How do you ensure a steady supply of electricity from fickle renewable sources such as solar, wind and biomass? 'Smart grids' that manage and distribute flows of electricity could be the answer.

     The EU's ambitious goals of a 20 percent increase in energy efficiency, a 20 percent increase in renewables and a 20 percent reduction of carbon dioxide emissions - all by the year 2020 - are a huge undertaking. Experts agree that none of the "20:20:20" goals are achievable without a functional smart grid that ultimately optimizes energy generation.

     That's because simply building more wind plants and solar collectors won't be enough, as renewable energy is hampered by the fact that it's not constantly available – after all, if the wind doesn't blow or the sun doesn't shine, wind turbines or solar cells don't generate energy.
A wind turbine 
     'Smart grids' on the other hand can manage and distribute intermittent energy supply from small power plants, wind mills or solar systems without a hitch, leading to a steady supply of electricity.   If there's too much electricity in the grid, it can be stored in batteries, for example when an electric car rolls up to a recharging point.

Smart energy draws big players
     Smart grids provide utilities with the information and flexibility required to manage intermittent electricity supply from renewable and micro-generation sources, allowing them to balance this with more traditional, consistent supply.

     Large companies such as Switzerland's ABB, a rival of Germany's engineering giant Siemens, say smart grids are a huge trend in the energy sector.

     "There are lots of solutions that are already available. We could begin with them right away," Peter Smits, the head of ABB Europe said. But Smits says incentives, like feed in tariffs, are still needed to encourage the switch to a bigger pool of renewable energy sources.

     "The more renewable energy we have to feed in the network, the more the utilities and electricity distributors are going to need this solution," Smits said. The International Energy Agency estimates that by 2030, worldwide investments worth several trillion dollars will be needed for modern energy generation and new electricity networks.

     Indeed, the booming market, which promises lucrative returns, has attracted new players to the utilities sector, including IT giants such as Google, IBM, Cisco, Microsoft or telecommunications firms such as Deutsche Telekom.

Various smart approaches
     From the use of smart meters in households in Italy or France, to government-backed pilot-projects in the US, there's a growing momentum for groundbreaking smart energy schemes.  In Germany, too, the government is trialing smart grids in a few hand-picked regions.
     The impression that Germany is lagging behind on smart energy projects is not true, says Hartmut Schmeck from the Institute for Technology in Karlsruhe.  He says selected regions in Germany are testing the entire supply chain - from electricity generation, and distribution to supplying the end consumer.  "Other countries are trying out projects where individual processes are monitored. But comprehensive, holistic approaches like the ones in Germany - they don't exist elsewhere."

Customers needed
     It's expected that in two years, Germany's model regions will have developed their smart energy concepts to the point where they'll be ready for the market and everyday use.  This summer, project organizers set up a model house complete with washing machine, refrigerator and an electric car. The latter plays a key role in the project - both to store electricity as well as consume it.

     Still missing are the thousands of electricity consumers needed to test the whole thing.  "The most important thing is that the customers play along because you can't have a smart grid without customers," said Joern Kroeplin from the energy utility firm EnBW, which is involved in the project.  Kroeplin says it is important to find tariffs and models that will create the necessary incentives.  "We also need the necessary appliances that customers accept and use. Without all that, it won't work," he said.

Not all smooth sailing
     A first intelligent washing machine manufactured by German company Miele was on display at this year's consumer electronics fair IFA in Berlin. It switches on when the electricity price falls below a certain level. But it also needs a smart plug which recognizes what the electricity currently costs.  For smart grids to work, a number of players will need to come together, including industrial and private consumers, to help share the introductory costs.

     Another obstacle remains. Aside from their upfront costs, smart meters also use a lot of energy to maintain, due to all the data flows operating in real time.  The required internet connection alone, which runs 24/7, uses over 100 kilowatt hours of electricity in a year – almost exactly as much as a modern refrigerator.

courtesy : http://www.dw-world.de


















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High Voltage probes are used to measure high voltages which are beyond the range of common measuring instruments.  For instance, ordinary multimeters may not be able to measure the high voltages generated in the Television set.  In these conditions, High voltage probes may be used.  High Voltage probes usually contain resistors in series.
High power probes can be used with multimeters, oscilloscopes, synchroscopes and a wide variety of industrial measuring instruments. 

