Download Article in English (Word doc)

TRANSFORM Partners present “TRANSFORMER 2020” in Vienna
World premiere: Technology Study for crucial Components of Power
Transformers
During the TRANSFORM 2015 event in Vienna the partner companies GEA, HSP
Hochspannungsgeräte, Krempel Group, Maschinenfabrik Reinhausen (MR), Nynas AB, Omicron
electronics, Pfisterer, Röchling Engineering Plastics and Thyssenkrupp Electrical Steel introduced for
the first time their vision of a future power transformer. It’s called TRANSFORMER 2020 and was
presented in a stunning 3-D-animation at the Austria Center Vienna.
As suppliers of essential components, the TRANSFORM partners collectively cover the range of
power transformers. The innovative power of these premium suppliers has now been consolidated for
the first time as part of the TRANSFORMER 2020 project. The aim of this technology study was to
gain a clearer insight into the challenges faced by the customers and to identify possible approaches
to find solutions. In addition to the technical experts of the TRANSFORM partner companies, the
recognized knowledge of the Technical Universities of Berlin and Dresden, the University of Stuttgart,
the Fraunhofer Institute for Production Technologies in Aachen and the specialized institute PMO for
Usability Engineering in Munich were also on board.
The attendees were faced with a number of challenges regarding the reliability, efficiency, condition
evaluation and diagnosis, as well as on-line monitoring of power transformers. They identified ideas to
address many of these challenges in every module of the power transformer and put these into
practice during the study. In terms of the overall concept, this has led to significant improvements in
important parameters such as, for example, power loss, noise emissions and size. The results were
discussed with chosen specialists from transformer manufacturers and operators and subsequently
the ideas and results of the discussions were designed by Design Tech, the leading industrial design
company in machinery design.
1) Core & Mechanical Structure
ThyssenKrupp Electrical Steel: Low loss GOES core
Grain Oriented Electrical Steel (GOES) is used for the core of the transformer. It is available in a
large range of thickness [0.30; 0.27; 0.23 mm]. The new GOES of 0.18 mm thickness presents
high permeability properties and low specific losses. This enables the OEMs to meet the
requirements of the European Ecodesign regulation for 2021. Stacking more laminates inside a
cross section of the transformer core enables a further optimization of the transformer design to
reduce losses and noise.
Röchling: Stray loss free iron core clamping beams made of Durostone® GFRP
To reduce losses and increase the efficiency of the oil immersed transformer steel beams are
replaced by Durostone® GFRP (glass fibre reinforced plastic) beams. Steel beams in the
magnetic field generate stray losses (load losses) that cause a heating of the beams - energy
losses are the result. Durostone® clamping beams reduce the load losses of the transformer
significantly.
Röchling: Self-adjusting winding clamping system
In current transformer designs the windings are clamped inflexible up to the maximum expected
short circuit force. Pressboard spacer between the windings are shrinking during their lifetime. As
a result the preloaded clamping force of the windings is decreasing.
A spring made of glass fibre reinforced plastic (GFRP) placed between the beams and the coil
clamping rings can compensate the shrinkage and keeps the clamping force of the windings
constant during the entire lifetime.
2) Insulation System
Krempel: Improved presspaper insulation for longer lifetime
The existing oil / paper insulation system has a limited thermal stability. Possible operating
temperatures higher than 90°C have a significant influence on the lifetime of the insulation system.
Especially the cellulose based materials like kraft paper, presspaper and pressboard will thereby
be affected. Due to the degradation of the molecule chains of the cellulose, the mechanical
stability of these materials will be reduced and finally this may induce insulation failures.
The approach is to further improve the insulation system. The cellulose based insulation materials
will be reinforced by using polymeric fibres and / or specially processed cellulose fibres. The goal
is to improve the mechanical strength and also the thermal stability to the paper and board
insulation.
Nynas: New oil additive concept
Prolonging the lifetime of insulation systems by up to 20 percent
Nynas has developed a new concept for an oil additive that could prolong the lifetime of a
transformer’s insulation system by up to 20 percent. The additive works by attaching itself to the
outside of the insulation system’s cellulose structure. As the structure degrades from the inside,
the additive braces it from the outside, thus prolonging its lifetime.
“The existing paper and board insulation systems in transformers have a limited thermal stability,”
says Per Wiklund, Research Manager and Head of Technical IP at Nynas. “High operating
temperatures have a significant negative influence on the lifetime of insulation systems. This idea
is about how to improve this system.” On the surface of a cellulose-based paper or board
insulation system there are reactive chemical groups. These groups can be used as attachment
points for a low-molecular-weight additive. The idea is to use an additive in the oil that would
protect the cellulosic fibres and slow down their rate of degradation.
3) Tap Changer & Control Panel
MR: On-load tap-changer arrangement for optimized transformer design
The new Servo-drive solutions substitute the conventional spring force drive mechanism. This
allows to relocate tap changer components based on their function: diverter switch, selector
switch, pre-selector switch. Utilizing well proven vacuum switching technology enables one
common oil volume in the transformer tank. The relocated tap changer components can be
preferably placed in any open space of a transformer.
MR: Integration of all control & monitoring functions into one control cabinet
Software and hardware is based on common platforms with open interfaces. So the integration of
all customer specific secondary functions becomes possible. Third party solutions like analytic
software or sensors are easily plugged-in to the platform, which guarantees the safety and
security features of the application. The connectivity to SCADA and Network Protection Systems
will be ensured by all necessary protocols.
