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Hi All, Interested in people's views on which method is better for providing backup protection at a generator for grid faults. i.e Distance or Voltage controlled Overcurrent ? Multiple small generators in parallel, each with their own protection relays.

Hi all, I am seeking some advice on applying ground distance to transformer-feeder circuits. In this particular application, there are two separated circuits running in parallel, one of them also has an underhung circuit from another network. I am concerned about mutual coupling during earth...

Thanks for the prompt response. 1) I can confirm there is no tertiary (delta) winding; and 2) MVA is 12.5 for ONAN operation.

Hi, I am doing some fault studies on a grid with 66kV/33kV Auto transformers YNa0, solidly earthed. I have their positive sequence impedances, but not any info on zero sequence impedance or X/R ratio. Has anyone had experience with these vector groups and what typical zero seq impedances and...

The inverter supplies the grid via a step up transformer and line. I can't determine the inverters behaviour during the fault, as there is no 'standard' for short circuit calculation when the contribution is purely from the IBR. We assume the anti-islanding protection will kick in and...

Hi, Looking for some help in calculating the 3U0 voltage during single phase to earth fault. I have limited information to begin with and I can't use modelling software as the source is an inverter so the algorithm will not converge :). I have: - Nominal L-L Voltage - Line impedance between...

Hi ZeroSeq, I see where some confusion has been added, but to clarify - having a "YNyn0" vector group doesn't predicate that the HV side is earthed. It's not uncommon for the neutral to be taken out on both sides, but left floating on the HV."YNyn0" and "Yyn0" would behave the same in this...

I agree with "dfdt" and my experience with ~50 Ynyn0 transformers in our fleet I can assure you that there certainly is fault current for secondary side earth faults. The zero sequence pathway is created via the 'Tank Effect', giving rise to a large zero sequence impedance( but not infinity) so...

Hi Mhobi, I have a 'leaflet' that you may find some answers in. Good luck.https://files.engineering.com/getfile.aspx?folder=37336e72-b262-4d3a-b915-ea8e85f33a7c&file=Reyrolle_Protection_Leaflet_-_4C21_Duo-bias.pdf