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#186161 - 04/22/09 04:46 PM Installing underground cables
C-H Offline

Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
Hi all!

I haven't posted here in ages, but still follow the forums.

This time I have something that I'd like your feedback on, since you people have the experience I lack. (I'm an engineer turned salesman and now I want to design the product I've already offered.)

It's a charging system for electric vechicles which can be employed both at home and at public charging stations. The "at home" part is easy, but the public charging points pose some difficulties.

Where I live, grey steel cabinets stick out of the ground everywhere, filled with various utility wires. You find them by the side of buildings, next to the road or even in the middle of the woods. This means that us locals are completely blind to them. But I realise that this may not be the case in other countries.

So, my first question is: What would you say if you were asked install cabinets similar to this next to a car park? It's about 1 x 1 x .3 m above ground.

Next, I want you to pull half a dozen screened 4 x 50mm2 (4-wire, 1/0 AWG) aluminium cables cables in a 30m (100 feet) long trench across the parking lot from the cabinet to the chargers. Quick and easy or a lot of work? (No worries, you don't need to dig the trench!)

How do you prefer to terminate the wires? In terminals, with crimped lugs or something else?

And lastly, would you prefer fuses or breakers in the cabinet? (100A for each outgoing cable) Both electricians and engineers here answer fuses.


Attachments
okab05_margin.jpg

Description: Cable distribution cabinet



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#186164 - 04/23/09 01:40 AM Re: Installing underground cables [Re: C-H]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Gidday there, C-H, I hope all is well in your neck of the woods. wave

My comments in Italics


Originally Posted By: C-H
It's a charging system for electric vechicles which can be employed both at home and at public charging stations. The "at home" part is easy, but the public charging points pose some difficulties.


First off, sort of current levels are we talking about here?


Quote:
Where I live, grey steel cabinets stick out of the ground everywhere, filled with various utility wires. You find them by the side of buildings, next to the road or even in the middle of the woods. This means that us locals are completely blind to them. But I realise that this may not be the case in other countries.


I think boxes like the type you describe, are pretty much generic in most countries, we have this sort of thing here, but the boxes are different coloured.

Quote:
So, my first question is: What would you say if you were asked install cabinets similar to this next to a car park? It's about 1 x 1 x .3 m above ground.


I don't have a problem with that idea at all, I would give this advice though, you'd want some sort of steel bollards next to the boxes for protection.
You wouldn't (or maybe you would) beleive how many power pillar boxes get struck by cars, especially in car parks.
mad

Quote:
Next, I want you to pull half a dozen screened 4 x 50mm2 (4-wire, 1/0 AWG) aluminium cables cables in a 30m (100 feet) long trench across the parking lot from the cabinet to the chargers. Quick and easy or a lot of work? (No worries, you don't need to dig the trench!)


Why Aluminium cables?, they require better terminating skills than copper by a long shot, ie; they need proper grease-filled lugs and good wire preparation.
Copper cables are also easier to bend.
Also remember, if you are thinking of using conduits as opposed to direct burial of the cables, there must be some sort of de-rating of them cables


Quote:
How do you prefer to terminate the wires? In terminals, with crimped lugs or something else?


Given the size of the cables you've mentioned above, and having a choice, I'd go with Hex crimped lugs fitted onto threaded studs, with a flat washer, a star washer and 2 lock nuts

Quote:
And lastly, would you prefer fuses or breakers in the cabinet? (100A for each outgoing cable) Both electricians and engineers here answer fuses.


Wether you use fuses or circuit-breakers, really depends on if these are going to be accessible to the people using the car charger.
If a car trips a CB, it can be reset easily.
If a fuse blows, people may be inclined to "upgrade" the circuit protection to get the car charged up, I mean, who carries spare fuses in thier car?
I'd personally go with circuit breakers, if it were my installation.


By the way, C-H, any chance of a bigger picture?
_________________________
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#186165 - 04/23/09 05:06 AM Re: Installing underground cables [Re: Trumpy]
RODALCO Offline
Member

Registered: 12/08/05
Posts: 863
Loc: Titirangi, Akld, New Zealand
I see that your attachement has CT's and a metering panel in it.

In public areas somehow a kWh or prepay meter has to be installed as different type electric cars will have different size battery banks, which also are in different states of discharge.

I don't see utilities offering this as a free service.

I second Mike's option to have MCB's instead of fuses.

Just my $0.02 worth on the topic.
_________________________
The product of rotation, excitation and flux produces electricty.

