Vandhanaa
I want to know about the Skin effect in transmission lines.. Please.. (13 years ago)

alien2012
hi 4nd i dnt knw much skin effect, well, when ac flows through a conductor, the current denesity is not same at all places. The current density is greater at surface then at core of a conductor. Thus skin effect is the tendency of ac to distrubute itself within the conductor. As charge is maximum at surface, it is just as like a skin. Thanks. N conductor may b transmission lines. (13 years ago)

PHOENIXBAALAA
Hmmm.. I know a little about Skin effect.. IN HVDC transmission, There is no inductance in dc and hence the dc current flows uniformally all over the surface area of the conductor.. But, in AC lines, when the ac current flows through the conductor, an alternative magnetic flux is induced in that conductor due to ac current.. See next post.. (13 years ago)

PHOENIXBAALAA
And we know the fact that is, in a magnet, the concentration of magnetic lines of force is higher in centre(core) of the material than its outer surface.. Similarly, in this AC transmission line, the concentration of Alternative magnetic lines of force is higher than its outer surface.. Due to the changing magnetic flux, the inductance effect is experienced... Due to the inductance effect, the inductive reactance(opposition to electric current due to inductance) is appeared.. See next post.. (13 years ago)

PHOENIXBAALAA
Due to this high inductive reactance in centre area of the conductor than its outer surface, the electric current is crowding at the outer surface.. This tendency of AC current is called Skin Effect.. Due to this skin effect, the effective area of the conductor is reduced.. Hence, it is taken as the resistance is increased(fore there, Resistance is inversely proportional to the area).. The skin effect depends on the nature of material, diameter and shape of conductor, and FREQUENCY of supply.. See next post.. (13 years ago)

PHOENIXBAALAA
The inductive reactance(XL) is proportional to Frequency(F).. Hence, when the frequency is high, the ind.reactance is also high.. And, the effective area on the conductor is reduced and hence the resistance is increased.. The, line drop due to reactance(IXL) and resistance(IR) is increased.. So, the receiving end voltage is less than sending end voltage... There are many reasons for that the receiving end voltage is less than sending end voltage.. Sometimes, the Vr is higher than Vs.. This is due to Ferranti effect.. You asked A nice Q.. And I want to know more about the skin effect.. And, Alien is said correctly.. (13 years ago)

Vandhanaa
Oh..! Great phoenix and alien.. Now I am clear about the skin effect.. Thanks friends.. (13 years ago)

alien2012
hi 4nz, i want to share another knowlege, we know current density is not same at all place. There is another term skin depth which is a measure of distance over which the current density fall to 1/e of its original value. Well, as current density is minimum at core, we may use pipe type conductor 4 the sake of weight n cost. If i did any wrong explaination let me know. well, thanks too. vandhana 4 this question. N thank you too bala 4 explaination in detail. (13 years ago)

PHOENIXBAALAA
You are correct alien.. But, the factor Sag in an important one in transmission lines.. The sag can be obtained more efficiently by bar conductors... (13 years ago)

Vandhanaa
Good.. Phoenix and alien.. Thanks.. (13 years ago)

alien2012
sory phoenix, i have no idea of sag. can u tell me in brief?.thank u. (13 years ago)

PHOENIXBAALAA
Sure alien.......... Sag is an important one in over head lines.. While erecting an overhead line, it is very important that conductors are under SAFE TENSION.. if the conductors are too much stretched between supports, the stress in the conductor may break due to excessive tension.. Hmmm.... In order to safe tension in the conductors, they are not fully stretched but are allowed to have a dip or sag.. See next post alien.. (13 years ago)

PHOENIXBAALAA
Sag in measured by The difference in vertical level between points of supports and the lowest point on conductor........ It depends on, length of the span.. Weight of conductor.. Wind pressure and temperature... We know that, the size of the material will be expanded due to temperature.. If we assume that a line is erected in winter season with Zero sag, it will be in FULL STIFFNESS.. When the summer season, the length of the line will be increased(few cm).. Due to this extra length, the conductor will go into excessive stress and the insulating supports will be broken.. See next post alien... (13 years ago)

PHOENIXBAALAA
If it is erected in summer season with too sag, the distance between conductor and ground level will be reduced in winter season.. So, to wash out these problems.. The line is erected with calculated sag... Before calculating the sag, we should notice that the weight of conductor, that area's wind pressure(average), and ice loading on O.H.L(in your state).. (13 years ago)

alien2012
thanks phoenix 4 detail n very informative knowldge. Thank u very much. (13 years ago)

PHOENIXBAALAA
Its kay alien.. You are welcomed.. (13 years ago)

SPpr23
I am a student of cox'sbazar government college.01830109523 (13 years ago)