Fascinating distribution system: Pitcairn Island

[Eleanor White]

I'm a retired distribution engineer, and I
thought some things I've recently learned
about the Pitcairn Island distribution
system might be of interest:

ATTACHED is a document describing, in
non-technical terms, what's there now, and
proposing a solar boost for the diesel
generators. (System description starts on
PDF page 4.)

What is equally fascinating is to take a tour
of the "streets" via google maps, using STREET
VIEW option.

There appears to be some 4160 volt primary
there, but hey, NO TRANSFORMERS. The
attached report refers to:

"All residences and government buildings on
Pitcairn are connected to a low voltage grid, ..."

If "low voltage grid" means end-user 120/240,
then what's installed there is apparently a
system of pole lines insulated for 2,400/4,160,
but right now carrying 120/240???

Improbable as it sounds, such a unique place
with a unique history might just have done
that! Fascinating!

Eleanor White
Ontario, Canada

 

[waross]

May I be the first to welcome you to Eng-Tips Eleanor.
That document was an interesting read, Eleanor.
Thanks

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

Apparently power on Pitcairn Island is 230/400 Volts, 50 Hz.
That lends itself well to feeding single phase 230 Volt circuits from a 230/400 Volt generator.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Eleanor White]

Where did you find that info, Bill? - I'd like
to read more.

So this must mean all appliances are 230 volts.

Thanks,

Eleanor White

 

[waross]

Try this link.
Link
2230/400 Volts is the nominal voltage under the EU harmonization.
The actual voltage may be 220/380 Volts.
Where North America uses 120/240 Volts, center tap grounded, Europe often uses a three phase wye system with the center tap grounded. hence, 400 Volts three phase may easily be separated into three 230 Volt, grounded, single phase circuits.
(If you are familiar with European systems, bear with me. Others following this thread may not be as familiar with EU systems.)

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

I typed "voltage pitcairn island" and DuckDuckGo found it.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Eleanor White]

Got it, thanks Bill.

The village appears to be at least a couple
of thousand feet from end to end, and more
for some of the outlying buildings.

One has to wonder about how voltage drops
are handled, given that the attachment
above says "... all households operate the
usual household appliances such as washing
machines, water kettles, electric stoves
and ovens, fans, irons ..." and
"... families at the top of monthly
consumption owning up to six or seven
fridges and freezers."

The images of the overhead wires in google
street view don't appear to show huge wire
sizes.

Eleanor White

 

[itsmoked]

With the average daily load being 35kW, bothering with high voltage does seem to be a nonstarter. Then you need someone who knows how to work with it which is another expense.

They should be able to entirely dump generators for solar. My sister-in-law has a 50kW array just to offset her biology lab that employs about 5 people.


Pitcairn:

150,000kW/year => 410kWh/day

410kWh/6hrs = 68kW of solar array.

65kW/320W/panel = 203 panels

Put in 300 panels and enough LiFePO4 batteries to carry the place for 3 days of overcast and keep the best generator as back-up.






Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Also, welcome Eleanor!

Likely when all this went in predates the skyrocketed copper prices so they could well have used monster wire. It would still be cheaper than calling for service calls out to there to deal with MV stuff.

Frequently whateverV to 600V and back down to whateverV is used in low-tech applications with long distances to reduce copper demands.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[stevenal]

How did you get 2,400/4,160? When I zoom in to the insulators, they appear quite small. Found a street light, which appears to be wired directly. Nice phase separation for 220V. Built for typhoons maybe?

 

[cranky108]

Interesting place. Where else might a power engineer want to retire?

 

[Mbrooke]

Any single lines diagrams? Or pictures? So the customers lose power when generators are changed over? I'm fascinated!

Thank you Eleanor!

 

[Eleanor White]

REPLYING TO THREE POSTS HERE - I don't see an option
to reply to individual posts:

stevenal (Electrical) posted:
How did you get 2,400/4,160? When I zoom in to the insulators, they appear quite small. Found a street light, which appears to be wired directly. Nice phase separation for 220V. Built for typhoons maybe?
Great post!

Eleanor replying to stevenal:

I noticed the small insulators too. I moved from distribution
to computer programming in the early 1980s, so I'm out of date,
but haven't I seen some surprisingly small diameter "rod" style
insulators used on distribution primary in recent years?

As to 2,400/4160, that's just what the general appearance
suggests to my eye. It looks to me as if they wanted to have
the ability to go to somewhere in the 2,400/4,160 range if the
demand were to grow.

I think what helps a lot is the absence of 120 volt appliances.
That could theoretically quadruple the reach. However, that
article about the existing system still makes it sound as if
there are lots of hefty appliances.

Probably, given there is no electric heating or air conditioning
mentioned, there's enough diversity to make the 230 volt system
workable.

Might a system like that benefit from a few capacitors?

I would imagine their general store is a goodly load, with the
fridges/freezers, but it's well placed, just a few doors uphill
from the generators.

Unfortunately, the street view footage does not reach down to
the powerhouse itself.

cranky108 (Electrical) posted:
1 Feb 21 20:29
Interesting place. Where else might a power engineer want to retire?
Great post!

Eleanor replying to cranky108:

Hey man (or girl, maybe) - if you go through the
articles and videos about the place, they DO WANT
people to immigrate there! All skills welcome.

One source mentioned that the fellow who put up
the lines and operates the generators was age 67
(but I didn't see a date on that item.)

The way the place operates is residents don't have
full time jobs, but instead each wear a number of
part-time "hats."

