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 10:36, wrote:

Not necessarily. A combined heat and power system could work out both
more efficient and less polluting than 50-odd diesel engines running
most of the time at far from peak efficiency.

True, but don't forget you have battery charging losses.


You also need a use for the waste heat, which is unlikely in a bus
depot, especially in Summer.

--
Tciao for Now!

John.

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.

In message , at 11:14:39 on Fri, 13
Jul 2018, John Williamson remarked:
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.

But the DC power supply wasn't capable of 19,200 amps!

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),

I used the 400 volts quoted earlier (which is highly likely to be the
same stuff that you've called 415 volts; three phase). We don't know how
many blocks of chargers that'll be split into, but thirty at 200 amps
each for two buses each seems rather spaghetti-like.

by the distribution network.

It will come into the site at about 120 Amps per feed at 11kv.

The copper I'm admiring is that carrying the 6,250 amps (for however far
before branching off to individual blocks of chargers).
--
Roland Perry

On 13/07/2018 10:51, John Williamson wrote:
On 13/07/2018 10:36, wrote:

Not necessarily.Â* A combined heat and power system could work out both
more efficient and less polluting than 50-odd diesel engines running
most of the time at far from peak efficiency.

True, but don't forget you have battery charging losses.


You also need a use for the waste heat, which is unlikely in a bus
depot, especially in Summer.


Making the tea?

--
Graeme Wall
This account not read.

On 13/07/2018 10:51, John Williamson wrote:
On 13/07/2018 10:36, wrote:

Not necessarily.* A combined heat and power system could work out both
more efficient and less polluting than 50-odd diesel engines running
most of the time at far from peak efficiency.

True, but don't forget you have battery charging losses.


You also need a use for the waste heat, which is unlikely in a bus
depot, especially in Summer.

Yes, CHP often works best as an area heating scheme. I'd thought
redevelopment was planned in that area which would offer scope. If not,
TfL could at least offer really, really warm seats on buses entering
service at Waterloo



--
Robin
reply-to address is (intended to be) valid

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?

On 13/07/2018 15:51, wrote:
240V isn't it or did it get dropped down at some point?

It used to be 240 plus or minus 5%, it's now 230 plus 10 - 0%. Not even
the transformer taps in the substations have been changed. Blame the EU.

--
Tciao for Now!

John.