Voltage too high 4

[roemer]

Hi everybody,
After installing modern lighting, in a school, the lamps flickered all the time, I measured the voltages:
L1=230V, L2=260V, L3=230V
Load is basically evenly distributed over the phases. In the Substation the transformer occasionally makes a bubbling sound suggesting gases rising in the oil.Any ideas as to possible causes of the over-voltage?

 

[oldfieldguy]

"The engineer from the electricity board reckoned that sometimes transformers do bubble and it doesn't necessarily mean there is a problem."

I've spent a bunch of years installing, caring for and repairing oil-filled transformers and it's been my goal to PREVENT bubbles. That's ONE reason we vacuum fill transformers. Once a transformer is filled, there is NO reason for bubbles under normal operation.

I recommend that you get a testing company to come in, do an on-site TCG (total combustible gas) test AND draw a sample for the dissolved gas analysis. Most testing companies can do the TCG within minutes. The equipment is relatively cheap and very portable.

The TCG test is quick and non-specific. If the results are high, there's reason enough right there to shut down the transformer without waiting several hours for the dissolved gas results to show up. I've had TCG results with elevated readings within a few minutes of a bubble/trip episode.

old field guy