OVER-CURRENT RELAY SETTINGS CALCULATION FOR TRANSFORMER and Relay Coordination

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[@Deb0029]

Very helpful ❤

[@pietervdberg7055]

Thank you for a very clear easy to follow video on the topic. Made a lot of things clear for me. I posted a question under another comment about t=0.6s for LV and t=0.8s for HV. If you could answer we will highly appreciate it.

[@relayprotectionelectrical]

Thank you for your valuable comment. Tms of LV and HV can be so chosen that both the HV and LV over current relat trip simultaneously. Now a days if LV OC trip then there will be an inter trip will be sent to HV master trip relay from LV OC relay. Now for the time 0.8 S. 0.8 S is the maximum time that can be given to the transformer to trip as it should not exceed far end line in zone-3 time which is normally set as 0.8-1 S . So if Zone3 encroach lower voltage level far end FDR should not trip prior to transformer trip and i.e. why 0.8 S is the time for transformer trip in back up OC.

[@pietervdberg7055]

Thank very much for the explanation.

[@pietervdberg7055]

@@relayprotectionelectrical Another question please that I forgot to ask. The I(set) value being 110% of full load current and then calculate I(set)(s) = I(set)/CT ratio, is it the same as relay pickup current that is used in some calculations. Some I have seen are 120% and others as 125% of full load current. Is the formula to calculate t.m.s. for normal inverse curve? Thank you.

[@surendrakverma555]

Excellent lecture Sir. Thanks 🙏🙏🙏🙏🙏🙏🙏🙏🙏

[@relayprotectionelectrical]

Most welcome

[@rakeshparmar8570]

Good explanation

[@taimur649]

Very informative

[@Abi-og5jr]

How did you got the value t = 0.6 for lv and t=0.8 for hv

[@syed_taha_ahmed]

Do you have posted video on transmission line over current relay settings? How receiving and sending end relays are set? Please make a video on current discrimination and overcurrent relay settings for transmission lines.

[@santhoshr53]

Plz make video on Calculation for instantaneous over current

[@salamkadhim6949]

شكرا جزيلا

[@samadhanmore3760]

Determine the time of operation of the two relays

[@MansourAlramlawi]

Many thanks for your explination, could u share with us a reference for these calculations?

[@syed_taha_ahmed]

What does numeric relay indications I> I>> and I>>> means?

[@KarrarH-el4th]

PLZ Why this values of t=0.6 & 0.8 from what get it plz

[@pietervdberg7055]

Yes please can you clarify the times of t=0.6s for LV and t=0.8s for HV. Is it a general norm for different voltages. Is specified in IEC etc Hope to hear from you.

[@relayprotectionelectrical]

@@pietervdberg7055 Thank you for your valuable comment. Tms of LV and HV can be so chosen that both the HV and LV over current relat trip simultaneously. Now a days if LV OC trip then there will be an inter trip will be sent to HV master trip relay from LV OC relay. Now for the time 0.8 S. 0.8 S is the maximum time that can be given to the transformer to trip as it should not exceed far end line in zone-3 time which is normally set as 0.8-1 S . So if Zone3 encroach lower voltage level far end FDR should not trip prior to transformer trip and i.e. why 0.8 S is the time for transformer trip in back up OC.

[@AjeetKumar-iq7fp]

Thanks sir

[@mustafakhalidjasim3160]

Why you have used z%equal to 12%,where you get it?, thanks

[@relayprotectionelectrical]

You can get %Z of Transformer in nameplate .

[@sudampatra5608]

Can we use relay rest ratio here

[@dawodtawer1953]

Hello everyone I hope someone answer my question I have six generators (1 MVA each)feeding 11 kv switchgear through transformer 0.4/11 kv i need to add two more generators (1 MVA each) with parallel transformer 0.4/11 kv to same switchgear. My question is do i need to change the protection settings?

[@mageshgopi5644]

System prospective current value increased and system impedance has reduced . So a comprehensive short circuit calculation and protection setting study is required

[@pietervdberg7055]

@@mageshgopi5644Yes agree with this reply. When operating transformers in parallel the total impedance of the transformer combination will reduce, depending on the number of transformers and their impedances. Similar to connecting resistors in parallel. This will cause the total system impedance to decrease resulting in an increase in the prospective short circuit current. So yes in depth calculations and analysis of the network is required. Consider introducing a busbar system with busbar incomers from generators and transformer feeders as well as bus couplers for different sections to avoid paralleling transformers but to provide flexibility of the network. Not sure what the network looks like. Also bear in mind that when the network is changed such that the system impedance is decreased and fault currents increase substantially you might reach a point where the fault current could exceed the max fault current rating of switchgear, cables, etc

[@badshahibrahim8475]

Sir please make for Motor feeder 🙏🏻🙏🏻🙏🏻🙏🏻

[@relayprotectionelectrical]

Ok I will

[@badshahibrahim8475]

@@relayprotectionelectrical yes sir I hope 👍🏻

[@Deepak_Kumar1993_]

​@@relayprotectionelectricalw8ing for long time

[@ganeshachally4881]

Sir why you didn't take the power factor in calculating the full load current

[@relayprotectionelectrical]

Maximum fault current is considered in this case and i.e. why unity pf is considered for this purpose.

[@badshahibrahim8475]

Thank for it 👍🏻👍🏻

[@lokeshjuneja2039]

volume is very low in video.

[@AjeetKumar-iq7fp]

Part 2

[@great_India3344]

TMS formula is written wrongly

[@relayprotectionelectrical]

Yes it is. But TMS calculated is right. Thank you for watching video carefully...

[@jitendragujarathi1282]

Volume very slow sir

[@relayprotectionelectrical]

Kindly use headphone for better hearing.

[@jitendrasoni4105]

Aawaaz khatam hai kya😢😢😢😢