Explain the process of Designing a Final circuit

Start with known factors and work from there.

You know the total length of the circuit and what it is serving.

nicebutdim said:

Start with known factors and work from there.

You know the total length of the circuit and what it is serving.

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I am new to the field and I am still studying electrician. I dont know what to do and how to proceed.

I'm a first year apprentice, but this is fairly straightforward. I haven't provided an answer for two reasons:

1. I'm not familiar with regulations in Cyrprus.
2. Doing so wouldn't assist with your learning, so I'm trying to point you in the right direction.

Ask yourself what additional factors are involved in the design of this simple circuit? Are you povided with details of luminaire or is this something you have to decide on? You need to specify cable size and type of breaker - both of which can be determined from available information.

nicebutdim said:

I'm a first year apprentice, but this is fairly straightforward. I haven't provided an answer for two reasons:

1. I'm not familiar with regulations in Cyrprus.
2. Doing so wouldn't assist with your learning, so I'm trying to point you in the right direction.

Ask yourself what additional factors are involved in the design of this simple circuit? Are you povided with details of luminaire or is this something you have to decide on? You need to specify cable size and type of breaker - both of which can be determined from available information.

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We are learning from the BS7671
I have to write about the overload calculations, voltage drop, shock protection and thermal constrains?

Is this part of an apprenticeship, study for basic electrical qualification or design course?

nicebutdim said:

Is this part of an apprenticeship, study for basic electrical qualification or design course?

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For us, yes!
Can you please provide me with the answer?

You've answered part of it by listing cosiderations which must be taken into account.

You know circuit length and number of points served. Do you know power consumption of luminaires? Have you been given information about containment ,or is this something you would have to determine? I ask as this impact upon thermal constraints.

Overcurrent protection will be determined from total load, cable type, inrush current etc.

So far you have made no attempt at answering the question and have simply provided some basic information in the hope that it will be answered for you. I'll attempt to help, and am certain others will step in, if you want help, but no one is going to provide all the answers as that won't help you to learn.

It looks like it's just for the lighting?
You might need to assess the current., and all the other things that @nicebutdim helpfully mentioned.
Can't give you the answer, as there will be many approaches here.
Put down your assumptions, then spec the design to those.
If you get bits wrong, you will have learned something useful.

read this 5 times and try again

john dem said:

Can you please provide me with the answer?

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No.

You need to provide with your answer and folks on here will try and help you improve it until it is acceptably good. Otherwise you have not demonstrated any learning!

Start with the spec of the lights, work out the total power (or more correctly, current) is needed. Assuming it's LED then it'll be fairly low.
You can now have a stab at picking a cable size - though in practice the answer will almost certainly be "the minimum allowed by the regs" (it's in there, you find it ).
You can then work out volt drop and check that it's within limits (again, it's in the book) - if not, then you'd have to up the cable size, find another way of improving things, or decide whether the excess is an acceptable deviation from the standard.
Pick an upstream overcurrent protection type and rating, work out if it's compatible with the fault impedance. Consider the characteristics of the loads when selecting the OCP - for example, if you had a big space with loads of flouro tubes, there's scope for significant inrush current. Most types of light have some sort of inrush - some more than others.
You'll also have to consider the CCC of the cable taking into account the installation method.

If necessary, you may need to iterate. E.g., if you have a larger than typical Ze or Zs, or a long circuit length, you might find that the overall fault impedance isn't acceptable for the OCP you've chosen. So then you need to consider what options there are to fix that.

So there's the steps you should already know - off you go, find the information, and do the calcs. Voila, circuit designed.