QUESTION:Which reductions must be implemented for protection and switching devices, and 3RA2, 3RV1, 3RV2, 3RT1, 3RT2, 3TF6, 3TC, 3TK1, 3TG10, 3RH2, 3RU2, 3RB2 and 3RB3 device combinations at installation altitudes of 2000 m to 5000 m above sea levelNote:The following are excepted:The following circuit breakers:- 3RV106, 3RV107, 3RV108, 3RV136, 3RV137, 3RV138The following contactors:- 3RT12 and 3TF69 vacuum contactors with electronic operating mechanisms (3RT12..-.N/P, 3TF69..-.C..)- 3RT1 in the operating mechanism version with fail-safe control (3RT1…-.S)- 3RT2 in the operating mechanism version with fail-safe control (3RT2…-.S)These devices are not rated for use at altitudes greater than 2000 m.ANSWER:For plants at higher altitudes, the reduced insulation strength and the reduced cooling effect of the air must be taken into consideration.Recommendations for the use of combinations and/or their individual components3RV1011, 3RV20 to 3RV24 motor starter protectors3RT1, 3RT2, 3RH2, 3TF6, 3TC, 3TK1, 3TG1 contactors and contactor relaysContactors: 3RT148 and 3RT135/6/7 are only approved up to 4000 m with the following derating.3RT12 and 3TF6 vacuum contactors are generally also suitable for use up to 3000 m. In addition, the following specified deratings must be observed for 3RT12 vacuum contactors with the standard operating mechanisms (3RT12…-.A…).The following reduction factors apply for thermal and electronic 3RU2, 3RB2 and 3RB3 overload relays at installation altitudes of over 2000 m above sea level:  Parameters Up to 2500 m Up to 3000 m Up to 3500 m Up to 4000 m Up to 5000 m Applies to MCB, contactors and OLR:           Permissible maximum operating voltage Ue 0.93 0.88 0.83 0.78 0.68 Permissible current load Ie 0.93 0.88 0.83 0.78 0.68 Rated insulation voltage Ui 0.93 0.88 0.83 0.78 0.68 Rated impulse withstand voltage Uimp *) 0.93 0.88 0.83 0.78 0.68 Applies to MCB           Short-circuit breaking capacity  Ics / Icu 0.93 0.88 0.83 0.78 0.68 Applies to device combinations           Short-circuit breaking capacity Iq 0.93 0.88 0.83 0.78 0.68 Applies to thermal MCB and OLR:           Current setting at motor protection device referred to motor current **) 1.02 1.05 1.08 1.1 1.15 Applies to 3RT10, 3RT14 and 3RT2 contactors           Switching frequency 1 1 0.5 0.5 0.5 Breaking capacity 0.93 0.88 0.83 0.78 0.68 Making and breaking capacity (overload switching capacity) 0.93 0.88 0.83 0.78 0.68 Coil operating range Us Conventional operating mechanism 0.8 – 1.08 0.84 – 1.02 0.87 – 0.96 0.89 – 0.96 0.89 – 0.96 These specifications refer to a maximum ambient temperature of 40°C.Additional information:Other technical specifications remain unchanged.*) The permitted operating voltage for safe separation can also be reduced depending on the reduction of the rated impulse withstand voltage Uimp **) No correction factors are required for the set motor current for 3RB (electr. OLR).