Electricity supply - Maximum Capacity of Connection 18 kVA

ElecExplorer · May 29, 2023

Hello everyone!

I have a question regarding the electricity supply and the maximum demand.

One energy utility supplies an 18 kVA maximum capacity of electricity for a three-phase connection, and I'm wondering what this means in terms of the appliances and equipment I can safely use without overloading the system.

Could someone please clarify what the maximum capacity of an 18 kVA connection means to normal residentials?

I'm particularly interested in understanding how many appliances I can run simultaneously and what the power limitations are. Any insights or advice would be greatly appreciated.

Is it safe to sign this agreement with an 18 kVA supply?
What is the kVA capacity for a basic electricity connection in Australia?

Thank you in advance!

Julie. · May 29, 2023

ElecExplorer said:
Hello everyone!

I have a question regarding the electricity supply and the maximum demand.

One energy utility supplies an 18 kVA maximum capacity of electricity for a three-phase connection, and I'm wondering what this means in terms of the appliances and equipment I can safely use without overloading the system.

Could someone please clarify what the maximum capacity of an 18 kVA connection means to normal residentials?

I'm particularly interested in understanding how many appliances I can run simultaneously and what the power limitations are. Any insights or advice would be greatly appreciated.

Is it safe to sign this agreement with an 18 kVA supply?
What is the kVA capacity for a basic electricity connection in Australia?

Thank you in advance!

Are you sure about those figures?

If it's a three phase supply as stated, then that's around 26A per phase

If it's a single phase supply, which is more normal, that would be circ 80A

If it is three phase, is it 18kVA per phase (so 80A each phase)

Do you have a photo of your connection/meter - or is this enquiry pre-connection?

"Normal" as I understand is 230V single phase 80A (18kVA)

MDJ · May 29, 2023

Julie. said:
Are you sure about those figures?

If it's a three phase supply as stated, then that's around 26A per phase

If it's a single phase supply, which is more normal, that would be circ 80A

If it is three phase, is it 18kVA per phase (so 80A each phase)

Do you have a photo of your connection/meter - or is this enquiry pre-connection?

"Normal" as I understand is 230V single phase 80A (18kVA)

18KVA would be the total for three phases not per phase as I see it Julie.

Julie. · May 29, 2023

MDJ said:
18KVA would be the total for three phases not per phase as I see it Julie.

Which makes it only circ 26A per phase, which appears somewhat low, hence why I think the figures aren't correct.

MDJ · May 29, 2023

Julie. said:
Which makes it only circ 26A per phase, which appears somewhat low, hence why I think the figures aren't correct.

yup understand what your saying, just never heard the figure mentioned per phase before, as you say, figures probably wrong

ElecExplorer · May 29, 2023

MDJ said:
18KVA would be the total for three phases not per phase as I see it Julie.

Hi Julie, yes, I am 100% sure it's three phases, so why total power is less than 18 kVA (see the attachment)?

My requested maximum demand is about 80A per phase for three phases of electricity connection. My drawing power is about 80A per phase.

Is it safe to get a total 17.21 kVA power supply?
I attached the screenshot. Many thanks.

Julie. · May 29, 2023

ElecExplorer said:
Hi Julie, yes, I am 100% sure it's three phases, so why total power is less than 18 kVA (see the attachment)?

My requested maximum demand is about 80A per phase for three phases of electricity connection. My drawing power is about 80A per phase.

Is it safe to get a total 17.21 kVA power supply?
I attached the screenshot. Many thanks.

Do you have an existing supply?

If so could you post a photo?

17.21 kVA is 25A per phase on a three phase supply if the 17.21 kVA is the total 3 phase power.

17.21 kVA per phase would be circ 75A per phase.

I suspect the figures are wrong, are they quoting for a single phase supply, or have they just mixed up the figures between single and three phase?

You would need to confirm with them.

Do you have the whole of the specification (with supplier and site/customer details removed) - the extract doesn't contain any real information.

ElecExplorer · May 29, 2023

Yes, 17.21 kVA is the total 3 phase power.

“ 17.21 kVA per phase would be circ 75A per phase.”
How did you calculate this? If per phase, then using line to neutral voltage which is 230V right?

There is an offer document binding with this agreement but I am asking for it.

What is basic connection power supply in Australia? Is it 100A per phase?

James · May 29, 2023

In the U.K. it is possible to have for instance a 100A 3 phase supply that would give in the region of 70kva.
however you may agree to have a lower maximum demand that will lower your bill.
so it would be possible to have a max demand of 40kva on a 70kva supply.
peak demand is measured by the meter and if you go over your maximum demand, it costs you a lot more than it would if you had agreed to it originally.

Julie. · May 30, 2023

ElecExplorer said:
Yes, 17.21 kVA is the total 3 phase power.

“ 17.21 kVA per phase would be circ 75A per phase.”
How did you calculate this? If per phase, then using line to neutral voltage which is 230V right?

There is an offer document binding with this agreement but I am asking for it.

What is basic connection power supply in Australia? Is it 100A per phase?

The standard connection is up to 100A single phase or up to 100A per phase on three-phase.

However in rural locations this could be limited to 32A (or 32A per phase) and in non-rural locations is normally limited by a fuse to 80A as a maximum (could be 45A, 60A, 63A.....)

To calculate Amps from kVA

Single phase

I = VA / Volts - so convert kVA to VA (x 1000) then divide by the voltage (normally 230V)

So 17.21 kVA single phase

17.21kVA x1000 = 17210VA

17210VA / 230V = 74.83A

Three-phase

Two ways

1)
Divide the total three phase capacity by 3 then continue as per single phase as above

17.21kVA / 3 = 5.737kVA per phase

5.737kVA x 1000 = 5737VA

5737VA / 230V = 24.9A per phase

2)
Convert kVA to VA

Use the following calculation

I = VA / ( L-L Voltage x sqrt(3))

L-L Voltage is normally 400V (actually 230V x sqrt(3) = 398V)

17210 / ( 400 x sqrt(3)) = 24.9A per phase

The square root of 3 is roughly 1.73

pc1966 · May 30, 2023

Interestingly enough, I was just watching an eFixx video of them in Italy and the norm there is 6kVA single phase / 18kVA 3P and it is accepted if you don't manage your demand sensibly then you have to reset the supply breaker following blackout!