Distance Protection of Transmission Lines | Example Using the SEL-421 Protection Relay

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In this video we discuss how to protect a transmission line implementing a distance protection scheme using the SEL-421 protection relay as an example. We go over how to calculate the Zone 1 (underreaching) and Zone 2 (overreaching) settings to develop a robust protection scheme that protects the entire transmission line.
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00:00 Intro
00:30 Mho element plotter spreadsheet
02:35 Zone 1
04:03 Zone 2
05:10 Example transmission line settings
12:30 Programming the SEL-421 Relay

[@romeroengineering]

Learn more with our online courses here: www.romeroengineering.co/courses

[@fioricoziuc1792]

You teach very well and in a clear way! Thank you! I wish you were my professor !

[@anandarajkarthikeyan3917]

I doubt that anyone can explain such complicated topic much easier than this. Thanks !

[@romeroengineering]

Glad it was helpful Anandaraj!

[@jeffwebb8208]

This was explained very well. The spreadsheet is very useful. Thank you!

[@romeroengineering]

Glad it was helpful!

[@TrentMRobertson]

You're awesome! Thanks for the spreadsheet and detailed, yet concise explanation!

[@romeroengineering]

Thanks Trent, glad you're finding the videos helpful.

[@sonaimuthu2060]

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[@surendrakverma555]

Excellent explanation Sir. Thanks 👍

[@romelbacay8325]

Thank you sir for this very informative and simple explanation..👍👍👍

[@romeroengineering]

Thanks!

[@pinankpatel7853]

This was great explanation!

[@romeroengineering]

Thanks!

[@Eng-MagnoSoares]

Great content Romero! Thank you!

[@romeroengineering]

Thanks Magno!

[@sergiopena1602]

Great presentation. Thank you

[@romeroengineering]

Thanks Sergio!

[@Alvin-og1li]

Thanks mate, keep it coming

[@romeroengineering]

Thanks, will do!

[@awareofdeath]

Thank you so much

[@martingreco7473]

Fantastic, Thanks

[@romeroengineering]

Thanks Martin!

[@user-ve5co6bk1g]

Thanks!

[@romeroengineering]

No problem!

[@romelbacay8325]

Sir, what are your assumptions about the 30 cycles of Zone 2? I've seen some Zone 2 settings as 75 cycles. Thank you.

[@romeroengineering]

Hi Romel, this depends on your coordination, there isn't a right or wrong answer here, it just depends on what you are coordinating with. A 30-cycle delay on a Zone 2 element is typical though, based on the fact that this would usually just need to coordinate with instantaneous protection at the remote end. So, 30 cycles (0.5 seconds) allows for enough time for instantaneous elements to operate, trip the breaker, and perform a breaker failure function if needed. Then, if none of this happens, the remote ends back up with a Zone 2 delay at 30 cycles. Again, it all depends on what you are coordinating with.