Fuse failures

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T.M.Haja Sahib

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A fuse clears a fault after its element arcing for some time.But if its arc continues beyond a certain duration perhaps due to inappropriate higher size of its element,its cartridge might also be damaged by the arc, as the fuse failed to clear the fault. Has any one come across such a situation ? Thanks.
 

Dennis Alwon

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I have seen fuses arc for so long that the pullout had to be replaced. Often times the fuse holder can be the reason the fuse is arcing and it will get pitted. Not sure I ever saw an element cause a solid connection to go bad.
 

jim dungar

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A fuse clears a fault after its element arcing for some time.But if its arc continues beyond a certain duration perhaps due to inappropriate higher size of its element,its cartridge might also be damaged by the arc, as the fuse failed to clear the fault. Has any one come across such a situation ? Thanks.
Catridges are damaged usually because they have poor connections (heating) or inadequated interuppting ratings. Fuse arcing is not a function of the continuous current rating of the fuse element.
 
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T.M.Haja Sahib

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Not sure I ever saw an element cause a solid connection to go bad.
The basis for successful operation of a fuse also depends on the instability of the arc formed inside it during its operation to clear a fault. But if the resistance of the circuit in which the subject fuse is a part is such that a stable existence of the arc inside the fuse during its operation to clear a fault is possible,then not only the fuse fails to clear the fault,but it might also be damaged catastrophically by the arc, if the arc energy is sufficient.And this arc energy also depends on the size of the fuse element........
 

templdl

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Wisconsin
Haveyou discussed this with the fuse manufacturer regarding this phenomena. For basic fuse applications I was assigned as a fuse application engineer but I conscidered myself under qualified in that subject I relied heavily on the actual engineering ataff when I came to a concern such as the one that y ou have. As such, call the fuse manufacturer and be persistant until you get to someboby who you have confidence in.
Often time though, asking question of qualified peoplle may not give you the answers that you want to hear and as such are reluctant to actually go to the source.
I have been of the oppinion that a fue characteristic may change over time due to currents that may stress its elements. But, that's only my opinion.
 
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T.M.Haja Sahib

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Haveyou discussed this with the fuse manufacturer regarding this phenomena. For basic fuse applications I was assigned as a fuse application engineer but I conscidered myself under qualified in that subject I relied heavily on the actual engineering ataff when I came to a concern such as the one that y ou have. As such, call the fuse manufacturer and be persistant until you get to someboby who you have confidence in.

Thanks for your suggestion.

I tried to know if there were any data from field were avail;able.

If the filler element such as quartz sand of 'right granular composition' is present,fuse arc might not do extensive damage......

But a cartridge fuse without filler element:a glass fuse is more vulnerable to arc damage.

Any glass fuse with at least its glass shattered was observed after a fault anywhere by anyone,please?
 

augie47

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I have seen glass fuses shatter, however, in those instances the fuse was on a circuit with a higher voltage rating than the fuse. Many of the glass fuses I encounter have a 32v rating. The higher voltage ones are often ceramic tube. ( I am aware that some glass fuses have ratings higher than 32v)
 

templdl

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Location
Wisconsin
I guess that I missed the point that these were fuses such as KTKR or FNM, FRS, DLN, DLS, to medium voltage fuses such as current limiting and expulsion fuses which are often as large as you forearm. I normally dealt with the medium voltage fuses and their applications and coordination but not LV fuses even though I sold fusible panel and switchboards correct fuse sizing was the only topic but never an application/coordination issue. Medium voltage fuses, fuse holders, etc are some serious issues.
Anything smaller than that were never any consideration which the OP may have been referring to since the discussion now has included glass type fuses. As I recall in my person experience glass fuses are commonly used for 120v and I I believe there are 250v rated glass fuses such as the busman Pk5, Ferraz Shawmut GSB, Mersen GDG5, etc.
 

SG-1

Senior Member
I have seen NON type fuses actually catch fire. 18 amperes flowing through a 15 ampere fuse for several minutes. This is a paper fuse filled with sand.

I have seen KTK-R type fuses ejected from the holder. Some partially ejected with the brass end missing. It was a one amp fuse. This 600 volt fuse has a 200,000 ampere fault rating if I remember correctly. It was the input protection for a 120 volt electric fence controller.
 

brian john

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Location
Leesburg, VA
I have seen fuses with thermally damaged cases, in those events it was always a lose or defective fuse clip that was causing excessive heat.

