Background
The specifications for the current AC power grid were developed by Nikola Tesla and used by Westinghouse at Niagara Falls in 1883. It was a state of the art technology at the time, but this technology is now obsolete compared to the technological advancements made since. Although minor improvements have been made to improve reliability of the grid, the framework of the grid remains unchanged. Lack of interest and financial motivation for utility companies has held back the evolution of the electric grid.
Power generation currently accounts for almost 40% of US's carbon footprint. Some projections indicate there will be a 30% growth in the demand of electricity by the year 2020. Our carbon emissions are at a record high. Building more coal fired power stations is going to increase our green house emissions tremendously and thus increasing the effects of global warming. Thus we have to come up with alternative sustainable energy solutions and also be able to efficiently transmit this energy to the load centers. Building more coal fired power plant is only a temporary solution out of the present energy crisis, which will have lasting negative impacts on our environment.
This paper proposes a long-term solution to get us out of the present energy crisis.
Quick Summary of Problems with Current Grid
Today’s electric grid has a lot of shortcoming. A lot of power is lost due to inefficient transmission and distribution over long distances because of the centralized generation system that we have in place right now.
Although the United States is rich in solar and wind resources, the present electric grid design does not have the capability to incorporate this renewable energy. There is enough wind in the center of US to power the whole nation, but the present electric grid is unable transport this huge amount of electricity to the load centers.
Besides this, the lack of deployment of proper storage techniques by utilities makes it impossible to provide power as and when it is needed.
The present electric meter provides only a reading of the electricity consumed and does not provide any information of total demand and supply. Utility companies currently use a flat-rate pricing system that does not motivate people to reduce unwanted consumption of electricity.
The present grid is interconnected such that a small technical or human error can cause a cascading grid failure. The 2003 blackout that occurred in the Northeast US region is a perfect example of this.
To solve these problems the present electric grid needs to undergo a complete makeover or in other words, we need a smarter grid.
Characteristics of the Smart Grid
The Smart Grid should be able to accommodate a variety of distributed generation, including renewable and still be able to operate efficiently and reliably. It should also be able to integrate a wide variety of distributed power storage systems to supply power during peak demand. Smart devices installed on the Smart Grid, like microcontroller relays and smart meters will notify system operators of rising demand, so that they can synchronize supply with demand and decrease wastage of power. A larger number of high efficiency decentralized power generation should be introduced into the system, which can provide electricity, heating and cooling, with very low transmission losses. Co-generation power plants are an example of this type of generation. This will greatly decrease our dependency on inefficient centralized thermal power plants, thus reducing green house emissions.
The main goals of our proposed Smart grid design include -
Increasing efficiency of generation, transmission and distribution.
To increase safety and reliability.
To be able to self heal after a disturbance or event.
To decrease unwanted wastage of energy.
To implement different ways of storing electricity.
To be able to accommodate distributed generation and storage.
To manage peak demand and supply.
Fast bidirectional communication network.
To decrease household electricity consumption.
To incorporate renewable into the grid.
No further fundamental scientific discoveries are needed to realize this vision of the Smart Grid. Existing nuclear, hydrogen and superconducting technologies, supplemented by selected renewable energy, provide all the technical ingredients required to create a Smart Grid. Mustering the social and national resolve to create it may be a challenge. But the benefits would be considerable.
Power generation for Smart Grid
The average total power consumption in the US is about 3.5 Terawatts. We mainly generate electricity using coal, nuclear and natural gas. Increasing demand has lead to an increase in the number of coal powered generation facilities because they are relatively cheap and can be constructed quickly. But the CO2 and green house emissions associated with coal fired power plants are extremely high when compared to natural gas power plants. We are presently generating very little electricity from renewable resources.
Problems associated with present generation
Power generation accounts for 40 percent of the nation's carbon footprint. 50 percent of the nation’s electricity is generated from inefficient coal fired power plants which have an average conversion efficiency of 40 percent. Increasing the number of plants to satisfy ever-growing energy demand will have a drastic impact on the environment. Global warming phenomenon has been proved to be more than just a myth. We presently have a centralized power generation model. In other words most of our power is generated at distant facilities and transported via inefficient transmission cables. Long distances account for increased transmission losses and also prevent the utilization of the excess heat emitted during generation.
