MAJOR POWER QUALITY ISSUES DUE TO SOLAR PV DISTRIBUTED GENERATION (DG)

Distributed generation (DG) refers to a variety of technologies that generate electricity near the end users. Some of the DG technologies are solar panels, and combined heat and power (CHP). They may serve a single structure (such as a home or an industry), or a major industrial facility, a large hospital, or a college campus, as part of a microgrid (a smaller grid that is also tied into the larger electricity delivery system). These systems may or may not be connected to the electric grid. When connected to the electric utility’s low voltage distribution lines, DG systems can support the delivery of clean, reliable power to additional customers and help reduce transmission and distribution losses.

Distributed Generation (DG) generally refers to small-scale (typically ranging from 1 kW – 50 MW) electric power generators that produce electricity at a site close to customers or that are tied to an electric distribution system. As of May 2015, India had a cumulative distributed Solar PV capacity of about 400 MW and is expected to witness significant growth owing to increasing economic viability and a facilitating regulatory framework in many states. It is one of the most promising DG source and their penetration level to the grid is also on the rise.

The integration of solar PVDG in power systems can alleviate overloading in transmission or distribution lines, provide peak shaving, and support the general grid requirement. However, improper coordination, location, and installation may affect the quality of power systems. When integrating DG, the inverter forms the heart of a grid-tied solar PV system and is responsible for the quality of power generated/injected into the grid. While it handles the important operating parameters such as voltage and frequency range, it also affects the quality of the solar power being injected into the grid.

Primarily through three major PQ issues:

Harmonics

Flicker

DC Injection

Long duration voltage variations

Harmonic issues due to DG

Harmonics are electric voltages and currents that appear in the grid as a result of non-linear electric loads. In the solar system,

Harmonics are caused in the conversion of DC to AC power by the inverter.

Another factor that influences harmonic distortion in a power system is the number of PVDG units connected to the power system. The interaction between grid components and a group of PVDG units can amplify harmonic distortion.

The increasing use of harmonic-producing equipment on the customer side such as adjustable speed drives also creates issues like greater propagation of harmonics in the system, shortened lifetime of the electronic equipment, and motor and wiring overheating. In addition, harmonics can flow back to the supply line and affect other customers at the PCC.

Flicker issues due to DG

A DG installation may increase the flicker level during start/stop or if it has continuous variations in input power because of a fluctuating energy source. In the case of a solar energy generator, the output fluctuates significantly as the sun intensity changes. Moreover, Squirrel cage induction generators have a high possibility to make flicker level worse because of an inability to actively control terminal voltage.

It is typically caused by the use of large fluctuating loads, i.e. loads that have rapidly fluctuating active and reactive power demand. Flicker effect occurs when one generating source reactive power output increases or decreases faster than the remaining generators can compensate. Flicker does not harm equipment, but in weak grids with a higher possibility of voltage fluctuations, the perceived flicker can be very disturbing to customers.

DC Injection issues due to DG

Grid connected inverters are used to convert the DC power, thus obtained into AC power for further utilization. Thus, inverters connecting a PV system and the public grid are purposefully designed for energy transfers. However, due to approximate short circuit characteristics of AC network, a little DC voltage component can accidentally be produced by grid connected inverters which can create large DC current injections. If output transformers are not used, these inverters must prevent excessive DC current injection, which may cause detrimental effects on the network components, in particular the network transformers which can saturate, resulting in irritant tripping. This may also increase the losses and reduce the lifetime of the transformers, if not tripped. Moreover, the existence of the DC current component can induce metering errors and malfunction of protection relays and can create an adverse effect on the overall functioning of the solar power plant.

Other effects within transformers include excessive losses (i.e. overheating), generation of harmonics, acoustic noise emission, and residual magnetism. In addition, there is evidence for the seriousness of corrosion risks associated with DC currents in the grid.

Long Duration Voltage Variations

Overvoltage and undervoltage are generally not the result of system faults but are caused by load variations on the system and system switching operations. DG technologies, mainly the renewable systems like solar can cause long duration voltage variations. Small-distributed generation (less than 1 MW) is not powerful enough to regulate the voltage and is dominated by the daily voltage changes in the utility system. Small DG is almost universally required to interconnect with a fixed power factor or fixed reactive power control. Large voltage changes in distribution network are possible if there is a significant penetration of dispersed, smaller DG’s generating power at a constant power factor. Suddenly connecting or disconnecting such generation can result in a relatively large voltage change that will persist until recognized by the voltage-regulating system.