I have seen damage from an arcing ground fault on 4000 amp and a 3000 amp, 480/277 solidly grounded systems, where the fuses were intact after a complete meltdown of the bolted pressure switch.
 

Besoeker

Senior Member
Location
UK
A fuse clears a fault after its element arcing for some time.But if its arc continues beyond a certain duration perhaps due to inappropriate higher size of its element,its cartridge might also be damaged by the arc, as the fuse failed to clear the fault. Has any one come across such a situation ? Thanks.
I have come across this kind of thing where the fault current was too low.
 

templdl

Senior Member
Location
Wisconsin
I appreciate the most awesome examples of the catastrophic fuse failure described. Being out off the loop I haven?t had the opportunity to hear these kinds of experiences with fuses. My only comments are ?WOW!!? I am not a LV fuse guy (600v and below) supplying fusible panels and combination starters only when requested. We used the ktkr and fnm with control transformers though and never in 18 years have I ever heard of this kind of issue.
We've had a few breaker failures occur most of which have been related to frying because of loose connectors, cable terminations on the lug and on a very rare occasion a braised connection inside the breaker has been defective. One of the common issues has been when there is a line side connection issue which caused heating. When any connection starts to heat the heating and cooling cycle often cause it to loosen more thus more heating. That heat is conducted into the breaker's stationary contacts, up into the moving contacts and cooks the moving contact springs causing them to weaken. Weak springs cause reduced contact pressure which causes the contacts to heat and often weld together or just start arcing. It isn't pretty.
Heating on the load side is more likely to heat the thermal elements in the trip unit causing the breaker to derate itself and trip.
Have there been some though given to the available fault current with some of these fuse failures? Short of the fuse clips weakening which caused heat that starts to cook the fuse maybe the available fault current might have been greater that what the fuse could clear.
One has to put on the forensics hat it determine tha cause of failure if there?s anything left.
 
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T.M.Haja Sahib

Guest
I have seen glass fuses shatter, however, in those instances the fuse was on a circuit with a higher voltage rating than the fuse.

It is clearly a case of exceeding the rupturing capacity of the fuse in which case any fuse including the glass fuse is liable for extensive damage.
 

kwired

Electron manager
Location
NE Nebraska
I have seen NON type fuses actually catch fire. 18 amperes flowing through a 15 ampere fuse for several minutes. This is a paper fuse filled with sand.

I have seen KTK-R type fuses ejected from the holder. Some partially ejected with the brass end missing. It was a one amp fuse. This 600 volt fuse has a 200,000 ampere fault rating if I remember correctly. It was the input protection for a 120 volt electric fence controller.

It wasn't by chance interrupting current from a lightning event (the fence controller application)?
 

templdl

Senior Member
Location
Wisconsin
I'm sorry. It was a long while ago and I don't remember the exact circumstances except that it was a 1500Vdc traction application.

I know with breakers it is possible to weld the contacts with an even that is not quite enough to open the breaker magnetically and not long enough to trip the breaker thermally which teases the breaker. Out of the thoudands of breakers sold there are just as many possible electrical instances where you put just the right conbination together to put a breaker on the ragged edge.
It could be the same with that fuse. Not enough current to cause it to clear buy just enough for the right legth of time to heating and fry causing it to fail physically.
And there's on thing for sure is that you can never duplicate such an event so your left with a calculated guest on how it could happen.
 

SG-1

Senior Member
It wasn't by chance interrupting current from a lightning event (the fence controller application)?

:happyyes:

These thunderstorms were ejecting the transformers out of the fence controllers & across the barn, before I tried that fuse. The 15 amp breaker never tripped. I made my own high voltage fuses for the high voltage side, that kept the KTK-R in the holder. The storms made some neat glass tubes out of the shot blast I used to displace the air in my HV fuses. The main problem was that I had no GES, & did not know it.

How much fault current do you suppose the fuse tried to interrupt ?
 
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T.M.Haja Sahib

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This is a paper fuse filled with sand.
You have got approved paper fuses?Because the problem is on heating, the paper emits conductive vapor which on being absorbed by sand makes it in turn conductive.The result is when the fuse tries to interrupt a fault current,the fault current may continue flowing through the sand even after the fuse element is broken!
 
T

T.M.Haja Sahib

Guest
How much fault current do you suppose the fuse tried to interrupt ?

The rupturing capacity of a fuse has nothing to do with lightning.In fact a fuse has nothing to do with interrupting a lightning current.My guess is the subject fuse in your case was not properly secured in its holder with the result the electromagnetic force of the lightning current displaced it .
 
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