Electrical power distribution alternating current

Inverters are required to make the PV cell generators compatible with the installed base of electrical consumers, because cells produce direct current and the power distribution grid uses alternating current. A simple electronic inverter is similar in function to the converters used in variable-speed drives to drive the load. One of the many inverters on the market is SMA Technolo-gie s "Sunny Boy," which has been used in nearly one million installations and is available in sizes from 400 Wp up to mWp capacities. 

Synchronous Inverter - An electrical inverter that inverts direct current electricity to alternating current electricity, and that uses another alternating current source, such as an electric power transmission and distribution network (grid), for voltage and frequency reference to provide power in phase and at the same frequency as the external power source. 

Alternating current electricity is generated in thermal power stations (coal-, gas- and oil-fired), in nuclear power stations, as well as using natural resources (e.g. wind farms). It is then transmitted by way of overhead lines at4(X)kV (i.e. at 400 000 volts) Figure 4.4.1), 275 kV or 132 kV to distribution substations where it is transformed down to 33 kV or 11 kV for distribution to large factories, or further transformed down to 230 V for use in domestic and commercial premises and smaller factories. 

When a very long, unprotected or poorly protected embedded structure such as a pipeline crosses different types of soil, the dissolution potentials of the metal with respect to the soil are not consistently the same. This leads to the circulation of currents, which results in localised corrosion at the exit zones into the soil. This is also observed with immersed or semi-immersed structures such as ship hulls. For this reason, the return current should not flow through the hull, as one would be inclined to do on a small craft with battery-powered electric equipment. One conductor for each polarity is required if the system is distributing direct current, and one conductor per phase (plus one for the neutral, if required) for alternating current. 

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