Solution: 

Emerich Energy have solutions for all types of Power Quality Challenges, The potential PQ Analysis and mitigation of Harmonics and other Variations are the solutions to increase hoisting of solar PV capacity in distribution grid.

IMPACT OF POWER QUALITY PROBLEMS

Power is simply the flow of energy and the current demanded by a load is largely uncontrollable. “Power quality” is a convenient term for many; it is the quality of the voltage, rather than power or electric current.

The performance of electronic devices is directly linked to the power quality level in a facility. The electric power industry comprises electricity generation (AC power), electric power transmission and ultimately electricity distribution to an electricity meter located at the premises of the end user of the electric power. The electricity then moves through the wiring system of the end user until it reaches the load. The complexity of the system to move electric energy from the point of production to the point of consumption combined with variations in weather, generation, demand and other factors provide many opportunities for the quality of supply to be compromised

Without the proper power, an electrical device may malfunction, fail prematurely or not operate at all. There are many ways in which electric power can be of poor quality and many more causes of such poor quality power. Some of the most common power supply problems and their likely effect on sensitive equipment:

1. Voltage surges/spikes

Voltage surges/spikes are the opposite of dips – a rise that may be nearly instantaneous (spike) or takes place over a longer duration (surge). A voltage surge takes place when the voltage is 110% or more above normal. The most common cause is heavy electrical equipment being turned off. Under these conditions, computer systems and other high tech equipment can experience flickering lights, equipment shutoff, errors or memory loss. Possible Solutions are surge suppressors, voltage regulators, uninterrupted power supplies, power conditioners

2. Voltage Dips

Short duration under-voltages are called “Voltage Sags” or “Voltage Dips [IEC]”. Voltage sag [5, 6] is a reduction in the supply voltage magnitude followed by a voltage recovery after a short period of time. The major cause of voltage dips on a supply system is a fault on the system, i.e. sufficiently remote electrically that a voltage interruption does not occur. Other sources are the starting of large loads and, occasionally, the supply of large inductive loads [6]. The impact on consumers may range from the annoying (non-periodic light flicker) to the serious (tripping of sensitive loads and stalling of motors.

3. Under voltages

Excessive network loading, loss of generation, incorrectly set transformer taps and voltage regulator malfunctions, causes under voltage. Loads with a poor power factor or a general lack of reactive power support on a network also contribute. Under voltage can also indirectly lead to overloading problems as equipment takes an increased current to maintain power output (e.g. motor loads) 

4. High-Voltage Spikes

High-voltage spikes occur when there is a sudden voltage peak of up to 6,000 volts. These spikes are usually the result of nearby lightning strikes, but there can be other causes as well. The effects on vulnerable electronic systems can include loss of data and burned circuit boards. Possible Solutions are using Surge Suppressors, Voltage Regulators, Uninterrupted Power Supplies, Power Conditioners 

5. Frequency Variation

A frequency variation involves a change in frequency from the normally stable utility frequency of 50 or 60 Hz, depending on your geographic location. This may be caused by erratic operation of emergency generators or unstable frequency power sources. For sensitive equipment, the results can be data loss, program failure, equipment lock-up or complete shutdown. Possible Solutions are using Voltage Regulators and Power Conditioners

6. Power Sag

Power sags are a common power quality problem. Despite being a short duration (10ms to 1s) event during which a reduction in the RMS voltage magnitude takes place, a small reduction in the system voltage can cause serious consequences. Sages are usually caused by system faults, and often the result of switching on loads with high demand startup currents. For more details about power sags visit our newsletter archives. Possible Solutions are using Voltage Regulators, Uninterrupted Power Supplies, and Power Conditioners

7. Electrical Line Noise

Electrical line noise is defined as Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) and causes unwanted effects in the circuits of computer systems. Sources of the problems include motors, relays, motor control devices, broadcast transmissions, microwave radiation, and distant electrical storms. RFI, EMI and other frequency problems can cause equipment to lock-up, and data error or loss. Possible Solutions are using Voltage Regulators, Uninterrupted Power Supplies, and Power Conditioners

8. Brownouts

A brownout is a steady lower voltage state. An example of a brownout is what happens during peak electrical demand in the summer, when utilities can’t always meet the requirements and must lower the voltage to limit maximum power. When this happens, systems can experience glitches, data loss and equipment failure. Possible Solutions are using Voltage Regulators, Uninterrupted Power Supplies, and Power Conditioners

9. Blackouts

A power failure or blackout is a zero-voltage condition that lasts for more than two cycles. It may be caused by tripping a circuit breaker, power distribution failure or utility power failure. A blackout can cause data loss or corruption and equipment damage. Possible Solutions is using Generators

