Technical Description: High Altitude Analysis

1. Technical Description: High Altitude Analysis • COOLING ISSUES: • Reference Document: ALMA memorandum n°203 and standard engineering thermal calculations; • Data from suppliers of electrical and electronics equipment: derating of 5% every 1.000 m of altitude increments (derating of 25% at 5.000 m a.s.l.); • a value equal to 35% for the electrical equipments, continuously working at the nominal power, should be considered conservative; • For users such as the Feed Shutter or Stow Pins, no derating can be applied; • In any case, the power derating factor of 35% should be taken as the basis for the electrical dimensioning of the equipment working at the nominal power; • Different deratings can be applied with a dedicated duty-cycle calculation vs. thermal dissipation (when in air); • Exceptions to reduction factor are possible were the cooling of the equipment is made by refrigerating liquids. • ELECTRICAL INSULATION ISSUES: • Reference Document: IEC 60664; • Evaluation of the “pollution degree”; • Over-voltage categories identification; • Analysis on the electrical/electronic apparatuses w.r.t. they working voltages; • Corrective Factors for altitudes above 2000m

2. The general effect of electrical and environmental factors on creepage distance and clearance: • pollution degree, • overvoltage category, • working voltage, • the previous factors cumulatively, • comparative tracking index (applies to creepage distance only), • altitude (applies to clearance distance only). • For elevations above 2000 m, the required clearance is increased by the following factors: to 3000 m, 1.14; from 3000 to 4000 m, 1.29; and from 4000 to 5000 m, 1.48