Recent content by czping

Also, we are using : Guide to the interpretation of dissolved and free gases analysis, IEC 60599, Second edition, 1999-03. as our reference.

Hi, thanks for all the replies! jbartos: Sorry for being lazy. I should have the full title instead of the shortcut. xabproject: We carry out DGA yearly but due to the increase of Ethane from 8ppm in yr 2002 to 52ppm in yr 2003, I carried out another one 15 days later to confirm the results...

Hi all, Just need to verify some doubts.. IEC 60599 Guide to interpretation of Dissolved Gas Analysis Page 49. I have 2 readings of Ethane taken in Nov 2003 & Dec 2003. PPM is as such: Nov 2003 - 52ppm Dec 2003 - 106ppm Oil Vol - 7950 cubic meters number of days interval - 15 Using the...

Hi, I understanding that a CT secondary shall not be open circuited due to the built up of high voltage across the CT secondary terminal. However, does this means that all CT secondary shall have shorting links? We have a CT feeding into a earth leakage relay (ELR) and when the ELR is faulty...

Thanks jghrist, that's very useful!

Yeah jghrist, you are right, the transformer 660V is the source for the excitation panel. However, the transformer is delta-delta and there is no neutral for grouding. The grounding is done at the panel in this case. However, our whole station makes use of a common earth grid, so I presume that...

Sorry jghrist, I might not have explained my situation properly. The excitation panel is already earthed through a earth bar in this panel. On the other hand, the transformer terminal box is not earthed locally but has this earth cable running all the way to be connected to the excitation...

Hi all, I found a earth cable linking the excitation transformer (230kV/660V) LV terminal box to the generator excitation panel (earth bar). The power cables from the transformer to the panel is single core without screen/shealth. I was wondering what is the purposes for this earth cable?? If...

Hi Jclough, I do not understand your statement: "changing to aluminum housings but couldn't live with the changes to the speed torque curves". Is there a change in the characteristic to the motor? For your information,I actually cover the hole in my motor housing using a steel plate...

ERaySir Thanks! So, if the stator is not damaged, and there is a hole in the housing (presume that nothing is falling into the housing), it should perform as good as ever? Then we do some people have the idea that the flux cannot be contained? Do you think it is applicable to some other cases?

Hi all, I was told that the motor housing plays a part in containing the magnetic flux generated when the 3 phase volatge is applied to the stator. Is this true? If there is a hole in the housing (happened actually, I ahve this motor which is exposed to acid and the acid actually burnt a hole...

Thanks Skogsgurra I will try to do some reading up on that!

Skogsgurra, thanks for the encouragement! If it is that simple, it the physical arrangement the same as that of a DC relay? Or there is a shade pole (a copper ring)in AC relay but not DC? I am asking because we are always being reminded that application of electromagnetism is always on DC...

Hmmm...pardon me for my poor knowledge. I may need a bit of time to digest the formula. What about the arrangement physically? Is the arrangement as simple as a coil coiled round a iron piece, just like DC electromagnetic theory? Any drawing/picture to refer me to? Sorry for so much trouble...

Thank you, nevakar, jbartos & skogsgurra, Would like to ask skogsgurra, are you saying that there r 2 coils in the realy, coiled in opposite directions? If that is what you meant by "squaring" the sine wave? If not, are you saying that electromagetic theory also applies to AC...