Our Smart Grid solution focuses on obtaining the extra energy needed to meet growing demands from highly efficient decentralized power generation facilities and renewable resources.
Incorporating Decentralized Power Generation
Decentralized power generation consists of a large number highly efficient distributed power generation facilities powering each town. Cogeneration is the best available decentralized power generation option.
Co-generation
Conventional power plants generate electricity using pressurized steam and waste heat is emitted as a by-product though cooling towers. Co-generation power plants generate electricity and the excess heat is transported by way of insulated tubing for local heating purposes and to provide hot water. This prevents the need for consuming additional natural gas and oil for heating during winter. During the summer, the excess steam can be used to drive refrigeration compressors to supply chilled water to air conditioning units, thus providing cooling. As the excess heat is not wasted, these power plants can achieve a conversion efficiency of up to 80 percent, making them one of the most efficient power plants. The only problem associated with cogeneration is that, the heat cannot be transported over very long distances. Hence every city should have its own cogeneration plant. Con Edison distributes 30 billion pounds of steam each year through its seven cogeneration plants to more than 100,000 buildings in Manhattan. This decentralized generation model is a proven technology which exhibits much higher generation efficiency compared to our present centralized generation system. Smart Grid should accommodate a large number of these highly efficient distributed cogeneration facilities.
Figure 2: The working of a Cogeneration model
Incorporating Renewable Power Generation
Increasing the number of thermal power plants is not a long term solution out of the present energy crisis. This will only further increase pollution and green house gases. Thus introducing more renewable energy generation and building a grid that can transport this huge amount of clean energy should be the goal of Smart grid design. Different ways of integrating various forms of clean renewable energy is discussed below.
Wind Energy
We need to have better measurements of wind power plants' output as we integrate wind energy into existing power systems. We also need to develop a way of managing wind power so it can be more readily called upon when needed. The major challenge to using wind as a source of power is that the wind is intermittent and variable and does not always blow when electricity is needed. Not all wind energy can be harnessed to meet the timing of electricity demands. The Department of Energy, the National Renewable Energy Laboratory, Universities and Utility Companies are researching the generation and transmission operational impacts that occur due to wind variability as well as the best practices for wind integration into the grid and the technical requirements of energy storage systems that would serve as temporary batteries for harnessing and releasing stored wind energy at optimal times.
The regions of the US with rich renewable resources like wind and solar, are mostly located far away from the existing grid, and for those that are nearby, the grid is operating at full capacity in those areas. This makes it impossible to accommodate renewable, unless more transmission capacity is added to the existing grid. Squirrel-cage induction generators are widely used as generators for windmill power systems, because they are inexpensive, have high durability, and are capable of operating asynchronously with power systems. However, induction generators suffer the drawback that they cause transient rush currents that are several times larger than the rated value when connected to power systems. Also since wind energy is influenced by geographic and weather conditions, start/stop operations occur frequently for windmill power systems. Therefore, connecting induction generators to power systems causes undesirable voltage fluctuations in power systems, which is the major obstacle against the practical use of windmill generator systems.
Thus continuous monitoring of wind speed and transient behaviour is necessary to ensure proper reliability. The problem can be overcome either by using pump storage or by implementing an HVDC transmission system.
In pump storage, the electricity generated from windmill is directly used by a generator isolated from the grid, to pump water into a reservoir, which is then let to run down through a turbine in a controlled fashion, thus generating electricity. This type of a system eliminates fluctuation in the current and voltage of the electricity generated directly from the windmill. Besides this, it also facilitates in better energy management. Wind mostly blows during the night time when the demand is low. Pump storage systems, store this energy which is produced during off-peak hours, and delivers it during peak demand. Thus the integration of windmills with pump storage systems should be an integral part of upcoming wind energy projects.
