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Voltage sags, transients, and momentary interruption of power together constitute 92% of the PQ problems encountered by typical industrial customers.
Productivity loss due to deep voltage sags and brief power interruptions has
been called the most important concern affecting most industrial and commercial
customers. These power quality (PQ) events typically last for less than one second,
impressing voltage sags down to 50% of nominal voltage, with occasional short-term interruptions lasting for approximately 6 to 10 cycles .However, when an industrial process is interrupted or shut down as a result of a power quality event, the process outage will be much longer than the duration of the PQ event itself.
Conventional solutions such as surge protectors and voltage regulator solve the predominant problem and, while noise filters can remove the electrical and magnetic noise from the power line.
This seminar and presentation is an attempt to condition the power line from momentary fluctuations which includes surges, over voltages and noise that are emanated from power line and there by improving the quality of power.
BHARGAV B. DESAI
MR.KALPESH R. PATIL
Power Quality is a technical term that has practical implications for your business and your equipment.
When power is generated, it has very predictable characteristics. It energizes all electrical equipment equally and satisfactorily.
However, as the power travels through the wires and energizes the equipment, the various pieces of equipment it energizes can change the quality of the power, making it less suitable for the next application.
These changes in power quality are especially common in large industrial and commercial complexes and include increases and decreases in voltage, momentary power outages, and noise on the electrical system.
At its most extreme, poor power quality can even cause equipment to malfunction.
Why Do You Need Power Quality Protection
While power disturbances occur on all electrical systems, the sensitivity of todayâ„¢s electronics makes them more susceptible to them.
For some sensitive devices,a momentary disturbance can cause scrambled data, interrupted communications, a frozen mouse, system crashes and equipment failure.
A power voltage spike can damage valuable components.
Power quality issues can cause business problems such as:
Â¢ Lost productivity and idle people and equipment
Â¢ Lost orders, good will, customers and profits
Â¢ Lost transactions and orders not being processed
Â¢ Revenue and accounting problem such as invoices not prepared, payment held up,and early payment discount missed.
Â¢ Customer and/or management dissatisfaction_ Overtime required to make up for lost work time
According to Electric Light and Power magazine, 30 to 40 percent of all business downtime is related to power quality problems.
Businesses have a lot invested in office and production equipment, and power quality protection is an inexpensive insurance policy against incidents.
2. COMMON POWER DISTURBANCES
Common power quality disturbances include surges, spikes and sags in power source voltage and harmonics (or noise) on the power line.
Each of these occurrences is discussed briefly below.
Surge â€œ A rapid short-term increase in voltage Surges often are caused when high power demand devices such as air conditioners turn off and the extra voltage is dissipated through the power line.
Since sensitive electronic devices require a constant voltage, surges stress delicate components and cause premature failure.
Spike â€œ An extremely high and nearly instantaneous increase in voltage with a very short duration measured in microseconds.
Spikes are often caused by lightning or by events such as power coming back on after an outage.
A spike can damage or destroy sensitive electronic equipment.
Turn the equipment off during a power outage.
Wait a few minutes after power is restored before turning it on, and then turn on one device at a time.
Sag â€œ A rapid short-term decrease in voltage.
Sag typically is caused by Simultaneous high power demand of many electrical devices such as motors,compressors and so on.
The effect of sag is to tarve electronic equipment of power causing unexpected crashes and lost of corrupted data.
Sags also reduces the efficiency and life span of equipments such as electric motor.
Noise â€œ A disturbance in the smooth flow of electricity often technically referred to as electro-magnetic interference (EMI) or radio frequency interference (RFI).
Harmonics are a special category of power line noise that causes distortions in electrical voltage.
Noise can be caused by motors and electronic devices in the immediate vicinity or far Away.
Noise can affect performance of some equipment and introduce glitches and errors into software programs and data files.
Outage â€œ Total loss of power for some period of time.
Outages are caused by excessive demands on the power system, lightning strikes and accidental damage to power lines.
