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© IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
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IEC 62271-1
Edition 2.0 2017-07
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –
Part 1: Common specifications for alternating
current switchgear and controlgear
INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 17: High-voltage
switchgear and controlgear.
The text of this interpretation sheet is based on the following documents:
DISH Report on voting
17/1090/DISH 17/1095/RVDISH
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.
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Interpretation of 4.2.2 of IEC 62271-1:2017 regarding the altitude correction factor
Subclause 4.2.2 of IEC 62271-1:2017 contains two references for calculation of the required
insulation withstand level at altitudes higher than 1 000 m, IEC 60071-2:1996 and
IEC TR 62271-306. The two references are in conflict, as the altitude correction factor
according to IEC 60071-2:1996 starts at sea level and that of IEC TR 62271-306 starts at an
altitude of 1 000 m. This results in different altitude correction factors.
As already stated in 5.3 of IEC 62271-1:2017, the rated insulation levels refer to normal
service conditions. Altitudes up to 1 000 m above sea level are covered and need no altitude
correction.
For altitudes higher than 1 000 m the equation provided in 4.5.1.1 b) of
IEC TR 62271-306:2012 and in H.3.4 of IEC 60071-2:2018 shall be used, i.e.
H−1 000
m( )
8 150
k =e
alt
ICS 29.130.10; 29.130.99
IEC 62271-1:2017-07/ISH1:2021-05(en-fr)
– 2 – IEC 62271-1:2017/ISH1:2021
© IEC 2021
where
is the altitude correction factor;
k
alt
H is the altitude in m above sea level;
m is an exponent.
Conservative values for the exponent m are provided in Table 4 of IEC TR 62271-306:2012.
For further details about the exponent m, see H.4 of IEC 60071-2:2018.
– 2 – IEC 62271-1:2017/ISH1:2021
© IEC 2021
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
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