- This topic has 7 replies, 4 voices, and was last updated 12 years, 11 months ago by
.
-
Posts
-
Have you ever been in a situation where a short-circuit occured, involving equipment damages and/or people being injured?
Could you share your experience with others, to re-inforce awareness of the risks & possible consequences?
I would suggest using the KVA method in performing a short circuit calculation. You wouldn't have to use per units or complex numbers.
Being employed by a major switchboard manufacturer for the last eight years, I have been privy to a number of short circuits, which were caused by equipment failure and errors in either manufacture or modifications.
Depending on the nature of the fault, the damage of equipment can be extensive.
Unfortunately, I have been involved with one short circuit which has caused personnel injury and this occurred when modifications were performed to an existing switchboard. The works being conducted were straight forward and similar works had been performed by all personnel involved on multiple occassions.
The build of the switchboard meant that the main isolation point was behind a cover, which needed to be removed to return power. The cover was removed without any issue. However, once the switching took place there was a short circuit between a phase and earth (reasons still unknown). The subsequent arc gave severe burns to the person conducting the switching, who in turn required extensive plastic surgery and physiotherapy to recover. The fact that this person did not manage to close the switch completely and it sprung back to the isolated position, probably saved his and other peoples lives.
After assessment, it is thought that a small piece of conductive material landed across the cunducter and earth when the door was removed from the switchboard to access the isolation point.
Considering this incident was a minor one when compared to what could have happened if the isolating switch closed, it just enforces how dangerous a short circuit can be.
I hope this is the sort of information which you are after and don't hesitate to contact me should you feel the need.
Thanks,
Leigh
erickench said:
I would suggest using the KVA method in performing a short circuit calculation. You wouldn't have to use per units or complex numbers.
i m studying in electrical engg. will u plz help me in basic concepts?
Laurent said:
Have you ever been in a situation where a short-circuit occured, involving equipment damages and/or people being injured?
Could you share your experience with others, to re-inforce awareness of the risks & possible consequences?
yes, sort ckt will be the cause of sevier destruction of in strument .
like burnout of instrument
@Leigh: yes, it is precisely the type of experience sharing I have in mind, thanks for sharing it with others. I wonder what kind of measures were taken (or not?) after the accident you describe, to avoid this to happen again. Could you tell us more?
@all other visitors: please share also your experience here with others, it will help to highlight the risks related to electrical short circuits
Laurent said:
@all other visitors: please share also your experience here with others, it will help to highlight the risks related to electrical short circuits
Shorts cause many issues, One that I was privy to occurred in a large factory. During the installation of cables onto a cable tray one of the large supply cables suddenly pulled loose from the tray, and jumped approx 5 feet to the side causing a worker to receive a crushing blow to the side of his body, The force was sufficient to break the collarbone and cause additional injuries to the shoulder and arm regions. on investigation the cause turned out to be twofold.
1. A high fault current due to an insulation failure at the end of the cable run (not close to where anyone was working) created a large magnetic field arround the cable causing the cable to act like a solinoid, and move to the side, with sufficient force to cause injuries to the workers in the area.
2. The cable had not been secured sufficiently on original installation, and over many years the clips securing it had degraded and left the cable insecure.
Testing verified that electrical short circuit protection operated correctly, and that the supply had in fact been isolated inside the traditional 0.4 seconds required by our legislation. Subsequent testing and remedial action, also identified most of the tray earthing had failed over the years, and the tray was in very poor overall condition. It was then replaced, the earths renewed and the cables secured.
People often overlook the fact that high currents can cause mechanical forces withing cables, and all cables in the proximity of other cables (especially in Multi-Phase installations) must be physically secured to prevent the mechanical forces from causing sudden movement of the cables in the tray.
Laurent said:
Have you ever been in a situation where a short-circuit occured, involving equipment damages and/or people being injured?
Could you share your experience with others, to re-inforce awareness of the risks & possible consequences?
Cost analysis plays important role when evaluating
total asset maintenance cost, asset analytix provide comprehensive reports on
various cost like downtime cost, preventive cost etc. Its ready to you report
library helps decision makers take strategic decision.
- You must be logged in to reply to this topic.