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Current at short-circuit

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Current at short-circuit

Permissible short-circuit currents of conductor and screen within 1 second short-circuit is indicated in the table below.


Nominal conductor cross-sectional area, mm2

Permissible current short circuit for 1 sec.,
with copper conductors,
kA

35

5,0

50

7,2

70

10,0

95

13,6

120

17,2

150

21,5

185

26,5

240

34,3

300

42,9

400

57,2

500

71,5

630

90,1

800

114,4


Permissible short-circuit currents are calculated considerithe following conditions:

Ц temperature of the conductor: / before short-circuit 90 ∞—; / after short-circuit 250 ∞—;

Ц temperature of the screen: / before short-circuit 70 ∞—; / after short-circuit 350 ∞—.


Cross-section area
of copper screen,
mm2

16

25

35

50

70

95

120

Permissible current at short-circuit of screen for 1 sec., kA

3.3

5.1

7.1

10.2

14.2

19.3

24.4



For duration of short-circuit being different from 1 sec., the indicated value of the short-circuit current shall be multby the correction factor:




where: t Ц duration of short-circuit, sec.


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