Transmission network

Technical losses

Until the 1930s electricity was generated at local power stations and distributed to the local community. Each region developed its own methods of meeting customers’ electricity needs, resulting in many different network types developing. Large power cuts were common, as customers were often dependent on a single generator that was frequently turned off for maintenance or repair.

Electricity networks were developed in Britain during the 20th century to provide more reliable transmission of electricity supply. These networks connected the consumer with numerous large generators. Operating the transmission network at high voltages, typically 275,000V and 400,000V, meant that electricity could be transferred over long distances. Reliability was improved as access to numerous generators meant that customers no longer relied on single generators to supply them.

Losses are proportional to the resistance of the circuit between a generator and a customer. Losses will increase as circuit lengths extend, but using extra high voltages mitigates this.

The power delivered by a network is proportional to voltage and current. Transmission networks have low current relative to the amount of energy that they deliver and this reduced current helps to reduce network losses. In fact, despite the transmission network extending to a total length in excess of 27,000km, the associated losses account for just over 2% of Great Britain’s total. In contrast, distribution losses account for 6-7% of the overall figure.