A single blown fuse in a 3-phase industrial control panel catches on fire. WHY? 2

[bdn2004]

Inside this panel a single 300A fuse blows up and then catches on fire. The fuses upstream did not blow, neither did the adjacent fuses in the panel. The panel remained energized throughout the whole episode. This feeds an infrared heating system. Any ideas on WHY something like this could happen? And why didn't the fuse just open - instead blowing up ?

The fuse manufacturer was contacted and they said that fuses at low overload currents have trouble opening. They also said it could be there was a solder problem on the fuse or there could be sand fill issues that could cause internal arcing especially in the 600A range of overload.

Any thoughts? Has anyone seen anything like this before? What were your conclusions and things you did to remedy or see that it could not happen again ?

 

[bdn2004]

Kiribanda (Electrical),

I was thinking about that too....about the lack of short circuit current. I recently modeled a reactor in our power software that was installed just prior to a VFD input. The short circuit current is drastically reduced after the reactor. Then I thought about this situation.....doesn't the nature of the load downstream have an effect on the short current?

 

[bdn2004]

Here is pic of the damaged fuse in this post.

 

[Kiribanda]

Your latest photo shows that this is a typical case of not having enough current to melt the fuse.
That means you have to check about your zero seq. impedance during a single phase to ground fault.
As I enquired before what is your grounding method?
Can you please upload your SLD?

 

[LionelHutz]

Doesn't look like a loose connection. Check your operating currents vs fuse rating but my guess would be it was a bad fuse. Its rare but it happens.

 

[bdn2004]

This panel is fed from a 480/277 volt, solidly grounded 800A busway that runs the length of the plant. There's an upstream busplug (that did not blow btw). Upstream from that is a 1500kVA unit substation feeding the entire busway through a feeder breaker. Usually there is another small transformer in these kind of panels that produces the control voltage.

What they did on this I was told - was replaced all the fuses and the feeder cables to the heater - and it's now running without issues.

 

[che12345]

Dear Mr. bdn2004 (Electrical)(OP)11 Nov 21 17:48
"...Here is pic of the damaged fuse in this post."
This picture shows much better clarity that :
1. The top and bottom blades are clean.
2. Fusing element connected to the top end-cap are clean. Heat source/root seems to be at the lower end-cap. This indicates that there could be a high/dry connection between the fuse element and the bottom end-cap.
3. The current may be < than the fuse rating, but the i2[sup][/sup] R heat generated is sufficient to burn the combustible fuse body, which eventually caused the fire that generated more heat and damage.
4. Suggestion: replace the poor quality brand to a type with selenic (i.e. china) body, if available.
Che Kuan Yau (Singapore)