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#186166 - 04/23/09 05:46 AM Re: Installing underground cables [Re: RODALCO]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
A dozen 50mm2 aluminum cables sounds a bit weird to me - why not use larger wires?
Unless this is some kind of distribution to several boxes one large feeder would make more sense - anything up to 300mm2 copper goes, though above 240mm2 paralleling is preferred by most sparkies here.

If the fuses aren't supposed to be operated by customers I'd advise HRC fuses for financial reasons. Otherwise breakers are a must have.

I second the need of some kind of metering, either prepaid or cash/ bank/credit card.

In Vienna there's one (I think) charging station for electric cars which is built into a nice red and grey round pillar - a design object rather than the typical distribution box pillar (we've got plenty of them, power distribution, telephone, cable TV, tramway switchgear and signalling,...).

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#186187 - 04/25/09 01:33 PM Re: Installing underground cables [Re: Texas_Ranger]
C-H Offline

Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
First, thanks for your replies!

Starting from the bottom:

Ragnar,

there is one cable for each charger so this is a radial topology. The feed _to_ the box could well be supplied with two parallel cables.

The charging station in itself will be a designer item and kept as small as possible. That is why the equipment will go into a box. The idea is that customers see a bunch of nicely designed chargers and the sparkies see a single nicely ordered cabinet.

Rodalco,

All electricity will be metered and billed through subscription or prepaid. Otherwise this can never succeed. Hey, your $0.02 now can save $$$ later on! smile

Mike,

we are talking 63 - 100 A.

The over current protection is not supposed to be reset by the customers. If it trips, something has gone wrong and an electrician should investigate it.

Thick steel and good locks on the boxes will be required to deter theft, overfusing and what not people will come up with.

You're right: Steel bollards are a must for the boxes if placed in the parking. I've seen numerous boxes with damages from vehicles. The chargers will be denergised when not charging a vehicle. If someone runs one down, no danger arises and the rest still work.

The case for aluminium cables: Cost. The price is a third of the equivalent copper cable.

I thought crimped lugs would be best, but wanted to check with you.

It is good news that distribution pillars and boxes are common. I can paint them in any colour you want.

I'll see if I can find a better picture.

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#186704 - 05/25/09 03:40 AM Re: Installing underground cables [Re: C-H]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand


Again, my comments in italics.
Mike,

Quote:
We are talking 63 - 100 A.


Is that the current available to each charging station or the overall demand of the installation?
What voltage is each charging station going to be fed with?


Quote:
The over current protection is not supposed to be reset by the customers. If it trips, something has gone wrong and an electrician should investigate it.


In all reality, a trip should not happen, unless a wire has shaved inside a car, that should be investigated by someone competent.

Quote:
Thick steel and good locks on the boxes will be required to deter theft, overfusing and what not people will come up with.


Not sure what the environment is like there, but you could get better savings through using something like Stainless Steel for the actual cover plate of the control panel at each charging station, even galvanised (Zinc-Plated) steel no matter how thick has a limited life out in the open, especially when you add in moisture in the air and fumes from non-electric vehicles.
You could do the same thing with quite a thin SS plate and it would last a lot longer, provided you get the right grade of Stainless.


Quote:
You're right: Steel bollards are a must for the boxes if placed in the parking. I've seen numerous boxes with damages from vehicles. The chargers will be denergised when not charging a vehicle. If someone runs one down, no danger arises and the rest still work.


Good thinking, you just never know when people are travelling between parties and knock the bejesus out of your charging stations, steel bollards filled with concrete are a must around these parts, painted bright yellow, no less.

Quote:
The case for aluminium cables: Cost. The price is a third of the equivalent copper cable.

I thought crimped lugs would be best, but wanted to check with you.


C-H, I don't intrinsically have a problem with Aluminium cables, I use them all the time at work, but I think I mentioned this in my first reply to you.
The terminating of Aluminium cables is for qualified people only.

You need for a start, bi-metallic lugs that are copper at the termination end and aluminium at the core end.

You need to have proper wire preparation before the joint even occurs, this is the most important part of the actual termination, if this is not done properly, the aluminium part of the lug will melt due to I2R losses, aluminium has a very low melting point and it melts all of a sudden, not slowly like other metals.

The lugs have to have conductive grease impregnated into them.

The crimp tool is different for Aluminium crimps, as opposed to tinned copper crimps these tools are quite expensive



Quote:
It is good news that distribution pillars and boxes are common. I can paint them in any colour you want.


What we are seeing here, with respect to pillar boxes and what-not is black plastic or steel enclosures, painted to fit in with the surrounding colours, could be green grass or painted grey where concrete is abound, almost camoflague (sp??)
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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