Download Electrical power distribution of tomorrow

E-Installation 2/2014 | Cover story
Reliable power supply for the digital factory
Electrical power
distribution of
tomorrow
Professor Berger studied electrical engineering and design at TU Dresden and
wrote his doctoral thesis on the modeling
and simulation of low-voltage switchgear.
After more than 12 years of industry
experience as head of applied research at
Klöckner Moeller GmbH in Bonn, he was
appointed professor in the Electrical
Equipment and Systems Department at TU
Ilmenau in 2003. He is a member of the
International Council on Large Electric
Systems (Conseil International des Grands
Réseaux Électriques, CIGRE) and the
Association for Electrical, Electronic and
Information Technologies (Verband der
Elektrotechnik, Elektronik und Informationstechnik, VDE), head of the ETG/ITG
Department of Contact Behavior and
Switching, a member of the Scientific
Advisory Board of the VDE’s Power Engineering Society (Energietechnische
Gesellschaft, ETG), and a member of the
Electrical Engineering / Information
Technology sector committee of the
German national accreditation body
(Deutsche Akkreditierungsstelle GmbH,
DAkkS). Internationally, he represented
Germany in the International Advisory
Group for International Conferences on
Electrical Contacts.
Siemens AG / A. Kradisch
Univ. Professor D
­ r.-Ing. Frank Berger
Cover story | E-Installation 2/2014
Intelligent systems, networking,
and digitalization – these are
the key topics in discussions
today. But the networked
factory with automated
production processes also
poses new challenges for
electrical power distribution.
We spoke about this with
Professor Frank Berger of the
Department of Electrical
Equipment and Systems in the
Electrical Engineering and
Information Technology Faculty
at TU Ilmenau.
Professor Berger, digitalization in
production is making great strides
forward, especially in Germany.
More and more automation
components with their own
“intelligence” are being networked
together – in some cases over the
Internet – and autonomously
managing production. Yet for all
the independence and “intelligence” of these systems, they do
not work without electricity. What
does this new scenario mean for
power distribution?
Frank Berger: In networked production, which controls and regulates processes virtually independently, the locations to which electrical energy
must be supplied, and the times when
it is needed, change constantly during
production. Production machines are
flexibly turned on and off and dynamically regulated in terms of their process control. That means the electrical
power supply and distribution must be
designed to be flexible, and it must be
able to be adapted to current needs at
any time. Depending on the local conditions and opportunities, this can be
accomplished through flexible busbar
systems or cables with cable carriers,
for example.
In terms of devices, there will be
new challenges, such as for circuit
breakers, but also for the planning and communicating over the Internet. The
configuration of electrical systems in necessary structures would then be
general. New connection techniques available. It is about huge amounts of
will likely become necessary due to data that need to be prioritized. Data
higher demands regarding the electri- with short-circuit and diagnostic mescal loads, ambient conditions, and sages, for example, must always be
number of cycles. In the future, with transmitted, and other information
evermore transmission paths with nu- has a lower priority. In addition to new
merous contact points, greater joule data regimes, many new distributed
losses may occur. The probability of a energy systems are needed as well.
fault may rise, even as the reliability of This also results in a great deal of comthe individual components increases. munication between the switching
This means a great deal of information and protection equipment. In some
must be determined about the electri- cases, this must be carried out in real
cal power supply and the electrical time.
network, which requires more sensors,
A diverse array of control and reguwhich in turn also require their own lation processes needs to be adpower supply in some cases.
dressed, and this must be accomAnother trend can be seen with plished with high availability and secuplug-in connectors, for example. In rity. With Totally Integrated Power
the future, these should have electri- (TIP) and solutions for smart grid recal switching capacity, similar to elec- quirements, Siemens has laid a solid
tromechanical switching devices. This foundation for further developments
will make it possible to implement tool in this area.
changes on robots under electrical
In order to transport energy from A
load during the production process.
to B with minimal losses, in the future
In general, through automating and the use of DC voltage cables could be
increasing the flexibility of manufac- an option for low voltage. These have
turing processes, distributed electrical lower losses than cables carrying AC
loads (tools, machine tools) and dis- voltage. Another trend is the intercontributed power generators also need nection of conventional three-phase
to be controlled and regulated again current systems with DC power distriand again with regard to their avail- bution systems. Standardized interability and energy costs.
faces and modules are necessary for
these coupled AC/DC networks.
So energy management is the
catchphrase?
What does power distribution need
Frank Berger: It isn’t just a catch- to look like to be ready for the
phrase, but I will get to that later. Pro- future? What trends can already be
duction should always be organized in recognized today or are already in
an energy-efficient and cost-effective implementation?
manner. Constant change and rapid Frank Berger: In the production proreactions during highly flexible pro- cess, each function must be safeduction also mean a high volume of guarded individually and in interaction
data streams for wired or wireless with the system. For this, devices need
transmission of information. In harsh to be able to troubleshoot themselves.
industrial environments in which cur- When switches are installed in a parrents are connected, plant owners ticular location, they need to detect
must reckon with high electromag- how many times a fault current occurs,
netic interference caused by current for example – even when production
couplings and switching operations, is reorganized. After a production adso the electromagnetic compatibility justment, there may be other short-­
(EMC) requirements of electrical com- circuit levels in a “new” electrical netponents and systems will increase dra- work. This diagnosis is possible using
matically.
intelligent sensors in the switch and
The Fraunhofer Institute for Indus- their ability to communicate, including
trial Engineering (Fraunhofer Institut with regard to the diagnosis and prefür Arbeitswirtschaft und Organisa- cise localization and classification of
tion, IAO) predicts that in 2020 some faults. Electronic devices ensure fast
50 billion intelligent objects will be response times of the protection
7
E-Installation 2/2014 | Cover story
s­ ystems. Plug-and-play solutions are
ideal for quick replacement or exchange of switches.
