Control and Design of Microgrid Components - Power Systems ...

AWG 1/0 carries 150A and has the following parameters from tables in [10]:
R
R
o
1
= 5.54 Ω / mi
= 0.622 Ω / mi
X
o
X
1
= 0.246 Ω / mi
= 0.152 Ω / mi
Remembering that there are 5280 ft in a mile then:
r
o
180
= 5.54 = 0.1889 Ω
5280
r = 0.0212 Ω
1
x
1
x
o
= 0.0084 Ω
= 0.0052 Ω
Impedance Z2, Z3, Z4
Data:
Must be able to carry the current generated by the plant load demand of 25kW and its reactive
part, plus all the losses in the lines. All the cables are at 208 V and are 4 wires, with neutral cable
having the same size of the a phase conductor.
The first thing to do is to estimate the VA request from the active load and the expected power
factor:
P 25000
With PF=0.97 S = = = 25773 VA , with PF=0.9, S ≈ 27KVA.
PF 0.97
With a very poor power factor such as PF=0.7 then S ≈ 35 KVA. To get the current rating per
phase from the VA:
I
S
=
V
⎛ S3
⎜
⎝ 3
=
V
Φ
3
⎞
⎟
⎠
S
35000
=
208 3
rms 1Φ
3Φ
L =
=
rms rms rms
LN LL 3VLL
97.15 A
A cable that can carry at least 100 A is required. From tables [11] it is possible to see that size
AWG 3 is rated for 100 A and its parameters are [10]:
R
R
o
1
= 7.69 Ω / mi
= 1.2835 Ω / mi
X
X
o
1
= 0.283 Ω / mi
= 0.17 Ω / mi
Impedance Z2 is 20 ft long:
r o
r
1
= 0.0291Ω
= 0.0049 Ω
x
x
o
1
= 0.0011Ω
= 0.00064 Ω
impedances Z3 is 75 yd long (and remembering that there are 1760yds in one mile):
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