10. Very short interruptions

Total interruption of electrical supply for duration from few milliseconds to one or two seconds. Mainly due to the opening and automatic re-closure of protection devices to decommission a faulty section of the network. The main fault causes are insulation failure, lightning and insulator flash-over. Consequences of these interruptions are tripping of protection devices, loss of information and malfunction of data processing equipment

11. Long interruptions

Long interruption of electrical supply for duration greater than 1 to 2 seconds. The main fault causes are Equipment failure in the power system network, storms and objects (trees, cars, etc) striking lines or poles, fire, human error, bad coordination or failure of protection devices. A consequence of these interruptions is stoppage of all equipment

12. Voltage swell

Momentary increase of the voltage, at the power frequency, outside the normal tolerances, with duration of more than one cycle and typically less than a few seconds. The main causes are Start/stop of heavy loads, badly dimensioned power sources, badly regulated transformers (mainly during off-peak hours).Consequences is data loss, flickering of lighting and screens, stoppage or damage of sensitive equipment, if the voltage values are too high

13. Harmonic distortion

Voltage or current waveforms assume non-sinusoidal shape. The waveform corresponds to the sum of different sine-waves with different magnitude and phase, having frequencies that are multiples of power-system frequency. Main Causes are Classic sources: electric machines working above the knee of the magnetization curve (magnetic saturation), arc furnaces, welding machines, rectifiers, and DC brush motors. Modern sources: all non-linear loads, such as power electronics equipment including ASDs, switched mode power supplies, data processing equipment, high efficiency lighting. Consequences are increased probability in occurrence of resonance, neutral overload in 3-phase systems, overheating of all cables and equipment, loss of efficiency in electric machines, electromagnetic interference with communication systems, and errors in measures when using average reading meters, nuisance tripping of thermal protections.

14. Voltage fluctuation

Oscillation of voltage value, amplitude modulated by a signal with frequency of 0 to 30 Hz. Causes are arc furnaces, frequent start/stop of electric motors (for instance elevators), oscillating loads. Consequences are most consequences are common to under voltages. The most perceptible consequence is the flickering of lighting and screens, giving the impression of unsteadiness of visual perception 

15. Noise

Superimposing of high frequency signals on the waveform of the power-system frequency. Main Causes are Electromagnetic interference provoked by Hertzian waves such as microwaves, television diffusion, and radiation due to welding machines, arc furnaces, and electronic equipment. Improper grounding may also be a cause. Consequences are disturbances on sensitive electronic equipment, usually not destructive. It may cause data loss and data processing errors

16. Voltage Unbalance

A voltage variation in a three-phase system in which the three voltage magnitudes or the phase angle differences between them are not equal. Causes are large single-phase loads (induction furnaces, traction loads), incorrect distribution of all single-phase loads by the three phases of the system (this may be also due to a fault). Consequences are Unbalanced systems imply the existence of a negative sequence that is harmful to all three phase loads. The most affected loads are three-phase induction machines.

Types of Power System Stability and Stability Studies benefits

Power system stability is the ability of the system, for a given initial operating condition, to regain a normal state of equilibrium after being subjected to a disturbance.   The ability of the power system to return to its normal or stable conditions after being disturbed is called stability. Disturbances of the system may be of various types like sudden changes of load, the sudden short circuit between line and ground, line-to-line fault,  all three line faults, switching, etc.

The stability of the system mainly depends on the behaviour of the synchronous machines after a disturbance. The stability of the power system is mainly divided into two types depending upon the magnitude of disturbances

Steady state stability
Transient stability

Steady-state stability – It refers to the ability of the system to regain its synchronism (speed & frequency of all the network are same) after slow and small disturbance which occurs due to gradual power changes. Steady-state stability is subdivided into two types

Dynamic stability – It denotes the stability of a system to reach its stable condition after a very small disturbance (disturbance occurs only for 10 to 30 seconds). It is also known as small signal stability. It occurs mainly due to the fluctuation in load or generation level.

Static stability – It refers to the stability of the system that obtains without the aid (benefit) of automatic control devices such as governors and voltage regulators.

Transient Stability – It is defined as the ability of the power system to return to its normal conditions after a large disturbance. The large disturbance occurs in the system due to the sudden removal of the load, line switching operations; fault occurs in the system, sudden outage of a line, etc.

Transient stability is conducted when new transmitting and generating system are planned. The swing equation describes the behaviour of the synchronous machine during transient disturbances.

The transient and steady-state disturbances occur in the power system are shown in the graph below. These disturbances reduce the synchronism of the machine, and the system becomes unstable.

