All electrical rooms and substations need to have an air ventilation system.
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Electrical parts and switchgears generate heat. Without ventilation, the generated heat will cause the temperature in the room to rise.
If this heat is not discharged out of the room, sooner or later the room temperature can reach a level where it can be dangerous to operate the electrical equipment, theoretically.
The higher the room temperature, the lower the rate of dissipation of the generated heat from electrical parts and equipment to the surrounding air.
This can cause hot spots on equipment, especially at the connections between power cables and switchgears to reach a critical temperatures that eventually can lead to premature failure of the related parts (eg. Circuit breakers).
On top of that, nowadays many components of the electrical control and protection system use digital electronics and microprocessors.
These components are no doubt designed and manufactured to reliably operate at maximum possible temperatures inside electrical rooms and substations.
However, life is never perfect. Even good manufacturers nowadays outsource parts of the manufacturing process to some third parties somewhere.
In any case, electronic and digital systems are always composed of many small components.
The two facts above means more possibilities that s0mething can fail or malfunction at high room temperature.
So it is definitely important to have a reliable ventilation for and electrical room and substations.
The above picture shows a ducted mechanical ventilation.
For simple substation buildings that are small and isolated, natural ventilation accomplished through louvers that are suitable located for intake and exhaust are usually sufficient.
However, when a substation or an electrical room forms part of a main building, it can be difficult to provide suitable locations for the air intake and air exhaust openings.
In that case, forced ventilation by the use of a motor-driven mechanical exhaust fan may be necessary.
Even then the motorized fan alone might not be good enough. If only one of the four sides of the electrical room wall can be used for both inlets of outside cold air and the exhaust air, there may be a short circuit of the circulated air flow.
This may make the exhaust system ineffective.
That is why a ducting system is utilized in Picture 1 above.
With a ducting system, the outside air can be forced to flow over intended locations and equipment before it is sucked into the exhaust grilles when the fan is in operation.