Unpredictable transient behaviour in transmission lines carrying wind power that are connected to the grid can cause a variety of problems including line disturbances, over voltages, current fluctuation and arc flashes. Another method of overcoming these problems is to connect windmills to the grid using HVDC transmission. The high voltage of these transmission lines reduces the Infrared loses tremendously. Besides this, the DC system eliminates capacitive and inductive loses which contributes to line impedance of an average AC transmission line. DC transmission does not have to deal with the problem of transients because of the uniform unidirectional flow of current. It also eliminated the skin effect, which contributes to heating and additional transmission loses on an average AC transmission line.
There is enough wind energy is the central portion of the United States to satisfy the energy need of the entire nation. A network of east-west HVDC transmission line, running from this energy rich central portion to the Eastern and Western United states, will be able to supply tremendous amount of clean energy with high efficiency and low transmission loses.
Figure 3: The annual average wind power distribution across the United States
Solar Energy
Solar energy’s potential is off the chart. The energy in sunlight striking the earth for 40 minutes is equivalent to global energy consumption for a year. The U.S. is fortunate to be endowed with a vast resource – at least 250,000 square miles of land in the Southwest is suitable for constructing solar power plants, and that land receives more than 4,500 quadrillion British Thermal Units (Btu) of solar radiation a year. Converting only 2.5 percent of that radiation into electricity would match the nation’s total energy consumption in 2008.
Figure 4: Solar energy distribution across the US in KWh/m2/day
Some 30,000 square miles of photovoltaic arrays is enough to satisfy the needs of the entire nation. Although this area may sound enormous, installations already in place indicate that the land required for each gigawatt-hour of solar energy produced in the Southwest is less than that needed for a coal-powered plant when factoring in land for coal mining. Studies by the National Renewable Energy Laboratory in Golden, Colorado shows that more than enough land in the Southwest is available without requiring use of environmentally sensitive areas, population centers or difficult terrain.
Compressed-air energy storage has emerged as a successful alternative to expensive battery, for storing electricity. Electricity from photovoltaic plants compresses air and pumps it into vacant underground caverns, abandoned mines, aquifers and depleted natural gas wells. The pressurized air is released on demand to turn a turbine that generates electricity, aided by burning small amounts of natural gas.
Different types of technology can be used to harness this solar energy and convert into useful electricity.
Crystalline photovoltaic panels are traditionally used. (15% to 25% efficiency, 4$/Watt).
Thin film solar cells. (12% to 20% efficiency, 1$/Watt)
Solar concentrators using sterling engine
Solar concentrating dishes using highly efficient Photo-voltaic at the focal point.
Elongated concave mirrors with oil filled conduits at the focus that heat water, thus producing steam and generating electricity.
Power towers that make use of thousands of mirrors focusing sunlight onto the tower to generate electricity by producing steam.
Based on the availability of the sun and the topography of the area a variety of the options explained above can be used to tap into this valuable source of energy.
Micro-Hydro Generation
Hydroelectric power plants are one of the most efficient energy conversion technology known to man. We are already using all our major rivers to maximum capacity. Implementation of any more hydro projects can drastically affect the environment, wildlife and the population in those areas. Instead, implementing a large number of micro-hydro across rivers and streams can provide additional electricity for local needs. Micro-hydro employs the kinetic energy of running water to produce electricity. The amperage of the electricity thus produced will not be substantial. This method can be used to power houses and local street lights.
Tidal Energy
Considering the fact that US has a long coastline, tidal is also a good option. The energy in the changing tides can be captured by tidal energy plants, which use the motion of the tides to push air though a turbine that is connected to a generator, thus producing electricity. Presently there is very few commercial tidal energy plants because of a number of problems associated with them. The transmission of tidal energy is an issue, because it requires the installation high cost undersea transmission cable. It is also an obstruction to passing ships and barges. Large distances of shoreline need to be covered to get substantial amount of electricity. Thus the best solution is to employ tidal on a small scale to power local coastal cities.
