Increasing 3PH Supply?

[-Matt]

A company i do work for are running over the capacity of their existing 100A 3PH supply, they are pulling around 100-120A all day long.

I am trying to get them to get a bigger supply, they have tried asking for a 250A supply from the DNO, but they want £20K. (they reckon the transformer would need upgrading)

Its an overhead supply, and a transformer (pole mounted) is only 15-20 metres away, on boundary of customer property.

I don't know what size the transformer is, but its not the smallest I've ever seen, and only looks to supply 2 properties.

Ive just had the thought of a second 100A supply, as it would be dead easy to split the demand across two supplies.

Has anyone tried getting an additional 3PH supply? and was it more cost effective than a 250A supply?

I guess it still comes down to if the transformer has capacity, but i find it hard to believe it would be maxed out with 2 properties?

Cheers

 

[marconi]

I really liked plugsandsparks ideas and installing ammeters to allow some management of equipment is likely to be simple and effective - but probably not the complete solution. I thought though that maximum demand ammeters might be better which read actual current and integrated over time (rolling 15 minute interval) current being drawn. See:

Eltime - Maximum Demand Meters - http://www.eltime.co.uk/product.php/8/Maximum%20Demand%20Meters.html

 

[marconi]

I really liked plugsandsparks ideas and installing ammeters to allow some management of equipment is likely to be simple and effective - but maybe not the complete solution. I thought that maximum demand ammeters might be more helpful which display actual current and averaged current over a rolling 15 minute interval. See:

Eltime - Maximum Demand Meters - http://www.eltime.co.uk/product.php/8/Maximum%20Demand%20Meters.html

This was one has an alarm signal output:

Max. demand ammeter BRL-110CH : Daiichi Electronics Corporation - http://www.daiichi-ele.co.jp/en/product/product_0035.html

 

[-Matt]

Thanks Guys, Sorry about delay coming back, all been a bit busy!!!

Yes i would say from what I've measured with a clamp they are drawing around 100-120A/PH most of the day during business hours.
Each phase is almost exactly the same, as its 90% 3PH equipment (no neutral).

I have tried suggesting not using everything all at once, but this effects their production rate...

The biggest offender is a 25KW 3PH motor which runs all day, it does spike as a matter of operation, it uses a constant 35A/PH then around every 15 seconds it spikes up to around 65A for a couple of seconds.
It runs some heavy duty hydraulics.

Then there are around 15/20 smallish 3PH motors (around 1KW Each).

So all added up, its a fair amount of power being used, however they are yet to blow a service fuse.


I did have one thought while i was there earlier on another matter, they have an office around 30 Meters away which has its own 100A 3PH supply (separate meter), i would be amazed if they use 20A/phase in the office.
So there looks to be the potential to say run a 60/80A submain from here to the workshop, then take some load off the workshop supply.

This is not something i have done before and feels bit of a "bodge", and need to look at any regulations this would go against ( 2 supplies in one building). But it would certainly help with the overloading.

 

[westward10]

Is this 100-120A constant or occasional.

 

[marconi]

Re #18
The biggest offender is a 25KW 3PH motor which runs all day, it does spike as a matter of operation, it uses a constant 35A/PH then around every 15 seconds it spikes up to around 65A for a couple of seconds. It runs some heavy duty hydraulics.

The average line current of this motor is:

Iav = (65 x 4 x 2) + (35 x [60-8]) all divided by 60 = [520 + 1820] / 60 = 39A

 

[plugsandsparks]

No problem with two supplies into one building, very common in industrial. Easiest solution appears to be supply 35kw motor of the other board, hopefully not too far / difficult run. Also if its like that all day, chances are PF is pretty constant too, so a nice cheap and chearful capacitor bank sized accordingly would probably make a nice improvement. I have done this a few times, it really does bring those amps down

 

[davesparks]

No problem with two supplies into one building, very common in industrial.

It’s pretty common in theatres too, but it is necessary to do it in accordance with the DNOs requirements and get the earthing right. The earthing may need to be linked together in accordance with the DNOs requirements.