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Hi all friends, Do you have a circulating fault currents scheme in Star/delta, Delta/star, star/star transformers for differential protection? Circulating directions / current magnitudes... Also calculations which differential relay calculate.....There s no any details in manuals. Thanks a lot.

Hi guys, I was trying to synhronize two lines. Voltage difference-frequency difference and angle difference is almost 0. Values are always within limits. But relay inconsistenly gives Synchron OK. Sometimes it gives "OK", sometimes NOT. And there s no specific time for giving Synchron OK...

Hi guys, Do you know how we can set ct ratio in REF610 protection relays? Thanks

pwrengrds Thank you for your help. I would like to know more details from you or from other guys if it s possible.

Hi friends, I would like to ask you a question. If the residual overvoltage fault occurs on F1 , What will A and B see ? Same residual overvoltage magnitude ? Or Will they see the fault ...

I ve checked manuals but I couldnt find it. And I look for general standard, I guess there should be be a percentage...not specific values.

Hi to all, I would like to ask you a question about routine test of circuit breakers. I have a Medium Voltage CB to do maintenance. I know how to do contact resistance test, but I checked all standarts and I coulndt find a percentage about approving " Did the test pass or no" . Do you have...

I was talking about the magnitudes not angles...Because I did not know that is why current occurs on phase C in HV during occuring fault A in LV. If there is fault on phase A in LV, The fault should flow on phase current A , line current A and line current C. It s what I learned. Still not...

stevenal, Thank you..today I will try to do as what you said.

waross, Yes I got your point. By the way, I find out the problem which I faced. I just followed the diagrams's explanations in some pics and articles.I saw that they did not point out the Delta connection type.Some of them are DAB, others are DAC connection. In protection relays I saw the...

veritas , stevenal and waross ; On first diagram , Current occurs on line A and C ..Yes... But how about phase currents ? If there is a L-E fault on A , Will fault current flow on phase A or phase C? That s the point which I dont understand. And there is another diagram on attachment. I...

veritas , thank you . stevenal , I just saw your message. Can you please check this drawing? on attachment.https://files.engineering.com/getfile.aspx?folder=c04e8b50-3999-462f-a817-c7768dc16b11&file=111111111111111111.PNG

Yeah, But I m still confused. Because I saw many drawing like that in web and documents. Thanks

Hi everyone, sorry for my english..I m not well experienced guy. I just want to know that is there any much clear document about "current flows and calculations during faults in transformer" I checked many documents in this forum and in others.But I coulndt find it. By the way, Can you...

catserveng,rcwilson,RRaghunath thank you all. Your explanations and file are very clear to understand about harmonics..Thank you again.

hi friends, I was entering set values of differential protection relay. I realized that there are only 2nd and 5th harmonicc blocking. Why dont we use 3rd or other harmonic blocking ? Thanks

DiscoP Thanks For Your Time, I ve solved the problem , I just enabled the Line Charge Capacitance feature. And it didnt trip. Polarity,CT Taps were ok. Thanks.

Hi guys, I just wanna ask a question to you. I m at Power Plant and I m using L30 Line current differential relay. I tried to energize the line and then It trips ,I did three times and gave me same result. In relay software,there s no CT Polarity configuration , there s no even in manual. I...

Yeah , I know , but "the customer want that if there s earth fault trip , E/F trip led and Faulted phase should be latched." So I just wonder if it s possible or not,the relay is ABB REF615 Thanks...

Hi , I got earth fault trip on my MV incoming feeder relay. I wanna ask that if there is earth fault , how can we or relay determine the faulted phase ?Is it possible ? By the way , customer dont use the voltage information for this relay. Thanks...