I often find I have trouble understanding India accents, but your drawings and explanations were great. Plus your English was good. Thank you for taking the time for this lesson and sharing your knowledge. Very Good.
Very nicely explained. Thanks. Can you please put some light on power rating (Kw) of the NGR to be specified ? As the withstand current is limited to 10 sec. only, then the continuous power rating of the resistor can be quite less than the peak power rating. Any idea about it sir. ?
Thank u Sir... But this point explained on 2:12 always bothers me ... Let say an earth fault occured in system at 100 meter away from transformer... Then how it can be flows back to transformer neutral via EARTH!! I mean earth is a such good conductor??? Please guide me on this?
Thanks for the video i was searching for Impedance grounded system i found this and i think its same. One question. For commercial facilities and residential areas, grounding impedance shall be 1000 A, 10 Second Resistor. I found this in one standard book.
Sir if the fault occurs phase to phase and ground then phase to phase voltage shall be taken for grounding resistance calculation. In your case u have taken phase voltage because u have considered phase to earth fault. So when it is ph-ph and ground fault. There is line voltage that is driving current Sir please clarify?
Load voltage is 11kV , no load voltage is 11.5kV , because during faults in line to ground , loads shall disconnected, in that case voltage Come back to it original state ,11.5kV , 11kV is load voltage due to voltage drop
Thanks, sir for the video. Most clearly explained video about NGR on youtube. Also sir, requesting you to make that video you have mentioned that how to handle the fault current of the above 33KV Wye connected Transformer through its grounding. Thanks in advance sir...
Both NER and earthing transformer neutral need to be rated at earth fault current. 10 seconds to account for protection auto reclosing, can be longer if required. NER resistance calculated from earth fault current level, not power. So main aspects are resistance, current and current withstand duration
its excellent but one question about earth fault current consideration 400A. can we take it as standard value?? what is the basis for this consideration of 400A e/f current? please explain
i haven't found any basis, may be based on experience it has been standardized. more over it can be varied but you have to design the transformer core withstand capability accordingly. suppose your transformer core can withstand earth fault current of 200A, then your Earth Fault current should be restricted to 200A or less. you have to specify the earth fault withstand current of transformer according to the earth fault current
Hi, What is/are the exception/s for not installing NGR in 11,3.3 or 6.6 kv? Kindly share some info on this because I have a 5MVA x'mer with 3.3 kV without NGR and the computed L-G fault is lesser than the 3Phse fault... Is that enough reason or there few more reasons technically?
All thr above voltage levels are generally provided with ngr. 3.3kv with solid earth is a new type of system for me.... Is the transformer star star??? Or delta star???? What is the upstream configuration???
In UK, NER is selected to match the nominal current value of the power transformer winding. I suppose you want a duty that is enough to trip protection, but doesn't cause too much stress on equipment.
for high voltage earth fault current will be higher. also there shall be possibilities of ground potential rise and life threat due to step and touch voltage. so for high voltage ngr is used. but for voltage of and above 66kv again solid earthing is done, and the potential rise hazard is taken care off by suitable earthing design
Neutral of generator of large power plant is earthed through a single phase earthing Transformer. Primary is connected between the generator neutral and load resistance is connected across the secondary. So it will make a transformer with secondary loaded. I shall make video on that
NGR size will be bulky as the insulation will be larger. Also that will have huge cost. Also resistance size will be huge..... Okay i will make video on that.......
@@electricaltechnologyandind5335 Here at our Power plant site,, about 7-8 times NGR failed. NGR rated voltage given is 12 KV. and transformer is of 21/11 KV
Hello, first of all thanks for your training. I have seen that when you have done calculation, you have not used 10 sec so when or where is 10 sec used? Thanks
It is not necessary. It depend on power of transformer,and generator. Example: Power of generator = 3.75MVA Voltage line to line = 13.8kV Then full load current= 3.75* 1000000/1.732* 13.8 = 156.9 We will limit earth fault current to be approximately 30 to 35% of full load current. Then earth fault current = 156.9*0.32=50 amp Now ohmic resistance which limit the earth fault current will be R = voltage / earth fault current R= 13.8* 1000/ 1.732* 50 R= 160 Ohm.
