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  1. vidima

    Paralleling of autotransformer and normal power transformer?

    Thanks Waros. I'm wating for full details on the transformers to compare the X:R ratios and will post these for you to help with the analysis. Regarding the main winding connections(disregarding tertiary), are you saying it shouldnt be a big deal to parallel auto transformer with normal two...
  2. vidima

    Paralleling of autotransformer and normal power transformer?

    Thank you PRC for that insight. The tertiary for the autotrafo will be left open and the one for the two winding transformer will be used to provide auxiliary station suplly. So you are saying the vector numbers should not be an issue for the 275kV and 66kV windings? What is the effect of this...
  3. vidima

    Paralleling of autotransformer and normal power transformer?

    Dear collegues, Is it possible to operate an autotransformer 74MVA YN,a0d11, 275/66/11kV, 10%, in parallel with a normal three winding power transformer 74MVA, YNyn0d1, 275/66/11kV, 11.2%,? Can an autotransformer ever be operated in parallel with a conventional power transformer? Need help from...
  4. vidima

    paralleling power transformers with different impedances

    We have three 12/220kV, 40MVA generator transformers with impedance voltage at 10.8% that are paralled. We have run out of capacity and the only other transformer immediately available is rated 18/330kV, 125MVA impedance voltage at 12%. As an interim measure can we connect this unit in parallel...
  5. vidima

    HV shunt and series reactor application

    Thanks rbulsara for the insight. Could you also help me with some literature that explain in more detail the differences especially with regard to insulation design and the way both series and shunt reactors are constructed.
  6. vidima

    HV shunt and series reactor application

    Could someone please advise on whether it is possible to use a busbar connected series reactor (11kV, 5MVA) in shunt mode connected to the same busbar (i.e. converting a series reactor into a shunt reactor)? What are the design and construction differences between a series and a shunt reactor?
  7. vidima

    Current Transformers

    A current transformer has a primary and secondary windings. The primary in this case is the bus going thru it. The secondary which has 800/1200/1600:5 is wound on the core which make up the magnetic circuit.Here it about magnetic flux. On the CT surface check for P1 and P2 markings. P1 is to...
  8. vidima

    Reactor circuit breaker specification

    Is a reactor circuit breaker specified in the same way as that of a Transformer or a line? If not what special features make a different? Please help me.I have lost now two 66kV circuit breakers on the reactor even when the breaking current was far much higher and fault level was considered.
  9. vidima

    Specification of Neutral Earthing Transformers

    Thanks for the useful informatiion. As additional information, the short circuit current on the 33kV busbar is 3300A. The 33kV bus is feeding the distribution network. Our system is solidly grounded. I will be more confortable if you took me step by step through the specification/sizing process...
  10. vidima

    Specification of Neutral Earthing Transformers

    At one of our substation, we have two 40MVA, 88/33kV, star/delta transformers with 8.4% impedance voltage. These units are earthed through zigzag earthing transformers on 33kV side. Recently, we had a fault on 33kV side of one of these transformers (33kV surge diverter shuttering in the...
  11. vidima

    Three winding transformer commissioning test sheet

    okay. We have a 5MVA, 88/33kV transformer that we want to put in service. It was bought around 1985 (Iam told)but was neverput in commission.Over time the nameplate was removed and no one seems to have the details except that it was to be used to step down from 88/33kV at one of our stations...
  12. vidima

    Three winding transformer commissioning test sheet

    Can someone please post/mail me a typical commissioning scedule for power transformers including all transformer tests and functional tests.

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