Stability studies are helpful for the determination of critical clearing time of circuit breakers, voltage levels and a transfer capability of the systems.

Infographic: Understanding the Impact of Power Quality

Courtesy : schneider

Researchers develop new method to remove dust on solar panels

Taking a cue from the self-cleaning properties of the lotus leaf, researchers at Ben-Gurion University of the Negev have shed new light on microscopic forces and mechanisms that can be optimized to remove dust from solar panels to maintain efficiency and light absorption. The new technique removed 98 percent of dust particles.

In a new study published in Langmuir, the researchers confirmed that modifying the surface properties of solar panels may greatly reduce the amount of dust remaining on the surface, and significantly increase the potential of solar energy harvesting applications in the desert.

Dust adhesion on solar panels is a major challenge to energy harvesting through photovoltaic cells and solar thermal collectors. New solutions are necessary to maintain maximum collection efficiency in high dust density areas such as the Negev desert in Israel.

"In nature, we observe that the lotus leaf remains dust and pathogen free due to its nanotextured surface, and a thin wax, hydrophobic coating that repels water," says Tabea Heckenthaler, a master's student from Düsseldorf Germany at the BGU Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research. "In the desert, dust accumulates on the surface of solar cells and it's labor-intensive to clean them constantly, so we're trying to mimic this behavior on a solar cell."

The researchers explored the effect of modifying a silicon substrate (Si), a semiconductor used in photovoltaic cells, to mimic the self-cleaning properties of the lotus leaf, as water rolls down the leaves and removes contamination.

It is known that superhydrophobicity reduces the friction between water droplets and the surface, thus allowing water drops to slide clean particles from surfaces. However, the forces that attach and detach particles from surfaces during the self-cleaning mechanism and the effect of nano textures on these forces are not fully understood.

To shed light on these forces and the effect of nanotexture on them, the researchers prepared four silicon-based samples relevant to solar panels: (1) smooth hydrophilic (2) nanotextured hydrophilic surfaces and (3) smooth hydrophobic (4) nanotextured hydrophobic surfaces. This was achieved by wet-chemically etching the surface to create nanowires on the surface, and additionally applying a hydrophobic coating.

Particle removal increased from 41 percent on hydrophilic smooth Si wafers to 98 percent on superhydrophobic Si-based nanotextured surfaces. The researchers confirmed these results by measuring the adhesion of a micron-sized particle to the flat and nanotextured substrate using an atomic force microscope. They found that the adhesion in water is reduced by a factor of 30.

"We determined that the reason for the increased particle removal is not low friction between the droplets and the superhydrophobic surfaces," Heckenthaler says. "Rather, it is the increase in the forces that can detach particles from the surfaces. The experimental methods we used and the criterion for particle removal we derived can be implemented to engineer self-cleaning surfaces exhibiting different chemistries and/or textures."

Emerich_Invitation to CII Energy Efficiency Summit 2019

NEWS: Jaguar Land Rover to launch multiple electric cars in India, starting 2019

Latest News: Tata Motors owned Jaguar Land Rover (JLR) 

In line with Jaguar Land Rover's global commitment to introduce electrified options on its entire product portfolio by 2020, Jaguar Land Rover India proposes to offer multiple products, ranging from Hybrid Vehicles to Battery Electric Vehicles (BEV) over the next few years, starting from 2019.

Luxury car makers in India are all set to bring in hybrid electric and pure electric cars to India. Audi has already announced that the e-tron will make its debut in the country in 2020, while Porsche too is bringing in the Taycan next year. Volvo has already announced its roadmap for the country and Mercedes-Benz India is still doing feasibility studies to introduce electric cars in India and now Jaguar Land Rover is jumping into this scene. Jaguar Land Rover is proposing to launch its electrified products in India.

Why Earthing is Required & Earthing Components

Earthing is the method of transmitting the instant electricity discharge directly to the ground through low resistance wires or electrical cables. This is one of the significant features of electrical networks. Because it builds the most eagerly accessible and hazardous power source much secure to utilize.

The process of earthing in case of short circuit condition, the electrical wire carefully removes the overflow of current and allows it to flow through the earth. All this occurs without unnecessary problems, only through resourceful and inexpensive manufacture, plan as well as arrangement!

Why Earthing is Required?

The main intention of electrical earthing is to keep away from the danger of electric shock due to the outflow of current from ground through the not preferred path as well as to make sure that the potential of a conductor does not increase with respect to the ground than its planned insulation.

When the metallic element of electrical machines approaches in contact by an existing wire, due to a breakdown of fixing the cable, the metal turn into charged and static charge collect on it. If someone contacts such an electric metal, then the outcome is a severe electric shock. 

