Efficient operations and maintenance (O&M) of hydropower plants are crucial for ensuring their continued contribution to India’s energy security and environmental sustainability. O&M practices of plants should ensure reduced downtime of individual generating units and plants, as well as increased operational reliability. Maintaining efficient operations, adherence to all relevant rules and regulations, safety measures, and approved maintenance schedules are the key objectives of effective O&M practices.
O&M practices
The successful O&M of a hydropower plant relies on a dedicated team executing crucial tasks with precision and diligence. Operators manage the plant meticulously, optimising power output while prioritising safety. This involves controlling water flow, turbine settings, and generator performance, alongside monitoring key parameters and responding to alarms. Detailed shift records and regular reports provide insights into performance and guide preventative measures. Clear communication protocols ensure swift responses to emergencies, safeguarding personnel and equipment. Maintenance activities, including preventive schedules and repairs, are meticulously documented, aiding in future planning and optimisation efforts. Through these comprehensive responsibilities, the O&M team ensures the efficient, safe and reliable operation of the hydropower plant, contributing to sustainable energy generation.
Operational analysis: This involves assessing various factors such as inflow, water utilisation, reservoir levels, spillage, and compliance with regulatory codes. Methods for operational analysis include monitoring reactive power injection, implementing the restricted governor mode of operation (RGMO), and automatic generation control (AGC), as well as conducting mock black starts. RGMO sets specific operational constraints in hydroelectric plants’ governor control systems to address operational or regulatory needs, adjusting generation levels to compensate for frequency changes. AGC maintains system frequency by automatically adjusting power output in response to changes in generation demand, ensuring balance between generation and load. Integrating AGC in hydropower plants involves automated control systems to respond to frequency and demand fluctuations.
Breakdown/tripping analysis: Analysis of tripping and breakdown incidents aims to pinpoint the underlying cause of faults and promptly rectify them, thereby reducing their frequency. NHPC Limited’s corporate O&M division monitors forced breakdowns in power stations, providing technical assistance and logistics support, and overseeing restoration efforts. This focused approach has led to a decrease in breakdown incidents from 0.93 per cent in 2017-18 to 0.46 per cent in 2021-22. While potentially cost-effective for small plants, running equipment “until it fails” can lead to unplanned downtime, safety hazards, and expensive repairs.
Routine maintenance: Regular inspections, cleaning, lubrication, and minor repairs at defined intervals (daily, weekly, monthly, etc.) are crucial. Examples include cleaning commutators, replacing brushes, and oiling bearings. This proactive approach extends equipment life and helps identify potential issues.
Preventive maintenance: This goes beyond routine care, utilising diagnostic tests like insulation resistance, tan delta, and ultrasonic inspections to assess equipment health and predict future faults. Based on these assessments, preventative actions like timely part replacements can be taken, minimising downtime and costs associated with breakdowns.
Capital maintenance: Periodically (plant-specific intervals), complete equipment disassembly allows for in-depth inspection and major repairs or replacements of inaccessible components like stator windings and guide vanes. This comprehensive approach ensures long-term equipment reliability and performance.
Silt/sediment management: In regions like the Himalayas, sediment management poses a significant challenge for hydropower plants, particularly during the monsoon season. Sediment erosion can impair reservoir capacity and underwater components, necessitating mitigation strategies such as reservoir flushing and maintaining minimal draw-down levels during high inflow periods. Measures like desilting chambers, applying high-velocity oxygen fuel coating to turbine components, and implementing closed-loop water systems help address sediment-related issues. NHPC employs various methods to mitigate damage caused by hard particles in inflowing rivers, including using resilient materials or applying protective coatings on turbine components.
Critical spares and inventory management: Effective inventory management of critical spares is crucial for ensuring uninterrupted power station operation. NHPC meticulously monitors procurement processes to ensure the timely availability of essential spare parts, facilitating both routine and emergency maintenance activities. Each power station maintains minimum critical inventory levels, with NHPC setting minimum and maximum reorder levels for identified critical spares, enhancing operational resilience and response capabilities.
A combination of these maintenance strategies, tailored to the specific needs and size of a hydropower plant,can ensure the plant’s efficient, safe, and cost-effective operation.
