Testing and measurement (T&M) solÂutions are needed to operate poÂwer generation plants safely, produÂctiÂvely, and in an environmentally friÂenÂdly manner. They play a vital role in extending the asset life and in the early detection of failures, thereby minimising eqÂuipÂment outage. The implementation of these solutions involves the deÂployment of sensors, transmitters and related eqÂuipment for tracking the desirÂed plant parameters such as water quality, pressure, temperature, flow, emissions, and combustion efficiency. This requires several critical measurements, from combustion performance and water chemisÂtry to stack emissions, to enhance the opÂerational efficiency of power plants, lower emission levels, and optimise operations and maintenance. In renewable energy plants, T&M is helpful in moÂnitoring condition, structural health system architecture, etc. For hydropower projects, especially pumped storage plaÂnts, testing is becoming a key focus area for gencos to determine the hydrauÂlic/electrical efficiency of the units, fulfil contract guarantees and reduce contractual disputes.
Power Line takes a look at some of the T&M solutions being deployed by gencos…
Thermal power plants
- Emission and effluent monitoring: For online monitoring of emissions and efÂfÂluents, continuous emission moÂnitoring system (CEMS), predictive emissiÂon monitoring system (PEMS), contiÂnuÂous effluent quality monitoring systÂem (CEQMS) and continuous ambient air quality monitoring system (CAAQMS) technologies are being deÂpÂloyed by gencos. CEMS/PEMS and CEQMS are real-time air and water pollution monitoring systems respectively. CEMS technology involves the use of SO2, NOx and particulate matter analysers for stack emission while in CEQMS technology pH, TSS and temperature analysers are deployed for effluent moÂniÂtoring in all the operating statiÂoÂns/units. The Central PolluÂtion Control Board has mandated the installation of CEMS for real-time pollution monitoring of stack emissions and CEQMS for effluent quality monitoring in 17 categories of highly polluting industries, inÂclÂuding power plants. Meanwhile, CAAQMS is used for monitoring the ambient air quality in real time. Besides these, mercury analysers are deployed for emission monitoring wherever stipulated.
- CEMS: It deploys complex extractive analysers, which remove flue gas saÂmples from the duct and use a series of individual gas sensor modules or more advanced spectroscopic techniques to determine the composition. It is preferable to analyse flue gas as close to the combustion proÂcess as possible. Such in-situ analysis can take the form of sensors placed directly in the flue gas, or line-of-sight optical absorption meÂaÂsureÂments, for which a transmitter and a receiver are placed on either side of the duct or furnace. CEMS technology provides continuous measurement of data on a real-time basis at the moÂniÂtÂoring site of interest, and enables immediate corrective/preventive meaÂsuÂres in case of any disturbance. HenÂce, it can help gather real-time data, and allow plant operators to remotely access plant performance as well as conduct continuous performance checks on air pollution control devices.
In the adoption of CEMS, utilities face challenges in terms of choosing between different monitoring systems and instruments, different suÂppliers and multiple data formats, multiple platforms and communication protocols, and different data collected from heterogeneous systems. To overcome this issue, there is a need to have coherence between central and state regulatory systems, clarity in the CEMS audit protocol and a compliance mechanism.
PEMS: PEMS is the next level of emiÂssion monitoring and does not use hardware-based sensors to measure emissions. It uses unique algoritÂhÂms to predict the emissions of a plaÂnt, based on the input parameters. While there are standalone versions of PEMS available, these systeÂms are widely used as part of an integrated environmental moÂnitoring approaÂch, capable of adÂdÂressing mulÂtiple sources in a plant. WhÂen coÂmÂbined with data acquisition and handling systems, and integrated in plant-wide IT and communications networks, PEMS can be a viable diagnoÂstic tool for lowering emissions and improving combustion efficiency.
- Combustion efficiency: Efficient fuel combustion is essential for cutting opÂerating costs and reducing emissions from power plants. For efficient combustion, the ratio of air to fuel is a critical factor. Insufficient air leads to inÂcoÂmÂplete combustion, resulting in emission of soot, smoke and carbon monoÂxide, while excessive air reduces the overall boiler efficiency. The solution is to measure flue gas oxygen. The level of oxygen present in the combustion of waste gas is a key indicator of the amÂount of air supplied to the process. It can be monitored by using combustion gas oxygen analysers, which accurately measure the oxygen content in the combustion gas. Furthermore, these analysers can be used in conjunction with flow meters to regulate the amoÂunt of air supplied to the burner.
