Hitachi Energy India recently designed and manufactured India’s highest power-rated Scott-connected transformer at its Maneja facility in Gujarat, for the Indian Railways. Following this significant milestone, T&D India caught up with Atul Pandit, Senior Vice President- Transformer, Hitachi Energy India Ltd, to understand the significance of this landmark development. Atul Pandit, in this exchange with Venugopal Pillai, gives technical insights into Scott-connected transformers, and explains the criticality of such transformers in the infrastructure development programme of Indian Railways.
Let us start by understanding what a Scott transformer essentially is, and what its typical application areas are.
Electric locomotives are essentially single-phase loads whose load conditions and speeds vary over very short spans of time. These loads are generally unevenly distributed across different supply phases and are non-linear, asymmetrical, and non-sinusoidal, resulting in an imbalance and harmonic load on the source/supply grids.
The resulting voltage imbalance and a high amount of negative sequence current added to the power system led to: overheating of lines and system components; additional losses in lines and transformers; and, interference with communication systems
The Scott-T connection is a method of connecting two single-phase transformers to perform the three-phase to two-phase conversion, and vice versa. This Scott-connected transformer can convert a balanced three-phase supply into a balanced two-phase supply.
The Scott connection was originally proposed by Charles F. Scott and was primarily used in the early part of the last century to connect existing two-phase loads to newer three-phase sources. After a period of relative obscurity, this connection has been used extensively in railway electrification, electrical heating of long-distance subsea oil pipelines, glass melting furnaces, and, to a limited extent, in power electronics.
Please explain the role of a Scott transformer in the field of railway electrification.
Power is sourced from the State Electricity Board’s three-phase, effectively earthed transmission network, which operates at voltages of 220kV, 132kV, 110kV, or 66kV through Scott-connected transformers installed at the traction substations.
Since the power is supplied at a two times higher voltage (50kV), the 2x25kV at feeding system is suitable for a large power supply and has the following advantages compared with conventional feeding systems:
- Reduced voltage drops in the feeder circuit
- Larger spacing between traction sub-stations
- Reduced interference with adjacent telecommunication lines, if any
- Increase in train frequency (speed, throughput & revenue for operators)
Hitachi Energy India recently rolled out its highest rating Scott transformer of 100MVA. Please discuss its significance.
The offered transformer represents the first and highest-rated Scott-connected transformer manufactured by Hitachi Energy India.
This transformer was completely designed and manufactured at the Hitachi Energy India facilities. Moreover, we have successfully conducted a dynamic short-circuit test on the prototype unit at CPRI, Bengaluru.
Additionally, this transformer holds the distinction of being the highest rating required by the Indian Railways to enhance their railway network with higher speed and reliability. Specifically, it facilitates the transition from 1x25kV electrification to 2x25kV electrification across the country.
How will these 100MVA transformers benefit Indian Railways, which we believe is the biggest end-consumer of Scott transformers?
Hitachi Energy is a pioneer in India to supply the highest power-rated Scott transformers, with several units of 100MVA conforming to the specifications of the Research Design and Standards Organization (RDSO) for Indian Railways.
These Scott transformers are set to revolutionize the rail infrastructure’s electrical system in India, enabling trains to accelerate to speeds of up to 160 kmph. This is a significant improvement, marking a 20 per cent increase over the current maximum speed of 130 kmph. With enhanced capacity and speed, travel between four major cities in India will become quicker and more dependable.
Indian Railways has outlined plans for a substantial upgrade of a 3,000-km network (approved by the Railway Board) with a 2x25kV traction system. This upgrade is aimed at supporting the high-speed movement of trains at 160km/h, especially on High-Density Network (HDN) routes. Phase-I HDN network, will be followed by another 8119 km of Phase-II HDN network covering entire Golden Quadrilateral and Golden Diagonal (GQ /GD) Routes of Indian Railways by 2030 as per National Rail Plan 2030.
The push for faster and more frequent train services is a response to rapid urbanization and the increasing demand for mobility in the region. This requires an efficient and reliable rail transportation system. Scott-connected transformers emerge as the ideal solution to meet these power requirements to increase axle load, train frequency, and the power rating of locomotives or train sets, as they help balance catenary loads. This leads to improved power quality and a more stable power system, meeting the modern demands of India’s rail network.
We also gather that 100MVA transformers now manufactured by Hitachi Energy India are also the highest-rating Scott transformers by Hitachi Energy Group worldwide. Do you see the potential for exports of such transformers by Hitachi Energy India to Hitachi Energy’s global customers?
Yes, the manufactured transformers are the highest-rated Scott transformers. Based on the current scenario, we do not foresee a requirement for Scott-connected transformers in our exports business.
However, given the dynamics of the market, there could potentially be a global demand for such transformers in the future.
Additionally, our transformer facilities in India and in other countries can meet such requirements as and when needed.
We learn that 100MVA is the highest rating of Scott transformers in India. Is it also the highest globally?
Yes, it represents one of the highest ratings for Scott-connected Transformers in both India and globally.
Hitachi Energy India addressed various challenges to build a completely new transformer design and solution. This was achieved while adhering to the project schedule, with the highest quality standards and robustness while minimizing throughput time.
What is the current capacity of the Maneja plant with respect to Scott transformers, in general, and 100MVA Scott transformers in particular?
Currently, our Hitachi Energy India facility is capable of manufacturing approximately 80 to 90 such Scott-connected transformers annually, each with a capacity of 100 MVA.
Additionally, the production capacity can vary depending on the different ratings of transformers required in the segment.
In the years ahead, do you see the need for Scott transformer of ratings more than 100MVA?
Indian Railways, through their technical body, RDSO (Research Design and Standards Organization), has outlined a roadmap for upgrading the railway electrification network across the country with the use of both Scott-connected and V-connected transformers. The primary use of Scott-connected transformers is in the railway segment.
Given the current electrification plans of Indian Railways, we do not anticipate an increase in the rating of Scott Connected transformers beyond 100 MVA, at least for the next few years.
How do you see the demand for 100MVA Scott transformers from Indian Railways? Is there any capacity expansion plan on the anvil?
In an initial move, Indian Railways has unveiled a plan to upgrade 3,000 km of railway routes to a 2x25kV traction system, specifically for the Delhi-Mumbai and Delhi-Howrah routes.
The transformer we are supplying is designated for the priority section of the Delhi-Mumbai route.
Furthermore, Indian Railways has other packages in the pipeline that will require Scott-connected transformers. We expect a significant demand for such transformers for the next 10-15 years, at least.
Hitachi Energy consistently invests in capacity expansion to support growth plans and ensure business continuity. The development of Scott transformers is also a part of our strategy for capacity growth.
