Coal-based thermal power stations (TPSs) still hold the majority share in India’s installed power capacity. A number of these units were commissioned before the 1970s and have outlived their useful life, while many units commissioned in the early 1980s are also approaching that stage.
In India, the overall efficiency of coal-based power plants ranges from 28 per cent to 35 per cent, depending on factors like plant size, operational practices used and the capacity utilisation factor. For optimum performance, the upkeep of all components and equipment should be strictly in compliance with the operations and maintenance (O&M) manuals and guidelines provided by the original equipment manufacturer (OEM). However, when plants have operated machines for as long as they have in India, they develop their own experience and exposure, which they use with future equipment.
Over the years, without proper O&M practices, power plant equipment and performance has deteriorated. Therefore, the adoption of effective O&M practices has become particularly relevant for sustaining the performance of rehabilitated power plants.
O&M practices of state utilities
Operational practices vary widely among utilities, with the better managed ones exhibiting superior systems and procedures, and others facing critical gaps in many areas, resulting in lower availability, generation and energy efficiency.
This also leads to increased oil/coal and auxiliary power consumption. Most utilities still do not pay the required attention to energy efficiency. Energy audits are not carried out, and heat rate and specific oil consumption targets for the stations are not monitored. As such, unit-wise energy efficiency parameters are not identified and addressed. Auxiliary power consumption is not measured on an actual basis and is generally computed by deducting sent out energy from the total energy generated. In the absence of any proper analysis, measures for improvement cannot be identified.
A look at the O&M practices being followed by some of the key gencos.
West Bengal Power Distribution Company Limited (WBPDCL) follows the guidelines of the OEM when it comes to operations and preventive maintenance. A specifically formulated maintenance planning cell executes predictive maintenance based on condition monitoring and pre-overhauling. A separate operation efficiency cell looks after the deviation of operating parameters, controlling factors, efficiency measurements and health assessment of equipment through condition monitoring. Procedures for condition monitoring include vibration measurement, ferrography, oil analysis, monitoring of electrical hotspots and high energy drains using thermovision, and dissolved gas analysis of transformer oil.
In case of faults or trips in the unit, a designated trip committee analyses the root cause of the problems, to avoid recurrence. As per the standard operating procedure, WBPDCL effectively monitors the heat rate of its units and auxiliary consumption to ensure energy efficiency.
The utility appointed NTPC Limited to provide O&M consultancy for its power projects including the Bandel thermal power plant (TPP), Kolaghat TPP, Bakreswar TPP, Sagardighi TPP and Santaldih TPP. Based on NTPC’s recommendations, WBPDCL has set up an operation and efficiency department, a coal consumption and fuel efficiency cell and an operation services cell.
A distributed control system has been installed in place of the obsolete analog control system at the Kolaghat TPP among other technological interventions. In addition, safety certifications have been obtained and an on-site emergency and disaster management roadmap has been prepared for the Bandel TPP, the Kolaghat TPP, the Bakreswar TPP and the Sagardighi TPP. Enterprise resource planning (ERP) is under implementation for inventory control, fuel management, human resource management and finance management. WBPDCL has also started giving central simulator training at the Bakreswar TPP.
These initiatives have resulted in significant benefits for the genco including increased ex-bus availability due to online vibration monitoring systems in major load bearing equipment and the installation of equipment such as low NOx burners, modified air registers and dynamic classifiers, which have improved the utility’s performance on environmental parameters. Training of O&M personnel is also being undertaken by the genco to enhance their technical and managerial skills.
Haryana Power Generation Company Limited (HPGCL) appointed STEAG Energy Services India to provide recommendations on specific measures to strengthen the utility’s O&M practices in the Panipat TPS, the Deenbandhu Chhotu Ram TPS at Yamunanagar and the Rajiv Gandhi TPP. Some of the key flaws identified by the consultant were the practice of following a manual permit-to-work (PTW) system, and a manual system to notify defects. Such systems suffer from ineffective monitoring, incomplete defect liquidation and other non-standard practices. Also, many of the standard operational procedures for various systems needed modification. Moreover, a scheduled equipment changeover was not practised regularly, resulting in imbalanced equipment running time. The utility had not initiated any heat rate improvement programmes or equipment performance tests. Safety was also a concern at the plants because there was no system in place for indicating safety permits, or a programme for controlling overflows from the ash dyke. The utility had not installed any software packages for online performance evaluation. Further, no history of equipment breakdown or repair was being maintained, and teams were formed for overhaul or recommissioning. The majority of maintenance activities were being carried out based on personal experience and assessment, greatly affecting equipment reliability.
In view of these gaps, some of the key recommendations of the consultant being implemented by the genco are the deployment of a computerised PTW system and a lock out-tag out system for O&M, and an automated system for raising and closing defects. These will be put in place through a utility-wise ERP system. The history of equipment breakdowns and repairs will also now be made accessible online through ERP. A computerised maintenance management system is also being introduced.
Equipment changeover schedules and heat rate improvements are being regularly discussed at monthly review meetings. A pre- and post-overhaul performance monitoring system has also been introduced. Training programmes for staff are being conducted.
Meanwhile, steps for raising the ash dykes have been implemented by the genco. It is also planning to initiate a benchmarking system based on best performing similar units at its power stations. The existing management information system is also proposed to be strengthened.
Maharashtra State Power Generation Company Limited (MSPGCL) appointed NTPC as its consultant in order to strengthen its O&M practices at the Koradi, Nashik, Bhusawal, Parli, Chandrapur, Khaperkheda and Paras TPSs. Before any changes were made, these power stations were following all the conventional, routine processes for O&M. NTPC recommended the setting up of a committee and task force of efficient staff members to create a customised performance improvement programme. They also suggested that an online monitoring system be established for critical condition monitoring of equipment.
Based on these recommendations, the utility formed committees for its coal mill, coal handling plant, ash handling plant, water treatment plant, as well as for boiler tube leakage, electrical protection and heat rate improvement. Further, at the corporate level, committees were formed for the maintenance and planning department to carry out long- and short-term maintenance planning and for the field quality assurance department for quality checks of incoming materials and the work carried out; and a performance optimisation group was set up to regularly monitor parameters and enhance performance of the unit. An ERP system has also been implemented by MSPGCL. All stations are now ISO certified.
Further, a condition monitoring cell has been established at each of the power stations. Regular third-party coal sampling is carried out at all the power stations. All new units use systems like steam and water analysis and condensate polishing to maintain the quality of raw and demineralised water.
The utility has also addressed each of the technical changes suggested by NTPC, and is careful to follow the guidelines issued by Bharat Heavy Electricals Limited and other OEMs. MSPGCL has procured new energy efficient boiler feed pump cartridges as well as heat exchangers to replace the old ones. Further, senior-level executives have undertaken management development programmes and various other training and technical refresher programmes are being offered for various work groups. These measures resulted in significant improvements in the genco’s operational parameters between 2011-12 and 2015-16.
All state utilities operating TPPs have adopted their own set of standards and practices over the past many decades, each of which have resulted in varying degrees of efficiency. Going forward, they need very individual and specific recommendations to find the optimal O&M process that will enhance the life of plant machinery and equipment. n
Based on the Central Electricity Authority report, “Review of Experience in Strengthening of O&M Practices in Thermal Power Stations in India”