How to locate a fault on a circuit

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Clna68

Member
Location
El Paso Tx
Occupation
Electrician
Is there a formula to find a fault on a circuit if you know it is 75 feet long and you have 8 ohms on one end and 4 ohms on the opposite end
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
We need a little more context - Or I do any way.

What is the circuit?
Two conductors in conduit?​
Something else?​
What is the wire size?

What is the nature of the fault?
Two conductors shorted together?​
One conductor shorted to conduit?​
Something else?​
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
I will add that I do not understand what you mean by the two resistance measurements. How did you do the measurements, with what type of instrument, and to what did you attach the instrument's probes? In any event, there will not be a formula for just this situation. But it may be possible to discern the location of a fault, if more information were provided.
 

retirede

Senior Member
Location
Illinois
If we presume that you are referring to a simple two wire circuit that has the same gauge wire throughout and are trying to locate the point in the circuit where the two wires are shorted together, then you can simply ratio the resistance. In this case, it’s 1/3 of the total distance (25’) from the 4 ohm end.
 
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