BIL

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mike0w

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I know that BIL is short for Basic Impluse Levels, but does anyone know where I can find more information about this topic? Where it is explained in a little detail? Thanks.
 

jim dungar

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Location
Wisconsin
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PE (Retired) - Power Systems
Re: BIL

My old Handbook for Electrical Engineers says BIL, when referring to transformers, stands for Basic-Impulse Insulation Level. It is a test of a factory impulse-voltage waves (about 1.5 x 40 microseconds). It is used to define the ability of the insulation to handle travelling waves coming into a substation over the transmission lines
 

rcwilson

Senior Member
Location
Redmond, WA
Re: BIL

1.4 x 40 microseconds describe the surge voltage wave pulse shape used to test the transformer or other insulation system. The voltage surge must reach its peak in 1.4 microseconds and decay to 50% of its peak in 40 microseconds. Other test waves are 1.2 x 50 and 250 x 500. These are DC voltage surges, like a hypot, only a lot faster.

A 95 kV BIL transformer winding will be designed to withstand a surge voltage that hits 95 kV in 1.2 microsecond and drops to 42.5 kV in 50 microseconds. It imitates a lightning surge.

There are several other tests that use different wave shapes to test for other characteristics.

Wave shape has an impact on transformer winding, arrestor and bushing design.

Think of comparing a 12-foot tide change on a beach with a 12-foot tsunami. The tsunami wave has a lot more destructive power when it hits the seawall even though high tide reaches the same water level. It is the same with a voltage surge hitting the transformer winding impedance. A fast rise time wave, like lightning, can cause more damage than a gentle voltage wave.
 

charlie

Senior Member
Location
Indianapolis
Re: BIL

Line construction is also rated in BIL. Various line insulators all have a BIL rating as well as the type of construction. :D
 
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