No standard. It is common industrial value taken l. However i have seen 200A, 800A also. But for mines area HT earth fault is restricted at 50 A and LT earth fault is restricted at 750 mA. That can be found in CEA guidelines also in IE rules
In IEEE 142, page 13, it stated: "Low resistance grounding is designed to limit ground fault current to a range between 100A and 1000A, with 400A being typical"
I need to restrict fault current in LT side as the fault current can damage the cables as cable fault level is very less (28kA for 1 sec for 300sq mm) wrt Transformer fault level (70kA).
Why your transformer fault current is so High? There is mistake. Lt trafo fault current should not go beyond 50 kA for trafo upto 2.5 mva and 65 kA for 3.15 MVA. Your cable is suitable for 28 ka for 1 sec. But you don't need to let the cable handle fault for that time. Watch my cable sizing video. You can restrict earth fault current, but phase fault you can't restrict. So select higher cable size. Watch my cable sizing calculation video......
Transformer size is 3 MVA & %Z is 6%. This is the reason for very high current in 415V side. Feeders are low capacity, I.g. 500A, so I can't choose 400sq mm cable size. Only thing is that I have to control these things by tripping time. Correct me if I am wrong
@@electricaltechnologyandind5335 Yes, but since the resistance is calculated to withstand a load of 400A for 10s, I think it must be a high power one. e.g. for 16.6 ohms /11.5KV, it must be 2650 KW resistance.
There are two possibilities 1. NCT connected at transformer neutral bushing 2. NCT connected to NGR. Both are used in industry. Transformer having solidly earthed neutral nct shall be connected at bushing only. Earth fault current returns through the neutral. So nct is required to detect earth fault current. I will make a vdo in nct selection. So please stay tuned.
This is a simplistic approach often considered in industry. Yes there is a method with other sequence impedance. But the difference will be absolutely negligible because the ngr resistance is very high compared to the transformer and also it will 3 times while considered in the zero sequence network. So both will give you same result.
400 A is not common earth fault current for all voltage level 33,11,6.6,3.3 kv Please clear that Here same voltage level have two type ngr 1. 9.90 ohm 2. 18 ohm
Sir equation is showing 11.5*1000/1.732*400 k but when u calculate 11.5*1000/1.732/400 after that only value will be come so please check that equation in video.
11.5 *1000/(1.732*400) or 11.5*1000/1.732/400 ohm, may be i have missed a bracket. Simple ohm's law, for 11.5 kv line to line voltage the phase voltage is 11.5*1000/1.732, dividing this by 400A you will get the ohmic value
@@ajinkyakhandare190 Earlier NER design it is considered as 30 sec on liquid resitors but now a days NER design for 10 sec chosen to allow occurence of multiple events.
I often find I have trouble understanding India accents, but your drawings and explanations were great. Plus your English was good. Thank you for taking the time for this lesson and sharing your knowledge. Very Good.
খুব সুন্দর ও সহজ করে বোঝানোর জন্য অনন্ত ধন্যবাদ আপনাকে💕 স্যার💕🙏💕
great explanation
may this channel will be more great
Very nicely explained. Thanks.
Can you please put some light on power rating (Kw) of the NGR to be specified ?
As the withstand current is limited to 10 sec. only, then the continuous power rating of the resistor can be quite less than the peak power rating.
Any idea about it sir. ?
explained in a very simple way... amazing work!
Very much interesting....awasome
Thank u Sir... But this point explained on 2:12 always bothers me ...
Let say an earth fault occured in system at 100 meter away from transformer... Then how it can be flows back to transformer neutral via EARTH!!
I mean earth is a such good conductor???
Please guide me on this?
Sir, what is the criteria to select 400A as upper limit for neutral current.
I have the same queries
Whts the basis to restrict e/f to 400amps.
Can u give any reference of IS
Thanks for the video i was searching for Impedance grounded system i found this and i think its same.
One question. For commercial facilities and residential areas, grounding impedance
shall be 1000 A, 10 Second Resistor. I found this in one standard book.
Thanks for this wonderful video. What is the guiding factor of selecting 400A or 600A.
Very nice explained 👍. Put this information over your blogs as well.