Figure 5: Tidal power generation model
Geothermal Energy
Large scale geothermal plants are presently located in California, Nevada and Arizona. Other areas are not very favourable for large scale geothermal electricity production. However geothermal energy can be used to provide heating during winter to residential areas. This is done by burying a network of metal rods into the ground. These are also called ground source heat pumps. During winter, ground heat is pumped into the house and during summer, heat is used to drive a refrigeration compressor that provides cooling. If this technology is used for residential heating and cooling it will tremendously decrease peak summer and winter load. Thus coal fired generators will not have to run at full capacity to meet the peak demand, if this technology is implemented on a large scale. This will significantly reduce the emission of green house gases, cut down residential electricity bills, and avoid the construction of more power plants and natural gas facilities.
To implement this technology on a large scale, the government will have to raise public awareness and provide subsidies and grants to residential owners who would like to adopt this technology.
Figure 6: A ground source heat pump system for residential heating and cooling
Increasing Transmission Efficiency and Reliability
Problems associated with current transmission system
The US has 300,000 km of transmission lines operated by over 500 companies. This enormous transmission distance accounts for energy losses. Presently about 10 percent of the power generated is lost during transmission. Besides the cost factor, today’s transmission system also has reliability issues. For example, the transmission grid is interconnected in such a way that, a tree falling fault on a single line can cascade into a massive power failure. This was the cause of the 2003 blackout. Thus the future grid should be able to detect the transmission faults and isolate it before causing a major outage.
Figure 7: United States Transmission Grid
A figure of the US power transmission grid is shown above (Figure 7). It is clear from the figure that the central-western portion of the United States has low density of transmission lines. But these are the areas which are rich in renewable energy like wind and solar. Thus, Smart Grid needs to be modelled in such a way that this valuable energy can be utilized.Most of our transmission lines are high voltage 3 phase AC transmission lines coming straight from the power generating stations and energizing the transmission bus which then steps down that voltage using a transformer and energizes the distribution bus, which provides power to the consumers. At peak load, multiple generation stations are cranked on to energize this transmission bus, to meet peak power demand. A slight variation in the phase of this power delivery from multiple generation stations can cause power transients, voltage fluctuations and even burn down the cable.
Figure 8: A transmission line model
Figure 8 shows a transmission line model. From the figure it is clear that it has a series resistance and inductance, and a parallel resistance and capacitance. So in every AC transmission line these three primary loss mechanisms exist. As the distance of transmission increases, so do these losses.
Two ways of increasing transmission efficiency is proposed below - using HVDC transmission lines and superconducting lines.
HVDC
HVDC stands for High Voltage Direct Current. The main advantage of using HVDC is that it has much lower losses compared to AC. HVDC uses only two lines for power transmission. One line is the primary power carrying line and the other one is the neutral or static. Two power carrying lines are introduced on each side of the tower to maintain the physical load balance. Multiple power carrying lines can be introduced on the same HVDC transmission tower, so long as the balance is maintained. The resistive loses of HVDC are comparatively low because of very high transmission voltage. The inductive and capacitive losses are negligible, because based on the transmission line model the inductor acts as a short and the capacitor acts as an open circuit in DC transmission. Therefore, HVDC overcomes these primary loss factors.
Besides this, HVDC does not have to deal with the transient problems that multiple unsynchronized networked transmission lines have. Thus interconnecting the grid with HVDC lines coming from different power station is less painstaking. In other words, to transmit AC power as AC when needed in either direction between Connecticut and Boston would require the continuous real-time adjustment of the relative phase of the two electrical grids. With HVDC instead the interconnection would: (1) Convert AC in Seattle into HVDC. (2) Use HVDC for the three thousand miles of cross country transmission. Then (3) convert the HVDC to locally synchronized AC in Boston, and optionally in other cooperating cities along the transmission route.
HVDC also facilitates in interconnecting grid of different frequencies, which would not be possible with AC. For example, the Mexican power grid runs at 50 Hz, whereas the US power grid operates at 60Hz, thus interconnecting these two grids using traditional AC would be impossible. However, HVDC could easily accomplish this task.
A national east-west HVDC line will be able to transport tremendous amounts of renewable wind and solar energy from the center of US and power big cities with clean energy. This should be a priority of future energy policies. Dwindling coal deposits and other conventional forms of fuel can cause nationwide energy shortage if such a plan is not implemented quickly. Interstate HVDC connections operated by different system owners do not have to deal with the fluctuation and transient problems associated with AC transmission. Hence HVDC transmission of the valuable renewable energy in the central portion of the US, to the major load cities is the quickest, cleanest and safest solution out of the present energy crises.
