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| Output of metering CTs https://brainfiller.com/arcflashforum/viewtopic.php?f=2&t=5867 |
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| Author: | aguywithfeet [ Fri Oct 25, 2024 5:45 am ] |
| Post subject: | Output of metering CTs |
Many moons ago i found a white paper regarding the output of 5A CT's for switchgear meters. The paper basically said there was some level of concern over the infinite potential that could be reached and an arc that could be generated. It came up again and i can't find anything regarding it. i know this is the reason shorting blocks are used but does anyone have any reading that i can share to convince a person of this potential hazard? |
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| Author: | bbaumer [ Fri Oct 25, 2024 5:11 pm ] |
| Post subject: | Re: Output of metering CTs |
Pull a lead off without shorting and you'll be convinced. E = IR What happens to E if R approaches infinity when you pull a lead off without shorting first and I is somewhere between 0 and 5 amps? When I was just a lad in EE 201, 35+ years ago, I could do the basic circuit analysis math easy enough but couldn't visualize an example of a current source we so often saw in the diagrams in that class. I didn't know what a CT really was back then. Fast forward a few years and I sure found out when I was replacing a dead PML meter in a switchboard and didn't short out the CT's before pulling off a lead. It made an awful growling noise and nice arc. Fortunately I was able to stick the lead back in the block immediately and think about what just happened. Ah, a current source. E = IR. E must have gotten pretty high for a split second. |
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