Zach Stone P.E.
Well-known member
This is a short clip taken from last semester's fall 2021 live class for the Power PE Exam on protection.
In this video, I'll show you why the relay current input from delta-connected current transformers is increased by a factor of the square root of three (√3):
Another way to think about this, is if a protection relay (like the ANSI #50 or ANSI #51 relay) is fed from delta-connected current transformers instead of wye connected current transformers, the current fed to the relay will be larger by 1.73.
If you're not careful, this can affect pick up settings and cause the relay to operate for non fault events since the relay input current will be artificially larger.
The most common application of delta connected current transformers is for differential protection of delta wye or wye delta power transformers.
Want to learn more about protection for the new CBT format of the NCEES® Power PE Exam?
Our first class of the Spring 2022 live class semester for the Power PE Exam starts tonight! Tuesday, January 25th, 2022.
We will be meeting online, remotely, for 21 total live classes spread across 11 weeks.
The Spring 2022 Live Class Semester starting tonight is scheduled for January 2022 through April 2022.
Join me, and the rest of our electrical engineering students taking the Power PE exam LIVE in real time and learn everything you need to pass the power PE exam in real time. Ask your questions directly to me in our live chat and interact with the rest of the student class.
If you're planning on taking the PE exam this year and would like to learn more about our live class, please visit www.electricalpereview.com.
In this video, I'll show you why the relay current input from delta-connected current transformers is increased by a factor of the square root of three (√3):
Another way to think about this, is if a protection relay (like the ANSI #50 or ANSI #51 relay) is fed from delta-connected current transformers instead of wye connected current transformers, the current fed to the relay will be larger by 1.73.
If you're not careful, this can affect pick up settings and cause the relay to operate for non fault events since the relay input current will be artificially larger.
The most common application of delta connected current transformers is for differential protection of delta wye or wye delta power transformers.
Want to learn more about protection for the new CBT format of the NCEES® Power PE Exam?
Our first class of the Spring 2022 live class semester for the Power PE Exam starts tonight! Tuesday, January 25th, 2022.
We will be meeting online, remotely, for 21 total live classes spread across 11 weeks.
The Spring 2022 Live Class Semester starting tonight is scheduled for January 2022 through April 2022.
Join me, and the rest of our electrical engineering students taking the Power PE exam LIVE in real time and learn everything you need to pass the power PE exam in real time. Ask your questions directly to me in our live chat and interact with the rest of the student class.
If you're planning on taking the PE exam this year and would like to learn more about our live class, please visit www.electricalpereview.com.
