Making
Germany’s
Energy
Transition
Possible
Germany has boosted renewables production over the
last decade, reaching 31 percent in the first part of 2014.
­However, efficient use of that energy requires that
­transmission and distribution networks be updated.
Text: Rhea Wessel Photos: Andréas Lang
Green switch
Solar rooftops are contributing
to Germany’s goal of raising
the share of renewables
to 35 percent by 2020.
Kolumnentitel
Across Europe, demand for renewable power is increasing rapidly. Governments and the EU are pushing to achieve energy independence, and have introduced market incentives to stimulate both production and, more recently, consumption of green energy.
24 Living Energy · No. 11 | December 2014
Kolumnentitel
Local grids must be updated for efficient distribution of energy generated in wind parks (above: Netze BW wind park at N
­ iederstetten)
and locally from solar, biogas, and ­hydropower installations.
Living Energy · No. 11 | December 2014 25
Energy Management
ower generated from renewable energy sources, such as
wind, sun, and water, is not
­only increasing stability demands on
grids, it is making them more complex: The once linear path of power
from the producer to the user is
­becoming a power matrix of multilayered systems, with dispersed
­renewable power sources being fed
into the grid at multiple voltage
­levels, often far from where the energy will be consumed.
To accommodate these changes in the
energy mix and various voltage levels, transmission networks must be
bolstered to carry energy across long
distances with low losses, and to
maintain stability – particularly in
heavily loaded AC systems. Likewise,
distribution networks must become
smarter and more capable of controlling and regulating a network with
­multiple fluctuating infeeds.
Germany, in particular, looks set to
benefit from new technologies in both
network areas that will help the country
efficiently transmit high-voltage power
made far from the place it is needed,
and then convert and distribute it more
Dispersed generation leads to “fuzzy” load
flow, creating new challenges for grid
operators.
26 Living Energy · No. 11 | December 2014
efficiently on a local basis. German
companies have built some of the
world’s largest offshore wind farms
in the North Sea and operate large
­onshore wind farms in the country’s
northern flatlands, yet demand for
power is high in economic centers like
Munich, hundreds of kilometers to
the south.
As we follow the stream of energy
from way up north where it is produced to deep in Bavaria, we see how
new technologies – HVDC PLUS (highvoltage direct-current transmission)
in full-bridge topology with DC compact switchgear, and intelligent substations – will help enable the socalled “energy transition” in Germany
and support the country in meeting
its goal of using 35 percent renewables by 2020.
These technologies are making it possible to move from an energy chain to
a power matrix in the transmission
and distribution grids. They help operators deal with what is often called
“fuzzy” load flow that comes from
dispersed generation, such as rooftop
photovoltaics producing energy in
low and medium voltage, or offshore
wind parks producing high volumes
in high voltage.
HVDC PLUS will help German energy
transmission companies provide dynamic, reliable grid access to offshore
wind farms at the required voltage,
and it can also be used to support the
AC system at particular nodes. HVDC
is seen as the backbone for what some
experts and policy makers have
dubbed the “super grid,” or a high-­
capacity transmission network for efficiently moving high-voltage power
to load centers.
By 2018, Germany plans to have parts
of its first HVDC overlay grid in operation, which will, along with other
links, eventually carry power from the
North Sea to the south of Germany.
Some 6.5 gigawatts of offshore wind
power are expected to be produced in
Germany by 2020, and these lines will
play a crucial role in bringing that
­energy to load centers. An important
feature of HVDC PLUS based on voltage-sourced converter (VSC) technology is its black-start capability. This significantly improves system recovery
after a blackout. In 2010, Siemens
built the first HVDC PLUS link with undersea cables in San Francisco in the
Trans Bay Cable project. Similarly, the
first HVDC PLUS project with a land
cable will connect the power grids of
France and Spain in 2015. The projects
in Germany present an additional
technical challenge due to plans to
use DC transmission lines on existing
AC overhead towers.
SylWin converter station
SylWin1 in the North Sea provides offshore grid connections and can transmit enough
wind power onshore to power
900,000 homes. Space-saving
gas-insulated switchgear from
Siemens serves as the “fuse
box” of this installation.
From North to South:
a Vision for an HVDC
Overlay Grid
A segment of the project in Germany,
dubbed the Ultranet, is being planned
by Amprion and TransnetBW and
would back up existing AC networks
by carrying energy from Osterath to
Philippsburg by overhead line (in a
so-called point-to-point configuration). Siemens has bid to provide an
HVDC PLUS system that would later
operate with multiple terminals.
