002. Idea: One Line Diagrams and Where to Start
All right. Welcome to this episode of EECO Asks Why. Today we are digging into a fun topic. One that’s generated a lot of buzz for us internally and externally as well around how to read a one line, or you may want to call it a single line. That’s part of the fun of the topic.
So today we’re speaking with the author of the article, Mr. Jonathan Fuller, who is our Automation and Power Product Manager in South Carolina. Very excited to have Jonathan with us today. Jonathan, thank you so much for taking the time. So let’s just start off with the burning question. The one that’s got everybody fired up. Is it a one line or a single line?
Hey, thanks Chris. Happy to be here. So it can be both really. I would go by one line, but I have heard people call it a single line before. Most everybody I know in the engineering community, they’re going to refer to it as the one line, but either way, one line single line, they’re both correct. As long as the people that you’re talking with, understanding that you are actually talking about either a one line or a sigle line.
I got you. I got you. I know there’s some of our listeners that they may want to take this discussion to the parking lot if it gets too serious, but in all seriousness, let’s start at the very beginning.
There are some people who may not even know what we’re referring to when we say one line or single line. So can you give a basic general overview of what we’re speaking of here?
Yeah, sure. So a one-line is going to be a graphical representation. So something on paper, or, you know, on your computer screen, but it’s going to be a graphical representation of the physical power layout that you have in your facility or it could even be your home, for example. But it’s gonna have a line on there, that’s going to represent the power. And it’s going to have other symbols and things on there that are going to represent things like your circuit breakers or fuses or relays and protective devices. But it’s basically a graphical layout that kind of represents the physical layout that could be there in front of you.
Very good description. So let’s pretend that this is the first time someone hands me a one line and it’s in my hands. Where do I start?
So, if you’re in front of a certain piece of equipment that you need to work on and that’s why they handed you this one line, I would start and identify from the name plate on that piece of equipment. the name of it and what you’re looking at. And then you can find that on your one line diagram that you have in front of you. But you know, typically you also could start in the top of the one line and work your way down. So the top of that one line is gonna generally have your income and power, whether it be from utility source or a generator or things like that.
And it’s going to work down the one line of the power architecture in your plant. So you’re going to have like your main piece of switch gears, switch board, and you’re going to branch out from there and go to the different areas within your facility that have the gear in it. But you know, everything’s going to be labeled on that one line with, or it should be labeled on that one online with the names of the piece of equipment.
So you can also do it that way. If you know, you’re standing in front of MSB-1, you can look on that one line and find it there. And then you’ll be able to kinda trace upstream and find what’s protecting, or providing power to that piece of gear. So that way you can safely open that breaker and do the lockout tagout procedure.
Okay. I got you. So when you’re handed that one line, though, for the first time, is there a legend or something on it to give you an idea of what the different symbols and things like that mean? Cause I know sometimes you get them. They’re so complex. They’re so convoluted. It almost looks like you’re walking into the pyramids and you got the symbols all over the wall. Is there something to give us a, okay this means this when I’m looking at it.
Yeah, absolutely. So any good one line should have a legend on it similar to a map legend that you might see on the map of the United States or your home state or anything like that. But it should be a box in one of the corners and it’s going to have, It’s going to, it should say, one line legend and it’s going to have symbols on there. The different squiggly lines or hieroglyphics, if you will. And it’ll have that graphical representation, but they don’t also have the word next to it. As this is a breaker. This is a meter. This is a relay. So that you can quickly identify all of those lines and symbols on your one line.
Very good. What about some, the symbols, when you think about, and you’re looking at it and you’re reading the legends, what are some commonly misinterpreted symbols that, users typically could make the mistake with when they’re trying to interpret the one line?
Yeah, so some of the common mistakes that I’ve made and I’ve seen are some of the different kinds of breakers, you know, versus a bolt on or a draw out breakers. Those are going to be different as well as, you know, a lot of relays and motors and things like that tend to be a circle with a letter in it. So if you don’t pay close attention to what that letter is, you might mistake a motor for a relay and vice versa.
