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1. West Yangon Technological University Department of Electrical Power Engineering Power System Reliability EP-61012 (5.1.2024) Third seminar Supervisor by: Presented by: Dr Theingi Htun Ma Hnin Hnin phyu VI.EP-1 1

2. Outlines of presentation Introduction Changing scenario Probabilistic reliability criteria Statistical and probabilistic measures Absolute and relative measures Methods of assessment Concepts of adequacy and security System analysis Reliability cost and reliability worth Concepts of data Conclusion 2

3. Introduction The degree of redundancy has had to be commensurate with the requirement that the supply should be as economic as possible Overinvestment can lead to excessive operating costs which must be reflected in the tariff structure The economic constraint can be violated although the system may be very reliable Typical criteria are planning generating capacity, operating capacity and planning network capacity Typical probabilistic aspects are forced outage rates of generating units, the failure rat of an overhead line and all planning and operating decisions 3

4. Changing scenario All power systems either have been state controlled and hence regulated by governments directly or indirectly through agencies Deregulation of private companies and privatization of state controlled industries has now been actively implemented The intention is to increase competition, to unbundle ot disaggregate the various sectors, and to allow access to the system by an increased number parties not only consumers but also traders of energy This trend has therefore been towards the ‘market forces’ concept , with trading taking place at various interfacing levels throughout the system The need to assess the present performance and predict the future behavior of systems 4

5. Probabilistic reliability criteria System behavior is stochastic in nature It remains a fact that most of the present planning , design, and operational criteria are based on deterministic techniques These have been by utilities for decades, and is argued that they have served the industry extremely well in the past These eminent gentlemen identified some 50 years ago the need for ‘probabilistic evaluation ‘, relating economic to reliability’ , and the ‘assessment of benefits or worth’ the main reasons cited for this situation are lack of data and realistic reliability techniques, aversion to the use of probabilistic techniques , mis understanding of the significance, probabilistic criteria and risk indices 5

6. Statistical and probabilistic measures Identify weak areas needing reinforcement or modifications Establish chronological trends in reliability performance Establish existing indices which serve as a guide for ace[table values in future reliability assessments Enable previous predictions to be compared with actual operating experience Monitor the response to system design change 6

7. Absolute and relative measures Absolute indices are the values that a system is expected to exhibit The models used are also not entirely accurate representations of the plant or system behavior but are approximations The benefit of the change is obtained by evaluating the relative improvement Indices are therefore compared with each other and not against specified targets Both the model and the technique must reflect and respond to the way the system operates and fails 7

8. Methods of assessment Power system reliability indices can be calculated using a variety of methods The two main approaches are analytical and simulation The vast majority of techniques have been analytically based and simulation techniques have taken a minor role in specialized applications Analytical techniques represent the system by a mathematical model and evaluate the reliability indices from this model using direct numerical solutions Simulation methods estimate the reliability indices by simulating the actual process and random bebavior or the system 8

9. Concepts of adequacy and security The concept of adequacy is generally considered to be the existence of sufficient facilities within the system to satisfy the consumer demand Security is therefore associated with the response of the system to whatever disturbances they are subjected The implementation of this division is that the two aspects are different in both concept and evaluation This concept of adequacy considers a state in complete isolation neglects the actual entry transitions and the departure transitions as causes of problems Power system enginers tend to relate security to the dynamic process that occurs when the system transits between one state and another state 9

10. System analysis Generating stations-ach station or each unit in the station is analyzed separately Generating capacity–the reliability of the generating capacity is evaluated by pooling all sources of generation and all loads Interconnected system-in this case thee generation of each system and the tie lines between systems are modeled Composite generation/transmission-the network is limited to the bulk transmission, and the integrated effect of generation and transmission is assessed Distribution networks-the reliability of the distribution es evaluated by considering the ability of the network fed from bulk supply points or other local infeed in supplying the local demands Substations and switching stations-these systems are often quite complicated in their own right and are frequently analyzed separately rather than including them as complete systems in network reliability evaluation Protection systems-the reliability of protection systems is analyzed separately 10

11. Reliability cost and reliability worth The economic impact of these outages is not necessarily restricted to loss of revenue by the utility or loss of energy utilization by the customer As stated a number of times, costs and economics play a major role in the application of reliability concepts and physical attainment It is therefore evident that reliability and economics play a major integrated role in the decision-making process The basic concept pf reliability –cost, reliability worth evaluation is relatively simple and can be presented by the cost/reliability This total cost exhibits a minimum and so an optimum or target level of reliability is achieved 11

12. Concepts of data Meaningful reliability evaluation requires reasonable and acceptable data These data are nor always easy to obtain and there is often a marked degree of uncertainty associated with the required input The factors that must be identified are hose that have an impact on the utility’s own planning design, and asset management The processing of this data occurs in two distinct stages The component approach is more preferable in these cases, and therefore data collected using this approach is more convenient for such applications 12

13. Conclusion It cannot be considered generally however because different systems, different utilities and different customers all have differing requirements and expectation There should be some conformity between the reliability of various parts of the system There should be some benefits gained by an improvement in reliability The techniques often utilized for assessing this benefit is to equate the incremental or marginal investment cost to the customers incremental or marginal valuation of the improved reliability In conclusion, this illustrate some methods by which the reliability of various parts of a power system can be evaluated and the types of indices that can be obtained 13

14. 14 Thanks for Your Attentions