It is well known that open-circuiting the secondary circuit of CT while carrying primary current will create overvoltage on secondary terminals. But will this lead to violent failure of CT with explosion? Has anyone noticed CTs in service with open-circuited secondary terminals?
I believe eng-tips do not have an illumination engineering forum, so I am posting this query here.
What is the best lamp (eg LED) for the reading desk? What is the optimum lumen for comfortable reading?
I have compiled Instrument Transformer books published so far. May be of interest to some of you.https://files.engineering.com/getfile.aspx?folder=89382716-425a-46ba-b1fb-ac37d68d3a9a&file=2021-02-_Books_on_Instrument_Transformers.pdf
I have a query on protection. Request guidance from learned protection Gurus.
Let us take a 400 or 220kV transformer. Imagine a flash over from the bottom tail of bushing to tank. The system fault current will go into the arc in oil. In such a case, how much time will it take for the incoming...
Let us consider a case of a 220/132/11kV auto-transformer with and without stabilizing delta tertiary winding. Secondary is not connected to grid. Transformer is 3phase 3 limbed core type with solidly grounded HV neutral.
In case HV primary is fed with rated voltage, but with one line open (...
Normally LV side of large Generator Transformers(GSU) are connected in delta and HV side in YN. It is claimed by some experts that this is done to avoid flow of zero sequence currents through generator stator windings during an LG fault on HV side lines of GSU. Why Generator windings cannot...
In my country Generator transformers are provided with DETC (de-energized Tap-changers). In case of transformers for thermal sets (50-800 MW) tap-changers with +- 10 % tap range(9 tap) were used to be there. Later this range was reduced to 5 tap with +- 5 % range as these tap-changers are never...
When star neutral point of CT secondary is formed in substations where this is to be grounded -at CT secondary box near to instrument transformer in the yard or at the panel in control room?
Is it mandatory to provide fire protection for power transformers? What is the rule or limits of transformer ratings in various parts of the world?
There are various types of fire protection available-Mulsifyre ( spraying with water actuated by thermal fire detecting sensors) Nitrogen...
For many decades, I was maintaining a list of standards relevant to Transformers -for application, specification, manufacturing,testing and maintaining transformers. Attached please see the updated list. May be useful to some of...
Last month in India a 2000 MW solar power farm was commissioned, said to be the largest in the world. This is in Karnataka state where Bangalore is located. Farm covers an area of 13,000 acres and the entire land was leased out from farmers. Farmers claim they get more income from lease rather...
GE's Transformer factory at Pittsfield had a great legacy. See the attached links.
http://ethw.org/Archives:Transformers_at_Pittsfield,_part_1
http://ethw.org/Archives:Transformers_at_Pittsfield,_part_2
http://ethw.org/Archives:Transformers_at_Pittsfield,_part_3
Neutral of large Ac generators are grounded through Neutral grounding resistors to limit the zero sequence currents. How the neutral of motors is grounded? Same way or through inductors? If later is the case, reason for the same.
Normally one corner of delta connected stabilizing tertiary winding is grounded in service or neutral grounding achieved through grounding transformers or star connected electromagnetic PTs connected to tertiary terminals. Latest IEC 60076-3 Insulation levels of Transformers proposes as below...
When LAs are used on the delta tertiary of transformers 110% rated voltage arresters are used, being ungrounded system.So in a 33 kV tertiary, 45 kV LAs are used to get 36 kV continuous power frequency voltage withstand performance. If a delta/star transformer is fed from a star/star (132/33...
I have a query -How the power is transferred from the primary winding to secondary winding in a transformer? General answer is through electromagnetic field, electric to magnetic and then to electric. But how? Can we explain this clearly so even a layman can grasp.
In some utilities, as annual routine, they conduct hot oil circulation in transformers in service ( may be for 3-4 days). Taking oil from bottom of transformer tank, circulate through a filter machine(with a shrouded electrical heater to raise oil temperature to 70C + vacuum chamber to remove...
Three winding transformers are usually used for collecting the power from solar power inverters, popular connection being Delta/Star-star. The neutral of secondary stars is never earthed, many times it is not even brought out. In one case, it was inadvertently kept earthed and inverters started...
Dry type transformers, (500 kVA to 3150 kVA 33/0.415 kV-Delta /star)) used in metro stations, are switched on by VCBs through a short length of cable. Power reach VCB through long cables. Usually when VCB switching is involved, surge arresters( between line to ground and line to line) and or...