Figure 9: Comparison of AC and HVDC loses with respect to transmission distance
Figure 9 shows a comparison of AC and HVDC line loses with respect to transmission distance. From the figure it is clear that HVDC is the better option for long distance transmission.
Superconductivity
One theoretical solution to loss-free transport of energy is superconductivity. A lot of research is still being done to bring down superconductivity to room temperature. This method has proved its potential in the Maglev transportation system. Whether this same technology can be practically implemented to carry power over long distances still remains an issue. Some of the transmission solutions based on this technology are as follows.
Superconducting connections to new power plants would provide both a source of hydrogen and a way to distribute it widely, through pipes that surround and cool the superconducting wires. A hydrogen-filled superconducting channel would serve not only as a conduit but also as a vast repository of energy, establishing the buffer needed to enable much more extensive use of wind, solar and other renewable power sources.
These superconducting channels will be able to accept inputs from a wide variety of generators, from the smallest rooftop solar panel and farmyard wind turbine to the largest assemblage of nuclear reactors. Because a superconducting channel would use hydrogen as its cryogenic coolant, it would transport energy in chemical as well as electrical form. Next-generation nuclear plants can produce either electricity or hydrogen with almost equal thermal efficiency. So the operators of nuclear clusters could continually adjust the proportions of electricity and hydrogen that they pump into the Smart-Grid to keep up with the electricity demand while maintaining a flow of hydrogen sufficient to keep the wires superconducting. For example, every 70-kilometer section of superconducting cable containing 40-centimeter-diameter pipes filled with liquid hydrogen would store 32 gigawatt-hours of energy. That is equivalent to the capacity of the Raccoon Mountain reservoir, the largest pumped hydroelectric facility in the U.S.
Thus superconducting channels enable the transfer of huge amounts of energy at negligible resistance. The pressurized hydrogen can also be tapped into at the load end using a fuel cell, which will convert this waste hydrogen into electricity, before its temperature rises and it no longer acts as a cryogenic coolant. The main advantage of this technology is that hydrogen which acts as the cooling agent to achieve absolute zero temperature is also a rich source of fuel. The cost of implementing this technology is immense. But the current carrying capacity of such a line would be so high that it would be able to transport all the energy generated from windmills in an area, and still have space to accommodate the energy transmission of a nearby solar farms and power plants. At present the cost of implementing such a technology even on a small scale would be immense. Thus more research and government funding will be necessary to perfect this technology.
Figure 10: Structure of a 3 in 1 superconducting cable
Electricity Storage and Distributed Generation
There is a misconception among many people that electricity cannot be stored. Although electricity cannot be stored in the elemental form, it can easily be stored by converting it into another form of energy. Proper storage is a very important aspect of the Smart Grid because it enables peak time power to be provided, without the need for more fuel generation stations and also enables the timely supply of power from wind and other renewable based on demand. Therefore the implementation of proper power storage techniques is crucial to the proper functioning of Smart Grid. Different ways of storing electricity from supply and demand side are discussed below.
Pump Storage
Pump storage facilities consist of a top reservoir and a bottom reservoir with a turbine that allows bidirectional flow of water. Water is pumped up to the top reservoir at night, when demand for power across the country is low. When there is a sudden demand for power, the head-gates are opened, and water rushes down the tunnels to drive a turbine, which in turn drives powerful generators. The water then collects in the bottom reservoir, ready to be pumped up to the top reservoir during off-peak hours.
Dinorwig in Northern Wales has one of the largest pump storage plants in the world - it can provide 1320 Megawatts in 12 seconds. Thermal power plants take an average of one to two hours to reach full generation capacity. Nuclear power plants take much more than that.
