Components of Electric Power Systems
– Generators supply the power
– Transmission system carries the power from generators to load centers
– Distribution system feeds the power to nearby homes and industries
– Electrical grid provides power to homes and industries
– Single line diagram helps represent the entire system
– Power systems have internal and external sources of power
– Direct current power can be supplied by batteries, fuel cells, or photovoltaic cells
– Alternating current power is typically supplied by a rotor in a turbo generator
– Different techniques can be used to spin a turbine’s rotor, such as steam, falling water, or wind
– The speed of the rotor determines the frequency of the alternating current produced by the generator
– Alternating current generators can produce a variable number of phases of power
– Electricity grid systems commonly use three-phase power at 50 or 60Hz
– Design considerations for power supplies include power output, starting time, and availability of the power source
– The mechanical speed of operation and the type of generator and rotor used are also important factors
– Power electronics and HVDC links can operate at frequencies independent of the power system frequency
– Conductors carry power from the generators to the load
– Transmission system carries large amounts of power at high voltages
– Distribution system feeds smaller amounts of power at lower voltages
– Choice of conductors is based on cost, transmission losses, and desirable characteristics like tensile strength
– Copper and aluminum are commonly used conductors in power systems
History and Development of Electric Power Systems
– In 1881, the world’s first power system was built in Godalming, England
– Thomas Edison developed the first steam-powered electric power station in New York City in 1882
– Lucien Gaulard and John Dixon Gibbs demonstrated the first transformer suitable for use in a power system in London in 1882
– Ottó Titusz Bláthy, Károly Zipernowsky, and Miksa Déri perfected the transformer in 1885
– George Westinghouse licensed Nikola Tesla’s patents for polyphase AC induction motor and transformer designs in 1888
– By 1889, power companies had built thousands of power systems in the US and Europe
– The rivalry between Thomas Edison and George Westinghouse led to the ‘war of the currents’
– Westinghouse installed the first major power system designed to drive a synchronous electric motor in 1891
– Mikhail Dolivo-Dobrovolsky and Charles Eugene Lancelot Brown built the first long-distance high-voltage three-phase transmission line in Germany
– Alternating current was chosen as the transmission standard in the US in 1895
– In 1936, the first experimental high voltage direct current (HVDC) line was built
– The first solid-state metal diode for power applications was developed in 1928
– In 1957, the first thyristor suitable for power applications was developed
– In the early 1970s, solid-state devices became the standard in HVDC
– Information technology and telecommunication advancements allowed for effective remote control of power systems.
Advancements in Electric Power Systems
– Power electronics are semiconductor-based devices capable of switching large quantities of power
– They are commonly used for rectification in digital devices and in photovoltaic installations
– Power electronics are essential for electric and hybrid vehicles, as well as petrol-powered vehicles
– They are used in electric railway systems for grid power supply and speed control of locomotives
– Power electronics appear in a wide range of industrial machinery and residential appliances
– Fuses are protective devices that interrupt the circuit when the current exceeds a certain threshold
– Fuses need to be replaced after they have functioned and cannot be reset
– Circuit breakers are devices that can be reset after breaking the current flow
– Miniature circuit breakers are typically used in systems that use less than 10kW
– Protective relays detect faults and initiate trips, separate from the circuit breaker
– Synchronous condensers are synchronous motors that generate or absorb reactive power
– They are used to provide a solution to step changes of reactive power caused by switching capacitors
– Static VAR compensators switch capacitors using thyristors, providing a refined response
– Static synchronous compensators achieve reactive power adjustments using only power electronics
– Power electronics are used in HVDC systems to convert AC power to DC power for long-distance transmission
– HVDC is more economical than high voltage AC systems for very long distances
– HVDC allows frequency independence, improving system stability in interconnects
– Power electronics are crucial for photovoltaic installations that produce a DC output
– SCADA systems are used in large electric power systems for tasks such as generator control and system element maintenance
– The first supervisory control systems consisted of lamps and switches at a central console near the plant
– Today, SCADA systems are more sophisticated and can be controlled remotely
– SCADA systems are typically controlled with equipment similar to a desktop computer
– The increased use of computer control has also increased the need for security against cyber-attacks
Power Quality in Electric Power Systems
– Power quality issues occur when the power supply to a load deviates from the ideal
– Sustained overvoltages, undervoltages, and frequency deviations can affect power quality
– Temporal issues like voltage sags, dips, swells, and transient overvoltages can also impact power quality
– Power factor, phase imbalance, and high-frequency noise are additional power quality concerns
– Power quality is especially important for specialist industrial machinery and hospital equipment
Power Systems in Practice
– Power systems vary in design and operation
– There are different types of power systems with common components
– Understanding power system types helps in understanding their operation
– Power system design and operation depend on factors such as load flow, fault levels, and voltage drop
– Proper equipment sizing and protective device coordination are important in power system design
– Residential dwellings are usually supplied by low Source: https://en.wikipedia.org/wiki/Electric_power_system
An electric power system is a network of electrical components deployed to supply, transfer, and use electric power. An example of a power system is the electrical grid that provides power to homes and industries within an extended area. The electrical grid can be broadly divided into the generators that supply the power, the transmission system that carries the power from the generating centers to the load centers, and the distribution system that feeds the power to nearby homes and industries.
Smaller power systems are also found in industry, hospitals, commercial buildings, and homes. A single line diagram helps to represent this whole system. The majority of these systems rely upon three-phase AC power—the standard for large-scale power transmission and distribution across the modern world. Specialized power systems that do not always rely upon three-phase AC power are found in aircraft, electric rail systems, ocean liners, submarines, and automobiles.
