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The primary North American document that deals with outdoor high-voltage transformer fire barriers is NFPA 850. [1] NFPA 850 outlines that outdoor oil-insulated transformers should be separated from adjacent structures and from each other by firewalls, spatial separation, or other approved means for the purpose of limiting the damage and potential spread of fire from a transformer failure.
Design loads – Fire wall must withstand a minimum 5 lb/sq ft (24 kg/m 2), and additional seismic loads. [7] Substation transformer firewalls are typically free-standing modular walls custom designed and engineered to meet application needs. Building fire walls typically extend through the roof and terminate at a code-determined height above it.
Engineering fits are generally used as part of geometric dimensioning and tolerancing when a part or assembly is designed. In engineering terms, the "fit" is the clearance between two mating parts, and the size of this clearance determines whether the parts can, at one end of the spectrum, move or rotate independently from each other or, at the other end, are temporarily or permanently joined.
To reduce noise, enclosures are often built around the transformer and can also be added after the substation is built. [51] Oil-based transformers are often built with bunded areas to prevent the escape of flaming or leaking oil. Fire separation areas or firewalls are built around the transformer to stop the spread of fire. [52]
IEC 61472 Live working – Minimum approach distances for a.c. systems in the voltage range 72,5 kV to 800 kV – A method of calculation; IEC 61477 Live working – Minimum requirements for the utilization of tools, devices and equipment; IEC 61478 Live working – Ladders of insulating material
In civil engineering, clearance refers to the difference between the loading gauge and the structure gauge in the case of railroad cars or trams, or the difference between the size of any vehicle and the width/height of doors, the width/height of an overpass or the diameter of a tunnel as well as the air draft under a bridge, the width of a lock or diameter of a tunnel in the case of watercraft.
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Current and voltage transformers to step down the high voltages and currents of the electrical power system to convenient levels for the relays to deal with; Protective relays to sense the fault and initiate a trip, or disconnection, order; Circuit breakers or RCDs to open/close the system based on relay and autorecloser commands