Current Transformer Question
Current Transformer Question
(OP)
I have a bushing current transformer on a transmission circuit breaker. If I short the current transformer and ground it, does current still flow through the closed loop?
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
Download nowINTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
Current Transformer Question
|
RE: Current Transformer Question
RE: Current Transformer Question
RE: Current Transformer Question
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Current Transformer Question
What we were wondering was if we took a ammeter if we could test the current near the CT to see if this was the case. The ammeter would be a wrap-around type.
RE: Current Transformer Question
RE: Current Transformer Question
Make sure you don't accidentally open circuit the CT secondary as you are getting things fixed up.
David Castor
www.cvoes.com
RE: Current Transformer Question
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Current Transformer Question
RE: Current Transformer Question
When the CT is shorted, the resistance is very low so the I2R is very low.
I lost a good meter on an open CT. Someone cut the leads in a wire bundle behind the control board. I was trying to locate a particular CT so I took a voltage reading across the relay and was behind the panel checking voltages across CTs looking for a match. (Yes, I admit it, I was trying to get lucky.)
I measured one CT and my meter made a buzzing sound and never worked again. After safeing the CT I found the leads cut in a bundle. I thanked God that I hadn't been running my hands near the cut ends following a conductor.
I was sure glad to go home that day.
The joys of working in the third world.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Current Transformer Question
I lost some good underwear in similar circumstances.
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Current Transformer Question
RE: Current Transformer Question
You stated,
"We actually have a CT going to a relay but the relay is reading zero amps and zero degrees so we are thinking that a shorting screw was left in place somewhere."
Depending on the type of relay, don't forget to check the case. Over the course of time I have found several mismatched relay/case combinations.
Of course if you are using a clamp around type Amprobe to measure current then a defective or mismatched case will not be your problem.
Also check for a stray ground in the wiring. If the CT polarity side wiring (X1) is inadvertently grounded, it could shunt the current to the relay.
RE: Current Transformer Question