4) Bushings
Pfisterer: Compact Connection System for Substations of the Future
By the year 2020, there are expected to be 27 megacities each with over 10 million inhabitants.
Global energy consumption in conurbations will continue to increase – while the amount of space
available for substations is set to decrease. At the Transform trade convention, Pfisterer will
exhibit its pluggable Connex system – a connection solution for the construction of compact power
transformers. These can be installed on much smaller areas or even inside buildings to save
space. Thanks to their pluggable high and medium-voltage connecting elements, the transformers
are also quick and easy to replace and can be used flexibly in changing network infrastructures.
Compact substations cannot be realized using conventional transmission lines, which is why
Pfisterer decided to further develop its space-saving, pluggable Connex system, which was
originally designed for cable connections to handle voltages between 12 kV and 550 kV, into a
comprehensive connection system for transformers. It includes a new, ultracompact mediumvoltage connection and a solid-insulated surge arrester for high voltages. Since all components
are touch-proof, they can be safely erected and easily inspected in even the most confined spaces
without any need for barriers. Besides saving space, the pluggable connections also offer cost
benefits in terms of maintenance and spare parts, and also in view of the changing network
infrastructure.
HSP: Paper-less Bushings made of Resin Impregnated Synthetic (RIS)
Our bushings made using the proven RIP (Resin Impregnated Paper) technology include
materials such as special paper, vacuum impregnated with epoxy resin. While paper is a good
isolator, it is also hygroscopic, in other words it absorbs humidity from the surrounding
atmosphere. This humidity can have a negative impact in terms of power dissipation and ageing of
the bushings, which HSP has been able to reduce significantly thanks to a labor-intensive process
during manufacture. This process is time-consuming, however, and increases the costs
accordingly. Following an intensive program of research and development, we have replaced the
special paper in our bushings with a plastic web with homogeneous material properties and
minimal moisture absorption that substantially reduces the disadvantages described above or
removes them entirely.
5) Cooling System
GEA: Load dependent cooling with variable fan speed
Cooling systems are designed for the worst case scenario and therefore oversized for the regular
cooling needs. The goal is to develop standard coolers that have an 'intelligent' control. By
adjusting the fan speed via a control unit different cooling scenarios are possible; e.g. steady
transformer temperature based on load schedule, optimization of sound emission, less pollution of
cooler and fan due to less air volume flow and less energy consumption.
6) Control & Monitoring
MR: Continuous Online Monitoring
Continuous monitoring of the condition of the transformer enables a condition-based maintenance
strategy to extend the lifetime of a transformer. The monitoring system records and analyzes all
relevant operating data including monitoring of the tap changer, transformer utilization,
temperatures, online DGA and the status of protective devices. The system can be easily
extended with functions like automatic voltage regulation and intelligent cooling control based on
the common automation platform.
MR: Bushing-Monitoring via reference voltage measurement
The monitoring system is based on an innovative algorithm to supervise AC-bushings. Using the
bushing test taps as HV capacitances of a capacitive measuring divider, the resulting AC voltage
signal can be analyzed. Referring to an additional voltage signal from the grid, the validity of the
analyzed signal can be proven. The online diagnosis of the bushing main capacitance depends on
the assessment of the voltage amplitude and phase shift.
Omicron: On-line bushing and winding insulation system monitoring
Failure statistics of power transformers show that the majority of failures are caused by insulation
defects. Continuous on-line monitoring of key dielectric parameters to determine insulation
condition helps to optimize maintenance processes at different stages of the transformer life to
prevent the consequences of failure and to extend service life.
MR: Vibro Acoustic Measurement
Vibro acustic sensors give an in-depth view to mechanical structures like OLTCs, windings and
core. So noise patterns are monitored and irregularities are identified. This vibrations can be
detected easily by using acceleration sensors mounted on different places on the transformer or
sensors places in the OLTC. This enables us to react on sudden failures or sneaking
deteriorations before a failure will happen.
MR: Sensor Bus
The optical sensor bus integrates conventional sensors as well as a new generation of smart
sensors into your system. Due to its design it guarantees high reliability and robustness. Smart
sensors can be directly connected with the sensor bus whereas a minority is using a media
converter. The media converter fulfills two different functions. It converts conventional bus signals
into an optical bus signal. It also provides the required energy supply to conventional sensors.
Thus reduce the required engineering effort tremendously. The bus design covers the most
crucial application aspect a secure and reliable flow of information.
Omicron: Portable equipment for temporary monitoring and on-line diagnosis
The portable equipment is intended for the temporary monitoring and on-line diagnosis of bushing
capacitance and dissipation factor as well as partial discharges in the bushings and inside the
transformer tank. These are key dielectric indicators of transformer insulation condition. The
portable equipment allows you to perform an in-depth diagnosis of transformers once insulation
defects have been identified. A terminal box is installed in the transformer control cabinet and
facilitates the connection between the data acquisition unit and the bushing taps. This plug-andplay operation of the equipment makes it convenient to assess the insulation condition of an entire
transformer fleet.
As with all studies, Transformer 2020 presents the ideas to the industry and afterwards evaluates the
interest shown by the customers. Based on the response of customers, the involved TRANSFORM
Partner companies will decide whether to press on with the research and development of projects that
are required to realize the concepts.