Safeguarding
Power
in the Shaky Islands
With Haywards Substation, a key component of New Zealand’s
transmission network, placed on a major seismic fault line,
national grid operator Transpower confronted Siemens with
the strictest seismic requirements ever implemented. The
­replacement of the HVDC Pole 3 and upgrade of Pole 2 challenged
all partners to find unique solutions.
Text: Garry Barker Photos: Guy Frederick
A multitude of AC and DC lines come in and go out of
Transpower’s terraced substation built on the lush
green slope of Haywards Hill near Lower Hutt, some
20 kilometers from New Zealand’s capital Wellington.
S
Auckland
Haywards
Wellington
Christchurch
The HVDC Inter-Island link
connects the grids of the
North and the South Island
of New Zealand since 1965.
In 2012, Pole 1 was decommissioned and in 2013 the
new Pole 3 was added,
together with a control
­system upgrade for Pole 2.
Illustration: Mariela Bontempi
Benmore
ome call New Zealand the
“Shaky Isles,” recognition that
its two long, narrow main is­
lands straddle major fault lines in the
earth’s crust. The landscape is beauti­
ful, ranging from broad green pastures
and sapphire blue lakes to steep rug­
ged snow-capped mountains and wide
snow-fed crystal clear rivers. But be­
neath them lies the constant threat
of major earthquake activity.
Christchurch, a beautiful city, the larg­
est in the South Island, was nearly
destroyed by a series of disastrous
earthquakes since 2010. The first quake,
of magnitude 7.1 on the Mercalli scale,
struck in the early morning of Sep­
tember 4, 2010. Hundreds of after­
shocks followed until a catastrophic
6.3 magnitude quake struck at mid­
day on February 22, 2011. Major city
buildings collapsed, killing 185 people
and leaving thousands more injured.
Since then more than 11,000 quakes
have occurred, most small – magni­
tude 2 or 3 – almost all around Christ­
church but recently touching the
­national capital, Wellington, on the
southern tip of the North Island. It
was in this most challenging environ­
ment that Siemens, under contract to
Transpower, the government-owned
grid management company, de­
signed, built, tested, installed and
commissioned a high-voltage direct
current (HVDC) state-of-the-art thy­
ristor-based converter and intercon­
nector system, capable of withstand­
ing a one-in-2,500-years earthquake
event. It has an installed capability
of 1,400 megawatts, of which current­
ly 1,200 megawatts are used due to
the limited capacity of the submarine
­cables.
The buildings and the equipment now
running in the valve hall, switchyard
and transformer bays at Transpower’s
Haywards site, 25 miles north of Wel­
lington, and at Benmore, the hydrosubstation in the far South Island, have
been built to that incredible standard.
The system is unique.
Andrew Gard is Transpower’s project director for the
HVDC Pole 3 project and juggled the installation and testing
of the new equipment in a live environment.
New Zealand’s HVDC Link
The project involved replacing the
original Pole 1, a 49-year-old mercury
arc system with a new thyristor-based
Pole 3 as well as refurbishing Pole 2,
installed in 1992, with a new, state-ofthe-art control system. The original
interconnection consisting only of
Pole 1 was rated at 270 kilovolts,
540 megawatts but underwent a major
upgrade between 1987 and 1992,
producing a so-called hybrid link of
two poles, the existing Pole 1 and
Pole 2 rated 350 kilovolts, which add­
ed 700 megawatts with modern thy­
ristor valves.
u
Living Energy · No. 10 | May 2014 79
Reportage
A Visit at the Energy Minister’s Office in Wellington
“The HVDC project just
completed will support New Zealand’s
security of supply far
into the future.”
Hon Simon Bridges,
Minister of Energy and Resources
Hon Simon Bridges at
his office at the Beehive,
Wellington’s iconic
­parliament building.
On the South Island, the HVDC link begins at Benmore substation, where the hydropower collected from the surrounding lakes
is transformed to DC to travel north – or, in turn, North Island power is fed into the South Island AC grid.