Although the losses of the pumping process makes the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. Taking into account evaporation losses from the exposed water surface and conversion losses, approximately 70 to 85 percent of the electrical energy used to pump the water into the elevated reservoir can be regained. Pumped storage is the largest form of grid energy storage (in terms of capacity) available with the quickest load response time. Integrating large generating facilities like thermal power plants with pump storage enables the timely delivery of power based on the demand. Thus there won’t be a need to crank on expensive peak generators to supply power during peak demand. Besides this, pump storage can also deliver stored wind power more efficiently at the right time based on demand. Integrating wind farms with pump storage overcomes the transient and power unpredictability issues associated with wind generation.
Figure 11: Left- A pump storage facility in Wales.
Figure 12: Right- The working of a pump storage facility.
Batteries
Batteries store electricity in chemical form. This chemical energy stored in the battery can be retrieved as and when required. Using batteries to store the power produced by huge centralized power plants is not practical as it is very expensive. However batteries can be integrated into the existing residential generating facilities, like rooftop solar cells and micro-hydro facilities. Thus, in the case of rooftop solar cells, the extra energy produced during the afternoon, when no one is at home can be stored in batteries, which can then be consumed later. This ensures better energy management and the extra energy generated does not go wasted. A variety of batteries can be used to store household solar power. NiCd, Li-ion and lead acid are the common ones. Each has its own advantages and disadvantages. So the consumer must make a practical choice based on his or her need.
Compressed Air Storage
Compressed air storage uses electricity to drive a compressor to pump pressurized air into an underground cave during off peak hours. Then during peak hours this trapped compressed air is released in a controlled fashion to get back electricity. No large scale project implementing this type of energy storage has been undertaken, but it is a proven technology and with additional research and funding it can be perfected to store off peak electricity efficiently.
Figure 13: Compressed air storage model
Distributed Solar Power Generation and Dynamic Pricing Model
Utility companies should give consumers the option of selling electricity back into the grid. This encourages consumers to install rooftop Photo-Voltaic (PVs) and they do not have to invest in storage either, as the extra electricity produced can be provided back into the grid. If every house in residential areas has rooftop PVs that feed the grid during peak hours, then that accounts for a large amount of energy. This extra energy can power industries, businesses, companies, malls and hospitals in those areas during peak hours instead of cranking on a huge thermal power plant to supply that power. Households with PVs will have very low electricity bill. In fact it may also be possible to receive a refund from the utility if electricity production exceeds their electricity consumption.
The utility can also incentivise customers and earn more profits by introducing a dynamic pricing model. Presently our nation follows a flat-rate model, which means that we pay the same price for electricity during peak-time and off-peak hours. The peak time generation cost is equally shared by all the consumers in the state regardless of who used the electricity when. In other words, the person that used the dryer at midnight (off-peak) pays the same as the person who used the dryer at noon (peak). Dynamic pricing gives the consumer the option of paying lower rates during off peaks and higher rates during peak hours. This can cut down household consumption tremendously. This will incentivise residential consumers to conserve electricity and even produce extra electricity by way of rooftop solar cells and provide it to the grid for a higher price during peak hours. In this way residential consumption can be cut down, residential solar generation can be increased and pollution can be decreased because of lower number of thermal power plants operating at peak load. Utilities can also end up making more profits, because they won’t have to buy energy from the expensive peak time generators and from other jurisdictions, instead they can power factories and businesses using the power generated by the residential rooftop solar cells. Using this generation and distribution model utilities can make more profit, reduce greenhouse gases, and consumers are incentivised to conserve energy and install rooftop solar cells.
Smart Meter
A smart meter refers to a type of advanced meter that identifies consumption in more detail than a conventional meter. It provides details like how much energy is being used and the price of the electricity that is being used, based on the demand. So if the demand is high, smart meter charges a higher price for every Kilo Watt (kW) that is used at that time and if the demand is low then the smart meter charges a lower price for each kW. This is possible because, the smart meter is talking to other smart meter in the locality, to the power generation stations and to every equipment in the house. This enables better demand and supply management.
