[Question] The size Electrical Cables required to supply 50 households?

[ZJB]

I am member of 50 households which bought a 11kV 420 100kVA Transformer in an informal settlement. I am not knowledgeable on this subject. We want to avoid misinformation. Question: Electrical suppliers want to know the size of the overhead cable to run from pole to pole, which 20m apart. Each pole will supply 4 houses. Each household should limit its electricity requirement to 1x32A (Stove), 1x20A and 1x10A circuit breakers. Suggestions include 35mm (2core +1E [naked wire]) or 70mm (3Core + 1E) cables. What is the correct cable size required? Will the cable not overheat and burn the transformer at maximum use? Please help.

[GCE]

You need to employ the services of a contractor that can get sign off from an Engineer on design or a Consultant to carry out the design and appoint a competent contractor
Besides contravening the OHSA you are going to kill somebody and create a fire hazard

With correct protection on the transformer you will prevent the unit from catching fire but having 50 houses on a 100Kva transformer is going to be constant tripping problem

Electrical Installation Regulations
(5)
Where the voltage exceeds 1 kV, a person deemed competent in terms of paragraphs (b), (c) or (d) of the definition of a competent person in regulation 1 of the General Machinery Regulations, 1988, or a person registered in a professional category in terms of the Engineering Profession Act, 2000, shall approve the design of that part of an electrical installation.
(6)
Where the intention is to supply five or more users from a new point of supply, the user shall appoint an approved inspection authority for electrical installations or a person deemed competent in terms of paragraph (b), (c) or
(d)
of the definition of a competent person in regulation 1 of the General Machinery Regulations, 1988, or a person registered in a professional category in terms of the Engineering Profession Act, 2000, who shall ensure the compliance contemplated in subregulation (1) from the commencement to the commissioning of the electrical installation.

[ZJB]

You need to employ the services of a contractor that can get sign off from an Engineer on design or a Consultant to carry out the design and appoint a competent contractor
Besides contravening the OHSA you are going to kill somebody and create a fire hazard

With correct protection on the transformer you will prevent the unit from catching fire but having 50 houses on a 100Kva transformer is going to be constant tripping problem

Electrical Installation Regulations
(5)
Where the voltage exceeds 1 kV, a person deemed competent in terms of paragraphs (b), (c) or (d) of the definition of a competent person in regulation 1 of the General Machinery Regulations, 1988, or a person registered in a professional category in terms of the Engineering Profession Act, 2000, shall approve the design of that part of an electrical installation.
(6)
Where the intention is to supply five or more users from a new point of supply, the user shall appoint an approved inspection authority for electrical installations or a person deemed competent in terms of paragraph (b), (c) or
(d)
of the definition of a competent person in regulation 1 of the General Machinery Regulations, 1988, or a person registered in a professional category in terms of the Engineering Profession Act, 2000, who shall ensure the compliance contemplated in subregulation (1) from the commencement to the commissioning of the electrical installation.

DEAR GCE

Thanks for your thought provoking response, though it renders us helpless.
I agree, Acts & Regulations indeed are meant to provide safety and order. Unfortunately those who are supposed to provide essential services fail to do so, and this deepens poverty as this community of us must struggle with water and fuel. What's only decent here is that we avoid what other communities are doing by spanning unsafe wires and equipments across the length and breadth of the settlement, to to try sustain their livelihoods.
In the legal system there is something like 'pro bono' services by attorneys who offer their services free of charge. Is there such a thing in the electrical constructions sector. Or is there any electrical company or any organisation which may be willing to assist even for a minimal fee?
Thanks in advance.

[GCE]

Unfortunately a 100Kva transformer for 50 houses cannot work - It basically gives 9 amps per house and there will be no diversity factor in the evening when everyone is cooking and using lights
You need at least 300Kva to start with so anybody touching that installation is on a hiding to nowhere to begin with

[AndyD]

Eskom or City Council have a standard tghey work to for what they call maypole distribution for informal settlements which is basically what you're describing. As GCE suggests 50 dwellings on a 100KVA Tx would be optimism in the extreme. Personally I'd be looking to limit supply to 16 Amps or less per dwelling which is more than adequate for basic needs. I definately wouldn't try to accomodate a full 32A stove when firstly most informal dwellers only use a small portable 2 ring cooker and that role can easily be fulfilled by small LPG burners which are also already widely used because of loadshedding.

I'd suggest you should go some way towards managing expectations of the contributors and revisit your aims and goals regarding dwelling supply size first. You're going to need a professional design for the distribution so I wouldn't worry about that at least for now.

[Sparks]

My starting point would be to consult with an electrical engineer to design your reticulation. He will do all the math and provide you with a detailed CAD plan indicating all the relevant information which you need in order to approach an electrical contractor to supply you with a quote for the installation. With so many units there will have to be control points in reasonable proximity to the units, there will be underground cables. You will need to keep trenching in mind for cabling too.

[ZJB]

Thanks GCE, for additional info.

[ZJB]

Thanks AndyD, I appreciate your understanding of the informal settlement. I suppose this is the advice that should be communicated to households when the switch on happens. I guess we will have to work on additional transformer if we hope to have Eskom or City Council's standard supply to households.

[ZJB]

Thanks Sparks, I suppose this is what GCE suggested. With struggle to raise just enough money to buy the basic equipment, I wonder what the cost of these experts or professionals will be. Or am I overestimating the price tag on these professional fees?

[Sparks]

Or am I overestimating the price tag on these professional fees?

I doubt that, covid has affected more peoples brains than anything else. Everyone is trying to recover all their lockdown losses on each and every commission nowadays. Unfortunately, if you do not follow that route, I believe it will end up costing a whole lot more.

[GCE]

, I wonder what the cost of these experts or professionals will be. Or am I overestimating the price tag on these professional fees?

Tend to agree with Sparks - could cost you more in the end - A consultant will specify and invite pricing and check that the equipment priced is what is installed and installed correctly so that warranties stay in place , unless you know a reputable contractor.