The new Pole 3, installed by Siemens,
has a continuous rating of 700 mega­
watts in both directions and, as with
Pole 2, is capable of operating in
­bipole and individually in monopole
configurations. The bidirectional
­design is needed because, in winter
when power demands are high for
heating, water stocks in the dams
feeding the hydroturbines can run
low; rain becomes snow and snow
does not melt until spring. Then,
power from the North Island’s gener­
ators – geothermal, hydro, gas, wind
and the sole New Zealand coal-fired
station at Huntly – is needed to meet
South Island needs.
Similar standards and equipment up­
grades were built into the Benmore
substation in southern Canterbury
where hydro output is collected and
converted to DC current for transmis­
sion at 350 kilovolts over 611 kilome­
ters north to the three submarine
80 Living Energy · No. 10 | May 2014
c­ ables that carry it across the turbu­
lent Cook Strait and then on overhead
lines to Haywards. There it is converted
to 220 kilovolt AC for the 700-plus
kilometer journey through the North
Island to Auckland and beyond.
If Transpower’s new system is unique,
so, too, were the formidable construc­
tion and electrical engineering prob­
lems that were solved.
Firstly, Haywards is a mere 300 meters
from a major fault line; hence the seis­
mic standard demanded. Secondly,
50 percent of the nation’s total power
is supplied by hydro generating sta­
tions in the far south of the South
I­sland, but 76 percent of the 4.5 mil­
lion population lives in the North
­Island, one third of it (about 1.12 mil­
lion) in Auckland. If Haywards failed
or stopped for even a few hours, the
consequences for the national econo­
my and well-being would be huge.
Thirdly, the existing system could not
New Zealand’s energetic
Minister of Energy and Re­
sources, Hon Simon Bridges,
says the major upgrade to
Transpower’s high-voltage
transmission and control
system will secure New
Zealand’s electricity system
for the next 20 to 30 years.
be shut down while the build proceed­
ed. Concrete was poured, footings
were installed and equipment con­
nected while 350,000 volts surged
above the engineers and workmen.
Yet not one serious accident occurred
in the four years.
Built to Withstand the WorstCase Scenario
Dr. Günther Wanninger, the electrical
engineer who headed the Siemens
team in New Zealand for the four
years of the project, says the seismic
challenge was “the biggest we ever
had to face.”
“We had to apply the highest seismic
standards in the design for an inter­
connect that is a major part of the
New Zealand infrastructure. Recently
there was an earthquake in Welling­
ton, reasonably big – magnitude 6.7 –
but with the design we have applied,
there was no effect at Haywards.”
Security and reliability of
generation and supply are
not sufficiently discussed
by either Government or
the public, he says. “We take
it for granted and don’t de­
bate it enough, but we must
be sure of supply in our
challenging environment.
The HVDC project just com­
pleted will support New
Zealand in security of sup­
ply far into the future.”
u
It is the largest single com­
ponent of the NZ$5 billion
investment the ­Government
will make in the grid over
the next eight years, he
says. By increasing geo­
thermal and wind genera­
tion, the Government plans
to raise ­renewable supply
beyond 90 percent by 2025.
Ultimately, the country’s
only coal-fired power sta­
tion at Huntly in the North
Island will be closed.
2011, we can see population
and demand growing there,
too. In Christchurch we
have by some measures the
biggest rebuilding project
in the world going on, and
as that progresses and
business and industry re­
develop, demand for elec­
tricity there will also grow.”
“I believe our system, with
about 75 percent of total
generation from renewable
sources, is one of the best in
the world. It gives us ­many
advantages,” states Bridges.
Efficiency in use of energy
is constantly improving and
New Zealand now has more
than 1 million smart me­
ters, Bridges explains.
“There is also scope to im­
prove the use of electricity
in transport.”