­Marcus Häusler, Portfolio Manager
for HVDC solutions at Siemens, says,
“As it develops an HVDC overlay grid,
Germany is planning several multiterminal links. The idea is to develop
stepwise from point-to-point terminals to something like a radial DC
grid in the next 10 to 15 years. Eventually, Germany’s lines can be connected to those of other countries to create a European super grid.” He adds,
“Right now, we are planning a sort of
super highway with one-direction energy flow and with a few terminals.
The super grid would be an exciting
way to use renewable energy in a
more efficient way, to increase grid
stability and develop markets for exchanging energy across borders.”
The technical challenge for Siemens
in the Ultranet project was to enhance the HVDC PLUS system to be
able to operate with overhead lines
(as opposed to underground cables).
The answer it found was the new
Siemens HVDC PLUS technology in
full-bridge topology, which allows selective fault clearing on overhead
lines in radial multiterminal systems
through VSC technology. Fast disconnection, a prerequisite for selective
multiterminal applications, will be
made possible with 500-kilovolt DC u
To accommodate changes in the
energy mix and facilitate the shift
from several big nuclear power
plants to many distributed renewable sources, transmission grids
must be bolstered to maintain
stability and to allow low-loss
transmission.
Photo Offshore: Siemens
P
Living Energy · No. 11 | December 2014 27
Energy Management
The Expert Voice: Rik W. De Doncker
Rik W. De Doncker is the Director of the E.ON Energy
Research Center (E.ON ERC) at RWTH Aachen University in
Germany. He also directs the Research CAMPUS Flexible
Electrical N
­ etworks (FEN) of RWTH CAMPUS Cluster Sustainable Energy. He argues that there is a greater role for DC
in our energy systems.
Do you see DC coming back on a wider scale in power
­distribution?
The main problem DC faced during the early days of electricity was the fact that the DC transformer did not yet exist.
Since power semiconductor devices were invented, engineers
have been able to realize so-called “power electronic DC
transformers,” i.e., DC-to-DC voltage converters. Since these
conversion systems operate at higher frequencies than the
50- or 60-hertz AC grid, these DC transformers can be built
lighter, thereby using less materials (magnetic steel and
­copper). As the number of power electronic applications
increases, the cost of power electronic converters is decreasing. I expect DC transformers to become more efficient and
cheaper than classical 50- and 60-hertz AC transformers.
How can DC transmission and ­distribution help integrate
renewables?
DC transmission and distribution are ideal for renewable
power sources and more distributed generation systems
(e.g., small-scale combined heat and power applications),
since they offer higher efficiency than 50-/60-hertz AC solutions. We should not forget that photovoltaic systems basically produce DC energy. The AC grid (and the AC grid code)
requires expensive converters to regulate and convert DC
into AC. High-power wind turbines (above 2.5 megawatts,
typically built offshore) use full-converter systems to first
rectify to DC and then invert back to the grid AC voltage
and frequency.
Overhead line at Oberstetten
In the context of Germany’s
energy transition, innovative
solutions are required at the
intersection of transmission
and distribution grids.
28 Living Energy · No. 11 | November 2014
u
compact switchgear, a gas-insulated
technology ­under development that
will work in conjunction with the fullbridge technology. Häusler says the
full-bridge topology provides a powerful converter capable of reversing
the polarity of the line voltage, at
least for a short ­period of time, in order to extinguish DC current and deionize the electric arcs resulting from
lightning strikes on overhead lines.
“During normal operation, the DC
voltage is like a battery in your car.
It’s always constant at a certain voltage. But the full bridge allows us to
How do DC grids contribute to the safety, stability, and
cost-efficiency of power distribution?
DC transformers can actively regulate the voltage and the
power flow between DC voltage grids. Their multiterminal
capability allows DC grids to be interconnected so that the
energy can be routed in the local and regional grids and does
not need to be fed into the transmission grid. Classical AC
transformers do not have that functionality. That is why the
AC distribution grid is radial, top-down.
Furthermore, DC transformers intrinsically can limit overload
and short circuit currents, allowing operators to coordinate
short-circuit protection electronically. As DC distribution in
cables and wires has no skin and proximity effects, DC systems can carry twice the power rating of AC systems, keeping
the (peak) insulation voltage identical.
