Need for Thermal Power Stations Optimisation

The article discusses smart techniques aiming to optimised the operating parameters of plant and facilitating the work of operators and maintenance engineers. - Ashok Upadhyay

The country’s dependency on coal based thermal power stations for meeting its energy needs has resulted the environmental concern and focus its efficient and reliable operation. Out of the total installed capacity of over 350 GW, nearly 60 per cent is coal-based generation, the majority of which comprises of domestic coal with a high ash content. While thermal power stations are considered as base load stations and must ensure a secure power supply, recently efficient middle-range power operations and environmental preservation at thermal power stations are also becoming increasing important issues which have brought the need for more sophisticated operation and control. Government has also tightened the norms for emissions and water consumption for thermal power stations which need more efficient operation of the plant.

The digital revolution in the power sector has gained momentum. Power generation utilities across the world are undergoing digitalisation to make power plants smarter and more efficient to deal with the challenges of future. The sector’s landscape is expected to change significantly over the next decade with the increasing share of renewables in the energy mix, ageing conventional power plants, growth of distributed generation, and expansion of e-mobility leading to grid security, environmental protection, load balancing and energy accounting or settlement issues.

With renewable generation, the need for automatic load setting on the thermal plants through intelligent and smart features arises. As a result, there is a need for more sophisticated operation and control to keep pace with the increase in supervisory and operational control. Against this background, there is need to developed a supervisory and control system that not only maintains the high degree of reliability developed, but also seeks to be economical, while at the same time reducing the work of operators and maintenance engineers. A supervisory and control system that aims to deliver not only operability, reliability and maintainability, but also cost-effectiveness, while at the same time enabling labour savings in operation and maintenance.

The smart and intelligent operation of power station helps in maintaining operational efficiency under flexible power plant operations. A fleet-wide digitalisation of O&M practices helps plants meet these dynamic requirements. Meaningful inferences can be drawn from the operational data collected from different plant equipment through machine learning and artificial intelligence as well as plant specific algorithms that aid in maintaining plant performance under flexible operations. Another driver for intelligent operation of thermal power plants are increasing cost of complying with the environmental regulations. The revised norms are creating additional operational complexity in plants and staining their operating margins. Digital solutions can support and facilitate this transition to low-emission power generation through asset optimisation strategies that take into account emissions, abatement costs and equipment life. It also enables augmented reality-assisted maintenance, and robot and drone-assisted maintenance.

Intelligent operation

Tighter regulations, an ageing power plant fleet and variability in renewable energy generation are driving power generators to adopt smart and intelligent measures. Automation and digitalisation through sensors, devices and advanced analytics software can enable generators to derive actionable insight from a wide range of data and improve their decision-making. Intelligent operation can help generators to manage plant operations in a better way, get information about equipment performance both on-site and remotely, and optimise asset performance through predictive maintenance. For instance, IT-based solutions range from real-time fuel optimisation in conventional power plants to help control emission.

With the injection of renewable into the grid, the need arises for automatic load setting on the thermal plants through intelligent and smart features to respond to variations in renewable generation. Manual load setting has limitations of response time. Also, the ramping rate is also to be automatically set. When the load on the thermal plants goes below its technical minimum load, coal cannot be fired into the plant because of flame separation.

Over the years the demand for high quality, greater efficiency and automated machines has increased in power stations. The growing need for flexible power plants is another driver of intelligent operation. Smart and digital solutions can help plant owners to quickly ramp up and ramp down their generation as per grid requirements. With advancement in digital technologies, the complete remote operation of power plants has become a reality. Remote operation of projects located in inaccessible or far-flung locations also helps reduce the hardships of the workforce.

In the current scenario, one of the key growth drivers for the application of intelligent and smart techniques of thermal power plants is large scale renewable energy penetration, which requires flexible loading of thermal power plants and poses a threat to electrical grid stability. Renewable energy sources are characterised by variability and uncertainty of power generation, resulting in ducking of the load curve, leading to lower plant load factor. With increasing renewable penetration, thermal power plants need to frequently ramp up and down power generation, resulting in poor heat rate, high auxiliary consumption, increased forced outages, higher O&M and reduced equipment lifetime, finally, reduce the overall efficiency and increase the cost of generation.

