Siemens 8DJH Series - Page 51

500-8067.9 * INSTALLATION AND OPERATING INSTRUCTIONS 8DJH * Revision 03 51
Description
Fig. 34: Correction factor K
a
as a function of the site altitude in m above sea level
Example
Rated voltage (r.m.s. value) [kV] 7.2 12 15 17.5 24
Rated short-duration power-frequency withstand voltage (r.m.s. value)
- Across isolating distances [kV] 23 32 39 45 60
- Between phases and to earth 20 28 36 38 50
Rated lightning impulse withstand voltage (peak value)
- Across isolating distances [kV] 70 85 105 110 145
- Between phases and to earth 60 75 95 95 125
Rated short-duration power-frequency withstand voltage to be selected for site altitudes > 1000 m
≥ Rated short-duration power-frequency withstand voltage up to ≤ 1000 m * Ka
Rated lightning impulse withstand voltage to be selected for site altitudes > 1000 m
≥ Rated lightning impulse withstand voltage up to ≤ 1000 m * K
a
Example
3000 m site altitude above sea level
17.5 kV switchgear rated voltage
95.0 kV rated lightning impulse withstand voltage
Rated lightning impulse withstand voltage to be selected
95kV*1.28=122kV
Result
According to the above table, a switchgear for a rated voltage of 24 kV with a rated lightning impulse withstand voltage of
125 kV is to be selected.