My dear young friends,
While in BHEL, I remember once in 1981, Shri B.S. Kochar, chairman, BBMB walked in requesting us to study the overload margins in Bhakra turbine-generators. Though it appeared to be a small assignment to me, I was entrusted with it. I took it rather seriously and expanded the dimensions of the study from signature analysis of the machines to material testing to vibration analysis to design safety margins to furthering power generating capacity of the machines going beyond the overload margins by opting thinner and effective insulation in the stator slots and even changing the runner profiles to higher specific speed versions; little realizing that it was heading towards a New science of “Uprating & Refurbishment of Hydro Units”. Later it became a pioneering and trend-setting study in India. I shifted to NHPC in the year 1982.
With the awareness of uprating potential of Hydro Plants spreading across the power sector, during the Power Ministers’ Conference held in Jan’1987 a resolution was passed that an All India study of Renovation & Modernization of Hydro Electric Power Plants would be conducted by NHPC and with the background of Bhakra study naturally it was entrusted to me. I did it with full vigor and dedication. Having become one of its kind first National Study for a country of continental dimensions, we were invited to the First International Conference on Uprating & Refurbishing Hydro Power Plants” at Strasbourg, France during Oct’1987. I presented the study there. This study taking the shape of the first ever made national master plan on Hydro R&M across the globe became a star of the show at the Conference. Mr J.Warnock, Managing Director of Acres International, UK chairing the Conference said in the midst of a standing ovation “Here is the first ever attempted comprehensive study of all the operating plants in a country of India’s size dealing with all aspects from Civil Engineering to Electronics, which is going to become a forerunner of such studies by other nations.”
India has 275,935 MW of installed capacity today of which Hydro is 42,000 MW. By upgrading existing Hydro, following can happen:
- We will have more peaking power which is always in deficit.
- We will have cleaner environment, not needing any more environmental clearances.
- We will reduce to an extent our dependence on import of Coal, Oil, Gas and Nuclear Fuel (Uranium) with associated financial burden.
- We will reduce to an extent our dependence on import of Technology for Power Plants with associated financial burden.
- We will have more stable Grid, having higher peaking capacity supplying higher quality electricity.
- Higher utilization of indigenous renewable resource will lead to energy security and sustainable development.
Let us appreciate that if a 210 MW thermal plant is renovated, its de-rated capacity may be retrieved to 210 MW itself. But if a 210 MW Hydro Plant is renovated, it can be uprated to 250 MW by permitting higher water velocity levels and hence higher discharge from the same turbine passage, with advancements in Hydrodynamics and materials Technology.
In case of Hydro, we renovate, uprate and update together. Uprating is an inseparable element of refurbishment exercise. Its separation would be like removing music from dance.
In the past few decades, the research on hydrodynamics of cascades, computer aided design techniques like FEM and material science has been phenomenal, so much so that the Hydro Units installed 15-20 years ago can be uprated by 15-20 % and their efficiency improved by 2-3%.
Advancement in technology makes it possible to derive higher outputs from the existing hydraulic space in turbines by employing higher specific speed and better efficiency profiles (thereby changing the throttling characteristics of the runner) on one hand and development of class-F epoxy insulation makes it possible to use larger conductor size in the existing stator slots for higher outputs, on the other.
Temperature, mechanical and dielectric strength capabilities of insulation materials are being constantly improved. Typically, a class-B 13.8 kV winding requires 6 mm or more of insulation thickness for a maximum temperature rise of 60o C. For the same application, a modern class-F system can operate at 90o C temperature rise with an insulation thickness of just 3 mm. Thinner and effective insulation allows an increase in conductor size in the same stator slots for higher outputs.
Uprating ventures are cost-effective. Their investments are highly economical- only around 15% of new capacity additions. Payback period in most of the cases is less than 4 years. In case of Pumped Storage Project, Taum Sauk, turbine upgrade resulting in performance improvements coupled with increase in summer peak power rates completely paid off US $ 25 million modernization project in less than 4 months.
Uprating Hydro can be a continuous endeavor to enhance peaking power capacity, not only generating more with higher inflows during rainy season or summers due to snow-melt, but also during normal season re-scheduling peaking partnership with base load generation, regulating the pondage.
Satyamev Jayate !!!
Best wishes and Regards,
BE(Hons), M.Tech., Ph.D., CBI-Scholar, D.Engg. (Calif.), FNAE, Hon.D.WRE (USA)
Chairman Emeritus, Great Lakes, Gurgaon, NCR, New Delhi, INDIA
Former Director General (NPTI & CPRI / REL), Ex. Director (REC) / Executive Director (IREDA)
No job is small or big, the way in which you do, makes it small or big (c)