Restricted Earth Fault Protection|REF relay working principle

In this video the philosophy behind the restricted Earth Fault Protection has been elaborated. Restricted Earth Fault Protection is also known as differential earth fault protection. It is basically earth fault protection but works on differential relay principle.
Restricted Earth Fault Protection is used to detect earth fault inside a machine in general.
The explanation given in the video is applicable for all the below mentioned topic.
1. Restricted Earth Fault Protection philosophy
2. How restricted Earth Fault Protection works
3. REF principle
4. Differential earth fault Protection
5. working principle of restricted Earth Fault Protection relay
6. REF relay
7. Restricted Earth Fault Protection theory
8. REF Protection
#ElectricalEngineering, #ElectricalTechnology,
#RestrictedEarthFaultProtection
#REF
#ElectricalTechnologyAndIndustrialPractice
please like, share, comment and subscribe our channel.
Please also visit our website
electricaltechnologyrishi.blo...
for more technical articles

[@morraa13]

i need to thank you more , thanks thank thank , i had some problem in current flow , you solved this problem ❤️❤️❤️❤️❤️❤️❤️❤️❤️

[@firojalam3497]

perfectly explained...thanks for uploading the video.

[@Indian-ri4ry]

Superb master.... 👍👌Nicely explained.

[@richardbottrell5933]

Thank you for your reply. I thought I had missed something. Keep up the good work.

[@electricaltechnologyandind5335]

thanks a lot....😊

[@Doti_231]

very good explanation, keep going

[@chrisc3236]

Great explanation, thank you

[@muneeryou]

Sir, why did you change the direction of current in second case through NCT. Shouldn't the direction be same for both external as well as internal faults. Since the direction of fault current in either case is same.

[@electricaltechnologyandind5335]

Yes correct. That has been a mistake by me. However the result will be same. Glad to see your clear concept. Thanks for identifying it.

[@ikhairi83]

i was thinking the same thing.

[@sangeetadalai4111]

In trf, secondary current is always in opposite direction as of primary... (opposes the cause producing it)

[@dilipsiju9165]

How come result will be same if direction of current in NCT is not changing?

[@ANKURBARUA]

@@dilipsiju9165 relay will be energized irrespective of current direction

[@md.zahidhasan5148]

Nice Explanation

[@kammarianurag3687]

Explained crystal clearly

[@dhananjaykumar5114]

Very Good Lecture

[@richardcollingwood7484]

I don't understand how the current can flow in 2 separate directions on the Neutral CT secondary when the fault current up the NCT in the same direction when it is inzone and out of zone ? can anybody assist ?

[@khaledlameen3267]

excellent explanation sir, please upload videos in distance protection+power line carrier

[@prabhakarangovindaraj9238]

Thank you so much sir 👏👍

[@WYC-to3du]

Very good explanation

[@charinath5445]

How the positions (primary) of the CTs to be arranged (P1 & P2) for both the line and neutral CTs?

[@RahulThakur-li2rv]

Hello sir thank you for detailed lecture. Can you please suggest how we can understand why earth fault current flow back through neutral of transformer through earth path whereas earth considered as largest sink of charges

[@mohamedibrahim4592]

If I have a CT on the neutral of the solidly earth transformer , How can I size it to achieve 50N,51N on the protection relay

[@gunpowder98]

excellent...precise 87REF explanation.

[@osasumwenediae5393]

I love the usa from the bottom of my heart thank you

[@ankitkd6003]

Very good

[@dineshdubey2745]

Could you pl make a video on iec 61349 and its implementation in cabinets.

[@surendrakverma555]

Very good 🙏🙏🙏🙏🙏. Thanks

[@Onlineelectrical123]

kzbin.info/www/bejne/l4bXcoOPqN91jtE

[@healingmeditation5970]

sir please make a video on how to show diiferent relays connection diagram in sld used in LT panel ...