What will the future transmission and distribution grid
look like?
Most scenarios for CO2-neutral electrical energy production
in Europe show that about one third of the installed energy
production and power base will be installed at the transmission level, one third at the distribution level, and the remaining third at low-voltage networks in buildings and homes,
providing balancing power at each voltage level.
DC distribution lends itself better for underground cables.
Also, second-generation high-temperature superconductors
(HTS) are only superconductive with DC currents. As HTS
cables can carry very high currents, fewer transformation
­levels to medium- or high-voltage levels are needed. This fact
also saves costs when switching over to DC grid technology.
DC cables emit less electromagnetic noise and have ultralow
magnetic fields (about one tenth of the earth’s magnetic
field) compared to three-phase AC wires, which also produce
alternating fields. No doubt the public will accept DC cables
faster than AC overhead lines, due to the “Not in my backyard!” phenomenon.
control the voltage electronically.
This is important whenever disturbances on the DC side are to be
­expected,” Häusler says.
Offshore Gas-Insulated DC
Switchgear
DC compact switchgear technology
needed for multiterminal arrangements will be used to reduce the size
of components in converter stations
as well, and to provide safe encapsulation. Marking a major milestone
in ­innovative solutions for HVDC
­technology, Siemens has developed
­ as-insulated DC switchgear for
g
320 kilovolts, a typical voltage to
­accommodate offshore cable con­
nections.
The technology allows the size of the
DC switchyard in converter stations to
be reduced by up to 95 percent. This
is of special interest for installations
on HVDC offshore converter platforms,
since space can be reduced from roughly 4,000 to 200 cubic meters. The technology is market-ready, and the first
installation is expected by 2017.
Denis Imamovic, who is responsible
for gas-insulated solutions for DC at u
Living Energy · No. 11 | December 2014 29
Energy Management
Energy Management
Siemens, says: “As a portfolio manager,
it’s my job to look to the future. I have
to start developing products now that
will be needed in five years. We have
developed gas-insulated 320-kilovolt
DC compact switchgear for offshore
applications, and now we’re working
on 500 kilovolts for land-based projects in Germany.”
According to Imamovic, the main
­advantage of the technology is its
compactness. Compared to air-insulated technology that keeps high-voltage parts away from the ground and
from each other over distances of
­several meters, gas-insulated technology r­ educes the insulation distances
to several centimeters. By putting the
switchgear into a compact gas-filled
enclosure, Siemens reduces the size
of the equipment and provides safe
encapsulation. “We achieved gas
­insulation for HVDC systems by developing a new material that can
withstand the DC voltage, using resin-impregnated paper insulation
technology,” Imamovic says.
Experts believe that companies working in offshore energy are especially
interested in the compact switchgear
made possible through gas-insulated
technology since it reduces space
­r equirements. Furthermore, new
transmission technologies, partly underground, are needed, because in
30 Living Energy · No. 11 | December 2014
Europe production is far away from
where e
­ nergy is needed, and the energy must be delivered across long
distances to consumers. Gas-insulated technology has a crucial role to
play within the e
­ ntire system. If gasinsulated technology for DC can become as mature as it is for AC, that
would be a breakthrough. Germany,
in particular, needs space-saving solutions and transmission technologies with high efficiencies, due to the
energy transition.
Distribution: Welcome to
the Bavarian C
­ apital
Meanwhile, as we wind through the
half-timbered villages of Germany’s
north into the castle-studded hills
and mountains of the south, we arrive at the spot where Munich’s famous ­industrial brands and its equally ­famous beer halls need electricity
to sustain operations. There, in the
­Bavarian capital, energy provider
Stadtwerke München is aiming to
produce enough green electricity at
its own plants by 2025 to meet the
power requirements of the entire municipality of Munich, which stand at
around 7.5 billion kilowatt-hours per
year, ­according to Florian Bieberbach,
the head of the provider. This would
make Munich the first city in the
world with over a million inhabitants
breakers is added so that human
i­ ntervention is not necessary locally
at the substation and downtimes
can be minimized. If a line is hit, rerouting takes place at the control
­center or even in a decentralized
way in the distribution grid, making
the network a “self-healing” system.
Load flow optimization, on so-called
Level Three, is an important capability
in regions where lots of renewables are
fed into the grid, since it can prevent
energy losses and maintain stability. Features include regulation algorithms for
regulated distribution transformers.
