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What is the altitude derating of Blokset and Prisma panels?

Blokset and Prisma Plus panels comply with IEC standard 61439-2. IEC standard 61439-2 is valid for an altitude up to 2000m. With the altitude, the atmosphere is modified; cooling efficiency and the dielectric properties are impacted.
When installed above 2000m altitude, Prisma and Linergy BS, LGY, LGYE must be derated for the voltage Ui and current.
The most impact is on voltage (Ui, Ue). As Ui may decrease significantly with the altitude, it must stay valid for the real Ue.
About the current, the derating should be applied according to the device’s altitude derating. (i.e.: breakers NSX, NW . . .). These deratings are generally provided in devices catalogues and may change, depending on the ranges.
For Prisma range of products, deratings are:
Altitude 0-2000 m up to 3000 m Up to 4000 m Up to 5000 m
Voltages Ui            k= 1 0.88 0.78 0.68
Current                  k= As per installed devices altitude derating
 
More information on the physical phenomena is available in IEC60664 §5.1.2, and “Paschen law” (atmospheric characteristics modified with altitude)
 
As for Blokset switchboards, it is also possible to install Blokset switchboard in the high altitude but  it is required to apply the derating value as informed on the Technical guide 2013 item “3.1.1.1  Derting Coefficient” to the voltages and currents.
 
It means that all values of voltage as Rated Operational Voltage (Ue), Rated Insulation Voltage (Ui), Rated Impulse withstand Voltage (Uimp) have to be derated as per the table: “Derating Factor for the Voltage”  (for eg. 0.88=3000m ).
 
Similarly, for the current rating, the table: “Derating Factor for the Circuit Breaker" has to be followed (for eg. 0.99=3000m). This value must be applied on the current rating of all the conductors as the Circuit Breakers, connections and busbars. Please refer to the attachment (Blokset - Altitude Derating.pdf).
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