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Agree with Scottf. could attempt FRA and compare standard tests, if available.

Thanks for your replies. I am researching more on this. I shall let know when i find out more.

Basically for the following, probably only one of which may not be possible with a 50/51 a. High speed protection with POTT b. Breaker Failure c. Bus backup with either reverse zone or far looking forward opmgr1, By mitigating inrush, i meant logic/ways etc. in a relay to inhibit it from...

Distance relays have been proposed as backup relays for transformer protection, primary protection being Differential relays. Any thoughts on 1. what zones / logic should be used. 2. Some have recommended using POTT schemes. Anybody using this? 3. Ways to mitigate inrush Thx

Description : SF6 breakers are directly mounted with MOSA (station class)on the line side. The arrester neutrals are connected to the interrupter end plate (as ground). There is a gasketed joint and quite a few metallic joints before the actual ground. (the equipment is grounded and arrester is...

If you are talking about the conductor sheath grounding, i think: Due to varying magnetic fields there are induced voltages in the sheath and other conductors in the vicinity. Thus, The sheath should be grounded for safety reasons. There are a number of ways to ground though. Single, Both...

The transformer transferred surge, initially, is cosidered being transferred thru winding capacitance rather than inductance. How much gets transferred, is completely a transformer design parameter. but like someone suggested if properly corordinated arresters are used at the high side, surge...

Skogsgurra, Your explaining of energy storage in LC circuits brought my classroom days back to me. Ur teaching skills are praisable.

Scotty is abs. right. As u know the whole reason behind REF is to be insensitive to thru faults. I would think that this should be proven before hand by doing thru fault tests and checking current phasors @ the relay. In addition, The transformer should be tested periodically and the test...

I would be wrong if i meant that - gassing due to neutral CT saturation. I meant either misoperation due to NCT saturation and at the same time sudden winding stress / vibration caused by the thru fault causing the buchholz relay to operate (cause some older buchholz relays used mercury...

Was there any thru faults where in the NCT would saturate, it can also cause buchholz. But most likely what all the others have contributed. Winding resistance / Gas analysis ASAP

A quick point to remember: Make sure the test instruments u get use test methods and specs. etc per your relevent country standard. Also get the instruments with a cal. sticker. Google your test requirement. There are expensive test sets and economical ones too. Like AEMC, Vanguard. Visit...

Is this inhouse testing or field testing ? Routine testing or predictive maintenance testing ? I mean, please specify.

I dont think u need to apply 10kV. You can test the winding @ 1000V and then extrapolate it to 10kV. I do not think that the frequency of the test voltage can be changed. Your tester shall have test voltage @ 60Hz. Since P=V^2w.C.Tandelta, frequency will increase your insulation PF. The...

10-4, Thanks

try http://gilbertelectrical.com/library/document_library.htm

I am not very familiar with generator excitation systems but JUst a thought. Is it not possible to check the field winding resistance and check with manufacturers tested value to see if the winding is shorted or open etc.

I think although u can calculate the inrush by hand using formulaes given in IEEE 39.99-.... the most realistic switching transients can only be deciphered from EMTP modelling.

Obviously this is to protect from the over voltage condition in the tapwinding generated due to system transients. Delta line end tapwinding is where i used them but they may be used as deemed necessary.

Zno is Zinc oxide assemblies. They are used in some transformers, usually Delta connected regulating winding when the regulation is at the line end instead of the middle of delta.