How to determine the Line and Phase current and power of a three phase installation?

[AReynolds]

I am attempting to produce a design for a theoretical installation with a three phase incoming supply (presumably Star/Wye with PME to star point), and am having some trouble understanding and determining the current and power of each phase, and the whole installation at the incoming supply.
For example, if L1 has a single phase load of 80A connected to it, L2 has a single phase load of 30A connected to it, L3 has a 40A load connected to it, then is it possible to say that IL1 = 80A, IL2 = 30A and IL3 = 40A, with the current drawn by the whole installation being L1+L2+L3 = 80 + 30 + 40 = 150A?
What would happen if, in addition to the single loads connected to each phase above, a three phase load was connected to L1, L2, L3 and N?
For example, if the three phase load was 16A, does that mean that each line draws 16A, so that you would get L1 = 80 + 16 = 96A? Or is it the case that each line draws about 33% of the stated three phase current, so that L1 = 80 + ((16/100)*33) = 80 + 5.28 = 85.28A?

Am I on the right track with my calculations, or am I mistaken in my approach to these three phase calculations?

 

[telectrix]

in star configuration, the line current and the phase current are identical. if the load is unbalanced then there will be a neutral current, determined by : In = sqrt(Ia^2 + Ib^2 + Ic^2 -Ia*Ib - Ia*Ic -Ib*Ic)

 

[Toneyz]

in star configuration, the line current and the phase current are identical. if the load is unbalanced then there will be a neutral current, determined by : In = sqrt(Ia^2 + Ib^2 + Ic^2 -Ia*Ib - Ia*Ic -Ib*Ic)

I think you've knocked him dead with that one Tel buy the way how did you get on with that lamp post problem ?

 

[telectrix]

I think you've knocked him dead with that one Tel buy the way how did you get on with that lamp post problem ?

got a good quote from a supplier. passed it on to client ( he's buying so he can get the VAT back ). told him he's got to pull his finger out as the access ( JCB with a bucket ) might be gone next week, this was monday and I'm waiting for the ****head to get back to me.

 

[AReynolds]

in star configuration, the line current and the phase current are identical. if the load is unbalanced then there will be a neutral current, determined by : In = sqrt(Ia^2 + Ib^2 + Ic^2 -Ia*Ib - Ia*Ic -Ib*Ic)

So, referring back to my example, am I correct in saying that L1 coming into the installation will be drawing 80A, L2 will be drawing 30A and L3 will be drawing 40A? If an additional three phase load is connected to L1, L2, L3 and N within the installation- will that increase the current load on each phase by about 33% of said load's current demand? As for the Neutral, thanks for the equation, however I was under the impression that if the line conductors are appropriately sized, then matching that with the Neutral conductor size will ensure that the unbalanced current can be carried by the Neutral.
Basically, I am asking how one goes about determining what the power and current draw of the whole installation is, taking into account the single phase loads on each phase, and the three phase load connected across all of the phases, so I can provide appropriate over-current protection at the three phase cut out, and design the single phase distribution circuits running off each line.

 

[telectrix]

start by determining the 3 phase current/s ( per phase ) of all 3 phase equipment. then add each single phase in turn, adding it's current to the already established line currents as you add loads on each phase, keeping them as balanced as possible. then you will have your total line currents.