High-voltage switchgear & controlgear. Design classes for indoor enclosed switchgear & controlgear for rated voltages above 1 k V up to & including 52 k V to be used in severe climatic conditions Switchgear, Electric control equipment, High-voltage equipment, Electrical equipment, Insulating enclosures, Protected electrical equipment, Indoor electric equipment, Rated voltage, Condensation, Pollution, Environment (working), Classification systems, Testing conditions