In addition to shutting down all types of electrical equipment, outages cause unexpected data loss.
What Causes Power Quality Problems
Studies show that up to 80 percent of most small businessâ„¢ power quality problems are caused by disturbances created inside of a facility or business. (See the chart next page.)
When large power users in a building, such as fans and air conditioning equipment, cycle on and off, they can cause power dips and surges that affect other equipment in the building.
Lightning is another major source of disturbance accounting for more than 10 percent of power disturbances.
Thatâ„¢s why it is important to have power quality protection at the incoming utility meter and at each piece of sensitive electronic equipment throughout your facility.
3. WHAT IS LINE CONDITIONER
Also called a line conditioner, a device that sits between a computer and its power supply, typically a wall outlet.
The power conditioner provides protection against surges in power just as a surge protector does, but a power conditioner also maintains a continuous voltage fed to the computer during temporary voltage reductions, such as a brownout.
This is referred to as conditioning. Power conditioners also can filter EMI emanating from a power source and can smooth the rhythmic cycle of alternating current.
4. POWER CONDITIONING TECHNOLOGIES
Device and Principal functions & General Description
Surge Protection devices.
Divert or clamp surges.-
Various types of surge protectors are available to limit circuit voltages.
Devices vary by clamping voltage, and energy handling ability.
Typical devices are crowbar types like air gaps, gas discharge tubes, and non linear resistive types like thyrite valves, avalanche diodes, and metal oxide varistors.
Also available a reactive suppressors that are able to clamp, or limit, surges regardless of where on the power sine wave occurs.
These devices do not affect significantly
the energy consumption.
Noise filters (EMI/RFI)
Series inductors with parallel capacitor
good for low energy high frequency
Voltage regulators provide a relatively constant steady state output voltage level for a range of input voltage.
A variety of voltage regulation techniques are used. Common technique sinclude Ferro-resonant transformers, electronic tap switching transformers and saturable reactor regulator.
5. SURGE PROTECTORS
There are several instances when the elements of a power system are subjected
to over voltages i.e. voltages greater than the normal value.
These over voltages onthe power system may be caused due to many reasons such as lightning, the opening of a circuit breaker, the grounding of a conductor etc.
Most of the over voltages are not of large magnitude but may still be important because of their effect on the performance of circuit interrupting equipment and protective devices.
An appreciable number of these over voltages are of sufficient magnitude to cause insulation breakdown of the equipment in the power system.
A sudden rise in voltage for a very short duration on the power system is known as a voltage surge or transient voltage.
Transients or surges are of temporary
nature and exist for a very short duration but they cause over voltages on the power
They originate from switching and from other causes but by far the most important transients are those caused b lighting striking a transmission line.
In most of the cases, such surges may cause the line insulators to flash over and ma also damage the nearby transformers, generators or other equipment connected to the line if the equipment is not suitably protected.
CAUSES OF OVERVOLTAGES:
1. INTERNAL CAUSES:
2. EXTERNAL CAUSES i.e. lightning.
Internal causes do not produce surges of large magnitude.
Surges due to internal causes hardly increase the system voltage to twice the normal value.
However, surges due to lightning are very severe and may increase the system voltage to several times the normal value.
If the equipment in the power system is not protected against lightning surges, these surges may cause considerable damage.
An electric discharge between cloud and earth, between clouds or between the
Charges centres of the same cloud are known as lightning.
EFFECTS OF LIGHTNING:
1. The traveling waves produced due to lightning surges will shatter the insulators and may even wreck poles.
2. If the traveling waves produced due to lightning hit the windings of a transformer or generator, it may cause considerable damage.
The inductance of the windings opposes any sudden passage of electric charge through it.
Therefore, the electric charges piles up against the transformer.
This induces such an excessive pressure between the windings that insulation may break down, resulting in the production of arc.
While the normal voltage between the turns is never enough to start an arc, once the insulation has broken down and an arc has been started by a momentary over voltage, the line voltage is usually sufficient to maintain.
