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  Power Systems, Physics tutorial

Electrical energy:

Electrical energy can be produced through the variety of means that comprise burning of fossil fuels or heat from nuclear reactions to generate steam which power generators that, in turn, produce electricity. Otherwise, kinetic energy extracted from either wind or water can power similar generators. The generated electrical energy is available for use, it is frequently essential to use one method or other to transform or alter electrical energy such that voltage is increased while current is decreased; that makes it appropriate for transmission over long distances. Alternative methods for storage of electrical energy engage use of capacitors and accumulators or batteries. Electrical energy is presence and flow of electric charge and energy in form of electricity is found in the variety of phenomena that include static electricity, electromagnetic fields and lightning.

Electrical energy is result of interaction of subatomic particles with electromagnetic force. Within the atom, electrons and protons create electric charge that can be transferred between bodies through direct contact with conductive material like copper or aluminum wire. When electric charge moves the current is said to flow that may be direct or alternating current.

Electricity stored in the battery and that travels in one direction out of battery is direct current while alternating current takes place when current changes direction repeatedly inside the electrical system as in public electricity supply where current changes direction 50 times every second.

Electrical power systems:

In early days of commercial electric power, transmission of electric power at same voltage as utilized by lighting and mechanical loads limited the distance between generating plant and consumers. Also, lighting, fixed motors, and traction railway systems needed different voltages, and were forced to be powered by different generators and circuits

This was the fact that electricity generation was with direct current and this could not simply be increased in voltage for long-distance transmission.

Limitations to electrical energy delivery and specialization of power lines, and comprising fact that transmission was so ineffective that generators required to be near their loads, power industries developed in distributed generation systems with large numbers of small generators situated near their loads. Transformer, and Tesla's polyphase and single-phase induction motors, were necessary for first combined Alternating Current distribution system that served both lighting and machinery requires and that led to complete alternating current power system for both lighting and power.

Modern power systems are configured around non insulated high-voltage overhead Aluminium alloy conductors, made in numerous strands and reinforced with steel strands. Aluminium alloy is preferred to copper that is sometimes utilized for overhead transmission due to its lower weight and much lower cost for only marginally decreased performance.

Alternating Current:

Application of alternating current has rapidly progressed to point where today, alternating current is form in which electric power is delivered to businesses and residences worldwide. Usual waveform of the alternating current power circuit is sinusoidal wave. In certain applications, different waveforms like triangular or square waves are utilized and in audio and radio signals applications specially, signals are conveyed by electrical wires where objective frequently recovery of information encoded or modulated onto alternating current signal.

In alternating current movement of electric charge periodically reverses direction as opposed to direct current where flow of electric charge is only in one direction. Alternating current can be generated by the coil rotating in the magnetic field. This produces current that regularly changes direction and where if rotation is uniform creates the sinusoidal alternating voltage.

Direct current:

Direct current is flow of electric charge is only in one direction as opposed to alternating where movement of electric charge periodically reverses direction and direct current, as generated by, for example the battery and needed by most electronic devices, is unidirectional flow from positive part of circuit to negative.

Direct Current Power Systems:

Modern high-voltage, direct-current electric power systems contrast with more common alternating-current systems as the means for efficient bulk transmission of electrical power over long distances. Over short distances, high voltage direct current transmission tends to be more exclusive and less proficient than alternating current systems. The main benefit of direct current transmission lies in fact that direct current flows constantly and uniformly throughout the cross-section of the uniform wire that contrasts with alternating current of any frequency whatsoever that is forced away from centre of conducting wires towards outer surface.

This is due to acceleration of electric charge in alternating current generates waves of electromagnetic radiation which cancel propagation of electricity toward centre of materials with high conductivity in phenomenon known as skin effect. Whenever it is essential to stabilize against control problems with alternating current electricity flow, high voltage direct current links are at times utilized. Alternating current power when transmitted through the line increases as phase angle between source end voltage and destination ends increases.

Disadvantages of Direct Current:

When commercial usage of electricity turned out to be wide-spread, certain drawbacks in using direct current in homes became clear. If commercial direct-current system is utilized, voltage should be produced at the level needed by load. To properly light the 220 volt lamp, direct current generator should deliver 220 volts. If 110 volt load is to be supplied power from 220 volt generator, resistance should be placed in series with 110 volt load to make voltage drop of 110 volts. When resistance is utilized to decrease voltage, amount of power equal to that consumed by load is wasted. Another drawback of direct-current systems becomes apparent when direct current from generating station should be transmitted over the long distance through wires to consumer. The large amount of power is lost because of resistance of wires and power loss is equal to I2R where I is current through wires and R the resistance of the wires. This loss can be really decreased if power is transmitted over wires at the very high voltage and at low current. This is not the practical solution to power loss in the direct current system as load would then have to be operated at the dangerously high voltage and due to drawbacks related to transmitting and utilizing direct current, practically every modern commercial electric power companies produce and distribute alternating current that can be stepped up or down by transformer that allows efficient transmission of electrical power over long-distance lines. At electrical power generating station, transformer output power is at high voltage and low current. At consumer end of transmission lines, voltage is stepped down by the transformer to the value needed by load.

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