The Drawbacks of Using Low Voltages in Electrical Power Transmission and Distribution

Low voltages in electrical power transmission and distribution are advantageous in certain contexts, such as enhanced safety. However, they carry significant disadvantages, mainly in terms of power loss, conductor size, and current requirements. This article delves into the critical aspects of using low voltages in power transmission and distribution, shedding light on the challenges and inefficiencies it introduces.

Impact on Power Loss and Efficiency

For a given amount of power, lower voltages necessitate a higher current to maintain the same power level. This higher current leads to greater resistive losses in the conductors due to the I2R (current squared times resistance) principle, which can result in substantial energy wastage. The use of step-up transformers is essential to transmit power over long distances efficiently, reducing loss by increasing the voltage, thereby decreasing the current. Conversely, step-down transformers are used before the electricity reaches end-users to ensure safety.

Conductor Size and Cost Implications

Low voltages require larger conductors and better connections to transmit the same amount of power. Lesser resistance is crucial to prevent significant heat wastage. This is exemplified in the case of automobile charging systems, where cars and motorcycles often opt for 12 or 24 volts. A 12-volt alternator at 40 amps can supply more power than a 6-volt 60-amp unit. This highlights the advantage of higher voltage in terms of efficiency and reduced conductor size.

In the context of the United States and North America, the standard voltage supply is 234 VAC, with two legs of 117 VAC. Japan, however, maintains a lower standard of 100 VAC. These differences illustrate the varying requirements and considerations for electrical power distribution in different regions.

Motor Efficiency and Device Functionality

A lower voltage can lead to issues with certain electrical devices, especially those requiring significant power. For example, in devices like electric kettles or toasters, a higher voltage setting can significantly reduce the current requirement. In the UK, a 3 kW kettle or toaster using 240 VAC would draw only 12.5 amperes, but in North America with 110 VAC, the same power would require approximately 27.27 amperes, which far exceeds the standard 110 V receptacle limit.

Energy Transmission and Distribution

The ability to transmit a given amount of power is directly proportional to the square of the voltage. Therefore, at 120 V, you can transmit 100 times as much power as at 12 V, and at 240 V, you can transmit 4 times as much power as at 120 V. This means low voltage is not ideal for transmitting high amounts of power. Higher voltages allow for more efficient and cost-effective power transmission.

High current is a critical drawback of low voltage transmission. To maintain the same power level, the conductors must be larger to handle the higher current, which incurs additional costs and space requirements. This is why distributing power at higher voltages is more advantageous, as it allows for the use of smaller, more manageable conductors while maintaining efficient transmission.

Conclusion

The use of low voltages in electrical power transmission and distribution presents significant challenges, particularly in terms of power loss, conductor size, and the necessity for high currents. While enhanced safety is a notable benefit, the trade-offs in terms of inefficiency and cost make high voltage transmission the preferred and more efficient method for long-distance power distribution.

Keywords: low voltage, electrical power transmission, power loss, distribution efficiency