VD4-12

Normal Operating Conditions

Ambient Air Temperature

• Maximum +40℃

• Average over 24 hours not exceeding +35℃

• Minimum (Indoor) -5℃

Note: -25℃ operating temperature option available.

Humidity

• Average relative humidity over 24 hours not exceeding 95%

• Average water vapor pressure over 24 hours not exceeding 2.2 kPa

• Average relative humidity over 1 month not exceeding 90%

• Average water vapor pressure over 1 month not exceeding 1.8 kPa

Altitude ≤1000 m.

Seismic Performance Seismic intensity not exceeding magnitude 8.

Adaptability to Humid Tropical Climates VD4 circuit breakers are designed/manufactured in strict accordance with standards and can be used in humid, hot, and high-salinity climates. All critical components are specially treated to withstand the corrosion of Class C ambient environments specified in EN 12500 class 5. The galvanizing process is carried out according to UNI ISO 2081 standard, classification number Fe/Zn 12, with a thickness of 12 μm, and color chromate passivation is performed according to UNI ISO 4520 standard.

Altitude: The insulating properties of air decrease with increasing altitude; therefore, the impact of this phenomenon on the external insulation of the switch must be considered when using it at high altitudes. The insulation inside the arc-extinguishing chamber is not affected, as its insulation capacity is guaranteed by vacuum.

If the switch is installed in an area above 1000 m altitude, the effect of altitude should be considered during the design phase of the insulation components.

In this case, a correction factor must be considered, which can be found in the chart on the right, based on the IEC 62271-1 standard. An example calculation based on the above correction principle is given below. Example:

• Installation Altitude:

• Rated Voltage:

• Power Frequency Withstand Voltage:

• Lightning Impulse Withstand Voltage:

2000 m

1 2 kV

4 2 kVrms

75 kVp

• Ka coefficient, found from the chart: Ka=1.13

From the above parameters, the components must be able to withstand (test conditions at zero altitude):

• Power Frequency Withstand Voltage: 42 x 1.13 = 47.5 kVrms

• Lightning Impulse Withstand Voltage: 75 x 1.13 = 84.7 kVp

The above calculations show that circuit breakers used in high-altitude areas must be able to withstand higher insulation level tests at zero altitude. For specific circuit breaker selection, please contact the manufacturer.