Capacitance on bushings of tr

[Mlmlzx]

Dear sirs,

Factory value and site value for capacitance measurement for bushing test is 448.2 pF and 323.853 pF: and percentage diff is 27.74%.

As per my knowledge the acceptable range is from -5% to 10%.

Is this bushing faulty? But tan delta values are 0.35% and 0.362%.Diff is 0.01 and both are less than 0.5%.

Regards,

 

[scottf]

Are you measuring the capacitance via the capacitance test tap?

Is the measured value of 323.853pF the C1, C2, or overall capacitance?

I would check your test method and also confirm you are comparing the correct values.

 

[prc]

In case of a defect, usually, C will be more at the site. Hence please check the measurement.

 

[Kiribanda]

C1 totally depends on the design and therefore cannot change after installation.
But C2 can have variations because C2 depends on the grounding method used, contamination etc. etc. at the installation.
All in all per IEEE the acceptable capacitance variation based on bushing name plate values
should be +/-1% corrected to 20deg C for all bushing types (Oil impregnated, resin impregnated, solid etc.)

 

[Palletjack]

You guys install this bushing?
Is there a lot of paint on the mounting flange of the transformer?
As others have said, check your method and make sure your grounded.