Current transformer 1

[ayjayaych]

A meter measures both voltage and current. The instrument is used in a switch-over configuration for mains and a standby generator. The voltage connection for both is fairly straight forward. The current is measured by passing the necessary conductor through the integral CT of the instrument. Both conductors of the two feeds are passed through the CT. Only one feed is read as they are isolated from each other by the change-over switch. When reading mains, the current load is half the value of the generator load reading. What can be the problem?

Anthony

 

[davidbeach]

Different CT ratios? A path that allows part of the current to bypass the meter?

 

[zappedagain]

Does the voltage reading match? What if the mains are wired 240VAC while the generator is improperly wired and putting out 120VAC? Sounds potentially dangerous.

 

[electricpete]

One scenario which can get you in trouble is if there are grounds on a CT primary circuit on both sides of the CT to create a loop. Let's say there is maintenance being done on mains circuit and safety grounds were hung on that circuit on both sides of CT while the generator is supplying the load. Then you have a deenergized conductor loop passing through the ct window and returning through ground. Current would flow in this deenergized loop in opposite direction to the generator current, resulting in lower secondary current reading than we'd expect based on the generator current alone.



=====================================
(2B)+(2B)' ?