In this topic, we will learn about electrical system and introduction. At the end of this topic, you will be able to learn electrical system for powerplant, electrical system important facts and figures, power plant subsystems. We have learned about power plant mechanical processes and systems that run either gas turbine or steam turbine. The turbines then rotate the electrical generator and produce the final product of the power plant, that is electricity or electrical power, which is measured in megawatts. Let us now discuss some important facts and figures for electrical system of a power plant. The power plant output is measured in terms of megawatts. Output of a single turbine generator unit ranges from 250MW - 800MW. The power station houses multiple units of turbine generator. In order to generate so much bulk power, it also consumes a lot of power to the tune of 1-2.5 percent of its generation for a gas-based open cycle and combined cycle. While up to 5-6.5 percent for a coal-based power plant. This is significant and that makes power plant sometimes it's biggest consumer. Design of plants auxiliary electrical system is heavily dependent on mechanical systems and packages. Total number of motors or drives in a power plant could be more than 1,000. Total number of cables in plant ranges from 6,000 for a combined cycle plant and to 15,000 for large coal-based plant. To handle this huge power effectively and efficiently, we need to build a robust electrical system. Design of electrical system complies with customer specification and various standards, example, IS, Indian Standard for domestic projects, and IEC, International Electrotechnical Commission, IEEE, Institute of Electrical and Electronics Engineers for international projects. We have seen that in order to generate bulk power, lot many mechanical processes need to run which consumes significant power. Hence, we need to build a very robust electrical system within the power plant. Based on the function, electrical system for a power station is broadly classified into three subsystems. Main power system, which deals with generation of the power and stepping it up to an extra high voltage EHV level. The system also deals with unit startup power. Auxiliary power system, which deals with distribution of power to various auxiliaries, example, boiler feed pump, cooling water pumps, etc., within the station boundary. The power system is necessary for keeping the unit up and running. Evacuation system, which receives generated power from station at EHV level. The system also deals with export or import of generated power to the grid and deriving unit startup power. Let us summarize all that you have learned. Understanding electrical power plant, the important facts and figures of electrical power plant, three main subsystems of electrical power plant.
