In message , at 22:59:39 on
Thu, 12 Jul 2018, Mark Bestley remarked:
wrote:

On Thu, 12 Jul 2018 08:10:30 -0700 (PDT)
John Leach wrote:
On Thursday, July 12, 2018 at 3:04:30 PM UTC+1, wrote:
There was an article in the Evening Standard last night about the bus
garage near waterloo that has europes largest fleet of battery electric
buses. Apparently they had to install their own "generator". ....

I read that article too, according to this press release (link below) from
2016 the charging power comes from the grid. Not a local generator.

https://www.ukpowernetworks.co.uk/in...s/press-releas
es/Ele ctric-buses-are-breath-of-fresh-air-for-London.html#art-top

I suspected it would be something like that. Installing a generator
would seem
to defeat the point of having electric buses.

For a more detailed view see Ian Visits

https://www.ianvisits.co.uk/blog/201...dream-of-elect
ric-buses/

"They also needed 2.5 megawatts of electricity to recharge the buses
overnight — although the use of smart monitoring means they never reach
that full load.

In comes 11,000 volts to two new substations on the site, which is then
dropped down to 400 volts and sent via two routes to the various
charging points around the depot.

2.5 megawatts at 400 volts is 6,250 amps! But I suppose it's only one
and a half Eurostars.

Four fast chargers at 800 volts are also available if needed."

--
Roland Perry

On 13/07/2018 08:09, Roland Perry wrote:
In message , at 22:59:39 on
Thu, 12 Jul 2018, Mark Bestley remarked:

In comes 11,000 volts to two new substations on the site, which is then
dropped down to 400 volts and sent via two routes to the various
charging points around the depot.

2.5 megawatts at 400 volts is 6,250 amps! But I suppose it's only one
and a half Eurostars.

Not even a quarter of a Eurostar. They draw 16 megawatts flat out.

Another good argument against HS2, as a normal train only draws a
quarter of that.



--
Tciao for Now!

John.

In message , at 08:57:53 on Fri, 13
Jul 2018, John Williamson remarked:
On 13/07/2018 08:09, Roland Perry wrote:
In message , at 22:59:39
on Thu, 12 Jul 2018, Mark Bestley remarked:

In comes 11,000 volts to two new substations on the site, which is then
dropped down to 400 volts and sent via two routes to the various
charging points around the depot.
2.5 megawatts at 400 volts is 6,250 amps! But I suppose it's only
one and a half Eurostars.

Not even a quarter of a Eurostar. They draw 16 megawatts flat out.

Only on 25kV, look again at its consumption on DC, and it's the amps I'm
highlighting anyway.
--
Roland Perry

On Fri, 13 Jul 2018 10:27:30 +0100
Roland Perry wrote:
In message , at 08:57:53 on Fri, 13
Jul 2018, John Williamson remarked:
On 13/07/2018 08:09, Roland Perry wrote:
In message , at 22:59:39
on Thu, 12 Jul 2018, Mark Bestley remarked:

In comes 11,000 volts to two new substations on the site, which is then
dropped down to 400 volts and sent via two routes to the various
charging points around the depot.
2.5 megawatts at 400 volts is 6,250 amps! But I suppose it's only
one and a half Eurostars.

Not even a quarter of a Eurostar. They draw 16 megawatts flat out.

Only on 25kV, look again at its consumption on DC, and it's the amps I'm
highlighting anyway.

I wonder if the old eurostars have any of their DC equipment still on board?
If they do perhaps they could solve the overcrowding issues on Southern and
south eastern instead of being scrapped!

On 13/07/2018 10:27, Roland Perry wrote:
In message , at 08:57:53 on Fri, 13
Jul 2018, John Williamson remarked:

Not even a quarter of a Eurostar. They draw 16 megawatts flat out.

Only on 25kV, look again at its consumption on DC, and it's the amps I'm
highlighting anyway.