The instruments which are connected to the High voltage probes usually have a high internal impedance to limit the current.

High voltage probes have a voltage ratio similar to a transformer.  High voltage probes are also rated on the amount of power they can withstand.  Some High voltage probes are designed only for low power application.

















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Liquid Rheostats are variable resistors which use a liquid electrolyte.  The electrolyte, usually common salt, is used as the resistor whose resistance value is varied by changing the level.

The construction consists of two electrolyte placed in a container.  The container is filled with a solution of common salt.  There is a provision to vary the level of the electrolyte in the container.

This changes the conductivity and thus the resistance is varied.  At high levels of the electrolyte, the resistanc is very low and increases as the level decreases.

Liquid rheostats are silent and are supposed to have long life.  They are usually only used in AC circuits as DC may cause electrodeposition between the electrodes. 

Liquid rheostats can also be used as load banks to test generator output at testing facilities.  The output of the generator is connected to electrodes which are placed in a container filled with a salt solution.

Liquid rheostats are also used as resistances for starting induction motors.  Some large liquid rheostats have a heat exchanger to control the temperature of the electrolyte. 

















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Capacitors are components which are used in electric and electronic circuits to store charge, to filter dc, to improve power factor and so on.  There are many kinds of capacitors available.  Ceramic, Paper capacitors, electrolytic capacitors and so on.

Electrolytic capacitors are called as one of the plates of the capacitor is made of an ionic conducting liquid, an electrolyte.  These capacitors must be connected in a fixed polarity.  Hence, these capacitors cannot be used in AC circuits without a dc bias.  These capacitors have a high capacitance value.

Polarity is usually indicated in the capacitors with the positive lead longer than the negative lead.  Alternatively, the polarity markings are made in the capacitor body.

Connecting these capacitors in the wrong polarity will cause heating of the electrolyte and lead to an explosion, a catastrophic failure.  Most capacitors are provided with a vent to relieve pressure and prevent explosions.

















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Wound rotors are used in applications where high starting torque is required.  External resistances may be added to these rotors via slip rings shaft.  These resistances serve to increase the starting torque and ensure smooth starts.  

However, these rotors are more expensive than induction motors.  In the wound rotor, the rotor windings are insulated to the ground.  The slip rings and the brushes also require maintenance.

The starting current drawn by a wound rotor machine is lesser than that that of a squirrel cage motor.

The wound rotor is designed to have the same number of poles as the stator winding of the motor.  The windings are designed to with stand high mechanical forces as these motors are used for high-torque applications. 

Wound Rotors are used for applications which require soft-starts and adjustable speeds

Squirrel cage rotors are the most common type of rotors found in induction motors.  These rotors are simple to construct, robust and relatively inexpensive. 

They are particularly suited for low inertia loads.  Their easy construction enables lower rotor weight and lesser centirfugal force and windage losses.

















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A surge arrestor is an electric equipment used in substations and switch yards.  The surge arrester is used to protect the substation equipment from surges caused by lightning or by sudden switching.

The surge arrestor is an insulator which is a non-linear resistor. This means that the surge arrestor has high resistance at the operating voltage and low resistance as the voltage increases.

Thus when lightning strikes the overhead conductors in a substation, the arrestor acts like a conductor and discharges the surge to the ground.

Surge arrestors are usually constructed of MOV(Metal oxide varistor).  Zinc oxide is a widely used non-linear resistor.  The zinc oxide is the form of blocks which are stacked inside the arrestor.

















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Capacitors can fail due to a number of reasons.  The failure of capacitors can lead to short-circuit, damage to the circuit and sometimes even explosion. 

Let us look at some of the reasons for failure of capacitors.