Awsome video in details...Thanks
Sir if the fault occurs phase to phase and ground then phase to phase voltage shall be taken for grounding resistance calculation. In your case u have taken phase voltage because u have considered phase to earth fault. So when it is ph-ph and ground fault. There is line voltage that is driving current Sir please clarify?
NGR is in series or parallel ?
In NGR Resistor is connected in series or parallel ?
Impeccably Excellent. Make video on 66kV, 132kV, 220kV, 400kV, 765kV ground resistance calculation. Also on HVDC Earthing fault calculation. Thanks
Make video on 66kV & above voltage level sir
Very good lecture Sir. Thanks
Sir please clarify me earth fault current is grounded , afterthat why fault current is feeding to Source via neutral ?
Sir how to determine rated Current for NGR resistance value calculation
Verry good, easy to understand.
Please explain why you change 11kv to 11.5kv? I'm not clear to understand..thank you.
Load voltage is 11kV , no load voltage is 11.5kV , because during faults in line to ground , loads shall disconnected, in that case voltage Come back to it original state ,11.5kV , 11kV is load voltage due to voltage drop
Excellent explanation
Thank you very for explaining for sizing the NGR for various capacity of Trs.
Where is the power (Watts) capcity of resistor
Very nicely explained.
Very nicely explained
Very good information we got. Thanks to ETIP team. Please make a video on substation SAS and control. And scada architecture. Please
By using Earthing Transformer, what will be the connection diagram
Thanks, sir for the video. Most clearly explained video about NGR on youtube. Also sir, requesting you to make that video you have mentioned that how to handle the fault current of the above 33KV Wye connected Transformer through its grounding.
Thanks in advance sir...
What is the situation NET (nutral earthing Transformer ) is used. Can you please advice its calculation?
Very good explanation
How to calculate generator or transformer earth fault current which one we are limiting through NGR.
Can you please make video for Neutral current transformer.
Nicely explained. What IS is applicable for such calculations?
thank you so much sir for your explanation ... it's so useful and helpful
how come when you draw the vphase it looks like line voltage since it is between phase and neutral? sorry to ask.
Sir i want to request u to plz tell how to decide fault current for transformer of 15/20 MVA and ratting in 110kv /33 kv ..
Check my fault current calculation video. Method is same. But for suc high voltage there shall not be any significant motor contribution.
Sir why we taken 400 A limit current for 11.5KV,6.6KV,3.3KV. Those are different voltages.So why we taken same 400A limit current?
Great video
What it is rated for 10 sec.?
Is it necessary to specify power rating of NGR based on the fault current controlling through NGR during fault?
Both NER and earthing transformer neutral need to be rated at earth fault current. 10 seconds to account for protection auto reclosing, can be longer if required. NER resistance calculated from earth fault current level, not power. So main aspects are resistance, current and current withstand duration
Very nice 👍🏻👌
amazing video.
Good stuff!! 👍👍
Thanks sir and please make video on zigzag transformer of two winding transformer
Excellent explanation, but how you have selected 400 A and 10s for opposing EF current
Specified in ieee green book.
its excellent but one question about earth fault current consideration 400A. can we take it as standard value??
what is the basis for this consideration of 400A e/f current? please explain
i haven't found any basis, may be based on experience it has been standardized. more over it can be varied but you have to design the transformer core withstand capability accordingly. suppose your transformer core can withstand earth fault current of 200A, then your Earth Fault current should be restricted to 200A or less. you have to specify the earth fault withstand current of transformer according to the earth fault current
Would these calculations also apply for a neutral grounding reactor (coil) ?
Sir we have taken 100amp fault current for 15 MVA trafo,6.34%impedance.ngr-63.5 ohm.
Okay... No issue... Selection of NGR and earth fault current is industry dependent
Thanku sir..if ngr is off will the trafo trip on earth fault ,lighting load fluctuate
It shouldn't
Hi, What is/are the exception/s for not installing NGR in 11,3.3 or 6.6 kv? Kindly share some info on this because I have a 5MVA x'mer with 3.3 kV without NGR and the computed L-G fault is lesser than the 3Phse fault... Is that enough reason or there few more reasons technically?
