I am aware that the design ot a transformer such as these is certainly very involved and covers a wide range of things. I am also aware that many design or construction flaws show up as a temperature rise and a voltage drop. Certainly there are certain ways of testing already created that will provide quantitative data. Hopefully the TS has already studied those texts and standards, which often describe the test process in minute details. That is not what I was doing, OK?

I figure it this way. During the manufacturing process testing is done on those things which cannot be tested once there is a finished product. So there are limits. There are also limits as to what can be tested and how without using destructive testing. Fot example you run an insulation breakdown to breakdown that's it, game over for the part. The thread starter needs to figure out exactly what they want to test and how. We can suggest methods and procedure but that is as good as it gets.

Ron

 

The thread starter needs to figure out exactly what they want to test and how. We can suggest methods and procedure but that is as good as it gets.

I have following pdf
https://webstore.iec.ch/preview/info_iec61238-1-1{ed1.0}en.pdf

 

For 1.0 KV and below.

Ron

 

The TS has repeatedly referenced some standard test process, which I have not looked at.
While the very big transformers are certainly vital to power systems, I am not interested in testing them.

 

While the very big transformers are certainly vital to power systems, I am not interested in testing them.

I don't want to test transformer I want to test temperatures as per iec standards on lugs and power cable using transfomer.

 

OK, that is a good explanation, not what I had expected at all. Certainly the terminal lugs are very important and probably a major source of failure under some conditions. And testing the lugs would explain the setup shown in that early post.
The temperature rise would probably be mostly on the low voltage lugs because they carry far more current, while the high voltage lugs have the much higher voltage and carry much less current, but high voltage is more dangerous to work with.

So the question is just what part of the lug system is being checked and for what sort of problem?
There are at least two areas to be evaluated, the connection between the winding conductor and the lug material, and the connection between the lug material and the external connection part. So it becomes clear that if the design is not correct then the thermal cycling as the loading changes will lead to differential expansions and loosening of the connection, which will certainly cause a rise in resistance, leading to overheating and failure.
So this is why the temperature changes must be understood. Probably there has been a problem and the itention is to avoid additional problems.

 

So the question is just what part of the lug system is being checked and for what sort of problem?

In the test we have to find out if the lug connected with the cable is working good ( not melting, working well when I high current pass)

Have you seen the pdf posted in last post?

 

In the test we have to find out if the lug connected with the cable is working good ( not melting, working well when I high current pass)

Have you seen the pdf posted in last post?

I see the one about testing the terminals, which was a bit confusing because It had not occurred to me that transformer terminal connections could be a problem. Of course that is probably because I have not worked with those very large transformers. Ten KVA is about the largest individual one for the systems I designed.

 

In the test we have to find out if the lug connected with the cable is working good ( not melting, working well when I high current pass)

Have you seen the pdf posted in last post?

This is where I instrument the insulator with a temperature sensor or two or three and note the thermal rise as I apply a current. Note and chart the thermal rise. You also may want to look for hi potential breakdown (Hi Pot Testing). Try to use pretty much standard test methods and techniques and try to keep all testing non destructive.

Ron

 

Try to use pretty much standard test methods and techniques and try to keep all testing non destructive.

Ron

techniques are given in documents of iec standard. I have been gone through the pdf. I am trying to understand the test technique shown in pdf

I have attached snapshot of program there I am struggling

 

OK, now the problem is clear. the test is for unreliable crimp connections. Certainly there can be problems leading to complete failure with crimp connections. There are also no simple way to correct poor quality crimp connections, and in a transformer without a lot of extra wire available for a second attempt that can be a serious problem indeed. Thus welded or silver soldered or brazed connections are preferred.
I have seen failures of crimp connections on high voltage power cables, where with a high wind the tension was adequate to pull the cable out of the crimped connector.