- Boiler efficiency: To achieve the optimum performance of a coal-fired poÂwer plaÂnt, careful monitoring of the quality of water and steam in the feedwater is essential. Several chemicals neÂed to be monitored and controlled for optimum steam raising efficiency. Dissolved oxygen in the feedwater can cause pitting in the boiler and reduce its operating life. Dosing the feedwater with hydraÂzÂine can reduce oxygen to form nitrogen and water. At high temperatures and pressures, ammonia is formed, which raises the feedwater pH level, increasing the risk of corrosion. Further, silica can hamper heat transfer efficiency and increase the risk of turbine malfuÂnction by its precipitation on the blaÂdes. The solution includes pH anaÂlysers for monitoring feedwater acidity or alkalinity. By indicating the leÂvel of contamination, the type and duÂration of treatment can be determined.
Renewable energy plants
With the growth of renewable energy caÂpacity, there will be an increase in demaÂnd for the T&M of renewable energy eqÂuipment including solar cells, solar photovoltaic (PV) modules, and wind tuÂrbine generators, besides hydropower plants.
- Solar: Monitoring of solar PV plants can be done in both ways, that is, by usÂing human workforce or by using reÂmote monitoring systems. The monitoring methods to be adopted could vaÂry depending upon the size of the power plant and the site at which the plant is located. However, remote monitoring is preferred as it leads to reliable operation, better operations and maintenance, and improved output performance of the PV plant. For this, sensoÂrs, signal processing units, data traÂnsÂmission, data storage and logging facilities, and cloud-integrated data analytics are deployed. These help in condition as well as structural monitoring of solar plants and facilitate planÂned maÂintenance with deep insight inÂto the component failures before they affect energy production.
- Wind: In case of wind generators, condition monitoring of structural components, such as foundations, blades and towers, is critical, as failure of strÂuctural components can affect the operatiÂonal costs. Offshore wind turbines are particularly exposed to the harsh environments and are at a higher risk. ThereÂfore, it is essential to moÂnitor the structural components to reÂduce maintenance costs and avoid catastrophic faÂilures. Besides this, coÂndition monitoring of wind turbines is important to detect changes in the turbine beÂhaviour and predict faults so as to miÂnimise performance degradation and cost. The most commonly used seÂnÂÂÂsors for wind turbine condition moÂnitÂoring include accelerometers, temperature sensors, pressure seÂnsors, rotational speed sensors, and cuÂrrent clamps.
- Hydro: In June 2023, the Central EleÂctricity Authority notified the guideliÂnes for field efficiency test in hydroÂpower plants including pumped storage projects. The guidelines will be apÂplicable to any size/type of unit, comprising a generator–motor, an impulÂse/reaction turbine and a pump-turbiÂne with a unit size greater than 5 MW. These guiÂdelines specify a generaÂtor/moÂtor fieÂld efficiency measurement test to verify the efficiency of synchronous generators/induction maÂchÂiÂÂnes at site; and a turbine/pump efficiency measurement test. For these, instruments incluÂding flowmeters (to check the flow rate of fluids), thermal detectors (to determine the temperature rise of the liquid coolant) and coolers (caloÂrimeters needed for the bearing oil, and for the cooling water of air- or gas-coolers) will be utilised. Further, for measuring electrical quantities, insÂtruments such as micro-ohm meters for resistance measurement, digital poÂwer analysers, three–phase digital waÂttÂmeÂters, and digital multi–function meters shall be utilised.
Remote monitoring systems
Drones are being increasingly deployed to remotely monitor power plants as they can track changes in performance over time. The use of drones for inspection ofÂfÂÂers several advantages such as evaluation of the power plant condition, monitoring of inaccessible areas, reduced plant downtime and maintenance costs, and safety of power plant personnel. Drones are also relevant for monitoring of power stations with flue gas desulphÂuÂrisation equipment. Further, lining failure due to inadequate material quality or faulty workmanship, or even localised daÂmage, can lead to immediate corrosion and, possibly, structural damage. During a unit outage, drones can be operated inÂside the chimney to provide a comprehensive, high resolution image of the inÂternal lining system.
Gencos are also keenly opting for control solutions that enable them to monitor and control equipment parameters thÂrouÂgh automation. For example, ML-algorithms have gained traction for intelligent fault detection, predictive maintenance capabilities as well as monitoring of the whole compressor system from the same human-machine interface usÂed for conventional process control. The T&M sector will witness many developments in the coming years due to the path-breaking innovations in recognition technology, artificial intelligence and machiÂne learning. Further, internet of things enabled T&M instruments will gain traction going ahead.
Conclusion
T&M solutions for power plants are necessary to identify and address challenges related to performance in real time. They help in maintaining the operational efficiency of a power plant as well as lowering emission levels. Further, they are useful in enhancing the life of power plant equipment, and in avoiding lapses in preventive and predictive maintenance that can lead to unsafe conditions, system brÂeakdown, and revenue loss. However, the right combination of T&M equipment plays a vital role in checking the health of the critical power plant equipment. GoÂing forward, the adoption of comprehensive T&M solutions for power plants will help utilities repair or replace faulty units in real time.