All thr above voltage levels are generally provided with ngr. 3.3kv with solid earth is a new type of system for me.... Is the transformer star star??? Or delta star???? What is the upstream configuration???
explain very nice
Why to taken 400A.....what is the reason
Please make video about Vector group of transformer as simple as exolain your this video👍
Is there an international standard to derive the 400A used as EF current limit?
In UK, NER is selected to match the nominal current value of the power transformer winding. I suppose you want a duty that is enough to trip protection, but doesn't cause too much stress on equipment.
Sir why limit the neutral current for high voltage. If any problem for winding like damaged for circulating current?
for high voltage earth fault current will be higher. also there shall be possibilities of ground potential rise and life threat due to step and touch voltage. so for high voltage ngr is used. but for voltage of and above 66kv again solid earthing is done, and the potential rise hazard is taken care off by suitable earthing design
Thanks
Time 10 sec means what and how is calculated
very good.
Can u tell me the purpose of loading resistor in NGTR and explain video about
Neutral of generator of large power plant is earthed through a single phase earthing Transformer. Primary is connected between the generator neutral and load resistance is connected across the secondary. So it will make a transformer with secondary loaded.
I shall make video on that
@@electricaltechnologyandind5335 sir please make video on NGTR which is generally used in large generating station
Please do a video on
1) NGR with transformer. (to reduce size of NGR)
2)
How do you restrict it to only for 10 sec.
explanation good 👍
In our Ngr fault current is 1400 A @ 6.6 KV system voltage. Can you please make a video on t/f S.C caliculation
I will make shortly...
@@electricaltechnologyandind5335 Thank you sir. Sir please make a video on CVT also
Excellent .kindly make a video on earthing transformer stressing upon zero ph seq imedence and sizing
Why ngr not provided at 220kv transformer, please make video on that
NGR size will be bulky as the insulation will be larger. Also that will have huge cost. Also resistance size will be huge..... Okay i will make video on that.......
Thanks for such information. can you give information about NGR supplier? I need it urgently.
Generally transformer suppliers supply NGR. You can contact the trafo manufacturers
Ampcontrol pune
Contact-
Rameah Amale
7620552513
Earth fault current is Max 50A as per CEA 2010
What will happen, if we select NGR for rated line voltage,, remaining condition same as explained by you?
Unable to understand... Give example
@@electricaltechnologyandind5335 Here at our Power plant site,, about 7-8 times NGR failed. NGR rated voltage given is 12 KV. and transformer is of 21/11 KV
@@electricaltechnologyandind5335 Here,, i am not able to attach my NGR rating. my whatsapp no is 9109174024. can send on it,, if you are ok with it.
Email me at
electricaltechnology04@gmail.com
Send me the details
Thanks 👍
How to find out the earth fault current of the transformer
Outstanding vedio
Thank you very much
Sir give explain abought 11kv alternator ngr
Hello, first of all thanks for your training. I have seen that when you have done calculation, you have not used 10 sec so when or where is 10 sec used? Thanks
10 SEC IS THE WITHSTAND TIME OF THE FAULT CURRENT. THE NGR IS CAPABLE TO WITH STAND 400 A FAULT CURRENT FOR 10 SEC.
@@electricaltechnologyandind5335 Okay, thank you a lots
@@electricaltechnologyandind5335 how can we vary withstand time & it's effect on NGR value
Indian standard specifies 5 sec, 10 sec rating for NGR. So those are followed. But actual earth fault get cleared much earlier i.e. 0.5 sec at max
How this general current of 400A is defined?
It is not necessary. It depend on power of transformer,and generator.
Example:
Power of generator = 3.75MVA
Voltage line to line = 13.8kV
Then full load current= 3.75* 1000000/1.732* 13.8
= 156.9
We will limit earth fault current to be approximately 30 to 35% of full load current.
Then earth fault current = 156.9*0.32=50 amp
Now ohmic resistance which limit the earth fault current will be
R = voltage / earth fault current
R= 13.8* 1000/ 1.732* 50
R= 160 Ohm.
Why no need of NGR for 11kv/433v transformer
appreciate! good effort.
why we use 100 Amp or 400 Amp NGR only
In which standard If is noted as 400A
No standard. It is common industrial value taken l. However i have seen 200A, 800A also.