Siemens intelligent transformer substations are designed holistically from
end to end, with a focus on compatibility, standards, and reduced size. “Our
application starts at the bottom with
the switchgear, including the motors,
the IEC sensors, the c­ ommunication,
and all the equipment for the control
center,” says Schüpferling. “With a
complete Siemens solution, our customers know that all components are
compatible and optimized for working
together.”
In addition, due to the standards to
which the technology is designed,
­operators have full data compatibility
at all levels. Opitsch says, “If you once
enter a parameter, for instance for the
RTU, the same parameter can be used u
Loads to match renewable feed-in
Increasing sales of electric cars like the BMW i3
are creating new demands on the grid, for
instance at solar-powered charging stations.
Making Germany’s Energy
Transition ­Possible
Germany alone has roughly 575,000
transformer substations, many of
which are ending their technology life
cycle and are up for refurbishment or
replacement to keep outage times low.
Across Europe, the number of transformer substations (often called Ring
Main Units) in operation is estimated
at 4 million. In the USA, the number
of pole-top stations is roughly 11 million. “Replacing these is always a
question of money and a question of
time,” says Bernd Schüpferling, the
Senior Key E
­ xpert for Control Technology MV Switchgear at Siemens.
Siemens offers new installations of
intelligent transformer substations
or retrofits conventional transformer
substations with electronics for
­monitoring and telecontrol, making
the substations progressively more
intelligent.
Photo : Siemens
Intelligent substations can monitor and control both medium- and
low-voltage distribution grids and actively ensure stable voltage.
Level One intelligence for monitoring
allows for fast fault localization in
the distribution network. The substation’s remote terminal unit (RTU) is
equipped with a communications
­connection and short-circuit, earthfault direction indicators, along with
current sensors and voltage sensors.
If a construction crew hits a line and
the associated substation is outfitted
this way, the short-circuit indicators
will note the failure and communicate it through the RTU.
When a substation is upgraded to
Level Two intelligence for telecontrol,
a motor operating mechanism of the switch disconnectors or circuit
to achieve this goal. As part of this,
Stadtwerke München is investing in
offshore wind production in the North
Sea. “Wind is a good source of renewable energy for us because we can make
great progress toward our goal with individual projects,” says Bieberbach.
Once that energy arrives in Munich –
perhaps through a
­ dvanced transmission lines like the ones discussed
above – the local grid will also ­require
updating, if the ­energy from the north
is to be distributed efficiently, along
with the power being produced locally
with traditional methods or solar panels, biogas installations, and hydropower stations.
That’s where intelligent substations
from Siemens can help by providing
network monitoring, remote control
of networks, and regulation of the
load of energy in medium- and lowvoltage distribution grids, without
grid ­expansion.
Essentially, intelligent substations
are compact medium-voltage switchgears (also gas insulated) with communication capabilities that can detect potential overloads of operational
equipment and ensure voltage stability, said Bruno Opitsch, Senior Key
Expert Energy Management, Energy
Automation at Siemens.
Living Energy · No. 11 | December 2014 31
Turning Point
Germany’s Shift to Renewables
Global oil production
throttled; the government promotes
energy efficiency
with regulations for
maximum usage
amounts.
Unlike other European
countries, Germany
completely opens up
the retail electricity
market to competition.
1974
Germany founds
the ­Federal
­Environment
Agency.
Plans are sealed to
decommission
nuclear plants in
Germany until
roughly 2022.
Fuel-efficient and
clean cars get
a boost due to an
incremental tax
on ­gasoline.
1998
1977
Germany’s energy transition, its move to increase the amount
of renewables in the German grid, experienced fits and starts
as the country’s capacity for generating renewable energy
was expanded rapidly over the past decade.
After the nuclear accident at Fukushima in 2011, Chancellor
Angela Merkel sped up plans to phase out nuclear plants. The
2000
1999–2003
1980
1999
2000
2005
A key study says that
Germany could make
an economically
­sustainable transition
from fossil and nuclear
fuels to renewables.
Scheme announced
to spur demand for
solar roof panels.
The Renewable Energy
Act (EEG) goes into force,
guaranteeing preferential
prices to producers of
renewable energy
financed by end users of
electricity.
Germany’s Network
Agency takes over
as the regulator of
the electricity and
gas markets.
last shutdown is planned for 2022. Looking ahead, some consumers are worried about the costs they carry for the energy
transition through a renewable energy surcharge. Still, by
2022, the goal is for Germany to use 35 percent renewables.
