( 1 ) Critical disruptive voltage
VC
= m0go δ r Loge ( d / r
)
Where
VC = Phase to neutral voltage
r = Radius of conductor
d = Diameter of conductor
g0 = Breakdown ( Dielectric ) strength of air at 76 cm of mercury at 25 degree centigrade
= 30 kV / cm ( Max )
= 21.2 kV / cm ( RMS )
m0
= Irregular factor
=
1 for polished conductor
=
0.98 to 0.92 for dirty conductor
=
0.87 to 0.8 for stranded conductor
( 2 ) Air
density factor
Air
density factor δ = 3.92b / 273 + t
Where
b = atmospheric pressure of b cm
t = Temperature in centigrade
Line
voltage = √ 3 × VC
( 3 ) Visual Critical voltage
VV
= m0go δr { 1 + 0.3 / √
δr } Loge
( d / r )
Where
m0
= Irregular factor
g0
= Breakdown ( Dielectric ) strength of air
r = Radius of conductor
d = Diameter of conductor
δ = Air density factor
( 4 ) Power
loss due to corona
P
= 242.2 ( f + 25 / δ ) √ r / d ( V – VC )2
× 10 – 5 kW / km / Phase
Where
f = Supply frequency
V = Phase to neutral voltage ( RMS )
VC = Critical
disruptive voltage ( RMS ) per phase
δ = Air density factor
Power loss due to corona α ( V – VC
)2
You may also like :
Transistor Tuned Amplifier MCQs – 3
No comments:
Post a Comment