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.

1. 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.

1. 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.

1. 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.

1. 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.

1. 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.