What is an Electric Power System?
Ever wondered about the network through which you get the electricity to your home? We live in a world now, where electricity is the most important part of our lives. Almost everything we do in our daily lives is directly or indirectly assisted through an electrical system.
An Electric Power System is a complex but well-designed network of various electrical components deployed for the Generation, Transmission, and Distribution of electricity to serve the needs for electricity of human beings.
An Electric Power System can be categorized majorly into three parts:
Electric Power Generation System
Electric Power Transmission System
Electric Power Distribution System
Electric Power Generation System:
"Energy can neither be created nor destroyed" I am sure we must have heard this line so many times in our lives. The generation of electricity is also the conversion of energy from one form to another form. We can say that the Electric Power Generation systems are simply the combination of a potential or stored energy converter providing kinetic energy, which, in turn, creates electric power for use in motors, lighting, heating, and other applications of modern life.
Power transmission lines run over long distances to transfer the electricity from the generation point to the point where it is being used by various levels of consumers. So, we have the luxury of generating power at far distances from its load point. Therefore, these generation systems are divided into types as per generation at source and generation at need (some lies in between) are mentioned below.
Generation at the source systems describes the traditional, electric power production model. The hydropower plant is the best example of this. In hydropower plants water is stored at a high point or head and its stored potential energy is converted into rotational kinetic energy when the water pressure is released onto the turbine blades. The synchronous generator coupled with the turbine rotates and the electricity is generated at the required voltage level.
Fossil fuel generation systems can be located near the source of fuel with electric power transmitted to the point of use, or the fuel can be transported closer to the point of use. Fossil fuels such as coal, petroleum, or natural gas are combusted to create heat. Generators can be driven directly from combustion as in gas turbines or steam created by fuel combustion can be used to drive the turbine generator.
Nuclear power generation systems locations are dictated by adequate water availability but also by political and regulatory restrictions as well. These systems also use a steam generation process to generate electricity.
Geothermal generation systems can only be placed where subsurface heat conditions are hot enough and close enough to the surface. For the most part, favorable conditions exist where there is high seismic and volcanic activity.
Tidal energy generation systems use the natural throttling action created by shoreline geography to drive turbine-generator systems.
Generation systems near use have the advantage of higher efficiencies due to low transmission loss.
Wind energy generation is possible anywhere wind is prevalent. Wind generation exists at many scales from backyard to large wind farms. Linear wind energy is converted to rotational kinetic energy via large turbine blades, which, in turn, is converted to electricity by a generator.
Solar power generation can be either thermal or photovoltaic. Thermal systems have limited options for location and are placed where sunlight is plentiful and clouds are few to focus solar energy onto a “solar furnace” using mirrors. This generates enough heat to drive a steam turbine.
Photovoltaic generation systems can be large commercial “farms” or individual residential or commercial systems. Photovoltaic cells convert solar energy directly to electric energy. The DC output is converted to AC for consumption using inverters.
Other point-of-use generation systems include standby and portable generators. These generator systems use petroleum fuel and natural gas to power an internal combustion engine that drives a generator. Other larger systems may use a gas turbine as a motive source.
We will discuss the Electric Power Generation System in detail in the next post.
Electric Power Transmission System:
The Electric Power Transmission System is the medium of transmitting the electricity generated at the power plant to the Grid Substations. We are basically transmitting electricity in terms of power(MVA, MW). If we consider an Electric Power System network to be lossless, power is constant throughout the system(i.e. from Source to Load). Only Voltage levels at various points can be stepped up or stepped down using Power transformers. This Step Up or Step Down of Voltage is done in the Grid Substations. If we talk about the Indian Transmission system network, Transmission of power is done at various voltage levels in India.
In INDIA we have the nominal Extra High Voltage lines in vogue are ± 800 kV HVDC & 765 kV, 400 kV, 230/220 kV, 110 kV, and 66 kV AC lines.
As no system designed ever is completely lossless, the same is true for transmission lines as well. But we need Maximum power transferred from the source to the load system. Therefore, over the year we have improved our systems to make the minimum loss. That's why the transmission of power happens at very high voltage levels. Since power is constant throughout the system, If the Voltage level is high, low current flows through the transmission line and therefore low power loss(I^2R).
There are two types of transmission lines, both have their own pro and cons. They are:
HVAC Transmission lines
HVDC Transmission lines
We will discuss the Electric Power Transmission System in detail in the next post.
Electric Power Distribution System:
Electric Power Distribution is the final stage in the delivery of electric power from the source to consumers. Transmission lines deliver power to various distribution substations. From there the electricity is distributed to different consumers at various voltage levels through different types of feeders.
Distribution of electricity to consumers popularly starts from the 33kV voltage level. Large plants have their own substations to step down the voltages as per their need. They do so using the suitable voltage ratio Power Transformers. So, large plants are sometimes supplied power at 33kV voltage level only. Then, for other consumers, power distribution utilities have their own 33/11KV or sometimes 66/11KV substations. Some industrial consumers are given electricity connections at 11kV voltage level only. From there they have their own system in place to use electricity at different voltage levels.
In India, in 2017-18, about 31.59% of total energy consumption happened for residential, commercial, and public sector consumers. Most of these consumers are being fed electricity at 11kV, and 0.44kV voltage levels. So, In the Distribution System, the major infrastructure of electricity lines are at 11kV and 0.44kV voltage levels.
In our household, we get electricity at 230-240V. That is a single-phase supply, or we can say that we take the connection of single-phase supply, because all the household appliances we use are designed for single-phase supply and for voltage between 230-240V. There is also a concept of frequency of power supply, which in India is 50hz. I will write all these in detail in a further post.
Moreover, there are different types of feeder connections in place to provide electricity to the consumer in the most reliable way. After all, because of consumers, only distribution companies earn. so, there are multiple types of feeders, their protection systems are in place to provide high-quality electricity (i.e. free from Undervoltage, overvoltage, or flicker problems) to consumers with minimal interruptions. So, there are Reliability Indices regarding guidelines from CEA, which most of the distribution utilities follow.
Electric Power Distribution is a very big area to explore I will discuss that in a part-wise manner in the next few posts.
Keywords: Electric Power System, Reliability, Technical Writing, SAIFI, SAIDI, Distribution System
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