Correlation of Load-Point Reliability Indices with Power System Fault Levels

No Thumbnail Available
Date
1982
Authors
Awosope, C.O
Journal Title
Journal ISSN
Volume Title
Publisher
University of Lagos
Abstract
Extensive literature abounds on the evaluating techniques of load-point reliability indices of electrical power systems. On the whole, all the efforts of the published works have been the establishment of conventional methods to evaluate load-point reliability indices from raw component reliability data. Any system change that warrants new set of load-point reliability indices would require the whole process of reliability evaluation to be repeated. That is an inherent characteristic of these conventional evaluation techniques. For consistent and proper system operation and monitoring, the effects which any changes (such as addition of new lines, transformers or shunt reactors or their removals in order to cater for changes in the load demands) in the system have on the various load-point reliability indices, must be adequately assessed. In effect, this means that a new set of load-point reliability indices will have to be evaluated for the modified system in order to get the true picture of the system performance at the load point. Thus, repeated reliability indices evaluation can not be avoided in a successful system operation. Experience with the conventional method of reliability indices computations indicates that this repeated evaluation could be very expensive and time consuming in terms of repeated component data collection, computer storage requirements and the associated computer time. In order to repeatedly estimate these changing load-point reliability indices without the need to seek new set of component reliability data and indirect estimating technique is proposed in this thesis. This new technique involves the normal fault level analysis. The principle of the method is based on model building techniques. By the application of regression and correlation analysis to the separate calculation of both the load-point reliability indices and the associated load bus fault levels, models are carefully built and analysed. The conforming models permit the prediction of the reliability indices for the relevant outage conditions given that the system corresponding load busbar fault levels are known. Foe each of the above models, a test of satisfaction significant is performed. This gives the probability of error in the model’s prediction of reliability index of failure rate from the knowledge of faults levels. This significance test follows t-distribution with (n-2) degrees of freedom where n is the number of data points. In this way the criterion for choosing the optimal prediction model is formulated. The resulting model so constrained is found to have a high degree of statistical confidence and is unique to the system so long as the number of load busbars of the original system remains unaltered. The validity test is carried out on the models built for the three samples selected for study in the Thesis, for each system, the validity test shows that such an optimal prediction model will always correctly represent system structure in the face of any branch outage. This is so, because in each case, the results obtained are in agreement with those obtained using the binary formulation algorithm of the minimal cut-set theory. The Nigerian (NEPA i.e National Electric Power Authority) 330-KV system 1980 stage is one of the three simple electrical power systems selected for study in the Thesis. As far as the author is aware, the research work carried out in this Thesis on the reliability assessment of electrical power system is the first of its kind in Nigeria (i.e. reliability studies on NEPA system). This is a break – through in the past and present efforts to solve the varied and numerous Engineering, Technological and scientific problems.
Description
Full Text Attached
Keywords
Load-Point Reliability , Indices , Power System
Citation
Awosope, C.O, 1982. Correlation of Load-Point Reliability Indices with Power System Fault Levels. A Thesis Submitted in Fulfilment of the Requirements for the Degree of Doctor of Philosophy in Eletrical Engineering , University of Lagos.