Siemens AG / A. Kradisch
The trend toward decentralization
in power networks has been in full
swing for some time. Power
generation sources range from
power plants to wind turbines to
photovoltaics. What requirements
does power distribution need to
fulfill here?
Frank Berger: For the decentralization
of power grids, good solutions have already been developed under the smart
grid concept. For factories with their
own photovoltaic systems, plant owners can decide whether the power
generated will be used in the company’s electrical network. Depending on
the requirements, this generated
power must be controlled, and a decision must be made regarding whether
the power is fed into the production
process, the external power grid, or a
storage system.
In solar cells, the solar radiation is
converted into direct voltage, and an
inverter converts this voltage into AC.
In Germany, DC power supply for
low-voltage networks is currently not
a focus of consideration. In Finland
and Sweden, there is a variety of considerations in this regard. For example,
in DC systems there are reduced losses,
but there is also no current zero-crossing for the power-off process of the
electrical network. This makes it difficult for circuit breakers to clear electric
arcs. With photovoltaic systems, arc
faults can occur as a fault source.
These need to be quickly detected and
switched off. This makes reliable differentiation of switching arcs necessary.
8
In the departmental
laboratory for switch
technology at TU Ilmenau,
high-energy electric arcs are
generated for test purposes
What role does the circuit breaker
play, especially the compact circuit
breaker, in low-voltage?
Frank Berger: A circuit breaker is the
central element in the protection of
the electrical system. It is installed in
what are known as the nodes of the
network. A switch in a networked grid
that is constantly changing in terms of
structure and load must quickly provide, control, and communicate protection and selectivity information in
almost real time. It should have a
self-configurable trip unit and be able
Cover story | E-Installation 2/2014
to reliably detect and differentiate between faults such as short circuits,
overloads, and fault arcs, and then trip
in response. As a data collector, a circuit breaker should be able to compress and manage data – not just data
from the network but also from the
production process, as well as data relating to efficient and economical energy production and distribution. In
this way, it would be conceivable that
the circuit breaker would use sensors
to detect a change in the location of
production equipment or the frequency of tool changes as well as provide information about the network
load and the grid fee settlement.
Energy efficiency remains one of
the most important issues. What
contribution can a sophisticated
energy distribution system make
here, and how important is the
circuit breaker?
Frank Berger: This is something I
would like to consider from the perspective of energy technology; this as-
Siemens AG / A. Kradisch
The 3VA molded case circuit
breaker from Siemens already
work operation, the production process, or the system load should be
measured and transmitted to the control and management systems. Another possibility would be the implementation of an intelligent “rate
switch” for power management tasks
to take advantage of the power provider’s different rates, such as daytime
and nighttime electricity rates.
performs operationally relevant
tasks such as detecting energy
data and reporting critical system
states to higher-level systems
using the overcurrent release,
auxiliary switches, and alarm
switches. What will a circuit
breaker need to do to meet all the
requirements in the future?
Frank Berger: Circuit breakers should
be self-configurable and communication capable. Relevant faults must be
detected reliably. Data regarding net-
tors). The more of these components
the electrical network contains, the
more sources of loss there are. Equipment and components must therefore
be optimized with respect to power
loss reduction, such as through the
use of new contact materials and contacting technologies.
In summary, it can be said that in an
increasingly complex production environment, the power distribution must
be continually adjusted to keep pace
with the changing requirements of
the production process. The more systems present and networked, the
higher the probability of faults. Plant
owners will have no choice but to record more data and implement diagnostic functions on switchgear for
low-voltage and medium-voltage
“In terms of devices, there
will be new challenges, such
as for circuit breakers, but
also for the planning and
configuration of electrical
systems in general.”
Univ. Prof. Dr.-Ing. Frank Berger, TU Ilmenau
pect is often neglected. There are a
wide range of interfaces. In production, electrical power distribution and
switching and contact components
cause a variety of losses: resistive
losses, eddy current losses, hysteresis
and remagnetization losses, dielectric
losses, and corona losses (the latter
occur only at high voltage). Resistive
losses occur on busbars, in cables, and
at contact points, for example. Hysteresis losses and restraint current losses
occur on switching devices (contac-
technology. Depending on the level of
availability required for the process,
the components must have a long service life, offer secure data exchange
over the Internet, and eliminate
sources of interference – including
those stemming from the Internet.
Communication on all these levels
poses new challenges for standardization work.
Professor Berger, thank you for the
interview.
9