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Eng Tips Family, DO any of you guys have any good material on calculating setpoints for differential relays? I am working on a SEL 487. Any help would be appreciated.

Do any of you here have experience with IWBC AL bus for a substation? I am trying to find the short circuit forces between the buses and also trying to figure out the support spacing. All the material that I see online is for round busses. Any help would be highly appreciated. Thank you in advance!

RRaghunath, DO you know of any paper, or other document on this? I cant seem to find anything online. Muhammad Siddique

ET Family, Does anybody have any experience energizing a power transformer by a temp generator with the breaker closed? Will there be a reduction in the inrush current because the generators voltage will rise from zero to nominal voltage and the transformer will not be supplied with the line...

EngTips Friends, I have a few 35kV collection circuits coming from a PV farm to a substation. A small portion of the collection circuits will be overhead at a canal crossing. I am trying to determine, do I run separate over head ground conductors for the crossings? Or should I use earth as my...

Waross, Is single phase loads the only reason to add the neutral? Nothing to do with protection scheme for Multi point grounded neutral system? Also do you know the reason of why California Utilities not have neutral conductors?

Hello Eng Tips Family, I have a question about the Neutral conductor in medium voltage distribution upto 33kV. Why is the neutral required even though there is absolutely no single phase load connected, specially towards the 33kV? Also I have noticed that This Neutral is provided almost through...

crshears, Thank you for sharing your experience. I greatly appreciate it. Also thank you for pointing out the error in my subject line.

Eng Tips Family, I hope all of you are doing good. I have a question about grounding switches. We have a 230kV switching station with (1) 230kV double circuit double bundle line coming in. It is about 16 miles long. I am trying to figure out whether the disconnect switch intercepting this line...

Palletjack, 69V is L-N.

davidbeach, Thank you for your answer. Is there a reason for using 69V tap for relaying? Why not make it simple and use same voltage for both metering and relay. I am just trying to understand the logic.

Eng Tips Family, I hope all of you are keeping safe from the current pandemic. I have a question about the turn ratio of HV potential transformer. In west coast I have noticed that the most PT specified are Y connected with center tap on secondary side. For example for a 230kV system, PT would...

Eng Tip Family, I know I have asked a similar question before. But I still have some concerns, I am sizing the bay jumpers and I have questions about the behavior of jumpers under fault conditions. I calculated the jumper size based on steady state current and limited the temp to 160 deg F. But...

scottf, Thank you very much. It makes sense now.

Eng Tips Family, Can anyone please help me explain the Standard Burden for VTs(Table 15, IEEE C57.13). Also I have seen VTs with multiple burden ratings. What does that mean? For example, a VT with 0.15-WXYZ. Thank you in advance.

dpc, Thank you very much. As always, i really appreciate the help.

Eng Tips Family, Can you guys please give me any physical implications of choosing nitrogen blanket vs oil conservator for power transformers? I have a 50MVA transformer and I normally leave upto manufacturer to suggest the oil preservation system. But I am trying to understand the effects of 1...

dpc, Thank you very much. I know a grounding factor k is used to include the effect of different grounding types. Could you please give names of some easy references?

Eng Tips Family, Can you guys please help me with an easy reference to how to calculate the required MCOV rating surge arresters for different pieces of equipment. For example, how to determine the MCOV of required surge arrester for a transformer or for an underground feeder etc. Thank you...

ED-GEE, You need to find the unbalanced current first. But lets assume that you can connect a 400A single phase load on 3 phase 4 wire system, then your unbalanced load is 400A. NEC 220.61(B)(2) allows 70% on neutral current in excess of 200A. So your neutral current in this case will be 340A.