3. If the arc is initiated in any part of the power system by the lightning stroke, this arc will set up very disturbing oscillations in the line.
This may damage other equipment connected to the line.
PROTECTION AGAINST LIGHTNING:
Transients or surges on the power system may originate from switching and from other causes but the most important and dangerous surges are those caused by lightning.
The lightning surges may cause serious damage to the expensive equipment in the power system either by direct strokes on the equipment or by strokes on the transmission lines that reach the equipment as traveling waves.
It is necessary to provide protection against both kinds of surges.
The most commonly used devices for protection against lightning surges are:
The earthing screen and ground wires can well protect the electrical system against direct lightning strokes but they fail to provide protection against traveling wave which may each the terminal apparatus.
The lightning arresters or surge diverters provide protection against such surges.
A lightning arrester or a surge diverter is a protective deice which conducts the high voltage surges on the power system to the ground.
It consists of a spark gap in series with a non linear resistor.
One end of the diverter is connected to the terminal of the equipment to be protected and the other end is effectively grounded. The length of the gap is so set that normal line voltage is not enough to cause an arc across the gap but a dangerously high voltage will break down the air insulation and form an arc.
The property of the non linear resistance is that its resistance decreases as the voltage increases and vice versa.
ACTION OF LIGHTNING ARRESTERS:
1. Under normal operation, the lightning arrester is off the line i.e. it conducts.
2. On the occurrence of over voltage, the air insulation across the gap breaks down
and an arc is formed, providing a low resistance path for the surge to the ground.
In this way, the excess charge on the line due to the surge is harmlessly conduced
through the arrester to the ground instead of being sent back over the line.
3. It is worthwhile to mention the function of non linear resistor in the operation of
As the gap sparks over due to over voltage, the arc would be a short circuit on the power system and may cause power follow current in the arrester.
Since the characteristic of the resistor is to offer high resistance to high voltage, it prevents the effect of a short circuit.
After the surge is over, the resistor offers high resistance to make the gap non-conducting.
TYPES OF LIGHTNING ARRESTER:
1. Rod gap arrester
2. Horn gap arrester
3. Multi gap arrester
4. Expulsion type arrester
5. Valve type lightning arrester
6. NOISE &ITS ERADICATION
Recent years have witnessed tremendous advances in electronics.
In the field of personal computers, word processors and other computer related equipment, legal restrictions regarding safety and noise generation have grown more strict with each passing year.
In most cases, electronic devices exported must now conform to the noise regulations of the target country in order for them to be given market approval.
The following is an introductory description of the ways in which noise is
generated and the various noise regulations currently enforced throughout the world
NOISE GENERATION AND TRANSMISSION
The noise generated by electronic device consists of two kinds. Radiated noise is transmitted directly into the air from an electronic device, taking the form of an electric wave that interferes with other electronic devices.
In contrast conductive noise interferes with other components and devices by being transmitted along power lines and the wiring of electronic circuits.
These two kinds of noise can be briefly explained in the context of an electronic device by means of the following diagram (Figure 1).
OPERATING PRINCIPLES OF NOISE FILTERS
A key counter measure taken against noise is the use of noise filters.
The operating principles of these devices are described below:
Viewed from the prescriptive of the circuit network, noise filter is a kind of low range or low pass filter.
It is designed to pass only frequency lower than cut off frequency, while attenuating or blocking all ranges higher than cut off frequency.
As shown in Figure 2, the filter operates according to a principle whereby
inductance connected directly in series with the line has virtually no affect on the
noise current at low frequencies, but at high frequencies it demonstrates a high
interruptive effect with respect to the noise current.
Also a capacitor connected in parallel with the line is used as side path tore turn high frequency back to the power line.
The result is that normal mode noise
passes through the capacitor and is then shunted back to the other line.
In the case of common mode noise, result is that noise passes through the midpoint of the two capacitors to the ground.
