Importance

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Abstract

An electricity substation 11 receives a high voltage electricity supply and transforms it to a low voltage supply distributed to a plurality of properties 13. The substation 11 is also provided with a demand management unit 14 incorporating a load monitoring means 15 operable to measure the load on the or each low voltage supply cable 12 and each property 13 is provided with at least one intelligent socket 20 for high load appliances. The intelligent socket 20 comprises contacts 21 for making a connection with the conductors of the charging lead; a use monitor 22 operable to detect when a load (i.e. an electric vehicle) is drawn from the contacts 21; a switch 23 operable to disconnect or connect the electricity supply to the contacts; and a control unit 24. The control unit is operable to communicate with the demand management unit 14 via a suitable communications link 16. In operation, the demand management unit 14 monitors communications from each intelligent socket 20 to determine which intelligent sockets 20 are in use and the measured load on the low voltage supply cable 12. When the measured load exceeds a threshold, the demand management unit 14 enters a power rationing mode. In this mode, the demand management unit 14 sends signals to the control unit 24 of each intelligent socket 20 in use. In response to the signals the switch 23 is cyclically operated. This causes the contacts 21 (and hence the electric vehicle 18) to be cyclically disconnected and connected from the electrical supply.

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First Claim