Primary protection of instrument PT

[william879]

Hi All,

working on a 25kV GIS gear. the Primary of the instrument PT on the voltage bus does not have Over-current protection. Is that typically acceptable? To add primary fuses, we need to add another section to the GIS since the PT is plug in type and I can't attach a fuse to the PT body.

I know the differential protection 87 with clear the fault happen to the bus. but I think the code still asks for a primary protection for PT.

thanks for all the help.

Best...Jake

 

[dpc]

There was an almost identical thread a couple of weeks ago. It is fairly common to not have primary PT fuses. The higher the primary voltage, the less common it is to have fuses. What code are you referring to?

 

[DTR2011]

Also closely check. The PT is very likely included in zone of protection of busbar or line.

 

[william879]

Thanks dpc and smallgreek. I found that thread.
Very informative and gave me a lot of confidence after reading the material.

Thank you very much