One Line Diagram Design

Hi Simon,

GA.

It's been a two decades or so since I have designed generation and distribution systems. These were for offshore rotary drilling rigs. 4000KW of generators, a half-dozen 200hp traction motors, and a large MCC. I tried to zoom in on your one-line but couldn't read the details. Do you also perform a short-circuit study and do you still do it by hand or are you using a program? I remember that it was one of the most difficult aspects (and rewarding) of a system design.

Nice work, Simon.

Yes, After design all these network and calculated all the connected load, we also perform a short-circuit study by hand and calculate the faults level of the network. Then we will size the upstreams VCB sizes and the faults level.

Most of us use programs such as SKM Power Tools or Etap. It's somewhat simple if you know what your trying to accomplish and have an understanding of system applications. I live in the vicinity of Houston myself, go to here from a "home boy"

If you have more questions, don't hesitate to email me at jim@seaboardcontrols.com. I'll be glad to help you in anyway I can.

Simon, I've been drawing, designing for 45 years. But even after I was introduced to Autocad some years ago, I still don't understand why electrical engineers draw with layers! Could you please explain that to me as maybe I've missed something.

Thanks,

hi jraubsr,

if I may come ahead answering your question, basically drawing with layers is if you had to draw many different utilities on a single floor plan or a single main frame. with that you can specify each name of them, visibility, color, or layers' inclusion in the printing mode, hide, freeze etc in one go.

I don't have idea on what kind of drawing you're used to do but as it has not many different kind of components to draw in an one line diagram so layers seem not be necessary ,different from if you draw the lightings on the same floor plan with the power outlets, Air condition, telephone , sound system etc. layers will be so much important.

cheers,

As a preface to commenting on your thread, let me first say that I regularly use one - line diagrams in the preparation of Contract Documents for Building Plumbing Systems. The one - line diagrams I prepare are complementary to scaled floor plans and do not stand on their own. The scaled floor plans allow Plan Reviewers to assess Code compliance, Insurance Underwriters to assess risk and Contractors to estimate budgets, plan work and facilitate coordination between trades.

Now, with regard to the one line diagram, it is easy to DRAW; designing the system is another matter. Presuming that you are designing the electrical interface to the pumps and lighting only, then your experience as an electrical engineering professional will determine the ease with which you will design.

Some concepts for you to consider as you embark on your design follow.

A floor plan would be useful to coordinate the relative location of pipes conveying fluids, air and gases and the location of electric panels, disconnects and the other electrical devices where minimum separation distances are either mandated by Codes, or good engineering practice. For example existing or proposed pipes running above panels; panels intended for installation where there might be an obstruction to the location such as a window.

Make sure you have adequate schedules and details. Label all your components with unambiguous references to your schedules and details. I have found it useful to keep in mind, that I design for the code officials, the insurers, and the owners budget. But of equal importance, I design in a way that the contractor will not have to be calling me because my drawings are not clear. This is a major issue. You will not be able to give adequate focus to your next project, if you have to stop and answer questions about past projects.

Good luck!

The design is reflected from one-line diagrams! Yes, they are easy to draw. What they should show is circuit breaker sizes, cable sizes (with voltage drop taken into account), type of motor starter, controls, etc. There is your start. From that point we enter into short circuit analysis and coordination studies. Different field but necessary for many reasons.

one line diagram supposes to show the whole system from a panel, at a glace of an one line diagram engineer will immediately know the incoming line, size of the cable connected , kind of protection devices and it's capacity ,and it's outgoing lines served to what and where ,kind of loads complete with each devices specification and cable dimension etc.

things you need to keep in mind is that , there must be one incoming line or sometimes lines usually from power source then several outgoings to feed them power..so in your case ,I would say it is one incoming line and 5 outgoings (4pumps + 1 transformer) with no spare.

cheers