Ambient Conditions; Installation Altitudes - Siemens 3AH3 Operating Instructions Manual

Description
Fig. 48

Ambient conditions

Insulating capacity
Fig. 49 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 volt-
age values given in Fig. 47 are valid up to an installation altitude of 1,000 m above
sea level.
At altitudes of 1,000 m and higher, the insulation level must be corrected as shown
in Fig. 49:
a
3AH3 vacuum 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
 0 
U U K
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 voltage (between
phases, phase-to-earth, applied longitudinally)
Example
For a required rated withstand voltage of 75 kV at an alti-
tude 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 9860 176 0E
2013-08-22