Relay Setting & Coordination II IDMT Protection for Transformer HV in ETAP II Manual Calculation

IDMT characteristic of protection relay can be used for low voltage electrical protection system also. LSIG release with Electronic Trip Unit (ETU) can be used for the protection of LV system incomer, outgoing motor feeder or any other LV protection application. These are also known as Solid State protection system as called by some of the manufacturers.
Thermal magnetic protection can also be used for overcurrent and short circuit protection applications.
#motor
#transformer
#protection
#idmtrelay
#tcc

[@nagendrakumar100]

Thank you so much for your valuable time and making videos for our improving knowledge in Electrical Engineering

[@SmartEducare]

Thanks for the valuable feedback, will keep sharing knowledge

[@subhendumukhopadhyay3535]

Good one.but 87T should be covered

[@SmartEducare]

th-cam.com/video/Hq2w1ewlKt8/w-d-xo.html
87T covered in the above video, can check out

[@priyal5354]

Do we have to do keep the relay curve within the inrush and damage curve of transfomer for HV side relay too?

[@SmartEducare]

Yes

[@asimrazajutt1616]

Sir how can I modelling ups in distribution network and then fed supply through ups meanwhile grid and generator are not available..?

[@SmartEducare]

You can model UPS in TAP just like any other equipment. For different case scenario with or without Grid/ Generator, refer Contingency Analysis video, link is provided below:
th-cam.com/video/-ZdVXc17wjY/w-d-xo.html

[@asimrazajutt1616]

@@SmartEducare Bundle of thanks I’ll check now. Actually I was faced issue with inverter side of ups inverter side still show like not connected means in grey Color

[@asimrazajutt1616]

@@SmartEducare can I get your mail..?

[@ahilcuts7971]

Hi. In pickup calculation how to you choose 0.9

[@SmartEducare]

Pickup= (Full load current X Overload)/(Under voltage X CT ratio)
This is already covered in the video as manual calculation, can watch again it..
Hope it's clear now

[@charinath5445]

Hi Sir,
Can you please confirm my below understandings, comment if anything is incorrect,
Transformer Primary winding protection:
50P - Set pickup value at 1.2 to 1.5 times the through fault current (or) reflected fault current
51P - Set pickup value at 1.1 times the full load current of the transformer.
50N - Set pickup value at Full load current of the transformer or at CT primary rated current
51N - Set pickup value at 10-20% of Full load current of the transformer or at CT primary rated current
Transformer Secondary protection (at the incomers of the secondary side switchgear):
50P - Set pickup value at the calculated minimum fault current.
Note:
If it is low voltage at the secondary side, normally there would be ACB or Power circuit breaker, therefore enable only S of "LSI" and disable I.
If it is medium voltage at the secondary side, use definite time to allow for the downstream relay to pick up first.
(This is allow for the downstream relay/ breaker to trip first by blocking/reverse interlocking/ZSI) the upstream relay incase of fault at downstream).
51P - Set pickup value at the value of current (Base loading + largest motor starting)
50N - Set pickup value at Full load current of the transformer or at CT primary rated current
51N - Set pickup value at 10-20% of CT Full load current of the transformer or at CT primary rated current
CT connected at the neutral of the secondary winding:
50G - Disabled
51G - Set pickup value at 10-20% of CT Full load current of the transformer or at CT primary rated current and delay greater than 51N

[@SmartEducare]

Thanks for your lovely effort!
Your understanding is almost correct.
Only few points need to be highlighted:
1. Transformer secondary side, instantaneous setting 50P not really required just like we keep "I" setting disabled of LV LSIG release. Trafo primary side will provide the backup protection in case of short circuit.
2. For 51P in trafo secondary side, pickup value better to be considered trafo secondary FLC. Because of any future loads may come into the picture.
3. 51N not required to activate if 51G is operational.
Hope, we are all aligned..

[@SmartEducare]

Also it's required to check that the transformer primary side 50P pickup value should be below the connected switchboard minimum 3 phase short circuit current.