. ▁ ▁References ▁▁ ▁Category : Pop ulated ▁places ▁in ▁Sar ay an ▁County <0x0A> </s> ▁Power ▁transmission ▁is ▁the ▁movement ▁of ▁energy ▁from ▁its ▁place ▁of ▁generation ▁to ▁a ▁location ▁where ▁it ▁is ▁applied ▁to ▁perform ▁useful ▁work . ▁ ▁Power ▁is ▁defined ▁formally ▁as ▁units ▁of ▁energy ▁per ▁unit ▁time . ▁In ▁SI ▁units : ▁ ▁Since ▁the ▁development ▁of ▁technology , ▁transmission ▁and ▁storage ▁systems ▁have ▁been ▁of ▁immense ▁interest ▁to ▁techn olog ists ▁and ▁technology ▁users . ▁ ▁Elect rical ▁power ▁▁ ▁With ▁the ▁w ides p read ▁establishment ▁of ▁elect rical ▁gr ids , ▁power ▁transmission ▁is ▁usually ▁associated ▁most ▁with ▁electric ▁power ▁transmission . ▁ ▁Altern ating ▁current ▁is ▁normally ▁preferred ▁as ▁its ▁voltage ▁may ▁be ▁easily ▁stepped ▁up ▁by ▁a ▁transform er ▁in ▁order ▁to ▁minim ize ▁resist ive ▁loss ▁in ▁the ▁conduct ors ▁used ▁to ▁transmit ▁power ▁over ▁great ▁distances ; ▁another ▁set ▁of ▁transform ers ▁is ▁required ▁to ▁step ▁it ▁back ▁down ▁to ▁sa fer ▁or ▁more ▁us able ▁voltage ▁levels ▁at ▁destination . ▁ ▁Power ▁transmission ▁is ▁usually ▁performed ▁with ▁overhead ▁lines ▁as ▁this ▁is ▁the ▁most ▁econom ical ▁way ▁to ▁do ▁so . ▁Under ground ▁transmission ▁by ▁high - vol t age ▁c ables ▁is ▁chosen ▁in ▁crow ded ▁urban ▁areas ▁and ▁in ▁high - vol t age ▁direct - current ▁( H VD C ) ▁sub marine ▁connections . ▁ ▁Power ▁might ▁also ▁be ▁transm itted ▁by ▁changing ▁elect romagnet ic ▁fields ▁or ▁by ▁radio ▁waves ; ▁mic row ave ▁energy