SMART GRID MODULE-1 Evolution of the Electricity Grid The first alternating current power grid system was installed in 1886 in Great Barrington, Massachusetts. At that time, the grid was a centralized unidirectional system of electric power transmission, electricity distribution, and demand-driven control. In the 20th century local grids grew over time, and were eventually interconnected for economic and reliability reasons. Since the early 21st century, opportunities to take advantage of improvements in electronic communication technology to resolve the limitations and costs of the electrical grid have become apparent. The first official definition of Smart Grid was provided by the Energy Independence and Security Act of 2007. Simply put, it is the integration of information and communication technology in to electric transmission and distribution networks. The smart grid is “an automated, electricity network characterized by a two-way flow of electricity and information, capable of monitoring, analysing, controlling and responding to changes.” It may be looked upon as a reform process by which the balance is accomplished between available energy and demand by putting in place appropriate policies and operational framework. This helps to improve efficiency, reduce the energy consumption and cost and maximise the transparency and reliability of the energy supply chain.
Characteristics of Smart Grid Characteristics Self-Healing and Adaptive Interactive with consumers and markets Optimized to make best use of resources and equipment Predictive rather than Reactive Distributed Generation Two-way communication across the grid Description Rapidly detects re-configures and restores power supply. Motivates and includes the consumer and stakeholders. Improved operational efficiency through optimal utilization of resources and assets. The system behaviour can be analysed and predicted to initiate advanced corrective action, as opposed to responding to emergencies. This virtue makes system resilient to physical/cyber- attacks. Accommodates all forms of generation like solar, wind, bio-mass and storage options. These are integrated in to the grid at various levels. Both energy and information flow in either direction there by enabling information based management. Why implement the Smart Grid now?/Need for Smart Grid Smart grids are required to overcome the following issues:Higher Penetration of renewable resources or distributed generation
Extensive and effective communication overlay from generation to consumers Use of advanced sensors and high speed control Higher operating efficiency. Greater resiliency against attacks and natural disasters Automated metering and rapid power restoration Provided greater customer participation Shortage of power Power Theft Poor access to electricity in Rural areas Huge losses in the Grid Inefficient Power Consumption Poor reliability 1. Ageing assets and lack of circuit capacity In many parts of the world (for example, the USA and most countries in Europe), the power system expanded rapidly from the 1950s and the transmission and distribution equipment that was installed then is now beyond its design life and in need of replacement. The capital costs of like-for-like replacement will be very high and it is even questionable if the required power equipment manufacturing capacity and the skilled staff are now available. The need to refurbish the transmission and distribution circuits is an obvious opportunity to innovate with new designs and operating practices. In many countries the overhead line circuits, needed to meet load growth or to connect renewable generation, have been delayed for up to 10 years due to difficulties in obtaining rights-of-way and environmental permits. Therefore some of the existing power transmission and distribution lines are operating near their capacity and some renewable generation cannot be connected. This calls for more intelligent methods of increasing the power transfer capacity of circuits dynamically and rerouting the power flows through less loaded circuits. 2. Thermal constraints in existing transmission and distribution lines and equipment are the ultimate limit of their power transfer capability. When power equipment carries current in excess of its thermal rating, it becomes over-heated and its insulation deteriorates rapidly. This leads to a reduction in the life of the equipment and an increasing incidence of faults. If an overhead line passes too much current, the conductor lengthens, the sag of the catenary increases, and the clearance to the ground is reduced. Any reduction in the clearance of an overhead line to the ground has important consequences both for an increase in the number of faults but also as a danger to public safety. Thermal constraints depend on environmental conditions, that change through the year. Hence the use of dynamic ratings can increase circuit capacity at times. 3. Operational constraints Any power system operates within prescribed voltage and frequency limits. If the voltage exceeds its upper limit, the insulation of components of the power system and consumer equipment may be damaged, leading to short-circuit faults. Too low a voltage may cause malfunctions of customer equipment and lead to excess current and tripping of some lines and generators. The capacity of many traditional distribution circuits is limited by the variations in voltage that occur between times of maximum and minimum load and so the circuits are not loaded near to their thermal limits. Although reduced loading of the circuits leads to low losses, it requires greater capital investment. Renewable energy
generation (for example. wind power, solar PV power) has a varying output which cannot be predicted with certainty hours ahead. A large central fossil-fuelled generator may require 6 hours to start up from cold. Some generators on the system (for example, a large nuclear plant) may operate at a constant output for either technical or commercial reasons. Thus maintaining the supply-demand balance and the system frequency within limits becomes difficult. Part-loaded generation ‘spinning reserve’ or energy storage can address this problem but with a consequent increase in cost. Therefore, power system operators increasingly are seeking frequency response and reserve services from the load demand. It is thought that in future the electrification of domestic heating loads (to reduce emissions of CO2) and electric vehicle charging will lead to a greater capacity of flexible loads. This would help maintain network stability, reduce the requirement for reserve power from part-loaded generators and the need for network reinforcement. 4. Security of supply Modern society requires an increasingly reliable electricity supply as more and more critical loads are connected. The traditional approach to improving reliability was to install additional redundant circuits, at considerable capital cost and environmental impact. Other than disconnecting the faulty circuit, no action was required to maintain supply after a fault. A Smart Grid approach is to use intelligent post-fault reconfiguration so that after the (inevitable) faults in the power system, the supplies to customers are maintained but to avoid the expense of multiple circuits that may be only partly loaded for much of their lives. Fewer redundant circuits result in better utilization of assets but higher electrical losses. 5. National initiatives Many national governments are encouraging Smart Grid initiatives as a cost-effective way to modernise their power system infrastructure while enabling the integration of low-carbon energy resources. Development of the Smart Grid is also seen in many countries as an important Economic/commercial opportunity to develop new products and services. A lot has been done to mitigate the potential for blackouts—particularly in the effort to provide new technologies that can help make electricity more reliable, in order to sustain an increasingly high-tech economy which is based, in part, on the use of power-sensitive equipment. Many of these technologies are ready for wide deployment now, while others are only now entering demonstrations. Benefits or advantages of Smart Grid ➨It reduces electricity theft. ➨It reduces electricity losses (transmission, distribution etc.) ➨It reduces electricity cost, meter reading cost, T&M operations and maintenance costs etc. ➨It reduces equipment failures due to automatic operation based on varying load conditions. Demand-Response reduces stress on assets of smart grid system during peak conditions which reduces their probability of failure. ➨It reduces sustained outages and reduces consecutively associated restoration cost. ➨It reduces air emissions of CO2, SOx, NOx and PM-2.5. Hence smart grid contributes to keep environment green. ➨It reduces oil usage and wide scale black-outs. Hence smart grid provides security to the people by providing continuous power. ➨Smart grid is capable of meeting increased consumer demand without ading infrastructure. Drawbacks or disadvantages of Smart Grid ➨Continuous communication network should be available. ➨During emergency situation, network congestion or performance are big challenges in smart grid system. ➨Cellular network providers do not provide guaranteed service in abnormal situations such as wind storm, heavy rain and lightening conditions.