Some highlights:
The EEG is amended to
improve conditions for
offshore wind power,
among other points.
In the first part of 2014,
a particularly sunny
period, Germany’s share
of renewable energy in
the grid was 31 percent.
2009
2014
2011
Chancellor Merkel, who had
in 2010 said she would
extend the life of some
nuclear plants, reverses that
position. The country instead
speeds up the phaseout of
nuclear power, with plans for
the last shutdown in 2022.
Sunset for Biblis
The nuclear plant at Biblis in Hesse, Germany (above) was closed down in March 2013. Using the electric generator as a motor (rotating
compensator/phase shifter), it continues to feed reactive power into the grid in synchronized condenser operation for grid stability.
at all levels – from the substation to the
controller. This seamless ­engineering
saves costs. With around 575,000 transformer substations in Germany, saving one hour per substation is a lot
of savings.”
Netze BW: One Operator’s
­Experience
Netze BW, a distribution network
­operator in Germany recently signed
a contract to modernize the distribution grid in the Niederstetten area
of the state of Baden-Württemberg
to accommodate the increasing
amount of renewables being fed into
the grid and improve stability.
It is installing a distributed grid area
controller (also called a regional
­controller) from Siemens in the
Nieder­stetten substation, which is
32 Living Energy · No. 11 | December 2014
based on a Siemens Sicam energy
­automation system that controls
voltage and fault management, and
provides the communications connection. In case of a fault, the system
can restore affected grid sections
without human intervention, acting
as a self-healing system.
Netze BW is equipping nine secondary
substations located at the most important nodal points with full energy
­automation technology and five substations with voltage measurement
systems in the dead-end feeders to
monitor the network.
Voltage management is made possible
using two medium-voltage in-phase
regulators, which include power quality measurement on the primary and
secondary sides. These are installed for
long-range voltage control.
The voltage controllers receive their
tap change commands from the distributed grid area controller, based on
the distributed voltage measurement
in the medium-voltage grid.
Martin Konermann, the technical head
of Netze BW, says, “Germany’s energy
transition will take place in the distribution networks. We want to make
the transition possible without huge
costs and without a loss of energy security. This project will make a big
contribution to these goals.”
Looking Forward: New Load
Demands Require Intelligent
Substations
Indeed, intelligent substations like the
ones being built and tested in
­Niederstetten are seen as the future of
energy distribution – and as a key en-
abler for Germany’s energy transition.
The substations are market-ready at a
time when two trends have converged:
Not only is demand for intelligent transformer substations high – to integrate
renewables in the grid and replace
­aging technology – advances in telecommunications and electronics have
made the technology faster and allow
for more cost-effective transmission of
monitoring and control data as well.
Without intelligent distribution networks, Germany’s move to renewables
would stall, not only due to grid instability from the overcapacity of green
energy, but also due to the sheer cost
of expanding the physical grid and
the large amount of disruptive construction that would be needed in
communities. Furthermore, it would
be ­impossible to implement
new-generation storage (see separate
article in this issue on page 36). “In
­Germany, i­ ntelligent substations are a
game changer,” says Opitsch.
Looking forward and outside of
­Germany, demand for renewable
­energy is increasing rapidly for a variety of reasons, such as a push by
­European leaders to become energy
independent and select incentives to
boost consumption of green energy
(after years of incentives to support
production by individual consumers,
or “prosumers”).
In Norway, for instance, the government’s tax regime to boost sales of
electric cars and penalize the purchase of traditional ones is creating
new demands on the grid. Opitsch
says, “It’s the counterpart to integrating renewables. Now we’ve got new
load demands, since most drivers
want to charge their cars at the same
time when they’re home from work in
the evenings.”
Schüpferling summed up the outlook
for intelligent transformer substations.
“Ten years ago, we saw small pilots and
installations of intelligent features for
substations. But now many factors have
come together. Renewables are being
produced in high volumes, operators
know something must be done to integrate them into the grid more efficiently, and the technology is now available
as an off-the-shelf industrial solution.
These trends are very promising for
­Germany’s energy transition.” p
Rhea Wessel is an American freelance writer
based near Frankfurt, Germany. Her work has
appeared in The New York Times and the Wall
Street Journal.
Living Energy · No. 11 | December 2014 33