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Thanks David. That's what I was proposing in order to be called series connected.

I totally agree with you Scott and David. On that note I would like to add that sometimes it's game a between the business and technology/science, and in that sometimes you end up having only 20% technology or science and 80% business! In fact a world known manufacturer has stated in fine-print...

Hi David, Thanks for your comments. Basically primary is 25kV and secondary side is 600V. Fuse suggested in design is rated for less than 25kV and fuse manufacturer suggests to use another series connected fuse in order to meet the voltage requirements. The concerned XFMR is a station service...

Two Questions: For transformer protection: 1) If I need to use series connected two fuses for transformer primary protection, can I use one fuse on the primary side and on the secondary side the other, or I must use both of them on the primary side in order to call it series connected? 2)If I...

Thanks odlanor. Thanks also for the book you suggested.

Hi odlanor, Thanks for your comments. Is there any added benefit if I set to quad instead of mho? I know that in quad you get more resistive coverage, but if I don't need that, can just set to mho characteristics for both reverse and forward zones? Or it's the quad characteristics that would be...

Hello everyone, I have an existing Quadramho relay setting (21 function). It has Zone 3 setting as forward and reverse (offset) settings. It gives me Offset Mho option to set. Now I need to transfer the same setting to a new Siemens 7SA522 relay. Question: What would be the best way to set...

Thanks burntcoil. I think CT's standard burden is different from the CT's total burden. In oder to calculate CT's per unit burden ratio, one needs to calculate both burden. ANSI C400 CT will give us a burden of 4 ohms. I'm not sure whether I need to add anything else to the ANSI standard burdrn...

When you calculate CT's ANSI/IEEE standard burden, do you have to include CT's internal registance? This is to calculate Per Unit CT burden (Zb)for the final calculation of CT's performance in terms of saturation at the time if there is a (severe) fault. For instance, for a CT C400 the ANSI...

Hello All, Sorry for not being able to thank you earlier for helping my question answered. I agree with Marmite & David that inrush would not change unless impedance change. It was my misunderstanding/miswriting. I'm in a situation where ONFA rating has been used to set transformer primary...

I completely agree with you Waross. I2R would be the thermal killer of the transformer if AF fans are not functioning. Using max MVA would also further increase transformer inrush current and thereby high side instantaneous setting might be shifting further right on the TCC.

Thanks a lot Waross & Burntcoil. I would like to explore your valuable comments as below: I'm using ETAP for protection coordination. Thinking that ONFA is installed and operating, what MVA I should be putting in the transfomer nameplate data in the ETAP model? If I want to use max MVA then, I...

XFMR(D-Y): 2MVA(ONAN) 2.66MVA (ONAF) Z% = 5.75, 2-windings Voltage: 4160V(D)/600V(Y) OCPD: High side has circuit breaker with protection relay (51/50). Low side also has circuit breaker with protective relay (51/50). I know that in this application high side relay can be...