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  1. SooryaShrestha

    Big blackout. What happened?

    After going through all the views here, I feel I should add some more. I think it will be helpful to all of our friends in Eng-Tips. I start with the contingency condition in the system. Contingency condition is the one of the conditions of study, which allow to verify what wil be the outcome if...
  2. SooryaShrestha

    Long Distance Supply at Low Voltage

    Drawing 3 kw at 11 kv with 12 km cable will have appreciable charging current. It seems not only not advisable but also, serious problem might arise. I have not done the calculations, but the losses will also be appreciable. There is possibility of supplying by non-standard voltage of say...
  3. SooryaShrestha

    Transformer life

    Bung has rightly said "Temp rises low enough to avoid accelerated failure (through burning or oxidation) are not likely to severely affect any inorganic materialsas much (copper, ceramics etc)." To add a few more to it: Becuse of the temperature rise the insulation deteriorates...
  4. SooryaShrestha

    Capacitive Breaking Capacity of a Breaker

    Recently I happened to go into the details of the specification of a Gas Circuit Breaker. I found that the breaking capacity of a breaker for line charging (Capacitive)is lower than that for the capacitive breaking current of a cable. The capacitive breaking current of a breaker for Capacitor...
  5. SooryaShrestha

    retrofitting transformers

    johnspark, Finding water in oil is scarry, but it is not unremovable. If for removing water it takes a long time various procedure can be applied like hot air blowing, vaccum drying or these days regenerating equipments are available, which can be used for dehydrating as well on top of some...
  6. SooryaShrestha

    wind farm connections

    single pole reclosing is good for the stability of the system. But if the wind farm is with single pole reclosing breakers, I think it will do more harm than good. The unbalancing stress on the generator is very heavy and not healthy for the generator. Single pole reclosing is good for...
  7. SooryaShrestha

    Earth grid construction

    Thanks for reminding the equations. I also use the same equations for determinig the safety of the designs, but was not physically aware of the situation. My interpretation was also same that the safe design is to have high resistivity layer on the top of the grounding grid. Thanks anyway and...
  8. SooryaShrestha

    Earth grid construction

    cucky2000, How will the step and touch potentials become lower in the concrete surface(low resistivity) than gravel(high resistivity)? With my limited knowledge,if that be the case, substation would have been covered with low restivity material.
  9. SooryaShrestha

    Leading Power Factor Issues?

    One of the possible problem with capacitors in distribution lines may be ferroresonance, if the transformers used are of three phase, low loading with single phase fuses as protection. Please check
  10. SooryaShrestha

    lightning protection for light poles

    The size of the pole with 7' under the ground means it is used not for very high voltage. I think the use of lightning safety for low voltage using Franklin rod or otherwise will be only cosmetic, as in such lines if the lightning strike takes place, because of lower insulation level there will...
  11. SooryaShrestha

    Condition of downconductor when lightning

    I think for lightning the ground resistance affects less compared to the grounding system reactance. Thushe difficult value to be obtained that is 1 ohm resistance value will have less impact. The reactance value will be in the range surge impedance value, which can be lowered by making...
  12. SooryaShrestha

    Definition of Substation

    After long time of absence from eng-tips, I find helpful stuffs I was missing.Thanks Redtrumpet who has given very helpful information.Deserve a star. GRpatel, yes I am 74 batch from MSU.
  13. SooryaShrestha

    Hi there: I have made an executa

    I meant ur EXE file; the file you created. Ur program may not work if u just coping the main exe file. Make an installation (it copies all dlls associated with ur program). And copy ur database too. Squall
  14. SooryaShrestha

    3 phase motor current imbalance test.

    electricpete, the true unbalance I had referred is given in IEEE Power Engineering Review on May, 2001 issue with the true definition of voltage unbalance factor. It also has got approximation to true definition.
  15. SooryaShrestha

    power factor correction on 1&3 phace motor

    Further to the above querry, please enlighten us by posting the following querries. 1) In high voltage capacitors for reactive compensation, why are the insulating transformers used? 2) How to calculate the sizing the insulating transformer? 3) What are the other equipment required for the...
  16. SooryaShrestha

    3 phase motor current imbalance test.

    Hi everybody. May I add some experience and some querry? dynets - May I know what type of unbalance are you expecting? Is it true unbalance or is it the unbalance as defined by IEEE or NEMA? IEEE or NEMA defines unbalance only in terms of magnitude. True unbalance requires the phase angle...
  17. SooryaShrestha

    Isoch vs. Droop for generator operation

    peterb, sorry being late. I was away for sometime. I have a little doubt. Please clarify. In the case of synchronising with grid when the utility power becomes available at 161 kV, the present case of GBell with three generators of two 20 Mw and one 40 Mw units will not be easy to synchronise...
  18. SooryaShrestha

    LOAD FLOW STUDY

    Go to www.powerworld.com site. It will guide you how to download a free software for 12 busses. It is very userfriendly. Even a novice can do load flow study with that software. There are many other free software for example PASHA 2000. The software given freely by Prof. Mack Grady of Univ. of...
  19. SooryaShrestha

    CT Accuracy result

    Thanks both of you. There are two cores one for measuring with 0.5 class accuracy and the other for protection with 5P10 accuracy. Yes the specification is 185 IEC-1987. The problem is like this: The material has already arrived at site. The equipment has been charged and supplying power to the...
  20. SooryaShrestha

    CT Accuracy result

    I have a 200/1 CT ratio tested with primary injection kit. I have given 100 amp on the primary and got 0.52 amp on the secondary. I have further given 200 amp in the primary and got 1.02 amp in the secondary. Can these values be used to determine the accuracy class of the CT? I have been...

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