[@mdthun4358]

Beautiful

[@ashokar9135]

Hi I believe in both the fault conditions NCT sec. Current direction direction will be same. Your considering two different directions for outside and inside faults. Could you please correct me if I am wrong

[@omarzeno6195]

thank u

[@surekhagaikwad5195]

Sir could you pls checkthe direction of current flow in d secondary ckt of NCT. There is an error.

[@mohamedibrahim4592]

and how to size the CT on the neutral to achieve 64 REF

[@habibulhuda6447]

Very good video. But I think the polarity marking you have shown (when you give the example for through fault) for NCT is reversed. Because, the current direction of restraining current (Ia+Ib+Ic) and star point current (In) should be equal and opposite in direction. During the though fault you are showing the current direction of CT-A secondary and NCT secondary both are same direction. if so, the relay should sense and trip signal to concern breaker.

[@electricaltechnologyandind5335]

Yes, that was an on camera mistake

[@marcusrose9189]

The line ct polarity needs to be changed. Typically for differential forms of protection the CT polarity marks point away from the equipment it’s protecting. Reason being is that you will see current from power flow trying to flow back into the fault as shown in ETAP sims as AC current will always travel the section, in this case a fault within the zone, for a brief (if designed properly to trip) moment. The line CT’s will see that current.

[@bhaveshbarot186]

@bhaveshbarot186 7 minutes ago (edited) direction of current flowing through NCT secondary in internal fault diagram Shawn is wrong.i think its flow opposite of primary current. though its operate the REF relay but current direction would be entering from relay side. also during external fault fault current will flow through N of line CT. which will be equal and opposite of N CT current. and result will be 0 amp.

[@miladmnred]

Thanks alot. but what about REF Protection of delta side of the transformer?

[@MRJInspire]

pls practice and do this

[@pratikdutta5071]

For the HV side, what is the protection for internal fault? If the HV side is Delta.

[@mcmeddmc4152]

How does the primary current behaviour be on the healthe phases?

[@kumuddubey7188]

Sir explain about connection and it's secondary current direction

[@nishananda9838]

I have one technical doubt, in REF protection above diagram, where line CT connected? Inside Transformer or Switchgear side? Also in Motor or Alternator Differntial protection where CT's wilp be connected?

[@mdaashique3164]

In T/F REF Protection, Line CT HV Bushing ke turret me hota hai ( Bushing Ka lower part jo T/F tank ke under connect hota hai) Yani inside T/F.

[@richardbottrell5933]

A very good video but why do you show the current flow from the NCT changing direction in the second example of an earth fault.? The first instance follows Lenzes Law but the second does not.

[@electricaltechnologyandind5335]

i have admitted many times, also written in description that has been an on camera mistake as I usually deliver with out any script

[@vishalshah5913]

How CT polarity impact REF scheme?

[@007srv1]

sir your videos are good but i have a doubt about the placement of nct wheather it should be provided before ngr or after ?? kindly explain

[@Onlineelectrical123]

kzbin.info/www/bejne/l4bXcoOPqN91jtE Before

[@hajamohideen3776]

Hi Please can you explain why changing direction current through NCT when inside fault.

[@electricaltechnologyandind5335]

That was wrongly marked

[@bullisback6243]

Current direction should be same in NCT for Inzone fault too. Pl confirm

[@victormahadev7158]

Please answer my Question sir , in the 6.35 you saying due to polarity connection no current will flow on the stablizing resistance? How please explain.? As my knowledge current will flow in shortest path then the secondary current will flow through the stablizing resistance via why they will choose longer path. Please clarify my dear otherthan your explanation is great ..

[@Onlineelectrical123]

kzbin.info/www/bejne/l4bXcoOPqN91jtE

[@jayadasanvv9736]

Good

[@Onlineelectrical123]

kzbin.info/www/bejne/l4bXcoOPqN91jtE

[@jaynandan9937]

Sir in both case for neutral CT directions should not be same.