“Our population is growing,
particularly north of Taupo
(in the center of the North
Island) but, as Christchurch
rebuilds after its disastrous
earthquakes in 2010 and
“The HVDC upgrade is a
great success in terms of
knowledge and skills for
New Zealand,” says Simon
Bridges. “Return on this in­
vestment will be good.”
Benmore also had seismic challenges,
a little lower than Haywards, but the
same standards were applied there.
“It made commercial sense for us to
have a single design. The buildings
are identical,” Dr. Wanninger says.
Aurecon, a New Zealand company with
a worldwide reputation in seismic
engineering, produced new designs
for lead-rubber bearings, 600 milli­
meters in diameter, and sliders, to
protect the long, deep piles on which
the buildings and the equipment
are mounted from both vertical and
horizontal movement. Now the valve
hall, for example, can move up to
700 millimeters horizontally without
damage in an earthquake. Everything
in the switchyard is similarly isolated
from shocks.
“Aurecon tells me there is no build­
ing in the world that has such high
seismic standards as the valve halls
we have built for Transpower,”
Dr. Wanninger says.
“We have built for high seismic re­
quirements in California, China and
Chile, but those standards were not
high enough for New Zealand,” he
says. “So we had to design new equip­
ment, new damper solutions, and
most had to be put on a shake table in­
to which we put earthquake data for
the rigorous testing we carried out.
But the transformers (300 tonnes
each) were too big to do that, so in
parallel we made computer models
and ran those with several ‘design
earthquakes’ to show the equipment
could withstand such forces.”
Further electrical performance tests
were done on-site, but because of that
single-backbone configuration of the
grid, testing had to be done while the
grid was live. Nothing could be isolat­
ed; again, a unique problem.
Project director
Andrew Gard explains
the smoothing reactor’s special damping
system in front of
the camera.
82 Living Energy · No. 10 | May 2014
Live Market Conditions
Siemens designed new damper solutions
for each piece of equipment and built in
extra cable loops.
Electrical engineer Andrew Gard,
Transpower’s project director, explains
the problem: “New Zealand operates
a market system determined by sup­
ply and demand, governing price and
source of the power. Siemens at the fac­
“There is no building
in the world that has
such high seismic
standards as the
valve halls we have
built for Transpower.”
Dr. Günther Wanninger,
Siemens
tory in Germany tested every scenario –
1,500 tests over ten months testing
the control system to its limits. We
could not do that on the grid; it would
take years. So we chose a representa­
tive sample to test the boundaries of
those factory tests in the live environ­
ment – about 190 tests.
“Test plans had to be written for each
of those and submitted for approval
from the Transpower grid manager.
The plans went back and forth and a
security analysis was done on the
proposed test for the day, because
grid conditions vary, day to day, hour
to hour,” Mr. Gard says.
u
Living Energy · No. 10 | May 2014 83
Reliable power supply keeps
the lights on in “the coolest
little capital in the world.”
Wellington is New Zealand’s political center, its
second-largest city and an
important hub for the country’s world-famous film
industry.
84 Living Energy · No. 10 | May 2014
But it was not just a matter of starting
a test. Electricity flows had to be jug­
gled within the market. A test might
require 500 megawatts to go south
for an hour or two, but the market
might want to send 800 megawatts
north. “So we set up our own market
trading team,” Mr. Gard says.
Flow on the grid changes as market
traders do deals minute by minute to
get best prices and meet demand.
So, the test team’s traders had to pay
to control and, in effect, distort the
market and get the flows needed for
some of the testing. They had to
check that no maintenance was in
train and no AC transmission con­
straint that might block the flow.
“You are just juggling everything –
maintenance, generator situation,
and so on – two or three hours before
the test,” he says. “Some tests took a
few minutes, but the average dura­
tion was half an hour to an hour.”
