# Why we preferably use AC when power losses in AC are more comparable to DC?

AC power transmission losses
are greater than DC losses. but still we are using AC. i have read on internet that nowdays power companies are rethinking to switch to DC from AC. how far it will be helpful to reduce power losses such as skin effects and corona?

## Replies

• Ahsanul haque
its not depend on only one factor. large firms think about productivity and well economical structure that assure great output. Usually u know a power plant build near from city so thats why firm setup their powerplant close area. and In DC power system u need more powerful battery but battery life time not good as well. Solar panel also run DC form. so need both AC and DC.
• renu sharma
yeah that's true that we need both AC and DC. but most of the appliances or gadgets that we use in our daily life are based only on AC. Even for industrial purposes AC is preferred. But while transmitting the power through transmission lines, the power is lost due to the resistance of the transmission cables. my doubt is that when there are more power losses in AC compared to DC then why can't we design such appliances that could be based on DC which could help to minimise the losses? 😨
• Ahsanul haque
U can use solar panel on ur building roof its DC . and Usually in Big cities using self solar panel for save power. 👍
• lal
Due to skin effect when alternate current flows through a conductor, its resistance is around 1.6 times that of when direct current is flowing. That is true. But, the advantage with AC is that, we can easily vary the magnitude of voltage. Using the only machine which gives almost cent percent efficiency - the transformer. In the case of DC, but, voltage cannot be easily varied like that of AC.

When AC is transmitted over long distances, its voltage is raised many times so that the current flowing through the transmission lines will be less. But for DC, since no such device to vary voltage easily is available, the magnitude of the voltage has to be that of the working voltage. Say if the voltage at consumer's end is 230V, in DC, it has to be transmitted at the same value. But of AC, the coltage can be stepped up severel times so that the transmission voltage is some Kilo Volts or higher.

So, to transmit the same power, DC conductors will have to carry a huge amount when compared to AC. This makes transmission losses very high for DC and less of AC. In fact, DC generation stations has to be made very close to load areas or within the load areas to compensate these losses.
• Jeffrey Arulraj
DC transmission is a problem Though VHVDC is there it can't be used effectively as the as most device can't be run in DC

The power factor improving technique allows AC efficiency to be increased and so there is better utilisation of AC power
• dhruba sunuwar
renu sharma
yeah that's true that we need both AC and DC. but most of the appliances or gadgets that we use in our daily life are based only on AC. Even for industrial purposes AC is preferred. But while transmitting the power through transmission lines, the power is lost due to the resistance of the transmission cables. my doubt is that when there are more power losses in AC compared to DC then why can't we design such appliances that could be based on DC which could help to minimise the losses? 😨
from what i have studied, in case of long distances establishing dc based transmission line system costs more than that of ac!!! so, ac system is preferred
• Prashant Munshi
The reason is simple - need for step up and step down of the voltage can be conveniently done in AC and not with DC. Long distance transmission of power requires very high voltage, since for the same power transmission you will require less current. The current has to be less since most of the resistive power loss (in the form of heat) is proportional to square of current (I^2 R). However utilization of power at such high voltage may not be possible as the appliances - industrial or domestic will require to use high quality of insulation to withstand such voltages. Hence the voltage will have to stepped down for industry - 6.6 KV or for domestic 440 (in 3 phase). This may be conveniently done using transformers and hence AC is convenient. However as said in the main problem, DC may have less wastage at the same voltage of transmission as AC (440 KV) since reactive losses are eliminated. So most modern transmission has been done in HVDC lines. Maharashtra state owned electric generation and transmission utility has been pioneer in the field. But again this DC will have to converted into AC at the utilization end since for many years the industrial equipment and domestic appliances have been AC. High voltage DC was difficult to obtain until very recent past due to non-availability of rectifiers to withstand those voltages. So it took long in waiting to develop such a technology but by then AC became widespread. Hope that explains.
• renu sharma
@ Prashant Munshi - thanku so much for this information. its really helpful. 😀
• Mabu Hussain
we generate the AC power at low voltage ratings (about 11kv) and transmit the same at very high voltages (220kv) to reduce the transmission losses. we get less losses at high voltages. In DC there is no chance to step up the voltage and it can not be transmitter over long distances.

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