ELECTROMAGNETIC NOISE
• The
• secondary winding (or the primary winding) is extended with an extra
winding with
• equal number of turns, connected in reverse phase to the existing
secondary winding through a capacitor
• At low frequencies, the impedance of the capacitor Cfp is high, the
capacitor acts as an open switch,
• only one secondary winding functions and thus the 50/60 Hz is free to
cross the transformer. At higher
• frequencies (above 1 kHz), the capacitor begins to act as a closed switch.
Both secondary windings are
• now at 180 degrees phase difference. Therefore the voltage induced in the
two windings cancel one
• another and no transfer of high frequency signals occurs. The transformer
acts as an effective low pass
• filter with adjustable bandwidth.
16. 3.COIL CLOCKS
• The Coil-Lock protects ac relay, contactor and
solenoid hold-in-devices by keeping motors
and other critical process control elements
engaged during those annoying momentary
voltage sags or dips. Literally, any device that
is controlled by energizing an ac coil, when
powered through a Coil-Lock unit will remain
latched through these power disturbances.
17. 4.POWER FACTOR CORRECTION
• Increased source efficiency
- lower losses on source impedance
- lower voltage distortion (cross-coupling)
- higher power available from a given source
• Reduced low-frequency harmonic pollution
• Compliance with limiting standards (IEC 555-
2, IEEE 519 etc.)
18. POWER FACTOR CORRECTION
TECHNIQUES
• PASSIVE METHODS:
LC filters
• ACTIVE METHODS:
High-frequency converters
19. 5.UNIFIED SWITCHED CAPACITOR
COMPENSATOR
• These loads are usually nonlinear and temporal in
nature.
• The proposed low cost (USCS) capacitor scheme
ensures
• both power quality (PQ) enhancement, RMS/power
• current level reduction, efficient power Energy
utilization
• and effective demand side management. The reduction
in THD of source
• current translates into improved power factor
20. BENEFITS OF POWER QUALITY
• Power quality in the container terminal
environment
• impacts the economics of the terminal
operation, affects
• reliability of the terminal equipment, and affects
other
• consumers served by the same utility service.
Each of
• these concerns is explored in the following
paragraphs
21. TYPES OF BENEFITS
1. Economic Impact
a. Power Factor Penalties
b. System Losses
c. Power Service Initial Capital Investments
2. Equipment Reliability
3. Power System Adequacy
4. Environment
22. POWER QUALITY CRITERIA
• As mentioned earlier, one can be aware of the
power quality issues, however, appropriate
criteria must be defined to insure the system
delivered properly addresses the needs of the
application.