But for mines area HT earth fault is restricted at 50 A and LT earth fault is restricted at 750 mA. That can be found in CEA guidelines also in IE rules
In IEEE 142, page 13, it stated: "Low resistance grounding is designed to limit ground fault current to a range between 100A and 1000A, with 400A being typical"
What about 6 MVA 11 kV/ 0.4 KV...also the Fault current is high
How 400A came? What will be this value for 415V NGR?
I need to restrict fault current in LT side as the fault current can damage the cables as cable fault level is very less (28kA for 1 sec for 300sq mm) wrt Transformer fault level (70kA).
Why your transformer fault current is so High? There is mistake. Lt trafo fault current should not go beyond 50 kA for trafo upto 2.5 mva and 65 kA for 3.15 MVA.
Your cable is suitable for 28 ka for 1 sec. But you don't need to let the cable handle fault for that time. Watch my cable sizing video.
You can restrict earth fault current, but phase fault you can't restrict. So select higher cable size.
Watch my cable sizing calculation video......
Transformer size is 3 MVA & %Z is 6%. This is the reason for very high current in 415V side.
Feeders are low capacity, I.g. 500A, so I can't choose 400sq mm cable size.
Only thing is that I have to control these things by tripping time.
Correct me if I am wrong
And I think due to Personal safety we dont use NGR at 415V side.
Yes isolate the fault with short time.... Wrong transformer selection is made.....
What will be temperature ?
Thats an instantaneous current. So there wont be significant temperature rise
@@electricaltechnologyandind5335 Design temperature ?
50 degree ambient. It is not a continuous operation. So what temperature are you asking???
@@electricaltechnologyandind5335 the withstanding temperature of NGR under fault current
Say something about the power of the resistance in every case. P=I^2* R
Current through ngr will be flown only during earth fault... So loss is irrelevant for that case.
@@electricaltechnologyandind5335 Yes, but since the resistance is calculated to withstand a load of 400A for 10s, I think it must be a high power one. e.g. for 16.6 ohms /11.5KV, it must be 2650 KW resistance.
@@spyrosn1950
What will be Wattage of resistance. Will it be. I*I*R ??
Thank u sir
Sir where NCT is connected?? And why its require?
There are two possibilities
1. NCT connected at transformer neutral bushing
2. NCT connected to NGR.
Both are used in industry. Transformer having solidly earthed neutral nct shall be connected at bushing only.
Earth fault current returns through the neutral. So nct is required to detect earth fault current. I will make a vdo in nct selection. So please stay tuned.
@@electricaltechnologyandind5335 sir thank you for your support
We have a NGR of 66.39 ohms at 11.6 KV
thanks
while calculating the value of NGR, you have not considered the X1, X2 & X0 of transformer, please check
This is a simplistic approach often considered in industry. Yes there is a method with other sequence impedance. But the difference will be absolutely negligible because the ngr resistance is very high compared to the transformer and also it will 3 times while considered in the zero sequence network. So both will give you same result.
Ngr is connected in HT generator.... Kindly check
didn't get you
❤
👏🏼
400 A is not common earth fault current for all voltage level 33,11,6.6,3.3 kv
Please clear that
Here same voltage level have two type ngr
1. 9.90 ohm
2. 18 ohm
400A is most common for 11,6.6, and 3.3 kv. There are exceptions also.... In mines these are Restricted to 50A
Here means where??? There are exceptions....
Why 400A not 100 A
Sir can u check your calculations
Please tell me in detail
Sir equation is showing 11.5*1000/1.732*400 k but when u calculate 11.5*1000/1.732/400 after that only value will be come so please check that equation in video.
11.5 *1000/(1.732*400) or 11.5*1000/1.732/400 ohm, may be i have missed a bracket. Simple ohm's law, for 11.5 kv line to line voltage the phase voltage is 11.5*1000/1.732, dividing this by 400A you will get the ohmic value
Where 10 sec time is in calculation.
10 sec is not there for ohm calculation. But when you select the cross section of the NGR conductor then the 10 second factor will come.
@@electricaltechnologyandind5335 can you please explain in detail about this 10 sec.
@@ajinkyakhandare190 Earlier NER design it is considered as 30 sec on liquid resitors but now a days NER design for 10 sec chosen to allow occurence of multiple events.
Not complete command on subject
I cant understand
Hindi mein hota to achha hota