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Transformer innovations aimed at the smart grid

Krishnan Narayan ,  Monday, November 25, 2013, 18:04 Hrs  [IST]

Krishnan NarayanPresently, transformers are single function devices – regulating voltages from one level to another. Transformers typically have long useful lives – in excess of 20 years and most transformers in use today were installed before the advent of effective communication technologies.

Captive power plants and electric grid are today operated in isolation. With addition of renewable power sources and maturation of smart grid technology, more of individual users’ generated energy would be transferred back to the grid using integrated power lines and feeders, causing traditional grid components such as transformers to fail, since present power lines and transformers cannot handle power flowing backwards. Thus, bidirectional transformers and voltage regulators would need to be installed throughout the grid, at both distribution and substation level.

With increasing variability issues, power utility companies would need to know more about power flow at all points of the grid, in order to have adequate control. This would involve installation of sensors and other monitoring equipment at various transformer levels, and also installations of increasing number of transformers with in-built monitoring functions.

Adapting to the smart grid would require technological innovation…
Solid state transformers are made up of power electronic devices such as transistors and diodes and are manufactured to handle high power levels and rapid switching in response to signals from the utility or consumer end. They possess inbuilt processors and communication hardware, which enables them to communicate with utility operators, other transformers and the consumers.

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Comparison between Traditional and Solid State transformer

Traditional Transformer
Smart Transformer
Rating
  • 2.7 MVA
  • 13.8 kV/450 V
  • 60 Hz
  • 2.7 MVA
  • 13.8 kV/465 V
  • 20 kHz
Weight
  • 6 MT
  • 1.7 MT
Volume
  • 10 m3
  • 2.7 m3
Output Configuration
  • Fixed, single output
  • Multiple outputs

Solid state transformers can potentially offer significant benefits as compared to traditional transformers – such as bidirectional power flow, high efficiency, superior power quality, high flexibility and lower maintenance costs.

In renewable energy circuits, solid state transformers would potentially allow DC power to be transmitted to the grid without the need for equipment currently being used for power conversion and reducing voltage fluctuations. Solid state transformers would also enable power consumers to switch electricity sources depending on the current price of electricity. Consumers could buy power from others having excess power in the same neighborhood – thereby leading to a more distributed nature of the electric grid.

Another benefit of using smart transformers is the ability to realize energy savings by setting the voltage of electricity provided to the minimum level required for running various appliances.

BeroeOnline Transformer Monitoring

Online monitoring of transformers is increasingly being considered essential, since it allows utilities to detect faults that could lead to transformer failure in real time. Prior to online monitoring tests, transformers would be sampled quarterly, semi-annually, or annually. Increasing developments in online tools for monitoring transformers offer numerous benefits, such as lower chances of failure, lower maintenance costs, and longer equipment lives.

The most essential part of any transformer maintenance program is often considered to be dissolved gas analysis (DGA) – which involves studying the dissolved gases in transformer oil. Online DGA monitoring tools can be classified according to the number of gases that they measure. However, it should be noted that the fewer gases a DGA tool can measure, the more likelihood exists of faults going undetected by the tool.
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Online DGA tools provide utilities the ability to detect faults, which if left undetected, could lead to equipment failures in a matter of days. There is a low probability of detecting these types of rapid faults by using laboratory or portable based methods. There have been developments with regard to using neural networks to utilize DGA data; however, such technologies are relatively nascent.

Manufacturers are focusing on new avenues for innovation…
Traditionally, global manufacturers such as ABB, Alstom and Siemens have dominated the electric transformer market. However, with increasing standardization of transformer technology and entry of local players in the transformer manufacturing market, global manufacturers have witnessed erosion of their market shares and reduction in their profit margins. Electric transformer manufacturers have increasingly shifted to focusing on complementing their hardware with the creation of new software products and monitoring tools.

The global transformer industry is currently undergoing consolidation, as global manufacturers aim to increase their technological capabilities, product portfolios and market penetration. Transformer manufacturers are increasingly partnering with AMI suppliers such as Landis+Gyr, Echelon, Iltron etc. to increase their product capabilities as well as to ensure interoperability among their products. Manufacturers such as Siemens have acquired AMI players such as eMeter and Senergy. Global manufacturers have also developed fleet management solutions which make use of asset condition information.
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Smart transformers need to be competitive in price terms…

One of the main challenges hindering the adoption of solid state transformer technology is the relatively higher cost of SiC components. It is already well understood that solid state transformers cannot be introduced to the market at the same price point as traditional transformers. However as the market for these products become increasingly wide, the costs are expected to reduce. This is in contrast to the price of traditional transformers which are already catering to a mature market and hence have a fixed pricing mechanism. In many cases, the installation cost of distribution transformers is almost twice the initial capital cost. In the case of newer technologies, reduction in sizes and weights of transformer components can significantly reduce management and operations costs. Though such devices are yet to be mass produced, it is estimated that SiC based solid state transformers will be commercially viable by around 2015, with overall cost reductions emerging by 2020.

One of the ways in which utilities can circumvent the challenge of high initial costs is to introduce solid state transformers on feeders which have high renewable energy penetration and electric vehicle load, thereby introducing smart devices at critical nodes.

Untitled Document
Attribute
Number of gases
8 Gas
3 Gas
2 Gas
1 Gas
Gases All IEEE and IEC fault gases CH4, C2H4, C2H2 C2H2, H2 H2
Fault Coverage All fault types Partial discharge, arcing, thermal faults Arcing, Undetermined faults Undetermined faults
Price High Medium Medium Low

Technological advancements shall lead to growth…
Solid state transformers are expected to grow at a CAGR of 82.3% during 2012-2017, amounting to USD 832 million by the end of the period. Growth of smart transformer technologies are primarily driven by development of GaN and SiC power transistors which have higher current and voltage ratings as compared to traditional silicon semiconductors.

Currently, the transformer monitoring hardware market is estimated to be around USD 113 million. However, most utilities are still in the initial pilot stage with respect to adopting smart monitoring equipment, and it is estimated that supplier consolidation, regulatory policies and continued development of software will push the adoption of new technologies among utilities.
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Procurement needs to be aligned with market trends…
With increasing innovation in the transformer market, it is essential for transformer asset managers to establish a strong procurement team, with a prime focus on effective negotiation, and build an effective knowledge base with regards to recent developments in the transformer industry, thereby enabling buyers to gain an advantage over their competitors in terms of procurement of transformer components.

Most utilities and industrial transformer users have an annual replacement strategy (around 2-4% of installed capacity) for aging transformers. With the maturation of smart grid technologies by 2017, industrial units would have to replace the bulk of their existing transformers with smart transformer technologies. As such any purchases of traditional transformers made in the coming years could lead to loss of capital investments, since these units would have to be replaced in spite of having around 15 years of useful life.

Industrial units are advised to adopt a wait and watch policy with regard to procurement of transformers. Currently, smart transformers are still nascent and any upgrading would require high capital costs. A hybrid sourcing model can be adopted, which involves replacement of only transformers with critical failures, and adopt retrofit options to increase the life of their ageing units so that they can buy smart transformers when their prices decrease.

(A graduate in Electrical and Electronics Engineering from Sastra University, Krishnan Narayan is a Senior Research Analyst with Beroe and specializes in tracking the mining and industrial durables industries.)
 
                 
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