AS 61869.1:2021 pdf free download.Instrument transformers Part 1: General requirements (IEC 61869-1:2007 (ED.1.0) MOD).
4.2.5 Other service conditions for outdoor instrument transformers Other considered service conditions are as follows:
a) the average value of the ambient air temperature, measured over a period of 24 h, does not exceed 35 °C;
b) solar radiation up to a level of 1 000 W/m2 (on a clear day at noon) should be considered;
c) the ambient air may be polluted by dust, smoke, corrosive gases, vapours or salt. The pollution does not exceed the pollution levels given in IEC 60815;
d) the wind pressure does not exceed 700 Pa (corresponding to a 34 m/s wind speed):
e) the presence of condensation or precipitation should be taken into account;
f) the ice coating does not exceed 20 mm.
4.3 Special service conditions
4.3.1 General
When instrument transformers are intended to be used under conditions different from the normal service conditions given in 4.2, the purchaser’s requirements should refer to standardised criteria given hereinafter.
4.3.2 Altitude
4.3.2.1 Influence of altitude on external insulation
At an altitude >1 000 m, the disruptive discharge voltage for external insulation is affected by
the reduction of air density. Refer to 6.6.2.
4.3.2.2 Influence of altitude on temperature-rise
At an altitude >1 000 m, the thermal behaviour of an instrument transformer is affected by the reduction of air density. Refer to 6,4.2.
4.3.3 Ambient temperature
For installations located in a place where the ambient temperature can be significantly outside the normal service condition range stated in 4.2.1, the preferred ranges of minimum and maximum temperature to be specified should be;
a) —50 C and 40 °C for very cold climates;
b) —5 C and 50 C for very hot climates.
In certain regions with a frequent occurrence of warm humid winds, sudden changes of temperature may occur, resulting in condensation, even indoors.
NOTE Under certain conditions of solar radiation, appropriate measures. e.g. rooting, forced ventilation. etc., may be necessary in order not to exceed the specified temperature rises. Alternatively, derating may be used.
4.3.4 Vibrations or earth tremors
Vibrations may occur due to switchgear operations or short circuit forces.
For an instrument transformer integrated within assembled equipment (GIS or AIS) the vibration produced by the assembled equipment shall be considered.
4.3.5 Earthquakes
For installations where earthquakes are likely to occur, the relevant severity level in accordance with IC 62271-2 shall be specified by the purchaser.AS 61869.1 pdf download.