Okay. So is there a bank of standards for this, or is it dependent on the particular one line that you’re evaluating at that time?
So there’s a couple of different standards. There’s no one universal standard. IEEE has a standard as well as NEMA and IEC. They all have their own kind of standards and symbols and they vary from standard to standard. So there’s no general universal standard, but they’re all pretty close.
Okay. Very good. Yeah. I noticed just in history for me, a lot of times you see some pretty standard symbols, a circle, meaning one of them. And that can mean many different things. Have you run across that before as well?
Yeah, I have. it’s, it’s like you said, most everything. you’re going to have a circle with a, with an R in it for a relay or a circle with an M in it for a motor. You’re gonna have a line with a semi-circle on it for a breaker in most all cases, whether it’s NEMA or IEC.
How about a draw out type breaker? How was that typically represented?
Yeah, one of the first things that I ran into and got confused and early in my career was a bolt-on breaker versus a draw out. And so they both have that same breaker symbol, but then the draw has some arrows on it at the top and bottom that point away from the breaker and I couldn’t for the life of me, figure out what that meant. Then I was able to understand that is a symbol for a drought breaker, like what you would have in a piece of switch gear.
Ah, very good. Very good. So hopefully there’s some good pointers there for our listeners on all symbols and understanding common mistakes. We know we’re trying to help everyone elevate their education when it comes to one lines.
So let’s assume that we have a one line now in front of us. How do I know, Jonathan, that the information that I’m looking at is accurate?
There’s no real way to know that. Chances are 99% of the time, you’re going to get that one line when you get that new piece of equipment, or you building your plant from scratch. And then over time whether it be the electricians or the maintenance people or whomever, they’re going to make changes to that equipment, as time goes on. And they’re not going to go back and update their one line either because they don’t know that there is a one-line, or they don’t know how, or they just don’t think about doing something like that.
So you could have an 800 amp breaker that’s shown on your one line that’s now a 1200 amp breaker. You could have a breaker on your one line that’s not there anymore. You’ve taken it out of service or vice versa. You could have put a breaker into service thats’ not on your one line. The really the only way to positively tell that could be to have your one line physically in front of you and then be standing in front of the piece of equipment. And you’re going to have to do a compare between the two. You’re going to have to look at that piece of equipment and say, okay, here’s, here’s my 800 amp breaker. Yep. Here it is on my one line. So you’re going to have to do a physical inspection.
Right to really get actually you got to get out in front of your equipment. So let’s go to the other extreme, okay? Let’s imagine that we’re a user or owner of equipment and we don’t have a one line and we really want to get one. What does that process look like to get us started?
So typically I would recommend, if you’ve got different areas in the plant and you’re responsible for a certain area, that’s going to be the area that you’re most comfortable with. So, you can start with a piece of paper or, even a napkin and a pen and just start drawing it out.
I would, if I had a panel board in front of me, I would sit there and draw a box and then just draw symbols in there for every single breaker that’s in it. Then you’re going to go upstream and downstream until you just can’t go anymore. And then you can get with your colleagues and other areas and combine all those into one large one line for the whole facility.
But if you’re responsible for doing the whole one line for your facility by yourself, I think it would be easier for you to start where power comes in. Where does that pad mount transformer outside? Or where does that generator outside? And trace it downstream from there. And find that piece of large, distribution equipment that provides different power to throughout your facility and just trace it down that way until you can’t go any lower. Once you get to your motors or once you get to your drives and different one lines go to different depths.
Some I’ve seen only go down to the panel boards, the lighting panel board. Only go down to the mechanical panel boards that feed things. And I’ve seen others that go all the way down to the motor, including the drives and starters. So it really just depends on how in depth you need to make it for your own application.
So does that process typically start with a pen and a pad and taking a walk around the facility, just doing a basic drawing with what you see. Is that typically what you would recommend?