So finally We can conclude that life is random, and one should always get ready for unexpected circumstances. So buildings and electric appliances have to be grounded to transfer the electric charge directly to the ground. The main benefits of grounding include protection from over voltage, stabilization of voltage, and prevention form injury, damage, and death.

Components used in Electrical Earthing System

The main components used in earthing system mainly include earth cable, earthing joint (earthing lead), and earth plate

Earth Cable

The conductor is used to connect metallic parts of an electrical system like plug sockets, metallic shells, fuses, distribution boxes. Metallic parts of motors, transformers, generators, etc. the range of these conductors depend on the earth cable size used in the wiring circuit. The earth wire in the cross-sectional area must be less than the solid wire used in the electrical wiring system.

In general, the copper wire utilized as an earth continuity conductor size is 3-standard wire gauge (SWG). Ground wires which are smaller than 14-SWG should not be used. In some situations, copper strips are used instead of a bare copper conductor.

Earthing Joint

The ‘ground electrode’ as well as conductors fixing to the ‘ground continuity conductor’ is called earthing joint (earthing lead).  The tip where the earthing joint connects the ground continuity conductor is known as connecting end. The lead of the ground must be low size, straight, & should include a minimum amount of joints. Although copper wires are usually used as grounding leads; whereas copper strips are selected for high fitting because it carries high fault current values due to its broad region.

Earth Plate

The last part of the electrical grounding system which is hidden underground and linked to the lead of grounding is known as the earth plate. Earth electrode is a pipe, plate or metallic rod, or plate; which has extremely low resistance for carrying the fault current to the ground safely.

It can be of iron or copper rod and must be placed in wet earth and in case the moisture content of earth is low then put some water in the earth plate. The earth plate is always placed in the vertical, and coat with salt and charcoal lime around the earth plate. This helps in protecting the earth plate as well as in maintains ground moisture around the earth plate. The earth plate must be placed four meters long for the better earthing.

Types of Electrical Earthing Systems

The process of Earthing or electrical grounding can be done in several ways like wiring in factories, housing, other machines, and electrical equipment. The different types of electrical earthing systems include the following.

Plate Earthing System

In this type of system, a plate is made up of copper or GI (galvanized iron) which are placed vertically in the ground pit less than 3 meters from the earth. For a better electrical grounding system, one should maintain the earth moisture condition around the plate earthing system.

Pipe Earthing System

A galvanized steel based pipe is placed vertically in a wet is known as pipe earthing, and it is the most common type of earthing system. The pipe size mainly depends on the soil type and magnitude of current. Usually, for the ordinary soil, the pipe dimension should be 1.5 inches in diameter and 9 feets in length. For rocky or dry soil, the pipe diameter should be greater than the ordinary soil pipe. The soil moisture will decide the pipe’s length to be placed in the earth. The pipe earthing diagram is shown below:

Rod Earthing System

This type of earthing system is similar to pipe earthing system. A copper rod with galvanized steel pipe is placed upright in the ground physically or using a hammer. The embedded electrodes lengths in the earth decrease the resistance of earth to a preferred value.

This is all about what is meant by earthing / definition of earthing and its types. From the above information, finally, we can conclude that the earthing system or electrical grounding system offers greater safety from electric shock for personal, equipment, buildings, etc. The ground sensitivity can be The earth resistivity can be affected by some issues like soil and climate, a condition of resistivity, moisture, melted salts, earth pit location, physical work, grain size effect, current magnitude, etc. 

Why Availability Tariff is necessary ? & Its Benefits

The regional grids had been operating in a very undisciplined and haphazard manner. There were large deviations in frequency from the rated frequency of 50.0 cycles per second (Hz). Low frequency situations result when the total generation available in the grid is less than the total consumer load. These can be curtailed by enhancing generation and/or curtailing consumer load. High frequency is a result of insufficient backing down of generation when the total consumer load has fallen during off-peak hours. The earlier tariff mechanisms did not provide any incentive for either backing down generation during off-peak hours or for reducing consumer load / enhancing generation during peak-load hours. In fact, it was profitable to go on generating at a high level even when the consumer demand had come down. In other words, the earlier tariff mechanisms encouraged grid indiscipline.

The Availability Tariff directly addresses these issues. Firstly, by giving incentives for enhancing output capability of power plants, it enables more consumer load to be met during peak load hours. Secondly, backing down during off-peak hours no longer results in financial loss to generating stations, and the earlier incentive for not backing down is neutralized. Thirdly, the shares of beneficiaries in the Central generating stations acquire a meaning, which was previously missing. The beneficiaries now have well-defined entitlements, and are able to draw power up to the specified limits at normal rates of the respective power plants. In case of over-drawal, they have to pay at a higher rate during peak load hours, which discourages them from over-drawing further. This payment then goes to beneficiaries who received less energy than was scheduled, and acts as an incentive/compensation for them.

