MV design guide - Schneider Electric
MV design guide - Schneider Electric
MV design guide - Schneider Electric
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Design rules<br />
Short-circuit currents<br />
Reminder concerning the calculation<br />
of three-phase short-circuit currents<br />
c Three-phase short-circuit<br />
Ssc = 1.1 • U • Isc • e=<br />
U 2<br />
Zsc<br />
1.1• U<br />
Isc = with Zsc = R 2 + X 2<br />
e • Zsc<br />
c Upstream network<br />
Z = U2<br />
Ssc<br />
R<br />
X<br />
={<br />
0.3 at 6 kV<br />
0.2 at 20 kV<br />
0.1 at 150 kV<br />
c Overhead lines<br />
R = ρ • L S<br />
c Synchronous generators<br />
X = 0.4 Ω/km<br />
X = 0.3 Ω/km<br />
ρ = 1.8.10 -6 Ω cm<br />
ρ = 2.8.10 -6 Ω cm<br />
ρ = 3.3.10 -6 Ω cm<br />
HV<br />
<strong>MV</strong>/LV<br />
copper<br />
aluminium<br />
almélec<br />
Z(Ω) = X(Ω) =<br />
U 2<br />
•<br />
Sr<br />
Xsc (%)<br />
100<br />
Xsc sub-transient transient permanent<br />
turbo 10 to 20 % 15 to 25 % 200 to 350 %<br />
exposed poles 15 to 25 % 25 to 35 % 70 to 120 %<br />
c Transformers<br />
(order of magnitude: for real values, refer to data given by manufacturer)<br />
E.g.: 20 kV/410 V; Sr = 630 kVA; Usc = 4 %<br />
63 kV/11 V; Sr = 10 <strong>MV</strong>A; Usc = 9 %<br />
Z (Ω) =<br />
U 2<br />
Sr<br />
Usc(%)<br />
•<br />
100<br />
Sr (kVA) 100 to 3150 5000 to 5000<br />
Usc (%) 4 to 7.5 8 to 12<br />
<strong>MV</strong>/LV HV/<strong>MV</strong><br />
c Cables<br />
X = 0.10 at 0.15 Ω/km<br />
three-phased or single-phased<br />
c Busbars<br />
X = 0.15 Ω/km<br />
<strong>Schneider</strong> <strong>Electric</strong><br />
Merlin Gerin <strong>MV</strong> <strong>design</strong> <strong>guide</strong><br />
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