Everybody does things differently. That’s the way I would do it. And that I would recommend is that pen and paper and kind of go and draw it out and you can make changes right there as you need to, before you actually make it permanent.
There’s also a software out there, a CAD software and things like that you can use to draw this in. But if it were me, I would definitely do, handwrite a copy of it and then bring that up to my computer and sit down with all the information at once and draw out my one line in my software and then save it. And then that way in the future, when you make changes to that one line, you can open up that software and make changes there and then print a new copy of it.
Good Point. And are there any software platforms that you’ve worked with in the past that you enjoy, or do you find have good maybe pre done drawings and things like that you would refer to our listeners?
So then the one that I use almost all the time was just AutoCAD with some built-in symbols in it. That’s how I did most, all of my one lines. I know there’s some tools out there that people use for arc flash studies and things like that, like SKM and tools like that. But I’m most comfortable and most familiar just with AutoCAD.
Very good. Very good. We’re just trying to help. So EECO Asks Why, we really want to dig into the why behind things to give a deeper meaning and purpose. So let’s just get right to it. Why should an end user care if they have a oneline or not?
I mean, that’s the easiest and safest way to ensure if I need to go work on this piece of equipment, I can turn it off right there at the source. But then if I’ve got my one line, I can trace things upstream and make sure that I’m opening that breaker, pulling out that fuse upstream, and then doing the lockout tagout procedure so that somebody doesn’t come along and reclose that breaker, turned the device back on and that can cause some serious consequences downstream on the piece of equipment I’m working on. But then also I can also see what’s downstream and what I might affect downstream in the plant. So I make sure I don’t turn something off that could cause issues in a process.
Absolutely. So it sounds a couple fold there from an operational standpoint. It gives you a good ability to understand what you potentially could be impacting, from the decisions you’re making. And then also from a safety standpoint, if I’m the technician that’s responsible for working on equipment, or maybe you’re bringing in some groups that are doing preventative maintenance on breakers or motors, or what have you, you definitely want to make sure that you have everything downstream cut off and a wireline sounds like a great place to verify all that information.
Very good. So let’s in closing here, we really try to on EECO Asks Why to help our users and our listeners in their development and their personal careers and how they’re growing as individuals. So pretend that’s your that new engineer right out of school or you’re that ENI technician. You’re that electrician working in a plant right now that the heroes of industry that we love and the whole point of while we’re doing this and you want to give us some advice and to help them increase their experience. And to be comfortable with a one line that’s put in front of them, where could they go? What should they do? What’s out there that they could invest their time to just increase their skill set in this area?
Yeah. I mean, when I was a new engineer, just starting out, there’s obviously now with the age of the internet, you can find all sorts of information out there. Some great information and learning guides. But when I was an engineer first starting out, you know, I had a mentor, his name was Robert. And so we took a piece of gear and a one-line that we knew was accurate and correct for that piece of gear. And I just asked him, I said, Robert, can you spend a little bit of time with me? So he and I sat down and went through it and went over it and he helped show me what some of the stuff was.
I didn’t learn everything from him right then and there, I picked up things as I continued on in my career. But, having a mentor is huge. If you’re at a facility and it’s all on you and there really isn’t a mentor, then that’s why we’re here at EECO. That’s one of the things we can help with as well as, the internet nowadays. So you can find a lot of good resources out there.
Good point. I loved it. I love the fact that you brought up the mentor. That’s so important in our listeners out there, they’re across, a big demographic. So maybe you’re the individual that’s looking for a mentor or maybe you’re the person that could be a great mentor for that young up in comer. So we want to encourage both of you, both sets to be there and to reach out. There’s just a ton of knowledge out there and transferring it down is important.
And Jonathan, thank you so much for your time and your insight. You wrote a great article. It’s caused a lot of buzz. Looking forward to the next, article that comes out from you. So just a great job on that again. And thank you for your time today.
Yeah, thanks for having me. I enjoyed it.