A power plant manager has to minimize operation and maintenance (O&M) expenses while ensuring the reliability, safety, and security of supply in order to remain competitive in the global market. The performance of a steam power plant (SPP) is a function of its basic structure (i.e., layout and design), availability (maintenance aspects), operation ef ciency (trained manpower), safety and security, and other regulatory aspects. Understanding of its structure will help in the improvement of performance, design, maintenance planning, and so on. A mathematical model using the graph theory and matrix method is developed to evaluate the performance of a coal-based SPP. Detailed methodology for developing a system structure graph (SSG), various system structure matrices, and their permanent functions are described for the boiler of an SPP (a macro level system). Structural interconnections between six systems of boiler are considered for developing an SSG of a boiler. To carry out complete structural modelling and analyses of the boiler, system structure graphs of its six systems and their subsystems are presented. A top-down approach for complete analysis of any system is also given.This method can be extended further for modelling a complete SPP by incorporating a turbogenerator macro system and its subsystems, thus converting real-life SPP from a block diagram into a mathematical model for analysis and synthesis of a power plant from different perspectives.

Maintenance cost and downtime losses of a steam power plant can be reduced by adopting a proper mix of maintenance strategies that ensure its reliable availability. The type of maintenance for different equipment in a power plant is decided as per its importance in terms of attributes such as maintenance efforts, loss of production, safety/reliability and efficiency. In the worst situation, failure of hypothetical equipment would affect all these attributes and would thus have maximum criticality. In general, the failure of equipment would not affect all the attributes and therefore its criticality will have some intermediate value. The level of criticality would decide the importance of the power plant equipment and choice of appropriate maintenance strategy. The procedures reported in literature are empirical co-relations to combine major attributes into a single index and have the limitation of using a number of attributes simultaneously. Using Graph theory and the Matrix method, a systems-based mathematical model has been developed for determining the maintenance criticality index of equipment of a coal-based steam power plant. The proposed model does not have any limitation either regarding the number of attributes or the interactions among these. Being a mathematical model, it is also not subjective. Plant equipment is categorized into four groups as per the ranking of its maintenance criticality index and a suitable maintenance strategy is recommended for each group. A step-by-step procedure for finding the criticality index has also been proposed in the paper. Using this procedure, an appropriate maintenance strategy for any other type of power plant/industry can also be recommended.

The present system of reporting reliability (also known as product performance) of a power generating plant on annualized basis has failed to serve the plant managers to take technocommercial decisions. Moreover, these indices show a wide variance depending upon the method of selection by the peer group for indexing purposes. For assessing reliability, a model has been developed for a steam power plant (SPP) in this paper using a systems approach of graph theory in conjunction with matrix method. A concept of real-time reliability index (RTRI) of the SPP has also been proposed, which overcomes the problems associated with the selection of a peer group for comparison. The value of RTRI indicates the probability of complete shut down or operation of the SPP at partial load.For finding the reliability of a SPP in real-time, its system structure graph (SSG), variable permanent system structure matrix and variable permanent function (VPF-s) have been converted into the corresponding reliability graph, matrix, and variable permanent function (VPF-r), respectively by associating reliability attribute to the nodes (S i ) and the edges (c ij ) of the SSG. When all the equipment, subsystems in different systems (S i ) of a SPP are performing as per design specifications, the corresponding value of the VPF-r is termed as VPF-r design. Under real-time operation when, some of the equipment/subsystem of a particular system(s) may not be available or not performing at the designed level; the corresponding value of VPF-r is different from its design value and is termed as VPF-r real-time and the ratio of the real-time-value to the design value is the RTRI value. The proposed model is capable of taking real-time situations of various systems of the SPP simultaneously. A step-by-step procedure for calculation of RTRI has been suggested and also been illustrated by means of an example.

The present system of recording efficiency parameters under process performance of a steam power plant (SPP) includes specific fuel consumption, auxiliary power consumption, and demineralized water for make-up used during past-specific period, without their integration into a single process performance or efficiency index. For developing integrated efficiency index in real time frame, the use of a process performance digraph (PPD) comprising of P i 's as nodes and p ij 's as interconnection among the nodes as obtained from the system structure graph (SSG) of SPP has been demonstrated. Each c ij of SSG corresponds to a process, such as air fuel mixing, combustion of mixtuer, generation and expansion of steam and its condensation back into water for recirculation in boiler, etc., taking place in the SPP and corresponds to a P i of PPD. The PPD is then analysed for determining the efficiency of the SPP using matrix method following systems approach.Variable permanent process performance matrix and its variable permanent function (VPF-p) have been derived from the PPD for the analysis. The real-time efficiency index (RTEI) has been introduced which is the ratio of the values of (VPF-p) in realtime (RT) situation (VPF-p) RT to its achievable design value (VPF-p). It reflects the RT rate of consumption of various inputs like demineralized water make-up, auxiliary power and fuel consumption, etc. It provides a more scientific method for ranking the performance of an SPP. The proposed model is capable of analysing in RT the performance of various systems of the SPP, taking into account simultaneously the failure of various equipments in these systems. A step-by-step procedure for calculation of RTEI has also been suggested and illustrated by giving an example.

Worldwide, the structure of the power industry is changing to that of a market economy to ensure commercial accountability. Resources, therefore, are allocated for operation and maintenance from commerical considerations rather than technical alone, necessitating the introduction of a commercial approach to analysis of reliabilty, efficiency, and maintenance criticality for power plants. These requirements suggest the need to introduce performance monitoring systems in the form of a single composite index encompassing the consequences of non-performance with respect to all these parameters and which can effectively respond to market demands. Such performance monitoring system is developed in the current paper.Graph theory has been applied to the complex system of a steam power plant to consider its structure explicitly and to derive reliability/availability, efficiency, and maintenance indices. Its representation at system level is modeled by system structure graphs to study reliability/efficiency indices (viz. RTRI and RTEI). The approach has already been applied by the authors for the development of an efficiency index, i.e. RTEI, and a maintenance criticality index to optimize the maintenance cost. In the current paper, it is applied to develop a single composite index, i.e., a real-time commercial availability index (RTAI) com . The various attributes that affect commercial availability are identified as also the interactions among them. With these, a commercial availability attributes' digraph is developed and its corresponding variable permanent commercial availability attribute interaction matrix is written. The permanent function of this matrix is then analysed to study the various aspects of commercial availability as well as to evaluate (RTAI) Com . A scheme for implementation of the procedure to develop a single composite index has also been proposed. This will monitor the health of the mechanical equipment of a steam power plant as Supervisory Control and Data Acquisition (SCADA) monitors its electrical equipment.during the available hours ([1]), the commercial consequences of non-performance of power plants during the required hours would have to be accounted for while determining the cost of generation. Therefore, from the generator's point of view, a power plant should operate reliably, efficiently, and within the prevailing market price to enable the booking of maximum profit margins. Hence, availability of a power plant is to be judged from market signals rather than technical (that is energy and time) alone. These signals are sent through the unscheduled JPE366