The use of special materials such as amorphous alloys and toroidal cores gives the Okaya noise filters excellent insertion loss characteristics and high voltagepulse attenuation capability.
EVALUATION METHODS OF NOISE
1. Static Characteristics
With a measuring impedance of 50 ohms, the amount of attenuation (insertion
loss) is determined by using a level meter to measure the voltage before and after
insertion of a noise filter into the test circuit.
Using this method, both normal mode and common mode attenuation can be measured.
Attenuation = 20log10 (V0 /V1) [dB]
V1: Level when test material is inserted
V2: Level when test material is not
2. Dynamic characteristics:
In order to achieve measurement results as near as possible to actual application
conditions, the following method is used:
With a noise simulator as the noise
generating source, a rated current is allowed to flow through the test device and asimulated power circuit network.
The amount or normal mode and common mode
3. Pulse Attenuation Characteristics:
The following method is used to measure the noise margin for the external noise
in an electronic device: a noise simulator is connected and the input/output voltages
The formula noted below is then used to calculate the amount of attenuation in the form of the pulse absorption effect produced.
In general, the noise condition used to test malfunctions is a high voltage pulse of 50nsec.to 1Ã‚Âµsec at 1kVto 2kV in amplitude.
Normal mode Common mode
The following points should be kept in mind with regard to the installation of
1. When mounting on the noise producing side, they should be mounted as close as
possible to the source of the noise with noise electrical or mechanical contact
between the input and output side of the filter.
(Example) When the input/output lines are bundled together or arranged parallel with
each other, high frequency noise components induced on the input side, results in the production of noise current on the output side.
Separation of input/output lines (good example)
Bundling or parallel arrangement of input/output lines (poor example)
2. When the device is directly installed on the equipment exposed to interference, it
is important to mount the noise filter as close as possible to the machines power unit or input wiring.
If a power line is allowed to enter the case of the equipment with out passing through the noise filter, noise current can be radiated throughout the inside of the equipment enclosure, affecting the internal electronics.
3. Precautions should be taken to insure that the ground line for the noise filter has
lower impedance than that of the noise current.
If this is not done, the noise prevention effect will be lost. Also, ground lines should be as short as possible.
The use of long ground lines will result in substantial reduction of the noise prevention effects (particularly in the high frequency ranges above several MHz.).
4. Whenever possible, the outer case of the noise filter should be mounted directly to the outer case of the electronic equipment.
When this is not possible, a short grounding line should be used to link the outer case of the filter and the equipment.
Line voltage regulators do exactly what the name implies their purpose is to
maintain reasonably constant output voltage to the load in the face of variations in power line voltage.
There are many different ways of accomplishing this and among the basic types there are innumerable variations, all with their own advantages and limitation the following covers one or two popular or generic versions of five basic types of voltage regulators.
(1). Most line regulators will correct utility voltage sags and swells of 15percent to output voltages to the load ranging from Ã‚Â±3 to Ã‚Â±7 percent of nominal
Many will bring extreme utility sags in the area of 20 to 30 percent, back to Ã‚Â±7 to Ã‚Â±10 percent of the nominal output voltage.
Some things to consider when picking a line voltage regulator are cost, speed of response, output impedance, audible noise, efficiency at part and full load, sensitivity to load power factor and unbalanced three-phase loads ,and harmonic distortion.
(2) A few types of line regulators can attenuate impulses to a modest degree,but most perform the regulation function only and pass impulses right through.
In fact, some types may create additional impulse noise by internal switching.
(3) There are two types of motor-actuated regulators, the motor -driven brush type and the induction regulator type.
The motor-driven brush type moves across many taps on an autotransformer, causing the series transformer to buck or boost the voltage to the load.
The same function is performed by an induction regulator where rotating the regulator on direction or the other varies the magnetic coupling and raises or lowers the output voltages.
The following covers one or two popular or generic versions of five basic types of voltage regulators.
