Notes On Electricity: Generation, Transmission & Distribution

• Electrical power system consist of 4 major categories:
  a. Generation System
  b. Transmission System
  c. Distribution System
  d. Utility System
• Majority of electricity (65-70%) is produced by steam turbine plants and fuel is Coal or Nuclear.
• Hydro electric generation (25-30%) forms the 2nd largest means of generating electricity.
• Renewable sources of energy fall in a very small range (2-5%).
• Renewable sources of energy – solar, wind, ocean, bio gas, geothermal, etc.
• Gas Turbines are used during short periods of high demand for Peaking.
• Large generators voltage rating or generation is @ 13.8kV to 24kV voltage levels.
• Generator voltage is stepped up to transmission voltage level using transformers.
  Because a. Generation and Distribution stations are far away, b. There will be huge I²R losses (transmission losses or copper losses) if the voltage level is low, c. Transformers can transform this energy to higher voltage levels, without much loss.
• Transmission voltage levels in the range from 115kV to 765kV.
• Standard transmission voltages are 115kV, 138kV, 230kV, 345kV, 500kV and 765kV.
• At distribution station, the transformer steps down the voltages.
• Low voltage ranges from 34.5kV to 138kV at distribution station.
• Distribution standard voltages are 4.16kV, 12.47kV, 13.2kV, 13.8kV and 34.5kV i.e. range is from 5kV to 34.5kV.
• Why we cannot use higher voltages directly?
  a. Difficult to have equipments with such a high insulation rating.
  b. Not economical.
• Distribution transformers are used to further step down to utilization voltage levels, usually at 600V.
• Standard utilization voltages are 480Y/277V, 460V, 208Y/120V, 240V, and 120V.
• Higher utilization voltages – 6.9kV and 4.16kV are standard voltages for supplying large industrial motor loads.

Wattage of Common Household Appliances/Tools

Wattage of Common Household Appliances/Tools
Appliances         Resistive Load              Reactive Load
Blender                   375 watts                  500 watts
Clock Radio               5 watts                        ---
Coffee Maker      1,700 watts                        ---
Computer - PC       300 watts                       ---
Cuisinart                 450 watts                   650 watts
Deep Fryer          1,800 watts                        ---
Electric Blanket       400 watts                        ---
Electric Curlers       300 watts                        ---
Frying Pan           1,250 watts                       ---
Hair Dryer 1,875 watts ---
Iron 1,200 watts ---
Light Bulbs see marking on bulb
Microwave 1,050-2,500 watts ---
Washing Machine 1,150 watts 2,200 watts
Water Heater 4,000 watts ---
TV - Color 300 watts ---
Common Tools Resistive Load Reactive Load
Air Compressor (1hp) 1,500 watts 4,500 watts
Cultivator 700 watts 1,400 watts
Freezer 800 watts 2,100 watts
Furnace Fan 875-1,200 watts 2,200 watts
Garage Door
Opener (1/4 hp)
550 watts 1,000 watts
Grinder, Bench 1,400 watts 2,450 watts
Heater, Kerosene (90,000 BTU) 500 watts 725 watts
Sump Pump (1/3 hp) 800 watts 1,250 watts
Well Pump (1/2 hp) 150 watts 1,950 watts
Saw, Band 1,100 watts 1,350 watts
Table Saw (10 inch) 1,750 watts 4,250 watts

History of Electrical Engineering:

The discoveries of Michael Faraday formed the foundation of electric motor technology.However, it was not until the 19th century that research into the subject started to intensify. Notable developments in this century include the work of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, Michael Faraday, the discoverer of electromagnetic induction in 1831, and James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise Electricity and Magnetism.

Electricity has been a subject of scientific interest since at least the early 17th century. The first electrical engineer was probably William Gilbert who designed the versorium: a device that detected the presence of statically charged objects. He was also the first to draw a clear distinction between magnetism and static electricity and is credited with establishing the term electricity. In 1775 Alessandro Volta's scientific experimentations devised the electrophorus, a device that produced a static electric charge, and by 1800 Volta developed the voltaic pile, a forerunner of the electric battery.Thomas Edison built the world's first large-scale electrical supply network.


 Nikola Tesla made long-distance electrical transmission networks possible.During this period, the work concerning electrical engineering increased dramatically. In 1882, Edison switched on the world's first large-scale electrical supply network that provided 110 volts direct current to fifty-nine customers in lower Manhattan. In 1884 Sir Charles Parsons invented the steam turbine which today generates about 80 percent of the electric power in the world using a variety of heat sources. In 1887, Nikola Tesla filed a number of patents related to a competing form of power distribution known as alternating current. In the following years a bitter rivalry between Tesla and Edison, known as the "War of Currents", took place over the preferred method of distribution. AC eventually replaced DC for generation and power distribution, enormously extending the range and improving the safety and efficiency of power distribution.

The efforts of the two did much to further electrical engineering—Tesla's work on induction motors and polyphase systems influenced the field for years to come, while Edison's work on telegraphy and his development of the stock ticker proved lucrative for his company, which ultimately became General Electric. However, by the end of the 19th century, other key figures in the progress of electrical engineering were beginning to emerge. The Darmstadt University of Technology founded the first chair and the first faculty of electrical engineering worldwide in 1882. In the same year, under Professor Charles Cross, the Massachusetts Institute of Technology began offering the first option of Electrical Engineering within a physics department. In 1883 Darmstadt University of Technology and Cornell University introduced the world's first courses of study in electrical engineering, and in 1885 the University College London founded the first chair of electrical engineering in the United Kingdom. The University of Missouri subsequently established the first department of electrical engineering in the United States in 1886.