132kV bushing

[Mlmlzx]

Dear sirs,

Tan delta test on 132 kV bushing for our tests are: factory value 0.311,% and site value 0.703%. but site value is greater than 0.5,%.

How to deal with this? Shall we reject this bushing? This is an autotransformer

Regards,

 

[RRaghunath]

At site, hope you have not connected the transformer winding terminal to bushing. Also, are the leakage currents bypassed using the Guard terminal.
Check the procedure followed and temperature at which the measurement is done.
Once you are convinced, you may like to take up with the vendor.

 

[prc]

When making bushing DF measurements at the site, make sure of the following:
1) There is no need for disconnecting the bushing from the winding. But bushings in three phases must be shorted outside.
2) Thoroughly clean the outer surface of bushings and take measurements when humidity is less than 50 %.