(4). Most actuated voltage regulator are generally inexpensive and can handle
heavy loads, but they are slow in response and can only correct for gradual voltage
In addition, their electromechanical parts require substantial maintenance and output impedance is high.
They are not often used with electronic equipment
(5). The Ferro-resonant voltage transformer regulator is one of the more
popular regulator., especially in the lower size ranges of 0.5 to 2 KVA.
The Ferro resonant transformer core structure is so designed that the secondary operates in flux saturation and secondary winding resonant with capacitor in tuned circuit.
As a result of this saturated operating mode changing the primary or line voltage may change the current but will not vary the flux or the secondary induced voltage.
Thus the unit performs voltage regulation action.
A unique characteristic of Ferro-resonant regulator is its ability to reduce normal mode impulses.
Since its regulating capability is based on driving the secondary winding into saturation, transients and noise burst are clipped.
(a) The basic Ferro-resonant transformer puts out a high harmonic content square
wave, not suitable for supplying sensitive electronic loads.
A properly selected neutralizing winding cancels out most of the harmonic content of the output voltage and yields a satisfactory low - distortion sine wave.
(b) The Ferro-resonant regulator has a response time of about 25 milliseconds or
1.5 cycles, good reliability, minimal maintenance requirements, reasonable cost, good normal-mode impulse attenuation, and good regulation.
Because of the tuned circuit on the output, it is sensitive to frequency variations (1 percent frequency change causes 1.5
percent output voltage change), but this is not much of a problem with tight utility
network frequency control.
More important are its high output impedance (again up to 30percent of load impedance), sensitivity to both leading and lagging load power factors, and low efficiency at partial loads.
Efficiency is about 90 percent at rated load, but since the unit wastes about 10 percent of rated load regardless of what load level it is operating at, efficiency drops with load.
This, in turn, results in heat dissipation and the generation of audible noise.
© In addition, Ferro-resonant regulators have poor capacity for handling momentary overloads such as might be caused by high motor starting current, and output voltage collapses at somewhere about 150 percent of full load.
Over sizing is not the whole answer to this problem, since this cause reduced efficiency and increased heat dissipation.
In summary, the Ferro-resonant regulator is useful in small systems that do not contain large motors.
(6) The last type of line voltage regulator to be looked at here is the electronic
With this unit the proper triac(or back-to-back silicon controlled Rectifier [SCR]) is energized depending on whether the power line voltage must be increased or decreased.
Voltage correction occurs in discrete steps rather than continuously.
Resolution depends on the closeness of the taps, and switching impulses are minimized by changing taps when the line voltage is near a zero crossing.
(a) The electronic tap-switching transformer has many good features.
Response time is fast at about 0.5 cycles or 10 milliseconds, regulation is good, output impedance is in the range of 5 percent of load impedance, efficiency is high at about 95 percent, and the units are insensitive to load power factor and load unbalance.
(b) The disadvantages are a somewhat high cost and slightly poorer reliability
when compared to the more rugged units.
© This type of regulator is popular and widely used in the medium sizes of 3
kVA and up.
After preparing and presenting for the seminar and presentation POWER LINE CONDITIONING can very well conclude that it is very essential for any power plant to condition itself so that it can have continuous and better quality of power.
Now if the quality of the power which is transmit and distribute to its consumer is not up to the mark and if it produces bulk quantity of losses then it won`t be beneficial to both power plant and its consumers.
POWER SYSTEM BY V.K. MEHTA
1. INTRODUCTION Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦.
2. COMMON POWER DISTURBANCESÂ¦Â¦..
3. DEFINITION OF LINE CONDITIONERÂ¦Â¦Â¦.
4. POWER CONDITIONING TECHNOLOGYÂ¦Â¦Â¦..
5. SURGE PROTECTOR Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦Â¦
6. NOISE& ITS ERADICATION VOLTAGE REGULATOR..
7. POWER CONDITIONING TECHNOLOGY Â¦Â¦Â¦Â¦Â¦Â¦Â¦