Power supply equipment/systems provide a vital role in the operation of CNS/ATM systems and consequentially to safe and orderly operation of air navigation services.
The electrical power supply sources/equipments/systems - quality, availability, capacity and reliability are one of the basic technical prerequisites for high integrity and reliability of CNS/ATM system services.
To fulfill the requirementsthe proper design, installation, maintenance, monitoring and control should be met according to electrical power supply standards and regulations, both national and international.
In terms of type and function, there is a clear difference between primary or  commercial power supply (EVN Macedonia) as an external element and the secondary power supply (backup, uninterruptible) as internal element of M-NAV.
M-NAV buildings and systems for provision of air navigation services, are properly equipped with power supply plants and installations, starting from the connection points to EVN Macedonia, through its own (internal) power sources and power distribution network, to the points of connection with  consumers - CNS/ATM equipment/systems.
Depending of consumer (load) type and requirements, it can be categorized according to “allowed” time failure in the power supply, as a :
         Cat. M loads (on Mains) - power supply interruption can be longer in time;
         Cat. G loads (on Generator) - power supply interruption shall be shorter in time;
         Cat. U loads (on UPS) - no interruption allowed (CNS/ATM flight operative loads).
Equipment and systems used for power supply can be briefly mentioned and described as abbreviations: commercial or public mains supply (Mains), stand-by engine-generator set (GenSet), uninterruptible power supplies (UPS), AC/DC rectifiers/chargers, batteries and battery station (Bat.), substations (SS), transformers (TR), control panels, switchboards, power supply distribution network, etc.