Type of climatic designs

Transformers are manufactured in appropriate materials to suit the operational climatic conditions. This information is usually included on the rating plate, in the form of an alpha-numeric symbol, in accordance with EN 60076-11, which describes the climatic class relating to humidity, condensation, contamination and ambient temperature. The classification is as follows:

  • E0 – no condensation occurs and pollution is negligible.
  • E1 – condensation and limited pollution may occur sporadically.
  • E2 – frequent condensation and high pollution may occur

Storage, transportation and usage environments are covered by EN 60721-3:

  • 1 to 7 - digits indicating the place of application
  • K, B, C, S, M, Z - letters indicating the type of environmental conditions which are taken into account
  • 1 to 7 - digits indicating the intensity of factor occurrence, a higher number indicates higher intensity

In accordance with EN 60076-11 standard the conditions in which the transformer is located are divided into two categories:

  • climatic classes and environmental classes. This standard applies only to dry-type transformers (including autotransformers) with power from 5 kVA (1-phase) and 15 kVA (3-phase) and highest voltage to 36 kV, in which the rated power of at least one winding is higher than 1 kV.

Climatic classes as per EN 60076-11:

Environmental class Description
C1 Transformer can operate at temperature T ≥ -5°C, but it can be transported and stored at ambient temperature T ≥ -25°C
C2 Transformer can operate and it can be transported and stored at ambient temperature
T ≥ -25°C

Environmental classes as per EN 60076-11:

Environmental class Description
E0 No condensation occurs on transformer and pollution is negligible. It is usually attainable in clean, dry indoor installations.
E1 Condensation can occur on transformer sporadically (e.g. when transformer power supply is disconnected). Limited pollution is possible.
E2 Frequent condensation and/or high pollution.

In case of dry-type transformers the environmental conditions are important not only during their operation but also when they are stored prior to installation.

Comparison of designations as per EN 60076-11 and PN-68/H-04650 (not applicable now)

Version of manufacture as per
PN-68/H-04650
Climatic class / Environmental class Comments regarding differences
N/3 C1 / E0 PN-68/H-04650 standard specified lower minimal temperature
(-40°C) and higher average maximal temperature (+40°C). In case of PN-EN 60076-11 standard it is (-25°C) and (+30°C) respectively.
W/3 C2 / E1 PN-68/H-04650 standard specified lower minimal temperature
(-40°C) and higher average maximal temperature (+45°C). In case of EN 60076-11 standard it is (-25°C) and (+30°C) respectively.

Standards of EN 60721 series classify the environmental conditions in which the products are stored, transported and used. Brief information on classification system defined in this standard is given below.
Identification system used for identification the class for given environmental conditions is very developed and consists of the following marks:
 

  • digit indicating the place of application
    • 1 - conditions at the place of storage
    • 2- conditions during transport 
    • 3 - conditions in places protected against the influence of atmospheric conditions 
    • 4 - conditions in places not protected against the influence of atmospheric conditions
    • 5 - conditions in land vehicles 
    • 6 - conditions in vessel environment 
    • 7 - conditions during portable and non-stationary using of products 
  • letter indicating the type of environmental conditions which are taken into account  
    • K - factors of climatic nature (temperature, humidity, insolation, etc.)
    • B - factors of biological character (e.g. attack of animals, termites, etc.)
    • C - chemically active factors (various chemical factors)
    • S - substances exerting mechanical influence (sand, dust, etc.) 
    • M - factors of mechanical characters (vibration, shocks)
    • Z - factors of special character 
  • 1 to 7 - digit indicating the intensity with which a given factor occurs. Higher digit indicates higher intensity.
  • H (high) or L (low) - H or L letters can be added additionaly after this digit and they indicate the frequency of specific conditions occurrence, e.g. temperature is mostly low and never high  

Example of full designation as per EN 60721 and including the occurrence of all environmental conditions in places protected against the influence of atmospheric conditions may have a very developed form, such as: 3K2/3Z1/3Z4/3B1/3C2/3S1/3M4.

In case of products manufactured by our company we try to replace N/3 and W/3 designations used in out-of-date PN-68/H-04650 standard with equivalents indicating the same or maximally close environmental conditions. For that purpose we use mostly the following designations of environmental conditions:

  • 3K3 or 3K4 as the equivalent of old N/3 designation; and
  • 3K7 or 3K7L as the equivalent of old W/3 designation.

The most commonly used designations of environmental conditions as per EN 60721 are as follows:

Environmental parameter Unit of
measure
Class
3K3
Class
3K4
Class
3K7
Class
3K7L
Lowest air temperature °C +5 +5 -40 -40
Highest air temperature °C +40 +40 +70 +70
Lowest relative humidity % 5 5 10 10
Highest relative humidity % 95 95 100 100
Lowest absolute humidity g/m3 1 1 0,1 0,1
Highest absolute humidity g/m3 29 29 35 35
Temperature variation index °C/min 0,5 0,5 1,0 1,0
Lowest air pressure kPa 70 70 70 70
Highest air pressure kPa 106 106 106 106
Solar radiation W/m2 700 700 1120 1120
Thermal radiation n/a 6) 6) 6) 6)
Movement of surrounding air m/s 1,05) 1,05) 1,05) 1,05)
Condensation n/a no yes yes yes
Precipitation accompanied by wind (rain, snow, hail, etc.) n/a no no yes yes
Water coming from sources other than rain n/a no no 6) 6)
Ice formation n/a no no yes yes
5) - if applicable then appropriate value may be given in accordance with table 2 (as per EN 60721-3-3)
6) - conditions existing in the location can be determined as per the table 2 (as per EN 60721-3-3)

In accordance with EN 60721 standard:

  • the conditions determined as 3K3 can occur in ordinary working rooms, e.g. offices, shops, production plants where electronic elements are assembled, warehouses of valuable and susceptible products.
  • the conditions determined as 3K4 can occur in some working rooms, e.g. production plants where the processes causing the occurrence of high humidity are conducted, normal storage rooms, garages, cellars.
  • the conditions determined as 3K7 and 3K7L can occur at the entrances to buildings, in garages, factory buildings, not guarded stations with equipment, storage rooms for products resistant to frost, etc.

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