PS98 Sequence Networks of Earthing transformer

Lectures on Power Systems By Dr. Tirupathiraju Kanumuri, Assistant Professor, NIT Delhi

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#SequenceNetworksofEarthingtransformer
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#zeroSequenceimpedanceofEarthingtransformer

[sunjang]

Thank you for providing comprehensive lecture

[paulthompson]

Good video. We have an 11kV earthing transformer with an earthed star connected primary winding and a secondary winding with a broken delta connection with a resistor that limits the primary winding current to 60A. How do you determine/model the zero sequence impedance of a broken delta connected transformer. thanks

[kmnkr]

Hi,
Thank you for your nice lectures ...
To enhance this lecture technically more correct, we can go by taking industrial powersystem as an example (where it ll be YNd1/11 - step down trafo ... and Delta side will be grounded via grounding trafo... )
and to add one more point, Generating stations usually have YNd1/11 (step up trafos)
:)

[MANOJKUMAR-mbuw]

Sir what happens if there is no path for circulating currents.

[sanjibkumardas]

Thanks a lot sir for the sequence diagram for earthing transformer..these kind of informative videos helps a lot in our work field....sir i have 1 more request..can u provide sequence diagram of autostransformer having delta as tertiary stabilising winding(YNyn0d11 as well as Yy0d11)?

[jyotishasikhya]

Sir can u provide a sequence network of 3 phase transformer consists of HV star, intermediate volatage star and lv voltage delta for example 220/132/33 KV transformer

[mallikarjunayh]

Hi Sir, its a very informative lecture. I have a question, can we convert IT Earthing network to TN using Zigzag transformer at LV side (415V), but we cant use Earthing resistor in neutral of Zigzag transformer. Is it possible?

[gonencakcam]

Hi, thanks for these kind of videos.

1- How can we calculate zero sequence impedance of zig-zag transformer ? As you mentioned, during phase to ground fault, only impedance that effect to our ground fault short circuit current is zero sequence of zig-zag transformer. Also other component will be effect on the path of that faulty line.

System Voltage (L-L)=10, 5Kv
Irated/phase=100A
Short Circuit current in neutral=1000A, 10sec
Ohm/per phase = 18, 2 ohm/phase

2- On ETAP program, below informations are needed. But I could not understand these value is ohm or pu values of zero sequence. Even I am not sure these values zero or not ? If I put ohm/per phase values, ground fault is going to limit from 15kA to 2kA. I do not know how it calculate ? Do you have any advice ?

Impedance;
Ohm= --> Etap Help page said that ''Enter grounding resistor or reactor in ohms''
X/R= --> Etap Help page said that ''Enter the grounding transformer X/R ratio''