Why is only 50 Hz standardized as power frequency in many countries?

Dear Sir !

Historically, the type of electricity delivered to homes and businesses was first DC but then changed to AC electricity. The standard voltage level started at110V, went to240V, back to110V, and then to220V. The frequency started at60Hz and then went to50Hz in most areas.

Early in the history or electricity, Thomas Edison's General Electric Company was distributing DC electricity at110 volts in the United States. Then Nikola Tesla devised a system of three-phase AC electricity at240 volts. He had calculated that60Hz was the most effective frequency. Tesla later compromised to reduce the voltage to120 volts for safety reasons.Tesla's AC system became the standard in the United States. Meanwhile, the German company AEG started generating electricity and became a virtual monopoly in Europe. They decided to use50Hz instead of60Hz to better fit their metric standards, but they stayed with120V.Unfortunately, at120V50Hz AC has greater losses and is not as efficient as60HZ. Due to the slower speed50Hz electrical generators are20% less effective than60Hz generators. Electrical transmission at50Hz is about10-15% less efficient.50Hz transformers require larger windings and50Hz electric motors are less efficient than those meant to run at60Hz. They are more costly to make to handle the electrical losses and the extra heat generated at the lower frequency.Europe stayed at120V AC until the1950s, just after World War II. They then switched over to230V for better efficiency in electrical transmission. Great Britain not only switched to230V, but they also changed from60Hz to50Hz to follow the European lead. Since many people did not yet have electrical appliances in Europe after the war, the change-over was not that expensive for them.The US has also considered converting to220V for home use but felt it would be too costly, due to all the120V electrical appliances people had. A compromise was made in the U.S. in that240V would come into the house where it would be split to120V to power most appliances. Certain household appliances such as the electric stove and electric clothes dryer would be powered at240V.The voltage and frequency of AC electricity varies from country to country throughout the world. Most use230V and50Hz. About20% of the countries use110V and/or60Hz to power their homes.240V and60Hz are the most efficient values, but only a few countries use that combination.

The reason is that, this is in the optimum range for power supply on a national scale. The use of lower frequencies would cause the size, weight and cost of the installed equipment to increase. In physically smaller power systems such as those on planes, ships, submarines and even railways, higher frequencies are used because they allow reduction in the power equipment size and weight. However,50 Hz is NOT standard in all countries.60 Hz is the standard frequency throughout North and South America. 

There are too many reasons,one is that60hz is more safe than50hz because in50 there are less cycle per second and the peak voltage may goes to325 which is dangerous and require more insulation while in60 hz there are more  cylce and the voltage remain110 and are not so dangerous also the no more insulation required

 because the number60Hz didn't fit the metric standard unit sequence (1,2,5). 50 Hz20% less effective in generation, it is10-15% less efficient in transmission, it requires up to30% larger windings and magnetic core materials in transformer construction. .Electric motors are much less efficient at the lower frequency, and must also be made more robust to handle the electrical losses and the extra heat generated. Today, only a handful of countries (Antigua, Guyana, Peru, the Philippines, South Korea and the Leeward Islands) follow Tesla’s advice and use the60 Hz frequency together with a voltage of220-240 V.

In general, AC Power is generated from the Synchronous Generators and the Power Lines are interconnected. Based on the number of poles in the generator and the synchronous speed, the frequency of50 Hz is fixed. For example, for a two-pole generator of rotating speed3000 rpm , it produces50 Hz source.

Countries with Hz distribution have higher voltages, compared with the regions with Hz distribution voltages. There is a long history to how they got standardized in the various systems. However BOTH the high frequency and high voltage do tend to transmit electrical power a little further depending upon the various circuit connections !

this is because at50hz the power is stable and efficient compared with lets say40hz and60hz...

because of safety, the wave form are almost the same frequency for humans hearts

 The reason why most countries standardized 50 Hz for their power generation as follow ;

1. GENERATION COST:

To generate power  with  frequency higher than 50- 60 Hz requires more poles  which increase the size of an alternator  

2.EDDY CURRENT LOSSES :

 As frequency increases eddy current and hysteresis losses increases and hence power loss also increases.

When electric power systems were being developed in the late 19th and early 20th centuries, many different frequencies and voltages were used. Large investments in equipment at one frequency made standardization a slow process. As of the turn of the 21st century, places that now use the 50 Hz frequency tend to use 220–240 V, and those that now use 60 Hz tend to use 100–127 V. Both frequencies coexist today (Japan uses both) with no great technical reason to prefer one over the other and no apparent desire for complete worldwide standardization.When large central generating stations became practical, the choice of frequency was made based on the nature of the intended load. Eventually improvements in machine design allowed a single frequency to be used both for lighting and motor loads.The first applications of commercial electric power were incandescent lighting and commutator-type electric motors. Both devices operate well on DC, but DC could not be easily changed in voltage, and was generally only produced at the required utilization voltage. If an incandescent lamp is operated on a low-frequency current, the filament cools on each half-cycle of the alternating current, leading to the lamps flickering. Generators can only be interconnected to operate in parallel if they are of the same frequency. By standardizing the frequency used, generators in a geographic area can be interconnected in a grid, providing reliability and cost savings.Very early AC generating schemes used arbitrary frequencies based on convenience. Frequencies between 16⅔ Hz and 133⅓ Hz were used on different systems. The proliferation of frequencies grew out of the rapid development of electrical machines in the period 1880 through 1900. In the early incandescent lighting period, single-phase AC was common and typical generators were 8 pole machines operated at 2000 RPM, giving a frequency of 133Hz. (The frequency is determined by the formula, f = NP/120, where N is the generator speed in RPMs, and and P is the number of poles. An 8 pole generator running at 2000 RPM would give us: f = 2000*8/120, which equals 133.33Hz. In the same vein, a 2 pole AC generator running at 3600 RPM will produce 60Hz.)There are many theories, as well as several urban legends, there is little certitude in the details of the history of 60 Hz vs. 50 Hz.After observing flicker of lamps operated by the 40 Hz power in 1891, The German company AEG built the first German generating generating station to run at 50 Hz, and their standard spread to the rest of Europe. In the US, Westinghouse Electric decided to standardize on a higher frequency to permit operation of both electric lighting and induction motors on the same generating system. Although 50 Hz was suitable for both, in 1890 Westinghouse considered that existing arc-lighting equipment operated slightly better on 60 Hz, and so that frequency was chosen.In Japan, the western part of the country (Kyoto and west) uses 60 Hz and the eastern part (Tokyo and east) uses 50 Hz. This is because the first purchases of generators from AEG in 1895, installed for Tokyo, and General Electric in 1896, installed in Osaka. Please see the Wikipedia article, "Utility frequency", at https://en.wikipedia.org/wiki/Utility_frequency It details what differing frequencies were used where and why...

"The first generators at the Niagara Falls project, built by Westinghouse in 1895, were 25 Hz..."

"Several 40 Hz systems were built. The Lauffen-Frankfurt demonstration used 40 Hz to transmit power 175 km in 1891. A large interconnected 40 Hz network existed in north-east England..."

"in the United States, Mechanicville Hydroelectric Plant, still produces electric power at 40 Hz and supplies power to the local 60 Hz transmission system through frequency changers..."

"In the early days of electrification, so many frequencies were used that no one value prevailed (London in 1918 had 10 different frequencies). As the 20th century continued, more power was produced at 60 Hz (North America) or 50 Hz (Europe and most of Asia). Standardization allowed international trade in electrical equipment. Much later, the use of standard frequencies allowed interconnection of power grids. It wasn't until after World War II with the advent of affordable electrical consumer goods that more uniform standards were enacted..."