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Nominal power of PV Modules P =
nom
222 W
Current at maximum power: I =
mp
7.07 A
Voltage at maximum power: V =
mp
29.84 V
Short Circuit Current: I =
sh
7.96
Number of panels in series in each array N :
p
16
Number of arrays N :
a
33
Maximum ambient temperature:
55 ºC
Solar Cable: Design Calculation for Maximum allowed voltage drop
Let us consider the following PV Modules for voltage drop calculation
Therefore,
The peak power delivered by PV module is given by
N *N *P
p
a nom
P=16 x 33 x 222 W = 117,216 W = 117.216 kW
The voltage at the junction box is
For a given array, the panels are connected in series, so the voltage of the array is the sum
of the voltage of the modules.
The applicable voltage at the junction box level is
V= V * 16 = 29.84 V * 16 = 477.44 V
mp
The total current is the addition of the current of each single array. There are 11 arrays
per junction box.
I = I *11 = 7.07*11 = 77.77 A
mp
The voltage drop between the generating point and the point of connection to the Public
Distribution Network or indoor installations shall not exceed 1.5% at nominal current.
The maximum allowed voltage drop is:
Vdrop = 0.01 x 477.44 V = 4.77 V
The cable section is, in this case, defined as follows
Where
L: length of the line (positive + negative)
2 x 42 = 84 m
I : nominal current
mp
77.77 A
γ: conductivity of copper (at 70ºC)
2
46.82 m
/Ω.mmV : Maximum voltage drop
drop
4.77 V
This leads to :
2
= 29.25 approximated to 35 mm ( i.e., required size of the cable)
Current Rating of Solar cable under different service Conditions
S =
L *
I
γ * V
drop
S = 84*77.77
46.82*4.77
Wires & Cables
mp
I
= rated current for continuous operation under standard conditions I in A
std
I
= rated current for continuous operation under different service conditions in A
ser
RF
= reduction factor for increased ambient temperature in A
1
RF
=
reduction factor for deviated conductor temperature in A
2
RF
=reduction factor for bundles cables
3
I
=
I * RF * RF * RF
ser
std
1
2
3