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BD2 <strong>System</strong> — <strong>160</strong> ... 1250 A<br />
© Siemens AG 2007<br />
Engineering information<br />
■ More information<br />
Rated currents and short-circuit currents of standard transformers<br />
Rated voltage U N <strong>40</strong>0/230 V 690/<strong>40</strong>0 V<br />
Relative short-circuit voltage u k 4 % 1) 6 % 2) 4 % 1) 6 % 2)<br />
Rated output power Rated current Short-circuit current I" 3)<br />
k Rated current Short-circuit current I" 3)<br />
k<br />
kVA A A A A A A<br />
50 72 1805 – 42 1042 –<br />
100 144 3610 2<strong>40</strong>6 84 2084 1392<br />
<strong>160</strong> 230 5776 3850 133 3325 2230<br />
200 288 7220 4812 168 4168 2784<br />
250 360 9025 6015 210 5220 3560<br />
315 455 11375 7583 263 6650 4380<br />
<strong>40</strong>0 578 14450 9630 336 8336 5568<br />
500 722 18050 12030 420 104<strong>40</strong> 7120<br />
630 909 22750 15166 526 13300 8760<br />
800 1156 28900 19260 672 16672 11136<br />
1000 1444 36100 2<strong>40</strong>60 8<strong>40</strong> 208<strong>40</strong> 13920<br />
1250 1805 45125 30080 1050 26060 17480<br />
1) u k = 4 %, standardized according to DIN 42500 for S NT = 50 ... 630 kVA.<br />
2) u k = 6 %, standardized according to DIN 42500 for S NT = 100 ... <strong>160</strong>0 kVA.<br />
3) I" k = Transformer initial short-circuit alternating current when connecting<br />
to a network with unlimited short-circuit power.<br />
Approximating formula<br />
Transformer rated current Transformer short-circuit alternating current with<br />
I N [A] = k X S NT [kVA] I" k = I N /u k X 100 k = 1.45 at <strong>40</strong>0 V<br />
k = 0.84 at 690 V<br />
5<br />
Dimensioning and selection<br />
Safe shutoff of the smallest single-pole ground short-circuit<br />
current<br />
Since the level of the loop impedance is decisive in determining<br />
the level of the single-pole short-circuit current, DIN VDE 0100<br />
Part 600 prescribes that the loop impedance must be determined<br />
between the following<br />
• external conductor and the PE conductor or<br />
• external conductor and PEN conductor.<br />
This value may be determined by<br />
• measuring with measurement instruments or<br />
• calculation or<br />
• simulation of the network in a network model.<br />
In the "Technical Specifications" section, the impedance values<br />
for the BD2A/BD2C busbar trunking systems are listed so that it<br />
is possible to calculate the loop impedances of a busbar system,<br />
which contributes to the total loop impedance.<br />
With the aid of the loop impedance of the entire busbar trunking<br />
system it is easy to calculate the smallest expected single-pole<br />
short-circuit current.<br />
I kl min =<br />
c×U n<br />
3 ×Z k<br />
where<br />
c = Voltage factor 0.95<br />
U n = Voltage between the external conductors<br />
Z k = Short-circuit impedance<br />
5/88 Siemens LV 70 · 2006
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