Transpower’s chief executive Patrick
Strange monitored the tests and the
cost. “We probably spent NZ$20 mil­
lion to achieve the flows we wanted,”
he says. “It was a world first. We were
nervous about doing it, but we
couldn’t see any other way, and it was
successful. It was a new experience
for Siemens, too, but they came to the
party and between us we achieved
the results we wanted.”
u
“We set up our own
­market trading team.”
Andrew Gard,
Project Director HVDC Pole 3
Living Energy · No. 10 | May 2014 85
Reportage
Reportage
Engineered for Highest
­Seismic Requirements
New Zealand
Facts and Figures
The HVDC Inter-Island Link
From Benmore substation on the South Island the HVDC line travels 534 km overland to Fighting Bay
in the Marlborough Sounds area.
3 x 350 kV/500 MW submarine cables of 40 km length bridge the Cook Strait from Fighting Bay to
Oteranga Bay on the southern tip of the North Island.
Further 37 km of HVDC line continue from Oteranga Bay to Haywards substation near Lower Hutt.
The upgrade increased the HVDC link capacity by more than 70% from 700
MW to currently
1,200 MW. The technology is future-proofed to boost capacity to 1,400 MW.
New Zealand’s electricity generation
by fuel type (2011)
New Zealand’s electricity demand by region (2011)
North Island
(Auckland and Northland)
Other Thermal 0.1 %
Bioenergy 1.3 %
28 %
Auckland
North Island (Other)
Hamilton
Tauranga
Wind 4.5 %
34 %
Coal 4.7 %
Geothermal 13.4 %
Wellington
Gas 18.4 %
Hydro 57.6 %
Christchurch
Dunedin
South Island
37 %
Source: Energy Data File, 2011 Calendar Year Edition
Award-winning filmmaker Gerard Smyth takes you on a visually stunning journey along the backbone of
New Zealand’s transmission system as raindrops feed rivers on the South Island, lakes generate power and
HVDC travels over land and sea to the North Island.
siemens.com/living-energy/pole3
Living Energy at
86 Living Energy · No. 10 | May 2014
Minister of Energy and Resources
Hon Simon Bridges says that New
Zealand aims to push renewable out­
put above 90 percent of national
needs, raising geothermal output
from the current 14 percent to above
20 percent and doubling wind gener­
ation, now at 4.5 percent, over the
next decade to 15 years. “And it is all
based on strong market principles,
not supported by government subsi­
dies,” he says.
New Zealand’s HVDC project was a
huge challenge for everyone involved,
from the Siemens and Transpower
engineers and site technicians to the
construction and transport teams
and the principals who took responsi­
bility for the venture’s success.
“This is the first of its kind and some­
thing nobody has done before,”
Dr. Wanninger says. “So now, we have
equipment certified to these extreme­
ly high levels. We will see if anyone
will ever ask again for such high re­
quirements. Maybe Japan in the fu­
ture after their recent earthquakes.
We are now building on a platform in
the North Sea and that also is very
challenging. Siemens is prepared to
take up any challenge and we never
give up. When we commit to a project
we will finish it, whatever the chal­
lenges, and that is good for me as an
engineer.”
Transpower CEO Patrick Strange, who
oversaw the four-year project, has
the last word: “We chose Siemens
because we know the quality of their
work. They don’t know how to build
bad products. They build to very high
standards and take great pride in
their engineering. We were confident
Siemens would build very high-quali­
ty equipment and systems and we
were right. Transpower and Siemens
can be very pleased and satisfied with
what has been achieved.” p
Patrick Strange was CEO of Transpower
until end of January 2014 and can look
back on the successful completion of
one of the largest infrastructure projects
in New Zealand’s recent history.
“Transpower and
Siemens can be
very pleased and
satisfied with
what has been
achieved.”
Patrick Strange,
Transpower CEO
from 2007 to 2014
Garry Barker is a technology editor at The Age
newspaper in Melbourne, and has worked as a
foreign correspondent in over 50 countries.
Living Energy · No. 10 | May 2014 87