How does it benefit everyone 

The mechanism has dramatically streamlined the operation of regional grids in India. Firstly, through the system and procedure in place, constituents’ schedules get determined as per their shares in Central stations, and they clearly know the implications of deviating from these schedules. Any constituent which helps others by under-drawal from the regional grid in a deficit situation, gets compensated at a good price for the quantum of energy under-drawn. Secondly, the grid parameters, i.e., frequency and voltage, have improved, and equipment damage correspondingly reduced. During peak load hours, the frequency can be improved only by reducing drawls, and necessary incentives are provided in the mechanism for the same. High frequency situation on the other hand, is being checked by encouraging reduction in generation during off-peak hours. Thirdly, because of clear separation between fixed and variable charges, generation according to merit-order is encouraged and pithead stations do not have to back down normally. The overall generation cost accordingly comes down. Fourthly, a mechanism is established for harnessing captive and co-generation and for bilateral trading between the constituents. Lastly, Availability Tariff, by rewarding plant availability, enables more consumer load to be catered at any point of time.

How do the beneficiaries share the payments  

The Central generating stations in different regions of the country have various States of the Region as their specified beneficiaries or bulk consumers. The latter have shares in these plants calculated according to Gadgil formula, and duly notified by the Ministry of Power. The beneficiaries have to pay the capacity charge for these plants in proportion to their share in the respective plants. This payment is dependent on the declared output capability of the plant for the day and the beneficiary's percentage share in that plant, and not on power / energy intended to be drawn or actually drawn by the beneficiary from the Central station.

The energy charge to be paid by a beneficiary to a Central station for a particular day would be the fuel cost for the energy scheduled to be supplied from the power plant to the beneficiary during the day. In addition, if a beneficiary draws more power from the regional grid than what is totally scheduled to be supplied to him from the various Central generating stations at a particular time, he has to pay for the excess drawal at a rate dependent on the system conditions, the rate being lower if the frequency is high, and being higher if the frequency is low.

For more details or clarifications and to know about  Advanced Power  Quality products Study & Completely Automated Report:  

Connect with Emerich Energy Please write to us info@emerich.in  Call: 044-48577667

Please subscribe our blog https://blog.emerich.in/

Follow us LinkedIn   https://www.linkedin.com/company/emerichenergy/ 

HANDLING HARMONICS WITH AC DRIVES

AC motors are abundant in the most of the industry. Every fan and pump application requires an AC motor. For efficient and reliable control, adjustable-speed drives are becoming a common companion for these motors. However, as drives are boosting production, they might also be contributing to electrical noise problems, such as line current harmonics.

Pumping and mixing motors are becoming abundant in industrial wastewater facilities as systems expand to keep up with population growth and demand for more water, distributed over larger areas. To maintain water pressure and control flow, adjustable speed drives are a valuable companion for these AC motors.

Drives are an efficient alternative to throttling values, as they match power needs and motor speed to the demands of varying flow. Drives can save energy and electrical costs, increase pressure reliability, reduce cumbersome pump changes and lessen damage to mechanical equipment. However, as drives are boosting efficiency and reliability, they might also be contributing to power quality problems, such as line current and voltage harmonics.

Harmonics are deviations from the sinusoidal fundamental AC line voltage and current. Most electrical power in North America operates at a frequency of 50 hertz. A harmonic frequency is an integer multiple of this fundamental frequency. So in a 50-hertz system, the second harmonic would be 100-hertz, the third would be 150-hertz, and so on. The addition of any harmonic to the sinusoidal fundamental current or voltage will create distortion. The greater the amplitudes of the harmonics present, the greater the distortion in the electrical waveform. Very simply, whenever a voltage or current does not look like a perfect sinusoidal waveform, it contains harmonics.

Compared to DC motor drives, AC motor drives cause very few problems. However, poorly designed applications can result in power line voltage distortions. These voltage distortions can cause problems for other equipment connected to the same power lines – resulting in erratic operation of controls, dimming of lights, audible noise on telephone systems, and static on AM and FM radios. The distribution transformers and cables feeding these drives will also experience additional heating, which reduces the power utilization of those components.

What Causes Harmonics?

