# CT's (Current Transformer) grounding



## magmash (Jul 20, 2012)

Hi guys

While going through a diagram for an synchronization panel today, i noticed that the secondary of all the CT's in the system has been grounded separately, not the way i am familiar with, which is grounding them from their common point as in the second attached picture. Any idea what is happening here ?.

The panel is yet to be put in operation.

Diagram below
























Thanks in advance


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## glen1971 (Oct 10, 2012)

Can't see either picture...


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## JRaef (Mar 23, 2009)

The reason for a single ground point is based on them being used in the same circuit or protection relay. If they are not being used that way, it doesn't actually matter. If they are, then it's likely indicative of someone not knowing what they are doing...


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## NC Plc (Mar 24, 2014)

Here are the images he tried to post. I prob could have made them bigger, they're a bit hard to see here. His original image is massive.


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## magmash (Jul 20, 2012)

JRaef said:


> The reason for a single ground point is based on them being used in the same circuit or protection relay. If they are not being used that way, it doesn't actually matter. If they are, then it's likely indicative of someone not knowing what they are doing...


Well when i saw this at first i was wondering what the guy who designed this was thinking about, because as you said, these CT's are used on the same protection relay so they should be grounded by there common point as in the second picture.

I reckon this will cause measuring problems if they are kept this way, so i am going to rewire the grounding on them.


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## DriveGuru (Jul 29, 2012)

I don't think it's going to make a difference which way you ground them, just the way somebody drew it. They might just want to make sure that input terminal is grounded, but it's not like you can induce noise into a CT. I would stick with the protection relay's OEM's diagram.


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