It is currently Tue Jun 17, 2025 2:57 am



Post new topic Reply to topic
Author Message
 Post subject: Output of metering CTs
PostPosted: Fri Oct 25, 2024 5:45 am 

Joined: Mon Mar 09, 2020 9:27 am
Posts: 31
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?


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Output of metering CTs
PostPosted: Fri Oct 25, 2024 5:11 pm 
Sparks Level
User avatar

Joined: Fri Jul 08, 2016 10:01 am
Posts: 393
Location: Indiana
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.

_________________
SKM jockey for hire
PE in 17 states


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2022-2025 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883