TRANSFORM Partners present “TRANSFORMER 2020” in ViennaWorld 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 medium-

voltage 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-and-

play 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.