Skin effect and Proximity effect both are AC effects not DC effects.
Because , In DC transmission, current uniformly distributed in conductor.
1. SKIN EFFECT
But in AC transmission, current is non-uniformly distributed over cross-section.
Current density is higher at its surface than the density at its center.
Current flow over the surface is called SKIN EFFECT
Due to Skin effect
(R)ac > (R)dc
because skin effect increases the conductor resistance.
SKIN EFFECT depends on Size, Frequency, Distance and permeability.
2. PROXIMITY (निकटता) EFFECT
In AC transmission line flux link with the other conductor.
More flux links with the nearest half of the other conductor than with the other half removed farther away.
Proximity effect increases the conductor Resistance.
Proximity effect depends on frequency , size and distance.
3. FERRANTI EFFECT
In electrical engineering, the Ferranti effect is an increase in voltage occurring at the receiving end of a long transmission line, above the voltage at the sending end. This occurs when the line is energized, but there is a very light load or the load is disconnected.
or
When long line is on no load or light load then ferranti effect occurs , this effect occurs due to the charging current of line.
where ,
CHARGING CURRENT - It is the value of current at sending end at no load & normal operating Voltage applied at sending end.
4. SURGE IMPEDANCE/ CHARACTERISTIC IMPEDANCE
Surge Impedance is the characteristic impedance of a loss less transmission line.
S.I = ( Z/Y )¹/²
Z = (R+jX)
Y = (G+jB)
where, Z = series impedance
Y = Shunt admittance
SIL (SURGE (लहर/बड़ी लहर/आवेश) IMPEDANCE LOADING)
Load that can be delivered by line having no resistance load being at unity power factor.
or
Load at which Induction and Capacitance VA are equal & opposite is called SIL or natural Load.
SIL = V²/Z MW
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