Description
50 Revision 03 * INSTALLATION AND OPERATING INSTRUCTIONS 8DJH * 500-8067.9
8.8 Gas leakage rate
Gas leakage rate The gas leakage rate is < 0.1% per year (referred to the absolute gas pressure).
8.9 Dielectric strength and site altitude
Dielectric strength • The dielectric strength is verified by testing the switchgear with rated values of short-
duration power-frequency withstand voltage and lightning impulse withstand voltage
according to IEC 62271-1 / VDE 0671-1.
• The rated values are referred to sea level and to normal atmospheric conditions
(101.3 hPa, 20 °C, 11g/m
3
humidity according to IEC 60071 and VDE 0111).
• The dielectric strength decreases with increasing altitude. For site altitudes above
1000 m (above sea level) the standards do not provide any guidelines for the insulation
rating, but leave this to the scope of special agreements.
All parts housed inside the switchgear vessel which are subjected to high voltage are
SF
6
-insulated against the earthed enclosure.
Site altitude The gas insulation at a relative gas pressure of 50 kPa (= 500 hPa) permits switchgear
installation at any desired altitude above sea level without the dielectric strength being
adversely affected. This also applies to the cable connection when using screened cable
T-plugs or cable elbow plugs.
A decrease (reduction) of the dielectric strength with increasing site altitude must only
be considered for panels with HV HRC fuses as well as for air-insulated metering panels
and a site altitude of 1000 m above sea level. A higher insulation level must be selected,
which results from the multiplication of the rated insulation level for 0 to 1000 m with the
altitude correction factor K
a
.
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