Welcome to the first topic in our journey to test a digital relay!
The single-line drawing is the perfect place to start our relay testing procedure because it provides an overview of the entire system. Watch this video as I work through the first step in our relay testing flowchart and record the important information on the comparison chart. If you want to follow along, you can download both documents below.
Obtain and Review the Relay AC Single-Line Drawings – Comparison Chart
Obtain and Review the Relay AC Single-Line Drawings -Single-Line Drawing
You should be able to see the video below. Use the controls on the bottom of the video to:
- Play
- Fast forward and rewind with the scrubber bar
- Adjust the volume
- Make the video full-screen
Click “Mark Complete” below after watching the video so you can keep track of your progress.
Hello,
I just want to ask about phase rotation, how do you know it is ABC from the symbol?
A means 0
B means 120
C means -120
is it right?
ABC rotation with your angles of 0, 120, -120 would be ACB. If you imagine a fixed point at +10 degrees and the phasors rotating counter-clockwise; A would cross first, then C would cross, then B would cross. I would recommend you take the other two online training classes which cover these principles in detail.
Did this video get cut short?
It did. This was the first video recorded and it went directly to the three-line drawing. Then I learned that you’re supposed to keep videos short for the modern age and had to do some weird splices. It gets better, I promise.
Sorry for the confusion.
How did you know the CT polarity is facing the breaker ? I know it is a tradition but here P1 and P2 are not marked ?
Thanks for the question.
The dot indicates p1 and is closer to the breaker.
Also, the relay is connected is connected to the breaker side.
In the end, the polarity mark doesn’t matter after the CT is tested. It’s more important that the relay is connected to the breaker side. Current flow would be the same regardless of where the polarity mark is located as we’ll show in a later video.
HI there. I am pretty unfamiliar with the standards of the electrical diagrams that we will be dealing with here and i was wondering if you had a downloadable list, or would know where to find a list of the various symbols/designations found in the diagrams being discussed. For example the IN101. Any information is appreciated. Thank you.
We plan on creating some print reading courses far into the future, but nothing in the near future. I believe Avo Training has a print reading class. Sorry I couldn’t help more.
It’s no problem at all. Thanks for the input!
Hey, I think 3 pt’s can be wired in delta or wye
They can be connected wye or delta, but the delta connections are applied with two PTs and are officially “open-delta. It’s sometimes hard to tell from the single line drawing. Three PTs should NEVER be connected in Delta because you would lose 1/2 of your measured signals (P-N) and just wasted all the money you spent on three PTs.