Transformer operations

[Asifraja786]

We have a 1000 kVA distribution transformer subjected to frequent load cycling — around 12 to 15 ON/OFF cycles per day. Each cycle consists of the load being ON for 30 minutes (reaching approximately 70% of the transformer’s rated capacity) and then OFF for 30 minutes. The connected loads are purely inductive.

Is this operational pattern considered safe for the transformer in the long run? Are there any thermal or mechanical stress concerns due to this frequent cycling?


Would appreciate your insights or similar experiences.

 

[davidbeach]

How much does top oil temperature vary with that cycle?

 

[Asifraja786]

Oil temperature not that much max reach was only 50 degrees. Because the transformer is indoor unit and there is three split ac unit in the room.

Recently, this transformer is failed , due to the internal short circuit..I suspecting that this kind of frequent cyclic operation lead cause for the failure.

 

[waross]

Thermal cycling, particularly in a room with A/C?
I would investigate the possibility that the cyclic temperature changes caused air changes in the transformer case.
If that is happening, there is a possibility of internal condensation.
Or the transformer may have just failed.
It happens.
Replacement; Consider a sealed case or a desiccant on the breather. Don't forget a schedule to check and change the desiccant charge.

 

[Asifraja786]

Thank you for the response, the transformer is hermetically sealed transformers., it doesn't have the conservator tank and breather systems. Hole at corrugated fins oil came out from those fins at the time of failure.

we observed there is no high temperature in oil at time of incident.

We investigate why this kind of faults happening in our transformers because this is 2nd case at last four months. Recently done the oil filtrations and maintenance of that transformer, every result showing good values.

Age of transformer is 15 Years. ratings 1000KVA, 13.8kV /0.4 , Load profile: Frequently fluctuating load

 

[Asifraja786]

Thermal cycling, particularly in a room with A/C?
I would investigate the possibility that the cyclic temperature changes caused air changes in the transformer case.
If that is happening, there is a possibility of internal condensation.
Or the transformer may have just failed.
It happens.
Replacement; Consider a sealed case or a desiccant on the breather. Don't forget a schedule to check and change the desiccant charge.

Thank you for the response, the transformer is hermetically sealed transformers., it doesn't have the conservator tank and breather systems. Hole at corrugated fins oil came out from those fins at the time of failure.

we observed there is no high temperature in oil at time of incident.

We investigate why this kind of faults happening in our transformers because this is 2nd case at last four months. Recently done the oil filtrations and maintenance of that transformer, every result showing good values.

Age of transformer is 15 Years. ratings 1000KVA, 13.8kV /0.4 , Load profile: Frequently fluctuating load