[@johnjafferjanardhanan8675]

I have one doubt.. I think there’s on mistake in your brief , only doubt... when the EF occurred inside the zone, the flow of the current in secondary should be reverse, as per your explanation the fault current will not flow through relay bcz of the resister.

[@flyhighwithyourdreams.2132]

Sir inside fault and outside fault accuse NCT current direction S1 not S2. Please correct ur video

[@kishorekrrishe]

Sir why we need REF when we have differential protection?

[@osasumwenediae5393]

I needs electrical principles and its applications toindustrial pratice

[@neerajpiplani185]

In one of our substation whenever the 66 kv voltage is on higher side may be greater than 70 kv and if power transformer after maintenance is switched On it trips with REF indication .Could you please explain the reason for same

[@electricaltechnologyandind5335]

Is the trafo star star??

[@neerajpiplani185]

@@electricaltechnologyandind5335 yes

[@neerajpiplani185]

66/11kv 20 Mva

[@electricaltechnologyandind5335]

I have seen this problem, also. If the trafo doesn't have delta winding then third harmonic current may be the culprit. It has the same characteristics as zero sequence current

[@neerajpiplani185]

@@electricaltechnologyandind5335 could you please elaborate

[@sarni0206]

I appreciate your effort, but kindly convey the universal application examples while explaining the topic. There was also some lack of information like you were only talking about differential earth fault protection, along with that you should have also told about the other types.

[@electricaltechnologyandind5335]

please note the heading of the video... the video is only about restricted earth fault protection and not about the other earth fault protection. i have another video on over current earth fault protection and relay co ordination, you can check that. also please note that it is not possible to cover all types of earth fault protection under a single video..... you please watch that earth fault protection video. also on restricted Earth fault protection i have made three videos, one is the principle and other two about the setting and calculation. so whatever practiced in industry is already available. please check all the videos. i hope your doubts will be cleared.... thank you

[@jamesowusu-ansah595]

so would it operate to protect against INTERNAL phase to phase faults which are NOT associated with ground?

[@electricaltechnologyandind5335]

Nopes.... For that you need differential protection

[@jamesowusu-ansah595]

@@electricaltechnologyandind5335 can you please explain why it wouldn't operate for such fault

[@electricaltechnologyandind5335]

No ct will be energized.and if the fault is out side and through the ct then also as the cts are residually connected so they will see the sum of fault current which is zero

[@bhaveshbarot186]

direction of current flowing through NCT secondary in internal fault diagram Shawn is wrong.i think its flow opposite of primary current. though its operate the REF relay but current direction would be entering from relay side. also during external fault fault current will flow through N of line CT. which will be equal and opposite of N CT current. and result will be 0 amp.

[@RK20505]

I have one doubt, both faults inner and outer current flow in earth to Nu , but secondary current direction changes in our explanation why?

[@electricaltechnologyandind5335]

THE DIRECTION SHALL BE OPPOSITE. I MADE AN ON CAMERA MISTAKE THERE...

[@RK20505]

@@electricaltechnologyandind5335 in my knowledge, , NU CT Current are never change the direction ,The power flow direction has been change at time of inner falut than only CT current will added

[@divyeshghiwala8502]

Need to know difference between REF & differential Relay?

[@Franceskineos]

REF have a differential principle so should be coded 87N. The 64R it used already for Rotor earth fault protection for generators

[@electricaltechnologyandind5335]

Won't disagree, but 64 also represents ref

[@mohamedabdelrashid3080]

I need to contact you in person

[@9561065980]

Pls check once again, u have drawn wrong current flow path on NCT secondary, when on Zone fault at Y -ph.

[@PTIrealsupports194]

Reason for stablizing resistor is not correct as through fault current increase magneticing current in excitation branch of cts due which CT saturate and differential current will pass through spill path and relay will operate

[@electricaltechnologyandind5335]

Explanation in video is correct. Reason behind the current flow due to theough fault is the Vs

[@Arijit_VU3ICT]

Nct dot will be parallel to line ct.

