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

Vacuum circuit-breaker module.
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Description
Fig. 30

Ambient conditions

Insulating capacity
Fig. 31
Altitude correction factor K
28
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. 29 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. 31:
a
3AK vacuum circuit-breaker modules 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
0 
K
a
U Rated withstand voltage U under standard reference
atmosphere
U
Required rated withstand voltage for the installation
0
location
Altitude correction factor
K
a
(H – 1000)/8150
m
= e
K
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:
(2500 – 1000)/8150
1
90 kV
75 kV
e
75 kV
1.2

Class
1)
3K4
,
2)
3K6
,
3Z2,
3Z5
3B1
3M2
3)
3C2
4)
3S2
:
a
9229 9923 176 0B
2013-09-09

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