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Fixed Phase and Earthing Points EaS Cables Phase Connecting Elements Earth Connecting Elements Earthing Sticks EaS Devices, Short-Circuiting Bars
4. Carry out Earthing and Short-Circuiting – EaS Devices

Calculation example: Table:
Known: Mains breaking capacity Sa Cable cross-section of the earthing and short-circuiting device depending
Short-circuit time Tk on the maximum short-circuit Ik and maximum short-circuit time Tk
Unknown: Required cable or bar cross-section A. • For copper (Cu)
The calculation is based on an off-generator short-circuit.
Cross-sec- Max. short-circuit current Ik
Sa tion of the at a duration of
Three-phase current Ik“ = Ik = Ia = ——— copper
√ 3 • UN cable 10 s 5 s 2 s 1 s *) ≤ 0.5 s *)
16 mm 2 1 000 A 1 400 A 2 200 A 3 200 A 4 500 A
Sa 25 mm 2 1 600 A 2 200 A 3 500 A 4 900 A 7 000 A
Single-phase alternating current Ik“ = Ik = Ia = —— 35 mm 2 2 200 A 3 100 A 4 900 A 6 900 A 10 000 A
UN
50 mm 2 3 100 A 4 400 A 7 000 A 9 900 A 14 000 A
The required cable or bar cross-section can now be calculated based on 70 mm 2 4 400 A 6 200 A 9 800 A 13 800 A 19 500 A
Ik“ of the above equations or can be taken from the diagrams. The per- 95 mm 2 5 900 A 8 400 A 13 200 A 18 700 A 26 500 A
missible current carrying capacity of an earthing and short-circuiting de- 120 mm 2 7 500 A 10 600 A 16 700 A 23 700 A 33 500 A
vice is based on the cross-section printed on the short-circuiting cables or 150 mm 2 9 400 A 13 200 A 20 900 A 29 600 A 42 000 A
bars. *) catalogue data

Note:
– Earthing and short-circuiting devices can only be loaded once with the
permissible short-circuit currents depending on the short-circuit time. • For aluminium (Al)
– Short-circuiting cables of multi-pole earthing and short-circuiting de- Cross-sec- Max. short-circuit current Ik
vices must have the same cross-sections. tion of the at a duration of
– Cable lengths of earthing and short-circuiting devices should be at aluminium *)
least 120% of the distance between two fixed connection points. They cable 10 s 5 s 2 s 1 s *) ≤ 0.5 s
should be as short as possible as the cables move violently during a 35 mm 2 1 400 A 2 000 A 3 200 A 4 600 A 6 500 A
short-circuit. 50 mm 2 2 100 A 2 900 A 4 600 A 6 600 A 9 300 A
– When connecting earthing and short-circuiting devices in parallel with 70 mm 2 2 900 A 4 100 A 6 500 A 9 200 A 13 000 A
cables for achieving certain total cable cross-sections, the following *) catalogue data
conditions must be fulfilled:
1. Identical cable lengths and cross-sections,
2. Identical connecting clamps and fixed connection points
3. Installing the devices directly next to each other, with parallel
arrangement of cables,
4. The current carrying capacity per cable must be reduced to 75% of
the current carrying capacity of the cable cross-section.

Remark:
If it is ensured that earthing and short-circuiting devices connected in
parallel are loaded with short-circuit currents only once (no interrup tion
of the short circuit), the devices may be exposed to the full load. Generally,
this applies to installations with nominal voltages above 110 kV.

4. EaS Devices

56 You will find detailed product information on our website Valid as of January 1, 2019

EaS Devices 4.