TAVRIDA ELECTRIC ISM Shell_2 Series, Applications Manual

Page: 23 / 83

23
Minimum Clearances due to Electromagnetic Influences
The following clearances must be adhered to (Figure 25):
Coordination of Minimum Clearances
In case the minimum clearance L
3
due to 25/31 kA short circuit current exceeds the minimum clearance L
2
due to the
rated insulation level, the higher clearance between ISM-frame and adjacent busbars is to be selected.
Heating
The ISM are designed in such a manner that at the rated current specified on the rating plate of the ISM and at 40°C
ambient temperature, with free surroundings, no impermissible high temperatures will arise at the hottest spots of
the ISM. In order to decide whether for an ISM in the respective panel more intensive heat dissipation or a reduction
of the rated current values are required, a temperature rise test according to the relevant standards is recommended.
Protective Grounding
For personnel protection the metal housing of the ISM must be
connected according to the applicable regulations, such as DIN
VDE 0141, DIN VDE 0151, IEC 6021-2 via the marked two ground
screws of the ISM to the ground arrangement of the particular
panel. One or both grounding bolts can be used. If two ground
connections are used, at each grounding bolt the half total cross
section shall be connected. The ground connections can be carried
out with cables or flat copper bars. The cross section must be
dimensioned such that a worst-case fault current (short circuit)
does not cause a weakening of the ground connections (Figure 27).
Reference values for total cross sections of ground connections (copper):
Duration of fault
current (1 s)
Max. temperature of
ground connection
Cross section
ground connec-
tion
<10 kA/10 kA 300 °C 35-70 mm²
16 kA 300 °C 70-95 mm²
20 kA 300 °C 70-120 mm²
25 kA 300 °C 95-140 mm²
31.5 kA 300 °C 120-190 mm²
The area around the ground screws shall be cleaned before
providing the ground connections. After the occurrence of a short
circuit, the proper condition of the protective grounding must be
checked.
Figure 27
M12 bolt
Washer
30 ± 2 Nm
Spring lock
washer
ISM-Type
Short-circuit current, kA
20 25 31.5
L
3
, mm
ISM15_Shell_2 120 150 190
3