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< prev - next > Energy Grid connection (Printable PDF)
It was in London in 1882 that the Edison Company first produced electricity centrally that could
be delivered to customers via a distribution network or ‘grid’. Since then electricity has become
one of the commonest energy sources for domestic use in the West. Electricity is extremely
versatile, clean, easy to use, and can be turned on or off at the flick of a switch. Electricity has
brought enormous social benefits in all areas of life. It is the preferred method of supplying
power for many household applications, especially lighting. However, some 1.6 billion people
still do not have electricity globally, with connection to the national electrical grid is a rare
occurrence in rural areas of the developing and under developed world. In the majority of the
worlds’ poorer countries it is estimated that significantly less than 5% of the rural population are
connected to the national grid. There are many reasons, both technical and economic, which
make grid connection unfeasible and these will be looked at briefly in this fact sheet. In urban
areas of the developing world grid connection is more commonplace, though not always in
‘slums’ or informal communities.
There are other possibilities for providing electricity in rural areas. In many areas where
electricity is required and there is no grid within easy reach then a localised grid (or micro-grid)
can be established using a local power source such as a diesel generator set or small-scale hydro
power scheme. Alternatively, individual households can be connected to stand-alone systems
which can be powered by any of a wide variety of energy sources.
The grid
The national grid is a network of power lines which allows distribution of electricity throughout
all or part of a country. The grid can be connected to a single power source or electricity
generating plant but is usually linked with other plants to provide a more flexible and reliable
network. The electricity is usually transmitted at very high voltage, typically several hundred
thousand volts (depending on power transmitted, national guidelines, etc.) as this reduces losses
and means that smaller cables can be used, reducing the overall cost of the network. Bulk
electricity is generated and transmitted in 3 phase, alternating current (a.c. - 50 or 60 cycles
per second) form and distributed to the consumer as three phase or single phase depending on
the end use requirements. Transmission by direct current (d.c.) is also used, losses associated
with d.c. electricity being lower than a.c., but other costs are incurred as heavy duty rectification
equipment is then needed to supply a.c. electricity to the consumer.
Electricity standards in selected countries
110/220 V
60 Hz
230 V
50 Hz
220 V
50 Hz
220 V
50 Hz
230 V
50 Hz
240 V
50 Hz
Philippines 220 V
60 Hz
South Africa 220/230 V
50 Hz
220 V
50 Hz
240 V
50 Hz
230 V
50 Hz
USA 120 V 60 Hz
After generation, the voltage has to be
stepped up (to a high voltage) for
transmission and distribution using a
transformer and then stepped down (to a
lower voltage) for end use, again requiring
a transformer. The step down process is
usually done in several stages as the
network is reduced in capacity. Typical
consumer voltage is 210V or 415 V for
three-phase and 120 V or 220 V for single
phase depending on national standards.
Three-phase electricity is used for higher
power equipment such as factory or
workshop machinery whereas all domestic
electricity supply is single phase.
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