Unlike an AC motor operating across the power line, the current drawn from a distribution transformer feeding a typical AC drive is far from a sinusoidal waveform. This occurs because the drive is taking current from the transformer only during certain times of the cycle to convert the AC line voltage to a fixed DC voltage within the drive. The drive then pulse-width-modulates this fixed DC voltage into variable frequency, variable voltage for the motor. The AC-to-DC conversion is what causes the harmonics. Current flows only during part of the cycle and is off during other parts of the cycle, creating the odd-looking current waveform. It is this distorted current that creates the voltage distortion.

As the number of drives employed in automation systems grows, so too does the misconception that drives are the only piece of the puzzle to harmonic problems. While they may comprise a sizable portion of non-linear loads, they are only one element in the harmonic equation. That's why it's important to analyze all electrical loads that could potentially cause problems for a system before making any final conclusions.

What Affects Harmonic Current?

The harmonic current created by the drive can be affected by the presence of a DC link choke, the DC bus capacitance and the line inductance between the drive input and its source of voltage; such as transformer inductance, cable inductance and additional line reactors.

The closer you are to the drive, the greater the voltage harmonic distortion. This is why the voltage distortion is greater at the drive than at the transformer. If other equipment needs to be connected to the same transformer as the drive, connect the other equipment as close to the transformer as possible. This will minimize the effect of the current harmonics produced by the drive on the voltage waveform, which can cause problems with the other equipment.

Reducing Harmonics

There are several methods and products to reduce the line current harmonics created by drives. Cost is not the only factor that distinguishes one solution from another. Even though the addition of line reactors or passive filters can help reduce the current harmonics, they will also reduce the DC bus voltage within the drive at full speed, full load conditions. This will prevent the drive from being able to provide full power to the motor, limiting the power out of the motor to about 95% of its nameplate rating.

Why would you install a 100 hp motor only to have its capability limited to 95 hp, especially under peak demand conditions? This is why multi-pulse solutions are a better fit for most situations, since no derating is necessary and it is less expensive than other mitigation methods.

Harmonic Mitigation Methods

For a 250 hp drive, the chart above details the typical harmonic current, I(THD), and relative installed costs associated with various harmonic mitigation methods.

(For simplicity, we will say that the 250hp drive is connected to a supply with a short circuit capacity of 60,000A, will draw 260Arms of fundamental current for its load, and will have a cost of 100%.)

The goal for those specifying harmonic mitigation solutions is to combine the most cost effective solution for the particular drive and power distribution system. Since several factors come into play in determining the harmonics in the drive system, Emerich Power Quality Analysis  needs to consider all factors before arriving at a final recommendation.

For Advanced Power  Quality products Study & Completely Automated Report:  

Connect with Emerich Energy Please write to us info@emerich.in  Call: 044-48577667

Please subscribe our blog https://blog.emerich.in/

Follow us LinkedIn   https://www.linkedin.com/company/emerichenergy/ 

Metals sector inattentive of its power quality losses! Why?

Metals manufacturing plants have a high demand for electrical power, are electric motor intense, have high raw material costs & rely heavily on sophisticated automation and on a skilled labour force.Common to these characteristics is that they all lead to significant operating losses when the electric power is interrupted.

The European Copper Institute (ECI) Power Quality Survey has identified that the metals sector loses over 10% per cent of its net bottom line due to Power Quality operating issues.

The domino effect of production stoppages

Manufacturing plants in the metals sector make generally intense use of electric motors of different ratings and specifications, often integrated in one controlled system. A loss of control of one motor caused by an unexpected and sudden power interruption or power dip can upset the general control and bring the whole production system to a complete standstill. Such an event can, in turn, result in a wide range of financial losses:

Both manufacturing and administrative staff will be made idle when “the lights go out”,often for several hours.

Irregularities in power supply can shorten the useful operating life of expensive high tech machinery or even permanently damage them, resulting in high maintenance and equipment replacement costs.

Raw material that was being processed at the moment of the event can be irrecoverably wasted, or if not will require additional reprocessing to make it again fit for purpose.

Unexpected stoppages play havoc with production planning, resulting in delivery delays, loss of reputation for reliability and consequently loss of business.

Different cost centers blur the reality

The cumulative financial losses caused by power interruptions tend not to be assessed as a totality, relating as they do to different cost centers and occurring at different moments in time.

This might explain why, despite those high potential losses, metal manufacturing sites are on the average not as immune to poor power quality as might be expected. In many of the cases,the total financial waste caused by these interruptions was equivalent to the organisations’ annual electricity bill.

