Recent content by jkristinn

Hi everyone, We have a situation where we have troubles with parallel operation of 11/0,4 kV transformers. The transformers are identical, same manufacturer, same ratings and impedance and operating on same tapping. Both are Dyn5 connected. During parallel operation we see difference in HV side...

prc says: The underlying physics are based on Arrenhius's equation (which describes the relation of a rate of a chemical reaction to absolute temperature, the chemical reaction being the degrading of the paper in our case). As such, it is the absolute temperature of the hot-spot that is...

FPelec: I assume you are referring to Terna and Tamini Group. If not, that is the obvious example.

111R: Your assumption regarding the reason for the price difference between no-load losses and load losses is correct, but the price ratio can be anywhere between 0 and 1, depending on the expected loading of the unit.

Thank you both for your replies. Scotty: The isolation valves seem to be solid. The idea of an spool piece is a very good one, thank you! Rcwilson: You have just added to my worries: metal debris from a failed pump, the impellers and motor body are cast aluminum (Al Si10 MG DIN 1725). I don't...

The proposal of adding oil pumps to a bank of 1 phase ONAF GSU transformers (100 MVA bank, 220/13,8 kV, conservator type) is under discussion. The reason is not to increase the power capacity of the transformers (as the capacity of the generators connected to the bank will not change), only to...

As you might guess, you need an auxiliary relay to multiply the GCB status, better have that a fast acting relay from a reliable manufacturer. You might consider connecting the GCB auxiliary contact directly to one protection channel (e.g. channel A) and the auxiliary contact in parallel. This...

To calculate the voltage drop (i.e. the regulation), you need the X/R ratio of the transformer impedance and the power factor of the total load (during motor starting). You should read thread238-221175, especially the files jghrist links to.

I agree with dpc, I would (and have) split them. But try to distribute them wisely (e.g. Buchholz and PRD on different channels, oil and winding temps on different channels, Buchholz and RPRR on different etc.).

I agree with ppedUK that this seems to be a cooling problem. I would suspect an oil flow problem rather than air flow problem, since only 56% of the rating can be reached (unless the ambient temperature is above rated). The incorrect working of the temperature alarms is also a possibility. My...

You are correct that the % value of the Z equals the voltage (as % of rated voltage) induced on the primary side when the secondary is shorted (and any other windings open-circuited) and the rated current flows into the primary terminals. But as soon as you have some other load than the...

Hi, You might find this thread useful: thread238-336030 How did you contact Siemens? At least my local Siemens representative is very helpful with requests like yours, even though the request may be quite vauge. Same applies to my local representatives for ABB, Möre transformers and many...

I have received the answer. The "s" stands for "sparkopplad" which means auto transformer in Swedish.

I'm trying to figure out what the "s" in the connection symbol YNd11+syn0 stands for. The +syn0 is a low power auxiliary winding. The rating plate is in english (as far as I understand) so "service" is my best guess, but I would appreciate it if someone could correct me or confirm my guess.

Here are a couple links: Link Link This is how wide the range for hydro-generation is. I'm not so familiar with other fields of power generation. Perhaps more details about your study might result in answers. rgs. jens