Electrolytic capacitors fail due to leakage or vaporization of the electrolyte inside.  This can be caused due to heating in operation.  Heating can be caused by either wrong connection or the use of under-rated capacitors.

In electrolytic capacitors heating can cause the formation of gas inside which can explode through the vent provided.

Voltage surges can also cause capacitor failure.  Overtime, capacitors re-form themselves to a particular voltage.  When an unexpected surge occurs, a failure can take place. 

Ceramic capacitors crack during overvoltages.  This may create an open or short-circuit.

Tantalum capacitors are specially sensitive to voltage.

Electrolytic and Tantalum capacitors have polarity.  The leads are marked positive and negative.  Wrong polarity connections of these capacitors can cause explosion or failure. 

In addition to these causes, mechanical damage, heat and ageing can also cause capacitor failure.

















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          Parasitic loads are electric devices and appliances which draw power even when they are off.  For example, the television which has been switched off using the remote but, is still connected to the power socket continues to draw a small quantity of power.  Parasitic loads are other known as phantom loads or
vampire loads.

          It is estimated that around 5% to 10% of the total load consists of phantom loads.  Phantom loads can be avoided by disconnecting any device not in use from the mains supply.

           For example, a kitchen mixer should be disconnected from the mains or the switch of the power socket switched off when the device is not in use.  Another example would be a laptop that is switched off with a power adaptor which is still connected to the mains. 

What causes Parasitic loading

          Devices which have windings, such as motors, transformers draw a charging current.  The charging current is constant throughout the loading cycle of the machine.  The charging current causes Iron losses due to eddy current heating.  This power is wasted as heat and hence is a loss to the power system.   

          Many countries such as the US, Britain, and the EU have initiated laws which stipulate that appliances in the switched off mode should not draw power more than 1 watt.  This is known as the One Watt Initiative.  Better design of transformer with Torroidal cores which generate lesser losses is one way of reducing phantom power.

















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Power Factor can be defined as the cosine of the angle between the current and the voltage.  This power factor is also known as the Displacement power factor.

The conventional measurement of the power factor is relevant only for loads that are linear and the waveforms are purely sinusoidal.  With the increase in non-linear loads such as inverters, drives, etc this definition of the power factor is not adequate.  This is because the harmonics have an impact on the power factor.

Thus, the total harmonic distortion should also be considered while calculating power factor. 

How is True Power Factor different from Measured Power Factor ?

The true power factor refers to the measured power factor at the system frequency which is adjusted for the Harmonic distortion








Thus for loads which have high harmonic content, the True Power factor needs to be calculated.

















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   Cambridge University has developed a new Photo voltaic technology which could enable house owneres to produce electricity from sunlight without having to install expensive solar panels.
 
The technology is being developed by Eight19, a new venture built on the collaboration between the Cavendish Laboratory of Cambridge University and a British Environmental group called the Carbon Trust.  

Organic Photovoltaic technology is different from conventional photo voltaic technology.  The technology mimics the process of photosynthesis in plants.  These solar panels are flexible and can be easily unrolled and installed in windows, walls and other flat surfaces.  This dramatically improves the scope of use for solar electricity.

More importantly, the low cost of this technology could enable wider installation of solar based power sources in remote places where there is no grid connectivity. 

For more information


image courtesy :  independent.co.uk


















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ABB, the leading power and automation technology group will design, supply and install all six main transformers for the 500 kilovolt (kV) Tongyu substation, under construction in the Jilin province of north-eastern China.

Tongyu will be the highest voltage substation in the country for the transfer of wind power. It is designed to integrate 2300 megawatts of electricity into the grid and plays an important part in the province’s wind power development plan.

“Renewable energy, especially wind power, is an important element of China’s focus on clean energy development,” said Tarak Mehta, global head of ABB’s Transformers business, part of the company’s Power Products division. ”The transformers used in this project will play a key role in integrating wind energy into the grid and ensure the efficient transmission of electricity to millions.”

