CT and PT failute temporary repair
CT and PT failute temporary repair
(OP)
lately on plant we faced aproblem with the secondary of one CT and one VT. CT was used for protection 8000/1 5P20 toroid, VT (or PT for US) was used for exciation control 15750/V3 / 120 V Cl.0.2s.
In order to put the unit back in service i put in parallel the secoindar of the PT of another phase , same class, to have the voltage measurements.
Also for the current i put the secondary winding of another phase in series in order to have the same current.
This worked but i dont know if i should keep it this way or change the failed CT and PT with new ones.
In order to put the unit back in service i put in parallel the secoindar of the PT of another phase , same class, to have the voltage measurements.
Also for the current i put the secondary winding of another phase in series in order to have the same current.
This worked but i dont know if i should keep it this way or change the failed CT and PT with new ones.






RE: CT and PT failute temporary repair
Maybe I didn't understand you:
Change phase of voltage for excitation it's maybe O.K., if AVR used only one phase meas.
But protection in series with another phase isn't possible , maybe you meant another core of same CT?
Could you please send scheme of changes.
Regards.
Slava
RE: CT and PT failute temporary repair
npower0073, it never works to put the output of two CTs on different circuits in series. There are useful things than can be accomplished by putting them in parallel, but series will always result in problems.
RE: CT and PT failute temporary repair
I assume was some misunderstanding wit Npower0073.
Regards.
Slava
RE: CT and PT failute temporary repair
RE: CT and PT failute temporary repair
Please send drw's: before and after changes.
Very difficult recommend something without drw's. Maybe, you didn't connect correctly star-points of CT's secondary.
Regards.
Slava