Question Corner: Electricity standard

In India, why do we use electricity at 230 volt and 50 hertz while other countries like US use at 110volt and 60 hertz?

PUSHPENDRA MUDGIL

New Delhi

The supply of electric power to our homes from generating station is mainly in the form of alternating voltage in which there is change in the polarity of voltage on a regular cycle. AC can easily be transmitted to large distance also it can be step up or down easily using transformer. The voltage, expressed in terms of root mean square value, and frequency are two important parameters of AC.

There is no common standard for these parameters and these vary among regions. The voltages are generally in the range of 100-240 V and the two commonly used frequencies are 50 and 60 hertz. However, many other combinations of voltages and frequencies, including direct current, were formerly used, with frequencies between 25 hertz and 133 hertz and voltages from 100 to 250 V. The choice of utilisation voltages is due more to historical reasons then optimization of the distribution system.

The system of three phase alternating current generation, transmission and distribution was developed in the 19th century by Nichols Tesla, George Westinghouse and others. Thomas Edison developed direct current (DC) system at 110 V. In the United State during that time AC power was distributed mostly for residential incandescent lighting, in competition with Thomas Edison’s DC power system.

Now the frequency of the AC supply depends upon the design and the rotatory speed of the generator. Generators operated by slow speed engines will produce lower frequencies, for a given number of poles, than those operated by for example a high speed steam turbine, these factors plays an important role to decide the operating frequency. When the German company AFG built the first European generating facility, they decided to fix the frequency at 50 hertz. Their standard spread to the rest of the Europe. Also India has adopted the same standard. On the other hand Westinghouse, an electrical company founded by George Westinghouse, in US decided on 60 hertz, eventually leading to the world being mostly divided into two frequency standard. Most 60 hertz systems are nominally 120 V and most 50 hertz are nominally 230 V

KUMAR VIMAL

Assistant Professor

Delhi Technological University