Generator Installation, Help Please.

[Marvo]

Hi Trainees,

I'm a bit of a novice with electrics and I'm scared to post on the main forums so I thought I'd get some help here.

I have an existing installation which is a pump house with several pumps in it. It has a DNO supply via a meter box which is about 155 meters away via a 25 mm² 4-core SWA cable.

I need to install a small 3-phase generator for power back-up which has a max output of 70Amps per phase. It's mountainous terrain and the closest we can locate the genset to the pump house without using a helicopter is 175 meters downhill from the meter box.

We're going to locate the Automatic Transfer Switch at the existing meter box location so I need to run a 4-core SWA cable which will be buried direct in the ground between the genset and the meter box.

Please help me work out what size SWA cable I need and also show your method of how you reached your answer.

Thanks in advance for your efforts.

 

[Marvo]

 

[Marvo]

No takers?

I could do with some assistance on this please so I can get my cable ordered.

If you need any more info about the installation just ask.

 

[pennychew]

Hi Marvo, why 4 core for the existing cable to the pump house, Have you used two cores for line and two for neutral?

Will have a go at this later today as I’m really rusty on it now.

Got to swap engines in my transit first as it’s melted another piston

 

[Richard Burns]

The whole installation is three phase isn't it, even though your diagram shows a single phase head?
Your diagram also seems to show, as one would expect in a remote area, that the supply is locally earthed forming a TT earthing arrangement at the service head.

Hmm, seems difficult, I think you will have to ask on a forum to get an answer, perhaps some trainee could help!

 

[pennychew]

Sorry you’re correct, it does state 3 phase generator, I was looking at the diagram

I’ll have a look once I fettle this van..

 

[Sparky_Wario]

Hi Marvo. I'll try give me a nudge in the right direction.

ib ≤ in ≤ iz
I assume ib=70amp
Cut out fuse? I'll assume it to be 80amp
Reference method D
Thermoplastic or thermosetting
Ground temperature? 20 degrees c? Am I barking up the wrong tree? I am not sure.

Let's say in ≤ iz thus iz=80a

Thermoplastic Table 4D4A volt drop table 4D4B
Thermosetting table 4E4A volt drop table 4E4B
I reckon it could be either 25mm or 35mm depending on volt drop. I don't know whether to apply +10%/ -6%.

 

[H]

Hi Marvo. I'll try give me a nudge in the right direction.

ib ≤ in ≤ iz
I assume ib=70amp
Cut out fuse? I'll assume it to be 80amp
Reference method D
Thermoplastic or thermosetting
Ground temperature? 20 degrees c? Am I barking up the wrong tree? I am not sure.

Let's say in ≤ iz thus iz=80a

Thermoplastic Table 4D4A volt drop table 4D4B
Thermosetting table 4E4A volt drop table 4E4B
I reckon it could be either 25mm or 35mm depending on volt drop. I don't know whether to apply +10%/ -6%.

Vd would be the same for 25mm and 35mm @ 1.77V (thermoplastic)

If using thermosetting cable I’d say 25mm would be suitable. Vd would be very similar @ 1.71V