nice information sir but if in our system some short times unbalanced current flow requirement then how it can save from earth fault maule protection in residual ct connection?
For the residual connection, I understand that each line is 120 deg out of phase, so in that case they are balanced. What i dont understand is why the resultant current would still be zero even tho the magnitude of each phase is different. Please explain? Most systems won't have exact same current magnitude on each phase.
sir pls correct me ...if i am wrong you said residual system the submission of current is zero , as it is balanced , if it is single earth fault in line R , how can the value of Ib and Ic is zero ...
Because it a short circuit, so all the other path will have no current. Suppose you have resistor connected across a battery. Now if you short the two end of the resistance, then shall there be any current through the resistance????
When an earth fault occurs in say R phase, the healthy phases i.e. Y and B phases will still deliver load current but the voltages of the said phases will overshoot.
Thank you sir But one question about NCT protection always bother me lot !! As per concept when earth fault occurs on system.. Earth fault current flows back to star point via earth !! I don't understand this.. Let say an earth fault occurs on system at 100 meter away from transformer... Now as per concept it will flows back to transformer neutral point via EARTH !! (Which can damage transformer winding hence in some applications we use NGR) I mean earth is such good conductor??? Please guide on this
Transformer neutral earth give a path to earth fault current . This current is very dangerous that why we use protection relay for sensing this fault current. If neutral not grounded then due to capacitance effect from phase to earth the other two phase voltage is very much high due to fault current in one phase which may lead to healthy phases insulation failure.
Thanks for this is a clear presentation. Could you also make a video on 1. Comparison/pros&cons of the 3 different CT connections? 2. If an ungrounded 3 phase system with a zig-zag grounding transformer, which CT wiring is best. 3. How to identify the phase or phases that are faulted to ground?
In residual connection 1 ph to earth fault that E/F current s max compare to other phases. So relay coil pick for only E/F current.ie Ir+Iy+Ib=0 In normal 1+(-0.7)+(-0.3)=0 (120deg ph shift) In fault 2+(-0.7)+(-0.3)=1relay picked. This is correct? But E/F time ph shift should be change like the fault ph current reflecting to normal phase.
Let me explain…Under normal condition, the vector sum of these three phase currents will be ZERO and NO CURRENT will pass through the E/F relay coil.Okay? Now, suppose there is an earth fault on the R phase. So, the current in the faulted phase will be HIGH compared to the other phases. Say the fault current be 2
Excellent,very much useful discussion
Very good. Thanks 🙏🙏🙏🙏
thanks for your help again. धन्यवाद
Sir aap neutral displacement par vedio banao how voltage get unbalance in unearthed system during earth fault
nice information sir but if in our system some short times unbalanced current flow requirement then how it can save from earth fault maule protection in residual ct connection?
Nice video sir thanks for sharing ur knowledge
Thank you sir for this video,
and one more think i want to know that in L-L-L-G fault how E/F relay detect current in first case
For the residual connection, I understand that each line is 120 deg out of phase, so in that case they are balanced. What i dont understand is why the resultant current would still be zero even tho the magnitude of each phase is different. Please explain? Most systems won't have exact same current magnitude on each phase.
Because it is a phasor sum . If all the three phase magnitude are equal and 120 degree apart then phasor sum will be zero
In case of residual connection- why current in y and b phase will be zero when earth fault in r phase?
In which CT SEF protection use?and what is its current setting formula.please learn
Thanks for information
Good brother
Could you please make a video about coordination settings of upstream and downstream breakers for short circuit..
Already there.... please check all videos...
@@electricaltechnologyandind5335 i couldn't find it brother
th-cam.com/video/OfvMOz5vNko/w-d-xo.html
@@electricaltechnologyandind5335 Thankyou very much brother
sir pls correct me ...if i am wrong you said residual system the submission of current is zero , as it is balanced , if it is single earth fault in line R , how can the value of Ib and Ic is zero ...
Because it a short circuit, so all the other path will have no current. Suppose you have resistor connected across a battery. Now if you short the two end of the resistance, then shall there be any current through the resistance????
When an earth fault occurs in say R phase, the healthy phases i.e. Y and B phases will still deliver load current but the voltages of the said phases will overshoot.
Thank you sir
Thank you sir
But one question about NCT protection always bother me lot !!
As per concept when earth fault occurs on system.. Earth fault current flows back to star point via earth !!
I don't understand this.. Let say an earth fault occurs on system at 100 meter away from transformer... Now as per concept it will flows back to transformer neutral point via EARTH !! (Which can damage transformer winding hence in some applications we use NGR)
I mean earth is such good conductor???
Please guide on this
Transformer neutral earth give a path to earth fault current . This current is very dangerous that why we use protection relay for sensing this fault current. If neutral not grounded then due to capacitance effect from phase to earth the other two phase voltage is very much high due to fault current in one phase which may lead to healthy phases insulation failure.
Nice
THANKS SIR
Thanks for this is a clear presentation. Could you also make a video on
1. Comparison/pros&cons of the 3 different CT connections?
2. If an ungrounded 3 phase system with a zig-zag grounding transformer, which CT wiring is best.
3. How to identify the phase or phases that are faulted to ground?
In residual connection 1 ph to earth fault that E/F current s max compare to other phases. So relay coil pick for only E/F current.ie Ir+Iy+Ib=0
In normal 1+(-0.7)+(-0.3)=0 (120deg ph shift)
In fault 2+(-0.7)+(-0.3)=1relay picked. This is correct?
But E/F time ph shift should be change like the fault ph current reflecting to normal phase.
your concept is not right bro.
Tell me bro what s correct ans
Let me explain…Under normal condition, the vector sum of these three phase currents will be ZERO and NO CURRENT will pass through the E/F relay coil.Okay?
Now, suppose there is an earth fault on the R phase. So, the current in the faulted phase will be HIGH compared to the other phases. Say the fault current be 2
Sir Please suggest how to earth failure detection
may be you are asking for loss of EARTHING.
@@electricaltechnologyandind5335 yes sir
But in residual CT connection you have mentioned the line to line fault can also operate the relay. It is not earth fault
Line to line fault if connected with earth. Then only it will operate