The transformers are based on ABB’s patented TrafoStar technology and designed to minimize power loss and maintenance needs. Their ability to withstand short circuits will be integral to the reliable and safe operation of the substation, mitigating the occurrence of power outages. They will be supplied from ABB’s state-of-the-art transformer manufacturing unit in Chongqing, one of the largest of its kind in the world.

Transformers are integral components of any electrical grid and are critical elements in the efficient and safe conversion of energy across diverse voltage systems. ABB’s transformer portfolio includes power transformers, rated up to 1,000 kV, dry- and liquid-distribution transformers, as well as related services and components.

Courtesy: http://www.robotautomation.com.au

















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Slip-over CTs are used in applications where it is difficult to install conventional Current Transformers. 

These current transformers can be "slipped over" bushings, terminals of Circuit breakers whenever any new upgradation or modification of the system needs to be carried out.

Slip over Current transformers are easy to replace with minimum downtime.

Kuhlman Electric Corporation (now acquired by ABB) has launched the Accuslip series of current transformers.  These current transformers can be used for both metering and protection.  ABB says that these current transformers can provide high accuracy measurement even at low ranges. The series is expected to deliver an accuracy of 0.15%.

According to ABB, these current transformers can be custom designed to meet any application.  The transformers can also be provided with an optional ground shield and mechanical supports.

















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The Basic Impulse Insulation Levels refers to the ability of electric equipment such as transformers to withstand lightning surges.  When lightning strikes a transmission line, a traveling wave is created.  This traveling wave travels along the line and damages the transformer winding.

Surge arresters mounted on the line can mitigate the surge, however, they cannot totally eliminate it.  Voltage surges can also be created by the switching of circuit breakers and switches. 

The BIL or the Basic Impulse Insulation level indicates the ability of the transformer to withstand these heavy surges.  Transformers with a rating of 600 volts and below are designed to have a BIL of 10 kV.

















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LEDs have found wide application in the field of lighting.  Homes can also be illuminated with LED lamps.  LEDs come in a variety of shapes and can be chosen to suit the decor and application.

The advantages of LED lighting over conventional lighting are
  • Longer life - The life of a LED lamp is 100000 hours(11 years) as compared to 5000 hours for ordinary bulbs.
  • Cheaper - While LED lamps are costlier than filament lamps, their long life more than compensates for the high cost. 
  • Reduced Power Consumption - The power required for LED lamps is lesser than that required for conventional lighting. 
  • LED lamps have high efficiency and produce less heat.
  • LEDs are available in a wide choice of colors
  • The LED bulbs can be made in a wide variety of shapes and designs
  • LED bulbs are Eco-friendly as they do not contain mercury unlike conventional filament lamps.

LEDs are today connected in the form of clusters containing a number of LED lamps.  Handheld torches are also being produced with LED bulbs.

LEDs have also found application in industry, in traffic signals and in hospitals.  LEDs also help avoid downtime due to bulb failure which can be expensive and interruptive in applications such as traffic signals, in street lighting, etc.

With improved manufacturing techniques, the price of LEDs is expected to continue to drop further.

















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          Negative phase sequence in induction motors is caused due to unbalanced voltages in the supply voltage applied on the stator terminals or unbalanced windings.
        
          Negative phase sequence components create a rotating magnetic field in the stator which moves in the opposite direction.  This causes a decrease in the torque developed by the motor.  The motor will thus have to draw a higher current for the same mechanical load.

          The rotating magnetic field which rotates in the opposite direction induces voltages in the rotor.  These voltages have a frequency that is double the system frequency.  Since the frequency of this rotor voltage is higher, it flows on the surface of the rotor due to the skin effect and causes surface heating which can lead to motor damage.

          Negative phase sequence relays can identify negative phase sequence condition and trip the machine.  Negative phase sequence relays work by using a special filter which filters out the positive sequence and the zero sequence components.  The filtered negative phase sequence voltage alone is measured.  When the measured negative phase sequence voltage exceeds the set value, the relay trips the motor.

















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          Georg Simon Ohm is credited with developing the first empirical relationship between voltage, current and the resistance of a conductor.  This relationship popularly known as Ohm’s law is one of the basic rules of Electrical Engineering. It is also the first step in electric circuit analysis.

