Transformer Inrush - theoretical or real - and sacrifices
Transformer Inrush - theoretical or real - and sacrifices
(OP)
I just reviewed a coordination study with a 750kVA transformer (5kv primary - 208Y/120v secondary. The primary protection is a 125E fuse. The coordination curves shows the transformer inrush trippng the 125E fuses. The trip is just on the border line of the fuse melting band.
If i use a 150E fuse the inrush is no longer a problem but the transforer damage curve is worse and arc flash hazard increases a level.
My thought is that the inrush will not occur all the time and is only a theortical value that has the potential to occur. Is there any industry standard i can reference to make a decison on which to sacrifice (nusiance inrush tripping or arc flash and transformer damage). Replacing the 5kv fuses with power breakers is not an option.
Also, is there a good article on how to read transformer damage curves?
Thanks.
c
If i use a 150E fuse the inrush is no longer a problem but the transforer damage curve is worse and arc flash hazard increases a level.
My thought is that the inrush will not occur all the time and is only a theortical value that has the potential to occur. Is there any industry standard i can reference to make a decison on which to sacrifice (nusiance inrush tripping or arc flash and transformer damage). Replacing the 5kv fuses with power breakers is not an option.
Also, is there a good article on how to read transformer damage curves?
Thanks.
c






RE: Transformer Inrush - theoretical or real - and sacrifices
RE: Transformer Inrush - theoretical or real - and sacrifices
There is also the thread about sympathetic inrush by Bronzeado. It is here: thread238-231422: Transformer saturation-driven neutral instability
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Transformer Inrush - theoretical or real - and sacrifices
What inrush was assumed in the coordination study?
RE: Transformer Inrush - theoretical or real - and sacrifices
thread238-317135: sympathetic inrush : sympathetic inrush. The thread you mentioned was for neutral inversion raised by Bronzeado.At that time he wanted from me reference to literature on Neutral inversion. I finally got the paper where I jotted down the reference in 1986. I dont know whether Bronzeado is following this site and whether he is still interested.Any way I am attaching it here.Six years have just gone like that!Neutral inversion was first reported in 1905 and these 1931 &1941 AIEE papers helped me in resolving a serious neutral inversion problem at a project in 1986.
RE: Transformer Inrush - theoretical or real - and sacrifices
You brought the thread back to order...
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Transformer Inrush - theoretical or real - and sacrifices
I still alive!
However, I am now working for in a big project to supply water to the Northeast of Brasil and I have no time to enjoy your nice discussions.
Thank you prc for posting the references on neutral instability after "sleeping" 6 years!
Best Regards,
Herivelto S. Bronzeado
Brasília, Brazil
http://www.linkedin.com/profile/view?id=46319837&a...
RE: Transformer Inrush - theoretical or real - and sacrifices
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Transformer Inrush - theoretical or real - and sacrifices
Best Regards,
Herivelto S. Bronzeado
Brasília, Brazil
http://www.linkedin.com/profile/view?id=46319837&a...
RE: Transformer Inrush - theoretical or real - and sacrifices
Interesting. We are building a couple of big motor starters (12660kW, 6900V) for an irrigation project in Brazil.
RE: Transformer Inrush - theoretical or real - and sacrifices
Those are ours, but they are not for irrigation.
We will do their inspection them soon. Be prepared!
The world is round and it turns!
Best Regards,
Herivelto S. Bronzeado
Brasília, Brazil
http://www.linkedin.com/profile/view?id=46319837&a...
RE: Transformer Inrush - theoretical or real - and sacrifices
RE: Transformer Inrush - theoretical or real - and sacrifices
I was born in an Indian village before India became a free nation and my earliest memory of life is that of the inauguration of an irrigation project in my village.It was more than 65 years back and the king of the country had come to switch on the 10 HP motor pump set imported from England ! Water was pumped out from the river to irrigate paddy(rice) fields. My mother lifting me up so that I could see the king among the crowd is still alive in my mind.Paddy cultivation, three times an year became possible with irrigation, alleviating poverty to a great extent.The same land now remain barren as farming is no more remunerative and all young people went for IT programming instead of planting paddy saplings in mud.Later I was involved in supplying 35 MVA 220 kV dedicated transformers to power 30MW motor pump sets for some large irrigation projects in the country.
RE: Transformer Inrush - theoretical or real - and sacrifices
I think we are about the same age (me 1940) and I also have strong memories of how technology has been introduced, lived and died in northern Europe. Technology as well as industries. I think it is about time to start a thread about that. We already have "where is industry going?" and I think that a thread "from where did we go?" could be a very valuable source of information.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Transformer Inrush - theoretical or real - and sacrifices
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Transformer Inrush - theoretical or real - and sacrifices
As I said before, the project I work for IS NOT a irrigation project.
The Project official name is "Projeto de Integração do Rio São Francisco com Bacias Hidrográfica do Nordeste Setentrional" or in short "Projeto da Integração do Rio São Francisco - PISF". It is a project of the Brazilian Federal Government, under the responsibility of the Ministry of National Integration to ensure water supply in 2025, about 12 million of small, medium and large cities in the semiarid region of the four states of Brazil (Pernambuco, Ceará, Paraíba and Rio Grande do Norte).
The Brazilian Northeast region has 28% of the population and only 3% of water availability, which causes great irregularity in the distribution of water resources.
The PISF is the largest piece of water infrastructure in the country and ranks among the 50 largest buildings infrastructure running in the world. Altogether, the project has an extension of 477 km organized in two axes water transfer - North and East. besides 470 km of canals, the work includes the construction of four tunnels, 14 aqueducts, and 27 reservoirs.
Regarding the electric system the PISF has 300 km of transmission lines (230 kV), 9 substations (230/6.9 kV) to supply 9 pumping stations along two axes. In the North Axis the nominal water flow will be 100 m3/s and there are 3 pumping stations, 8 pumps each. The pumps are from 5.5 MW to 13 MW.
In the East Axis the nominal water flow will be 28 m3/s and there are 6 pumping stations with 4 pumps each. The pumps are from 2.5 MW to 5.5 MW
I hope this information could "kill" the curiosity of you at the moment. I think we could start another thread to discuss this kind of matter, as Gunnar suggested.
Please, find attached some slides that show schematically the PISF. Also I include a 3 minutes video showing a general views of the Project. That´s is time to learn some Portuguese!!!!!
Best Regards,
Herivelto S. Bronzeado
Brasília, Brazil
http://www.linkedin.com/profile/view?id=46319837&a...
RE: Transformer Inrush - theoretical or real - and sacrifices
I will do as soon as possible.
Best Regards,
Herivelto S. Bronzeado
Brasília, Brazil
http://www.linkedin.com/profile/view?id=46319837&a...
RE: Transformer Inrush - theoretical or real - and sacrifices
I am a regular visitor to engineering history, but that forum is almost inactive.Gunnar, it will be great if you can start some threads there so that we can have your experience and memories on technology and social changes.Engineers should not be purely engineering oriented.
RE: Transformer Inrush - theoretical or real - and sacrifices
As for the "theory" of inrush, inrush is a result of saturation of the core caused by asymmetric offset of the core flux on step changes of terminal voltage. It is a statistical event with the worst case occurring when the angle is at 90 degrees. That's why the worst case doesn't always occur but is always possible the next time around.