Features of Smart Plants

Intelligent power plant automation is defined as a composite system of components which enables the operation, monitoring, control, co-ordination, security in real time mode from remote locations to fulfill the objectives of load management, energy efficiency, environmental control and resource conservation. Intelligent plants help to save resources of primary energy (coal) by avoiding shut downs to balance the system. The components of a coal fired station are boiler, steam turbine, generator, condenser, feed water heaters, lube oil coolers, heat recovery devices, steam condenser, stack steam condenser, vent steam condenser and auxiliaries like pumps, fans, mills. To handle the dynamic behaviour, power plant automation started with supervisory control and data acquisition, energy management systems, distributed control systems and field control stations with controls to maintain the operating safety band. Presently power plant automation encompasses control and monitoring systems for meeting the requirements of load control, fluctuating grid conditions, system security, communication, safety and operational energy efficiency. In a digital environment, information from all sources can be exchanged and utilised in any form creating a uniform digital currency which enables intelligent features. Some important features of smart and intelligent features used in thermal power stations are as follows;

  • Supervisory and control system for TPPs

Supervisory Control and Data Acquisition system (SCADA) is a centralised system used to supervise a complete plant and basically consists of data accessing features and controlling processes remotely. Since the increased the distance between the central control room and the site, supervisory robots were installed on-site to facilitate the work of on-site patrol. Requirements of the supervisory and control system and corresponding features are integrated operation from central control room; Implementation of protective functions by printed circuit board; Common sensor system; and Enhanced operability. Integrated Operation from Central Control Room With the aim of improving the working environment, the central operation room that had previously been located on the turbine floor was relocated to the top floor of the service building and made into a single central control room including a unit for future addition. Since this increased the distance between the central control room and the site, supervisory robots were installed on-site to facilitate the work of on-site patrol.

  • Intelligent Automation

Automation is based on the principle of converting all inputs and outputs into digital forms. The automation system can be designed and developed using information technology or embedded systems and integrating the same into the existing power plant systems. Components such as computers, Remote Terminal Units (RTUs), actuator control of motorised valves, breakers, switched capacitor banks, on-load tap changing transformers, load break/ make switches, auto re-closures, sectionalisers, and communication systems can be integrated into the automation system. An intelligent integrated distributed control, automation system enables power plants to have real time on-line control of energy efficiency, system security, safety systems at an improved energy efficiency that results in lower costs, better reliability, and optimum resource utilisation.

  • Smart Sensors

Smart sensors are those that have additional secondary sensors which measure secondary variables and then use them to correct the calibration of the main sensor. A smart pressure transducer is one where the deviation in calibration due to changes in atmospheric temperature and pressure are sensed (as secondary variables). These are used as inputs to calibrate the pressure transducer. An intelligent sensor has a logic based internal control system.

  • Intelligent Devices

Intelligent Electronic Devices (IEDs) available at the site such as relays, electronic energy meters, flow controllers, motor controllers directly communicate the data with the data communication system. Analog quantities and digital information, which are not available directly from the IEDs, are extracted through the I/O interfaces of the RTUs. Remote Terminal Units have provision to send the control command to the actuator of a switching element through the IED relay. Few analog and digital signals, which are not handled by any of the Intelligent Electronic Devices are directly connected with the RTU that communicates with data communication system.

  • Plant Outages Analysis

Power plants have basically five types of outages namely Forced outages, Pre-arranged outages, Planned annual overhauls, Planned capital overhauls and Planned outages associated with renovation/modernization/up gradation/ revamping/ retrofitting/life extension programs. Outage management involves a combination of modern technology, econometric techniques and data management. The ITs find application in minimization of deployment time, event management, knowledge application, use of public information to achieving reduction in cost and improvement in efficiency. Intelligent operation of thermal power stations involves Cold start, Warm start / hot start, Black start (grid has failed), and Absolute cold start.