          Georg Simon Ohm (1789 – 1854) was born in Elagen, Bavaria in Germany. He had his early education at the the Elagen Gymnasium.  In 1805, he joined the University of Erlagen and later moved to Switzerland where he took up the job of a Mathematics teacher.  He obtained his doctorate from the University of Erlagen in 1811.  He then took up various teaching positions in Germany.

          Ohm, however, was not satisfied with his teaching career which was not particularly well paying.  He strived to make his mark in research and establish his credentials as a scholar.   Towards this end, he wrote a book on elementary geometry.  Ohm had sent a copy of the manuscript to to King Wilhelm III of Prussia.  The King was pleased and offered him a position at the Jesuit Gymnasium at Cologne. 

          The position suited Ohm well as the institution had extensive facilities for research in Physics.  Ohm soon involved himself with research in the field of current electricity.  The Italian Alessandro Volta had invented the battery and Ohm found himself drawn into studies into the flow of electricity in substances.

          He published his findings in 1827 in the  his famous book Die galvanische Kette mathematischbearbeitet (translated as The Galvanic Circuit Investigated Mathematically).  The publication, however brought him little recognition or appreciation. Disappointed, Ohm resigned his position at the Jesuit Gymnasium and joined the Polytechnic School at Nuremberg.

          While Ohm was able to give an empirical relationship for the relation between voltage, current and resistance, he was unable to give a convincing mathematical proof.  This was one reason for his not getting the recognition he rightly  deserved.    In those days, electrical technology was principle a science of the laboratory with little practical applications.  A sound mathematical proof was essential to convince the scientific fraternity. 

          Finally in 1841, the Royal Society in London recognized his work and honoured him with the Copley medal.  He was admitted to the Society the following year.  1849, Ohm was offered the position of Professor of Experimental Physics at the University of Munich.  He died in 1854 in Munich at the age of 65.

          Though largely ignored during his lifetime, the discovery of George Simon Ohm is fundamental to Electrical Engineering.  The relationship he discovered is one of the most used formulae by an Electrical Engineer.

          In 1893, the International Electrical Congress named the unit of electrical resistance, the ohm, in his honour.

















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          Power factor correction involves improving the power factor of a system by adding capacitors to reduce the parallel. Power factor correction is used widely nowadays as utilities increasingly levy penalties for low power factor. Low power factor causes loads to draw a higher current for the same power factor.

         The capacitors draw a leading kVAr to compensate for the lagging kVAr drawn by the load. Thus the total kVAr required for the load is reduced.

Calculation of capacitors required

          The total value of the capacitors to be connected can be calculated from

KVARneed for correction = kW X (tan φ uncorrected - tan φ target )

         Where φ refers to the phase angle of the target and the uncorrected power factor


         
 Excess Power Factor Correction and Self Excitation

The total kVAR to be connected should not exceed the kVAr required to bring the power factor to unity when the motor is running on no-load.

          This is to prevent a condition called self excitation which can cause high voltages and excessive torque. Self excitation is a condition that occurs in induction motors which have capacitors connected to them. Consider a motor coupled to a load running with capacitors connected to it. If the supply to this motor is cut off.

         The motor will continue to run for some time due to the inertia of the load coupled to it. During this time, the energy stored in the capacitor begins to excite the windings. The inductance in the windings and the capacitors together form a resonant circuit. The oscillations produced in this resonant circuit can produce high voltages which can cause damage.

          If the supply is again switched on during this period, the motor can experience sudden movements with high torques.

















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Extra low voltage refers to reduced voltages which are used in houses, parks, gardens, swimming pools to eliminate the risk of electric shock.

AC voltages below 50 volts and DC voltages below 120 volts are considered to be Extra low Voltage.

In many countries, Extra Low Voltage supplies are used to power traffic signals.  This has been facilitated with the advent of LED lighting technology.

Extra Low voltage systems can also be easily integrated with solar panels as the generating voltage is lower.

















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