GM1 ADR-DSN.S.875 Electrical power supply systems for air navigation facilities

(a)The safety of operations at aerodromes depends on the quality of the supplied power. The total electrical power supply system may include connections to one or more external sources of electric power supply, one or more local generating facilities, and to a distribution network including transformers and switchgear. Many other aerodrome facilities supplied from the same system need to be taken into account while planning the electrical power system at aerodromes.

(b)The design and installation of the electrical systems need to take into consideration factors that can lead to malfunction, such as electromagnetic disturbances, line losses, power quality, etc. Additional guidance is given in ICAO Doc 9157, Aerodrome Design Manual, Part 5, Electrical Systems.

(c)Switch-over time is the time required for the actual intensity of a light measured in a given direction to fall from 50 % and recover to 50 % during a power supply changeover, when the light is being operated at intensities of 25 % or above.

(d)As a good practice, a measurement of the photometric parameters may be used for the evaluation of the switch-over time.

(1)If the switch-over time is greater than 1 second, the following corrective actions may be used to decrease the switch-over time:

(i)use of enhanced constant current regulators (CCR); or

(ii)use of uninterruptible power supply (UPS).

(2)If the photometric based switch-over time is below or equal 1 second, it is recommended to analyse the electrical system in order to find out an equivalent electrical switch-over time.

(e)For periodic measurement of the switch-over time a measurement of the equivalent electrical switch-over time at the feeding point of an aeronautical ground lights (AGL) system may be established.

[Issue: ADR-DSN/3]