Benefits

Various benefits can be realised by generators through smart and intelligent features as they can virtually see through what is happening at the operational level. Digitalised power facilities can enable predictive maintenance by continuously monitoring the health of the power plant. This in turn lowers operations and maintenance costs, the benefits of which can be ultimately passed on to consumer tariffs. Better monitoring and predictive maintenance limits the duration of downtime, and its impact on generation and revenue by rapidly identifying the point of failure. A reduction in network failures decreases coasts and increases the resilience and reliability of supply. The deployment of intelligent solutions at the boiler, turbine and generators level has gained traction in the past few years in view of the increasing renewable energy integration into the grid and tightened emission norms for thermal power plants.

Besides, the smart and intelligent operations of power plants ensure efficient and cost-effective power generation. It helps generate plant-specific operational and contextual data, including operational history, unexpected degradation of plant equipment, etc. It also offers tailor-made countermeasures for performance improvement. With the introduction of machine learning, artificial intelligence and cloud computing solutions, power plant developers have been able to achieve greater sophistication in their digitalisation efforts and solve complex problems with ease. Automation and digitalisation also provide assistance to the operations team and enhances plant performance by improving planning and overall project design, making it more efficient and less costly.

Another benefit of digital solutions in a thermal power plant is asset management. Remote monitoring systems and diagnostic centers play a crucial role in this. An interactive display is used for performance monitoring. It deploys advanced pattern recognition and machine learning to identify anomalies in the operation of power plant equipment. Beside this, data from various connected machines is collected and sent to the monitoring system through a secured communication channel. On the other hand, Intelligent and smart solutions ensure an optimal fuel mix in power plant boilers. This helps to maintain an optimal cost of power generation. Further, boiler efficiency can be calculated in real time, which can then be computed for different fuel types, bed material and limestone consumption. Optimum boiler efficiency can be achieved by analysing the long-term performance of boilers using different inputs. Apart from this, smart solutions help in managing merit order dispatch in multi-unit plants. Smart and intelligent operation of a plant also perform functions of predictive emission monitoring, performance monitoring, process optimisation, maintenance management, compliance reporting, coordinated boiler-turbine control and load fixing based on intelligent features in the event of a transient from the paralleled renewable generation in the grid.

Poor network connectivity between power stations and remote centers poses a big challenge as effective digitalisation depends on strong communications connectivity. Automation and digitalisation also increases the risk of cyber threats. For commercial confidentiality reasons, asset owners and operators may not be willing to share information about individual power plants and network infrastructure. Further, there is a lack of incentives in investment in smart technologies. In order to mitigate these risks, power plant developers need to increase awareness on cyber security, and build strong technical strategies. Another challenge in the implementation of digitalisation is the lack of financial incentives.

Way forward

Smart and intelligent operation helps better assets utilisation, promote real-time data monitoring, energy storage integration, and customer-centric solutions. Although digitalisation entails a high capex, its productivity and efficiency gains surpass the costs in the long term. Going forward, there is a need for policymakers to introduce standards and regulations, support information sharing on the digitalisation front, and draft exhaustive policy for developing the cyber insurance market. While digital control and automation have already been adopted on a wide scale, remote monitoring of power plants and implementation of condition monitoring systems are at a relatively nascent stage. Despite several challenges, digitalisation is being increasingly implemented in the thermal power segment for optimisation purpose. Going ahead, the projects, currently being implemented are likely to drive the implementation of future projects by setting benchmark metrics and sharing best practices in India.

Conclusion

Intelligent power plants help to save resources of primary energy and for accommodating variation arising from integration of sizeable renewable power. Present concepts of intelligent power plant automation involve operation and control based on optimal performance or optimum decisions emanating from on-line computation. New developments in non-interactive sensor technology now enable very sophisticated solutions at reasonable costs to meet the objectives of optimal operation of the power plant through intelligent systems. The smart techniques aim to optimised the operating parameters of plant and facilitate the work of operators and maintenance engineers. In future, power plants will be expected to be even more economical and environmentally friendly.