Transformer (XFMR) Sweep Frequency Analysis

[breny426]

I recently performed sweep frequency analysis on 2 pad-mounted, OA transformers. When running the curves through the analyzer it showed "R-HF above limit" for H1-H0 to H3-H0 (both open) and H2-H0 (both open).

Could someone explain what this means? Unfortunately, there already seems to have been some kind of significant event on this transformer and the customer does not have any previous SFRA results to compare to.

Thanks!

566

[rofo42]

I recently performed sweep frequency analysis on 2 pad-mounted, OA transformers. When running the curves through the analyzer it showed "R-HF above limit" for H1-H0 to H3-H0 (both open) and H2-H0 (both open).

Could someone explain what this means? Unfortunately, there already seems to have been some kind of significant event on this transformer and the customer does not have any previous SFRA results to compare to.

Thanks!

566
If I’m understanding you correctly, two different transformers with the same problem? One or both had a fault condition?

What did the other non sfra tests look like?

I haven’t seen that before but usually if I encounter an error or bad line, it’s a test connection issue. If it is on both transformers, that would further lead me to believe a test connection issue. I searched through all the literature I have and couldn’t find anything for that issue. Hopefully someone chimes in, SFRA troubleshooting seems to be some big secret.

[breny426]

If I’m understanding you correctly, two different transformers with the same problem? One or both had a fault condition?

What did the other non sfra tests look like?

I haven’t seen that before but usually if I encounter an error or bad line, it’s a test connection issue. If it is on both transformers, that would further lead me to believe a test connection issue. I searched through all the literature I have and couldn’t find anything for that issue. Hopefully someone chimes in, SFRA troubleshooting seems to be some big secret.

After speaking with the engineers at Megger, they also suspect a ground connection issue.

The biggest issue with SFRA is that if it was not done when the transformer was new, there is no baseline to compare it to in order to determine if there were any shifts in the physical integrity of the transformer.