Technological advancement
The traditional approach to O&M is evolving with advancements in technology. These innovations are streamlining processes, enhancing efficiency, and ensuring the sustained performance and safety of these crucial renewable energy sources. Some key O&M technologies are making waves in the hydropower industry. These include condition monitoring technologies such as sensors and data acquisition systems to continuously monitor critical equipment parameters like vibration, temperature, and pressure. Advanced analytics interpret this data to identify potential issues and predict equipment failures before they occur, enabling preventive maintenance. Vibration sensors on turbines are technologies that can detect bearing wear, while acoustic emission monitoring pinpoints leaks in pipelines.
Remote monitoring and control systems, including real-time data transmission from sensors, allow the remote monitoring of plant operations from centralised control rooms. Remote monitoring enables adjustments to turbine settings, generator output, and other variables based on real-time data. It can reduce operational costs, improve decision-making processes and lead to faster responses to issues.
Predictive maintenance practice is another efficient tool to ensure the smooth operations of hydropower plants. These practices utilise machine learning algorithms to analyse historical data, maintenance records, and sensor data to predict equipment failures and optimise maintenance schedules. It has been beneficial in ensuring reduced downtime, minimised repair costs, and extended equipment life.
Digital twins, technology for creating the virtual replicas of physical hydropower plants, are created using data and simulations, facilitating the virtual testing of operational scenarios and maintenance procedures. It has improved training for operators, optimised maintenance planning, and reduced risks during plant modifications.
Other advanced technologies such as augmented reality and virtual reality can be employed for enhanced training and troubleshooting. Robotics and drones can also be used for carrying out remote inspections and maintenance in inaccessible areas. Further, artificial intelligence-powered chatbots can provide maintenance support and automate routine tasks.
Health assessment of assets
Maintaining peak performance and minimising downtime in hydropower plants hinges on effective asset health assessments. These involve defining objectives, analysing historical and real-time data, and employing techniques like condition monitoring tests, machine performance data analysis, and new technology upgradation.
Condition monitoring test: This helps identify potential problems early on, preventing costly equipment failures and unplanned downtime. Vibration analysis, oil analysis, infrared thermography, ultrasonic testing, and partial discharge testing help in the detection of imbalances, misalignment, wear and tear, hotspots, contamination, and deterioration in plant equipment. Periodic offline condition monitoring tests allow for in-depth assessment and testing of equipment while it is temporarily shut down, impacting plant availability. Online monitoring tests are conducted continuously or at regular intervals while the equipment is operational. After this, preventive maintenance is scheduled as per the test results.
Machine performance data analysis: In hydropower plant asset management, analysing machine performance data has emerged as an effective method for optimising operations and maximising equipment lifespan. Data analysis techniques like machine learning, digital twin, and cloud computing play a crucial role in this process. Operating parameters like vibration, temperature, flow rates, and pressure are monitored daily, painting a detailed picture of machine health. Advanced analytics scrutinise this data, instantly identifying any deviations from normal operating ranges. These deviations trigger an in-depth root cause analysis, employing advanced algorithms to pinpoint the exact source of the issue. Machine learning algorithms analyse historical and real-time data to predict future performance trends, enabling preventive maintenance before issues escalate. Virtual models of the plant, fueled by sensor data, allow for the simulation and optimisation of operational scenarios in a safe and controlled environment.
New technology upgradation: Early warning systems have been implemented across all locations, providing real-time data on potential hazards like floods or equipment malfunctions, enabling proactive measures and safeguarding personnel and infrastructure. Supervisory control and data acquisition systems have been implemented across all NHPC power stations, offering centralised control and real-time performance monitoring, leading to efficient decision-making and optimised operations. The implementation of a new-age enterprise resource planning (ERP) system, integrated with advanced data analytics, is under way. This centralised platform will automatically store, analyse, and generate valuable insights, streamlining operations and enabling data-driven decision-making.
The way forward
India’s hydropower sector plays a vital role in ensuring energy security and sustainability. Effective O&M practices are crucial to maintain the efficient, safe and reliable operation of these plants. Each approach plays a part in optimising performance, minimising downtime and ensuring plant longevity. Apart from this, overcoming challenges, such as ageing infrastructure, sedimentation, and climate change, requires modernisation efforts, improved sediment management strategies, and adaptation to changing water availability. Hydropower plants are preparing for a future of automation and centralised control. New analytical software and ERP systems will automate asset management procedures, eliminating manual intervention. Real-time monitoring from a central location will enable rapid response to issues, while relay data management will be centralised for improved efficiency. The launch of a comprehensive breakdown, analysis and restoration portal accessible to all power stations will further enhance knowledge sharing and optimise operations. This shift promises increased efficiency, reduced downtime and improved decision-making across the entire network.