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Thank you so much 'esee135' for posting detail explaination. Now my doubt is clear, with present 776MVA generator we have this function, I have investigated few older generator where this function is not there, as you suggested we can retrofit old AVR with new one.

thanks ! esee135 What I understand is that before isolating generator from system during fault or shutdown condidions Zero reactive power function will be activated so that only active power current will be interupted by circuitbreaker, Which can save wear on breaker. One more question, is...

j3n5, you are right! the manual says that, 'An unloading facility is available which, when activated, will reduce the generator reactive power to zero or the power factor to 1,0.' perhaps it may be generator open condition. thank you so much!

Thanks! tlrols, there is separate power factor control function in addition to Zero reactive power command in AVR. I have encountered this(Zero pf) command in 270MVA as well as 776MVA Generator. I am doubtfull if they are usually using this function.

Hello Eevryone! I have come across one of a 'Zero reactive power function' while reviewing AVR document for 776MVA Generator. In AVR manual this functions is not described in detail. After googling few websites I found this function is incorporated in Power controller(VAR controller for...

Yes, 11.5kV tap can be considered as nominal tap for transformer. Many Power plats have ratings like this, Generator nominal voltage rating 11kV & Genr. Tfr. nominal voltage rating 132/11.55kV(5%more). It is General practice to keep nominal rating of Gen. Tfr. 5% more to compensate full load...

ScottyUK; Simultaneous, closing command for bus-tie and the opening command for incomer under detection of loss of voltage, under fault condition need to confirm CB open. There is facility in HSTS, we can programme logic upon loss of voltage & under fault condition. Under fault condition...

ofcourse there are many conditions to be verified to close tie-CB; loss of incomer voltage, incomer current, incomer CB aux. contacts etc.., even protective relays which blocks HSTS operation.

We provided ABB's HSTS(High speed transfer system)'SUE 3000' system which makes it possible to obtain transfer times equal to 100 ms with the use of all conventional circuit-breakers. With HSTS system for three circuitbreakers(Unit, Station & Bus-tie): when the loss of voltage in one of the two...

As soil is excavated and the same soil will be backfilled then there is no question of change in soil resistivity. But, possiblity can't be denied that backfilled soil may have higher resistivity initially, the reason is backfilled soil is not compacted so it forms cavities which may contain...

jghrist: Breaking ground grid area is not going to reduce sufficient overall grounding resistance. But to take care of step, touch potential in areas where personnel are expected to be working. I want reduce spacing, use more ground rods, use some backfilling material etc.

rcwilson: Thanks for detail reply. I am going to consider all your mentioned points while construction. But my client wants precalculation of 5ohm. To satisfy clients requirement, I am planning to break up ground grid area in to no. of parts such as Transformer area, Water treatment area...

thanks:bacon4life Transformer loading is nicely explained in IEEE C57-91, I think it can be easily applicable for distribution transformers. Grid connected and generating transformers are always running on full load I believe, and they are desigend like that I think.

Hi everyone, I am designing an earthing system for 240MW power plant, the area is 230x720m, average soil resistivity 14,000ohm-m(Sedimentary rock), fault current 20kA. I used 120sqmm cooper condr with 15x15m spacing, 0.5m depth. With this data I am getting ground grid resistance 9 ohm, GPR more...

thanks! :KH2 yes! IEEE C57.116-1989 is very helpfull.

This is base data from one of the Utility, which we used for design of transmission lines. This is max. power assumed at each voltage level. I don't have any reference but this data is based upon Utility experience & design practices. Refer if you found helpfull. 765 KV line having 4 X 686 sq...

thanks YIGO: will you please ref. SLD in my posting dt.14 Jul, 08 23:18. For aux. load we have UAT(Unit Aux. Tfr.) and it will be always feeding plant auxiliries. Station SST(Station Start-up Tfr.)will be used for starting purpose only, once Gen. is synchronised it will be off. So we need to...

Good explaination slavag: right, One pict is better than 1000 words! yes, I do agree, all CT's can't be used for BFP. I think for some old installations it can as there are lots of difficulties to install new CTs. thanks! ELEP;

slavag: We are also in favour to use dedicate CT & relay for BFP as it is the most important protection but due to economic problems many client ask us to use same CT(diff. or OC/E/F. slavag, I represent this scheme just for understanding, actually inside relay & wiring it is different. This...

thanks! slavag;scottyUK;wolf for your valuable suggestions. slavag: Please check attached LBB schemes, if you mean like this, if it is same then you have covered faults when HV CB open as well as HV CB closed. This is best LBB scheme I think...