A high price for an under-designed process system

Because of an inadequate power system design, this metals company was being crippled by power interruptions and sudden power reductions causing machinery to fail. In many cases,the precise power quality issue that led to such a breakdown was not known due to a lack of monitoring equipment. The power quality events resulted in production stoppages of 2 hours on average, causing about 300 production staff to be idle. The cost of poor power quality for this company was further exacerbated by raw materials wastage, equipment damage, reduction of operating life time of heavier equipment and the additional maintenance required to get production up and running again.

" Metal industry loses the equivalent of over 50% of its annual electricity bill due to Power Quality losses"

3.4 % of company’s annual turnover being wasted Each time the lamination process in this company was interrupted due to power quality problems, it resulted in high financial losses, consisting mainly of wasted raw materials, low revenues, and staff downtime. Those losses were calculated as equivalent to 3.4% of this company’s annual turnover and to 30% of their net profit.

Understanding the problems – designing the solutions

Emerich Energy Power Quality Survey demonstrates that the majority of the PQ problems faced by the metals sector could be avoided by a more appropriate design of the factory’s own electrical installations. The solutions therefore lie very much in the industry’s own hands. Electrical design engineers involved in this survey recommend a holistic approach to review all the issues at hand, based on three operational pillars:

Correct measurement, to assess the full impact of power quality events, and why they are happening

Appropriate design for the electric installations, ensuring reliability and resilience

Considered investment justified by assessing system renovation cost set against the accumulated losses. 

For Advanced Power  Quality products Study & Completely Automated Report:  

Connect with Emerich Energy Please write to us info@emerich.in  Call: 044-48577667

Please subscribe our blog https://blog.emerich.in/

Follow us LinkedIn   https://www.linkedin.com/company/emerichenergy/ 

IGBT & Its Application in Power Quality

An insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device primarily used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching. 

It consists of four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. Although the structure of the IGBT is topologically the same as a thyristor with a 'MOS' gate (MOS gate thyristor), the thyristor action is completely suppressed and only the transistor action is permitted in the entire device operation range. It switches electric power in many applications: variable-frequency drives (VFDs), electric cars, trains, variable speed refrigerators, lamp ballasts, air-conditioners and even stereo systems with switching amplifiers.

IGBT comparison table [1]
Device characteristic	Power bipolar	Power MOSFET	IGBT
Voltage rating	High <1kV	High <1kV	Very high >1kV
Current rating	High <500A	High > 500A	High >500A
Input drive	Current ratio hFE 20-200	Voltage VGS 3-10V	Voltage VGE 4-8V
Input impedance	Low	High	High
Output impedance	Low	Medium	Low
Switching speed	Slow (µs)	Fast (ns)	Medium
Cost	Low	Medium	High

IGBT Applications: Industrial

IGBT industrial applications are due to their use in driving motors. Availability of the IGBT in the early 1980s enabled development of cost-effective ASDs (Adjustable speed drives) for motors. These drives reduce energy consumption by more than 40%. Two-thirds of the electricity in the world is used to run motors, so IGBT technology has had a huge impact on energy consumption. 

These applications include:

Industrial Motor Drives

Adjustable Speed Drives for Motor Control

Pulse Width Modulated ASD

Factory Automation

Robotics

Welding

Induction Heating

Milling and Drilling Machines

Metal and Paper Mills

Electrostatic Precipitators

Textile Mills

Mining and Excavation

IGBT Optimization for Industrial Applications

IGBT Technology in Power Quality World

The versatile and adaptive design possibility of the IGBT system in all the areas where Power Quality is a mandatory requirement such as, 

• Power Factor Improvement using Static Condenser(AVG) using IGBT Technology
• Harmonics Mitigation by Active Harmonic Mitigator (AHM) - Voltage Source Converter using IGBT Technology
• Unbalance Compensation(AUG) (Negative Sequence) using IGBT Technology
• Active Front End DRIVES using IGBT Technology 
• Active Front End UPS (Uninterrupted Power  Supply) using IGBT Technology
• Voltage Dip/Sag & Surge Protection using IGBT Technology(Series Compensation)
• Industrial Power Automation solutions for Power Supplies using IGBT Technology
• Special DRIVES for LOCO applications using IGBT  Technology
• High Frequency and Higher Power Quality conversions for AVIATION Applications

And many more..

Conclusion

From the Power Factor improvement and Drive application to Voltage Dip / Surge correction, the IGBT Technology has it all. India is focusing on a Better Power Quality more than any other country in the world currently. 

For Advanced Power  Quality products Study & Completely Automated Report:  

Connect with Emerich Energy Please write to us info@emerich.in  Call: 044-48577667

Please subscribe our blog https://blog.emerich.in/

Follow us LinkedIn   https://www.linkedin.com/company/emerichenergy/