ABB UZE Tap Changer Sometime Leaks Insulating Oil Through The Breather

[isnata]

Hi everyone,

I currently have a situation whereby the Tap Changer sometime leaks insulating oil through its breather. I have researched the Tap Changer to Main tank configuration from the product manual(how they are physically mounted), and noticed that they both have separate conservators.

My diagnosis are:

* 1st Option - The leaking only occurs during high Tap Changer arcing activity, forcing oil through the breather​

* 2nd Option - Insulating oil is leaking from the main tank into the tap changer tank, thereby increasing the oil level beyond the breather. This alternative would require a considerable amount of oil leaking through the gaskets. We have checked around the Tap changer for any signs of leaking and can't find any.​

I would like to hear from you guys if you have ever experienced something similar with ABB UZE Tap Changer or any other Tap Changer. What do you think about my diagnosis? Any input will be more than welcomed.

Thanks.

 

[stevenal]

Option 1. Suggest gas in oil analysis to determine if excessive arcing is occurring. Gases will accumulate even in free breathing tap changers.

Option 2. No oil level gauges present? I'm aware of a separator board that leaked and required replacement many years ago. Not sure what symptoms occurred.

 

[krisys]

As I remember, the conservators of both main tank and the tap changer diverter switch are generally installed at the same height. So if the oil leakage (to be precise, it may be called as oil spilling out through the breather!!!) due to the Insulating oil is leaking from the main tank into the tap changer tank may not be happening.

Check whether the oil in the conservator is above the maximum level marked on the conservator? or the level gauge is showing wrong oil level.

 

[bacon4life]

We have had quite a few tap changers where the tap board leaks oil from the main tank into the LTC. A few gallons can easily raise the oil level in the LTC a noticeable amount, but the drop in the main tank may not be apparent due to the much larger volume of the main tank.

As far as I know, all of our leaking tap boards have been older kinds of LTC as we only started using ABB tap changers somewhat recently. In some cases of slow leaks, we have just added a periodic maintenance task of draining a few gallons from the LTC every few months. Replacing the tap board is a considerable amount of work. The outage has usually taken at least a week, plus time to setup & put away the vacuum processing rig.

 

[prc]

My comments are not for ABB Tap-changers,but for all types of in tank type and flange mounted tap changers. I have seen this problem many times either due to failure of oil seals or some body forgetting to put back the oil drain plug at the bottom of arcing chamber of in tank OLTC. You can confirm the leak by (a)Check DGA of main tank of transformer.If there is acetylene &other thermal gases, it is an indication of leak of OLTC oil into main tank.(b) If shut down for a short time is possible,then drain oil from the OLTC tank and watch the position where the oil is seeping in.It is easy to check in in-tank tap changer.

Smart manufacturers sometimes provide the main conservator and OLTC conservator at same level, by piggy riding the OLTC conservator on the side of main conservator. In that case, in the unlikely event of a above type leak, user can continue the service till the time of planned maintenance.A short time solution,provide a temporary vertical extension pipe on breather pipe,so that you can come out of topping up.