The lower power and speed restrictions on the third rail sections of the
original route was a deliberate restriction to prevent overload damage
to the ageing trackside equipment and speed related damage to the
collection shoes. As the third rail shoes have now been removed, this is
academic. They used to jog along at 65mph in the UK. accelerate to 85
mph or so for the tunnel, and then to full speed for the French and
other parts of the trip. They now do full speed along the HS1 track,
slow down to 85 for the tunnel, then accelerate again as they leave it.

The traction motors on a Eurostar are rated to draw 12 megawatts per
train at start, the garage is drawing a fraction of that. The 12
Eurostar motors are likely running at 600 volts or so, which means they
draw about 1,600 Amps each, at a megawatt a pop, but this is only of
concern to the designers and engineers. To everyone else, it's a black
box system that needs a megawatt per motor at whatever voltage and
frequency the pantograph is supplying at the time.

What's important to the grid is the input. Your 6,250 Amps for the
chargers will be split into chunks of about 200 Amps per bus (at about
600 volts, IIRC), by the distribution network. It will come into the
site at about 120 Amps per feed at 11kv.

--
Tciao for Now!

John.

On Fri, 13 Jul 2018 11:14:39 +0100
John Williamson wrote:
What's important to the grid is the input. Your 6,250 Amps for the
chargers will be split into chunks of about 200 Amps per bus (at about
600 volts, IIRC), by the distribution network. It will come into the
site at about 120 Amps per feed at 11kv.

Is 11KV the standard voltage for distribution within UK cities? I wonder
why they chose that particular value. Just curious...

On 13/07/2018 11:37, wrote:
On Fri, 13 Jul 2018 11:14:39 +0100
John Williamson wrote:
What's important to the grid is the input. Your 6,250 Amps for the
chargers will be split into chunks of about 200 Amps per bus (at about
600 volts, IIRC), by the distribution network. It will come into the
site at about 120 Amps per feed at 11kv.

Is 11KV the standard voltage for distribution within UK cities? I wonder
why they chose that particular value. Just curious...

If you check, there is a whole network of different standard voltages
starting with the 400kV supergrid, right down to the 415 Volt 3 phase
plus neutral feeder that runs under or over your street, with branches
off to give a single phase 230 Volt supply to your house or flat.

In general terms, the current at each stage is similar.

--
Tciao for Now!

John.

On Fri, 13 Jul 2018 11:53:44 +0100
John Williamson wrote:
On 13/07/2018 11:37, wrote:
On Fri, 13 Jul 2018 11:14:39 +0100
John Williamson wrote:
What's important to the grid is the input. Your 6,250 Amps for the
chargers will be split into chunks of about 200 Amps per bus (at about
600 volts, IIRC), by the distribution network. It will come into the
site at about 120 Amps per feed at 11kv.

Is 11KV the standard voltage for distribution within UK cities? I wonder
why they chose that particular value. Just curious...

If you check, there is a whole network of different standard voltages
starting with the 400kV supergrid, right down to the 415 Volt 3 phase
plus neutral feeder that runs under or over your street, with branches
off to give a single phase 230 Volt supply to your house or flat.

240V isn't it or did it get dropped down at some point?

In message , at 11:53:44 on Fri, 13
Jul 2018, John Williamson remarked:

If you check, there is a whole network of different standard voltages
starting with the 400kV supergrid, right down to the 415 Volt 3 phase
plus neutral feeder that runs under or over your street, with branches
off to give a single phase 230 Volt supply to your house or flat.

In general terms, the current at each stage is similar.

Broadly true, apart from the supergrid being 1000A, as far as I can
tell.

What's important for the EV-charging scenario is that is if several
dozen houses are supplied by an 200A street main at 230v from the local
substation, how can more than a handful charge an EV overnight at 50
amps?
--
Roland Perry

Most distribution Voltages in the UK are 10% higher than nice round numbers.. 11 and 33 kV are widely used, 66 kV for some large substations. 22 kV is not much used in the UK, more common on the mainland, but the London Underground has quite a bit of it, I think because joints in 33 kV were too large.

6.6 kV is still used, though becomming less common. Quite a lot of Croydon is still fed ay that Voltage.