The smart meter enables utilities to detect outages, connect and disconnect customers remotely, execute sophisticated demand-response programs and perform other customer services. They are able to improve efficiency in the use of the electricity they purchase and the ability to save money by employing time-of-use rates and taking part in automated demand-response programs to shave peak usage. Each meter must be able to reliably and securely communicate the information collected to some central location. There are several other potential network configurations possible, including the use of Wi-Fi and other internet related networks. Thus the smart meter enables a similar broadband communication network as today’s internet, thereby increasing efficiency and reliability.
The benefits of using smart metering technique are as follows:
Save energy and money: The energy use information collected by your smart meter allows you to make decisions about reducing your energy use. With the ability to know when prices are high, and when they are low, smart meters allows the consumer to save money on their bills by adjusting their consumption.
More Privacy: Because smart meters send information electronically, meter readers will no longer have to enter your property.
Find Problems Faster: Smart meters will enable us to complete service orders (such as turn-on and turn-off) more rapidly.
Help the Environment: Smart meters can help you save energy which saves natural resources and reduces the need to build new power plants or other equipment.
Enabling Future Smart Homes and Businesses: Smart meters can provide additional benefits including sending you notification when your bill reaches a certain amount.
Online energy management: Smart meter captures daily electric usage and can be viewed on a website.
e-Notification: With a smart meter, you can get an estimate of your monthly bill amount based on your month-to-date usage.
Smart Meters usually involve a different technology mix, such as real-time or near real-time sensors, power outage notification, and power quality monitoring. These additional features are more than simple automated meter reading (AMR). These electric meters can send data via radio signals to a collector unit, which transmits meter information to a computer. Suppliers will install two-way communication systems that display accurate real-time information on energy use in the home to the consumer and back to the energy supplier, thus enabling better energy management vital to 'Smart Grid' technology.
Figure 14: Smart metering system
Protection and Reliability
Power system protection is the part of electrical power engineering that deals with protecting the electrical power system from faults by isolating the faulted part from the rest of the network. The main objective of a protection scheme is to keep the power system stable by isolating only the components that are under fault, whilst leaving as much of the network as possible still in operation. Thus, protection schemes must apply a very pragmatic and pessimistic approach to clearing system faults.
Present Protection System
Electromechanical relays have been conventionally used in the power grid for many years. These relays are hooked up to circuit breakers. As soon as a fault occurs on the line, it leads to an increased flow of current through the line which in turn causes the relays to operate and open the circuit breaker. This was a good technology for the time, and most utilities still use it today.
Electromechanical relays have a slow operating time. Operating time is vital for the proper functioning of the grid. A slow operating time can cause a chain reaction due to a single fault which in turn can lead to the collapse of the entire grid.
'Smart Grid' Protection System
Proposed Smart Grid would use a microcontroller based relaying system to keep track of faults and over voltages. The operating time of a microcontroller is substantially lower than an electromechanical device. The digital communication used by the microcontroller uses less power and is more accurate. A single integrated microcontroller can be programmed to perform the functions of hundreds of electromechanical relays combined. Microcontroller relays hooked up to the smart meter will enable two-way communication between them, thus detecting local faults and disturbances as soon as or even before they actually occur. A remote microcontroller would be able to open the circuit breakers connected to a transmission line when a tree falls or in the event of a lightning strike, thus isolating the fault. It would also be able to measure current-voltage lag, and correct power factor accordingly by turning on capacitor banks connected to the line.
Thus a smart grid based on a microcontroller protective scheme is the technology of the future which will increase reliability, safety and efficiency.
Conclusion
An overhaul of the century-old outdated and inefficient grid is needed urgently. This report provides a framework for a new power grid – Smart Grid – that can address the energy demand of the future efficiently, reliably and safely. Methods of power generation, storage, transmission and distribution are recommended. The vision of Smart Grid proposed in this report incorporates these methods to provide sustainable energy production and management system. A major part of the Smart Grid is to incorporate renewable sources of energy into the grid and have a dynamic, real-time energy management system that matches supply to demand. Various methods of reducing losses have also been reported. For example, HVDC lines are recommended to reduce transmission losses, Co-generation plants and pump storage methods are recommended for efficient power generation and storage. All the technology required for a shift to the proposed system already exists. Smart Grid will also allow future technological improvements to be incorporated more easily.
