Medium Voltage technical guide - Schneider Electric

Design rules Busbar calculation
AMTED300014EN.indd
DE59010
Temperature rise
Taken from table 3 of standard IEC 62271-1 common specifications.
Type of device, of material
and of dielectric
(Refer to points 1, 2 and 3)
Temperature
θ (°C)
Bolt connected or equivalent devices (Refer to point 4)
Bare copper, bare copper alloy or aluminium alloy
In air 90 50
In SF6 * 105 65
In oil 100 60
Silver or nickel coated
In air 115 75
In SF6 115 75
In oil 100 60
Tin-coated
In air 105 65
In SF6 105 65
In oil 100 60
* SF6 (sulphur hexafluoride)
(θ - θn)
with θn = 40°C
Point 1 According to its function, the same part may belong to several
categories as listed in table 3.
Point 2 For vacuum switching devices, the values of temperature and
temperature-rise limits are not applicable for parts in vacuum.
The remaining parts shall not exceed the values of temperature
and temperature-rise given in table 3.
Point 3 Care shall be taken to ensure that no damage is caused to
the surrounding insulation materials.
Point 4 When engaging parts having different coatings or one part is
of bare material, the permissible temperature and temperaturerises
shall be:
a) For contacts, those of the surface material having the lowest
value permitted in item 1 of table 3.
b) For connections, those of the surface material having
the highest value permitted in item 2 of table 3.
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