Ambient Conditions; Installation Altitudes - Siemens 3AH37 Operating Instructions Manual

Description
Fig. 47

Ambient conditions

Insulating capacity
Fig. 48 Altitude correction factor K
36
Ambient conditions

Installation altitudes

The insulating capacity of insulation in air decreases with rising altitude due to the
lower air density. In conformity with IEC 62271-102, the rated lightning impulse
withstand voltage values given in Fig. 45 are valid up to an installation altitude of
1,000 m above sea level.
As from an altitude of 1,000 m, the insulation level must be corrected as shown in
Fig. 48:
a
3AH37/38vacuum circuit-breakers are suitable for use in
the following climate classes in accordance with
IEC 60721, Part 3-3:
• Climatic ambient conditions:
• Biological ambient conditions:
• Mechanical ambient conditions:
• Chemically active substances:
• Mechanically active substances:
1) Peak value of the 24-hour means: +35 °C
2) Without ice formation and wind-driven precipitation
3) Without occurrence of salt fog and simultaneous condensation
4) Restriction: clean insulating parts
5) Average value, measured over 24 hours
6) Average value, measured over 1 month
U  U  K
0 a
U Rated withstand voltage U under standard reference
atmosphere
U Required rated withstand voltage for the installation
0
location
K Altitude correction factor
a
m (H - 1000)/8150

K = e
a
Calculating the altitude correction factor K
H = Installation altitude in metres
m = 1 for AC voltage, lightning impulse withstand
voltage (between phases, phase-to-earth, applied
longitudinally)
Example
For a required rated withstand voltage of 75 kV at an
altitude of 2,500 m, an insulation level of at least 90 kV
under standard reference atmosphere conditions is
required:
1 (2500 - 1000)/8150
90 kV  75 kV  e 
75 kV  1.2
Class
1)
3K4 ,
2)
3K6 ,
3Z2,
3Z5
3B1
3M2
3)
3C2
4)
3S2
:
a
9229 9992 176 0D
2013-07-08