Thermal Effects In Substation
The operation of a system of natural ventilation is as a result of a decrease in air density as its temperature is raised due to the heat gain from various sources.
This decrease in air density causes a pressure differential which provides the energy to drive the natural ventilation system.
Because the pressure differential developed is relatively small, ventilation louvers and grilles, etc, need to be of a design that offers little resistance to air flow.
To harness the thermal effects and maximise the performance of a natural ventilation system the air inlet openings should be located at low level and the exhaust openings should be as high as possible.
Any ventilation ducts shall have a large cross sectional area and a minimum number of bends to minimise losses. Long horizontal runs of exhaust duct shall be avoided. Due to a natural ventilation system’s sensitivity to the direction of the prevailing wind, the location of ventilation openings on the external face of a building shall be carefully selected to minimise any negative effect.
The benefit of wind effects can be maximised by positioning ventilation openings on adjacent or opposite sides of the building, the inlet on the windward side and the exhaust on the leeward side.
Reference: Ausgrid NS200 – Major Substations Ventilation Design Standard
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Edvard Csanyi
Hi, I'm an electrical engineer, programmer and founder of EEP - Electrical Engineering Portal. I worked twelve years at Schneider Electric in the position of technical support for low- and medium-voltage projects and the design of busbar trunking systems.I'm highly specialized in the design of LV/MV switchgear and low-voltage, high-power busbar trunking (<6300A) in substations, commercial buildings and industry facilities. I'm also a professional in AutoCAD programming.
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I have a question . Are there any published values for required air flow rate needed to provide adequate cooling for transformers? Preliminary data that we have seems to indicate that 10,000 cfm of air (via natural convection) are needed per MVA of transformer. Also, this same data shows that only 7,500 cfm of air (via forced induction by fan) are needed per MVA of transformer. Somebody know if this data is right or some standard or manufacturers recommedndation about this issue.