[@electricaltechnologyandind5335]

Your point is not clear to me.

[@redolencerahul6080]

Please give video in hindi language also

[@learnbyshiva725]

Sir please make video for alternator Protection relay settings

[@electricaltechnologyandind5335]

Tomorrow I shall release restricted earth fault relay setting calculation. The video will be in two parts. Tomorrow the first part will be release, and Friday the final part will be released. Please note that the video shall be applicable for for both alternator and transformer ref Protection. Stay tuned.

[@sunilmahanta4589]

Why relay setting properly

[@tikshabhatt4816]

Please explain in hindi...

[@manoranjan4598]

Please hindi sir

[@KevinBosch-ru3if]

Your black arrow is the wrong way around

[@electricaltechnologyandind5335]

Yes correct

[@RoyKIype]

Neutral CT directions are wrong.

[@pradeeppandey-ml9me]

Downward direction of current is not assumed its according to the dot convention.... plz study properly and then deliver better quality information..

[@electricaltechnologyandind5335]

Thanks for your suggestion. But that mistake is not due to lack of study. I made mistake on the second occasion which doesn't match with the convention followed for first occasion. I usually deliver without any script, that's the reason for such on camera mistake. But I can assure you that I shall be careful in future to avoid such mistake. Moreover these conventions are convertible type. Only have to tally with the primary current direction. Because for each half cycle the direction alters

[@tikshabhatt4816]

Please explain in hindi..not understand in english

[@mdrazibhusain]

Why are you crying in the video!

[@ramkl1237]

Very good explanation

[@charinath5445]

How the positions (primary) of the CTs to be arranged (P1 & P2) for both the line and neutral CTs?

[@rajeshtk1246]

1. For Lines at a substation, place the P1 in such a way that the fault would be fed to the protected object, via P1. Hence, in this case, P1 of the CT to the bus side, p2 to the line side. 2. For Transformers also, follow the same principle. Place p1 of the primary side/hv side in such a way that a possible fault current will enter the protected object(in this case, the transformer) via P1 (P1 away from transformer, P2 near transformer). Similarly for secondary side/lv side also, Place p1 of the secondary side/lv side in such a way that a possible fault current will enter the protected object(transformer) via P1.(P1 away from transformer, P2 near transformer). 3. If there are neutral CTs, apply the same logic as in case 2. For Neutral CTs also, place P1 in such a way that a fault current will enter the transformer neutral point via its P1 terminal. (P1 away from transformer, P2 near transformer). To add onto the above points, starring secondary of CTs when connected as above should be done at the protected object side. i.e for case 1, s2 of phases should be starred. in case 2 also, s2s should be starred.

[@charinath5445]

How the positions (primary) of the CTs to be arranged (P1 & P2) for both the line and neutral CTs?

[@electricaltechnologyandind5335]

Okay I shall explain on a separate video

[@rajeshtk1246]

1. For Lines at a substation, place the P1 in such a way that the fault would be fed to the protected object, via P1. Hence, in this case, P1 of the CT to the bus side, p2 to the line side. 2. For Transformers also, follow the same principle. Place p1 of the primary side/hv side in such a way that a possible fault current will enter the protected object(in this case, the transformer) via P1 (P1 away from transformer, P2 near transformer). Similarly for secondary side/lv side also, Place p1 of the secondary side/lv side in such a way that a possible fault current will enter the protected object(transformer) via P1.(P1 away from transformer, P2 near transformer). 3. If there are neutral CTs, apply the same logic as in case 2. For Neutral CTs also, place P1 in such a way that a fault current will enter the transformer neutral point via its P1 terminal. (P1 away from transformer, P2 near transformer). To add onto the above points, starring secondary of CTs when connected as above should be done at the protected object side. i.e for case 1, s2 of phases should be starred. in case 2 also, s2s should be starred.