They have incomes, and are officially a colony of
the United Kingdom. Senior officials, like judges
and senior law enforcement, medical, politial (e.g.
governor) reside in Auckland, New Zealand.

There are professionals who travel and aren't
permanent residents. I think there is a rotating
doctor at their clinic, and a nurse's aide as well.

Governments kind of like their island possessions
and from what I've seen looking around the web, there
are serious efforts underway to upgrade facilities
and services, and encourage immigration.

At the moment, they are seeking a school teacher for
all levels up to high school. High school kids go
to boarding school in New Zealand - that seems like
a sensible move. The school enrollment is currently
just 3 kids, all different ages.

Oh, and hey, one source reported no snakes on the
island, which I would find a plus. They do have
lizards, but they can be kind of cute and help keep
insects under control.

Mbrooke (Electrical) posted:
3 Feb 21 09:07
Any single lines diagrams? Or pictures? So the customers lose power when generators are changed over? I'm fascinated!

Thank you Eleanor!

Eleanor replying to Mbrooke:

I haven't found any single line diagrams, but plenty
of glimpses of the overhead lines can be had by going
into google maps, calling up Pitcairn Island (be sure
you've got the inhabited island, and not one of the
surrounding atolls.)

Zoom in fairly close, then use the little STREET
VIEW stick figure icon and drop it on one of the
streets of interest. Fascinating.

They have a 25-ton mobile crane for offloading heavy
stuff at their rather small wharf - interesting.

This 32-min. video by a dentist who visited the island
is a rather good rundown on what it takes to get there,
first 11 minutes, and then what he found there:

https://www.youtube.com/watch?v=uYu95RXn1ao

And here is the government of Pitcairn's web site:

https://www.government.pn

(connects with the Auckland,
New Zealand seat of government)

* I have written to one of the staff at the government
web site and asked if I could be put in touch with the
fellow who runs and maintains the power system. She
said she would try to arrange that.

I don't know if they have satellite access to the Internet
or not, at this point.

If I find something interesting, I'll post that here.

** I have another thing I've been wondering about along
the same line. There is that fascinating rotating
restaurant and tourist inn way way up in the Swiss Alps,
which appeared in a James Bond movie:

https://schilthorn.ch

I'd love to know how they handle electric power, water
and sewage at that very high place. Anyone know?

Eleanor White

 

[stevenal]

In some places if you rotate the street view down, you'll see two guys on a motor bike. One guy is holding an object up. I think he's using it to fly the drone taking the pictures.

 

[FacEngrPE]

This is the address in google maps I think. Adamstown PCRN 1ZZ, Pitcairn Islands. Looks about as far from everything as you can get, unless you go to Antarctica.

 

[Eleanor White]

Looking at the street view images, my guess
is the system uses, oh, maybe #2 copper?

And itsmoked (post above) found a statement
that average load is 35 kw.

I found a statement that there are three
circuits (which makes sense from a 3 phase
generator.)

35 kw divided by 0.23 kv is 152 total amps?

That might mean each of the three 230 volt
circuits carry roughly 50 amps, with the
current dropping off a bit at each user.

I would suspect that the generators are run
at the maximum safe voltage for the appliances,
say, maybe 250 volts?

I'm not sure what the minimum voltage might
be for the appliances used there. I'd suspect
the fridges and freezers might be sensitive
to low voltage.

How about 200 volts?

With those numbers, is anyone current enough
to estimate the distance to the point where
250 volts at the source drops to 200, over
fairly widely spaced #2 copper, carrying 50
amps?

Eleanor White

 

[Eleanor White]

ANSWERING MY OWN QUESTION re estimated voltage drop:

I thought I'd try an on-line voltage drop calculator
to estimate the voltage drop around the average load
on Pitcairn Island. The image below is a quick
result:

That quick estimate suggests that under the worst
possible condition, i.e. a full 50 amps at the very
end of each of 3 feeders, it would take 3,000 feet
of #2 copper to drop 250 volts to 200 volts.

One factor the calculator page didn't take into
account is the wide spacing of the conductors,
which would mean the result is a little optimistic,
but still, three feeders branching out even 2,000
feet from the generator would cover most of the
closely spaced village.

Eleanor White

 

[Eleanor White]

FacEngrPE (Mechanical) wrote:
4 Feb 21 00:24
This is the address in google maps I think. Adamstown PCRN 1ZZ, Pitcairn Islands. Looks about as far from everything as you can get, unless you go to Antarctica.

Eleanor White replying:

If someone finds Pitcairn too close to civilization,
there is always Tristan da Cunha in the south Atlantic,
which I've seen claimed as the very most remote
inhabited island on the planet. Also a British colony,
a little bigger at around 250 residents.

Tristan da Cunha is going to be a little cooler too,
Pitcairn being roughly 25 degrees south latitude, but
Tristan da Cunha at roughly 37 degrees south.

Both Tristan da Cunha and Pitcairn would be fun places
for a ham radio operator.

Eleanor White

 

[itsmoked]

Eleanor; I think you've pretty much nailed it. With the ÷3 and the 2AWG (some I see might be larger than 2AWG). That would work great. At each end user they'd convert to 14AWG or something like that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I have seen some voltage charts that led me to suspect that the wire service provider was keeping the voltage as high as possible to drive up consumption.
Even higher than the supposedly regulated maximum allowable voltage.
Most customers are not as aware of overvoltage as you may think.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!