The three-line drawing is probably the most important drawing that is necessary for relay testing. Watch this video as I go through the three-line drawing and compare it to the single-line drawing. More importantly, learn how I connect my test-set to the relay to find the biggest mistakes that are often overlooked.
Download the Three-Line Drawing to follow along
Click “Mark Complete” below after watching the video so you can keep track of your progress.
This may seem obvious, but how come the synchronizing voltage is under the DC schematic/drawing? Shouldn’t it just be included along with the three lines? Where could I get more information on how sync check works?
Thanks for your question. I ran out of test switches, so I decided to use two of the DC switches and put them on the DC drawing to keep all of the test switches together. This way you won’t have to hunt for the missing switches. Most site drawings would likely have kept those two switches on the AC drawing with (hopefully) a note on the DC drawing telling you where they are.
The best reference I’ve read for synchronizing is the Basler BE1-25 instruction bulletin. I’ll put it on the list of future topics because I don;t think I’ve written anything on it to date.
The sign of voltage ACB was counterclockwise. The label of voltage ABC was clockwise. Is there any matter? It was contradictory!!
I’m not sure I understand the question. Rotation is sometimes defined as clockwise and counter-clockwise, but they are TERRIBLE labels because they don’t don’t have any meaning when we are talking about the power system. I believe those terms were originally used to describe the rotation of a generator or motor. The power system can rotate in either direction depending on connections as we describe in our Online Course 1-1: The Three-Phase Power System
All phasors rotate counter-clockwise, so I use the term ABC or ACB to describe the rotation because they are unambiguous.
Why is there no listed location for the return of the ct circuits.
Thanks for reaching out. I’m not sure what you are referring to. My code for the connections is *9 – 7, meaning polarity on terminal 9 and return on terminal 7. Is that what you are referring to?
This is a question regarding the method of your documentation. From looking at this 3-line drawing, there appears to be another PT entering the relay from a different test switch block (T1000_TS-DC1) connecting to the relay’s VS sync input. Because there wasn’t anything on the 1-line indicating VS to the relay, and assuming the relay operation notes do not mention VS as part of the control or protection, how do you handle discrepancies like this? Do you make a new row for VS on your comparison document, and show it as indicated on the 3-line with no corresponding indications for any of the other drawings? I’m mostly just curious if this is something you would typically track on paper and, if so, how you track these things.
Good eye! Thanks for the question.
If I was not on-site and noticed the Vs input on the print as it is shown. I would add it as a question for the design engineer that I would send along with all the other things I might have noticed.
If I was on-site. I would trace the wiring to the terminal block and make sure that the wiring truly ends at the panel. Then I would physically check that there was no PT on the load side of the circuit breaker. If there was no wiring and there was no PT on the load side of the circuit breaker, then everything seems to be OK and I wouldn’t mention it. If field wiring did exist or a PT was connected to the load side of the circuit breaker; I would ask the design engineer about it and there would be a note on my test sheet and report with the clarification to help future personnel who spot the same discrepancy.
Great explanation. I felt like the Beckwith M-0388/0389 Manual to have a really clear explanation of Synch Check if you are looking for other references.
Hi Chris, do you have any book or your notes recommend for perform the E2E test calculations. I like to do create the test plan by calculating the secondary voltage and current values. thank you.
You could use the chapter on 21-distance protection on the Relay Testing Handbook. However, manual calculations won’t find any non-obvious problems with the scheme and defeats the entire point of end-to-end testing.
Doble, Omicron, and very old Manta software have basic system modelling software that would provide slightly better numbers.