What is the derating when Prisma system is installed in altitude?
The standard 61439-2 is valid for an altitude up to 2000m. With altitude the atmosphere is modified, cooling efficiency and dielectric properties are impacted.
When installed above 2000m altitude, Prisma P, G 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 as per the devices altitude derating. (ie: breakers NSX, NW . . .). these deratings are generally given in devices catalogues and may change, depending the ranges.
For Prisma range of products, deratings are:
More information on the physical phenomena is available in IEC60664 §5.1.2, and “Paschen law” (atmospheric characteristics modified with altitude)
When installed above 2000m altitude, Prisma P, G 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 as per the devices altitude derating. (ie: breakers NSX, NW . . .). these deratings are generally given in devices catalogues and may change, depending 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)