Figure 1. A distribution power line.[1]

Distribution grid refers to the final stage of the electrical grid which distributes electricity to homes, industry, and other end users. Distribution both delivers the electric power to the every user on the grid and once delivered, it also reduces power to safe customer-usable levels.[2] The power level is reduced by step-down transformers, which lower the voltage of the electricity from dangerous levels (over 1 kV) to safer levels (100 - 400 V). The entire distribution grid includes lines, poles, transformers, and switching and protection circuits that deliver safe electrical power.

Figure 2. Pad mounted transformer for electrical distribution.[3]

Substations are located throughout the whole electrical grid, from the power plants all the way to the distribution grid. The ones near the power plant contain the transformers that step-up the electricity in order to reduce energy loss over its transmission, the ones before subtransmission lines step-down the electricity to lower voltages, and distribution stations connect the subtransmission lines to distribution lines.[4]

The distribution grid uses overhead and underground subtransmission power lines which operate between 26 kV and 69 kV.[2] These connect to the distribution substations that distribute the power to where it is needed via lower voltage distribution lines (2.4 - 33 kV), shown in Figure 1. These lines lead to transformers that step-down the electricity while also preventing circuit overloads from affecting voltages at other points on the grid. The transformers used for distribution can be seen on poles for overhead lines (Figure 1), or on the ground for underground lines, called pads (Figure 2).[5]

Distribution stations are either built within buildings or outdoors, but always in an enclosed area. The design of these stations depends on economic, environmental, legal and social factors.[4]

For Further Reading

For further information please see the related pages below:

References

  1. Wikimedia Commons, [Online], Available: http://upload.wikimedia.org/wikipedia/commons/3/33/240v_transformer_-_geograph.org.uk_-_1062014.jpg
  2. 2.0 2.1 R. Paynter and B.J. Boydell, "Power Transmission and Distribution: An Overview" in Introduction to Electricity, 1st ed., Upper Saddle River, NJ: Pearson, 2011, ch.25, sec.1, pp.1095-1097
  3. sdpitbull via Flickr [Online], Available: https://www.flickr.com/photos/stevestr/4624935949
  4. 4.0 4.1 R. Paynter and B.J. Boydell, "Transmission Lines and Substations" in Introduction to Electricity, 1st ed., Upper Saddle River, NJ: Pearson, 2011, ch.25, sec.3, pp.1102-1105
  5. R. Paynter and B.J. Boydell, "Distribution Grids" in Introduction to Electricity, 1st ed., Upper Saddle River, NJ: Pearson, 2011, ch.25, sec.4, pp.1106-1107