Determination Of Reliability Index Research Articles

Reliability Study of Electrical Distribution Network in Kampala East

This research focuses on the reliability study of the electrical distribution network in Kampala East, which is connected to Lugogo, Nakawa, Kireka and Ntinda substations. The network is unable to supply its customers with reliable power at all times. Methods used in this research involve data identification, collection, cleaning, analyzing and interpretation. Also conducted are determination of reliability indices, identification of causes of supply interruptions and improvement of reliability. Depending on the reliability study outcome, the electrical distribution network in Kampala East has customer hours lost (System Average Interruption Duration Index) of 8.34 per month per customer, number of outages per month per customer (System Average Interruption Frequency Index) is 5.65 hours, Energy not served to customers of 2.14 GWh per month and Faults resolution time (Customer Average Interruption Duration Index) of 1.58 hours. The major cause of interruptions are system faults and emergency shutdowns. In this study, Reconfiguring network through use of appropriate combinations of opening of sectionalizing (normally Closed) switches and closing of tie-line (normally- Open) switches on feeders, the reliability is improved to 4.18 customers hours lost per month per customer and the number of outages per month per customer is 5.35, the energy not served of 0.18 GWh and faults resolution time of 0.84 Hours. This gives percentage improvements of 49.88%, 5.31%, 54.2%, and 88.61% in SAIDI, SAIFI, ENS and CAIDI respectively. The current level of reliability of electrical distribution network in Kampala East exceeds the target set by the regulator for 2022.

Estimation of Fatigue Longevity of Rod Elements of Complex Form

The questions of design maintenance of a given fatigue longevity of rods of complex form during the intensification of load modes without changing of geometric, inertial and rigidity parameters of roads are considered. The study is conducted on the example of needles of circular machines with a small diameter of cylinder (automatic half-hose machines). An approach, based on the system of calculation of loads, loadings and resources under the criterion of fatigue strength, is proposed. The key link for the transition from the results of dynamic analysis to the determination of reliability indices is the dependence of limited longevity of needles on the cycles of load to fatigue failure with the use of statistical data on operating time to fatigue failure of the needles in production conditions. Since the random values of loads of the needles do not obey the normal law of distribution, the general description of density of distribution of amplitude of loads is presented. The influence of increase in speed parameters and constructive measures, aimed to reduce the corresponding loads at a current size of critical section of the needles, on the fatigue longevity is analyzed.

Effective Safety Assessment of Aged Concrete Gravity Dam based on the Reliability Index in a Seismically Induced Site

The seismic performance of the aged-concrete gravity dam (aged-CGD) by safety assessment based on the reliability-index is the main focal point of this study. Determination of reliability-index has been handled by the site seismic hazard analysis with the help of PSHRisk-tool (developed by the authors) and risk assessment. Incorporated with the uncertainties, the failure probability has been carried out by the IDA and fragility analysis. For the nonlinear finite element model of the CGD, the concrete damage plasticity (CDP) model is adopted. To investigate the aging effect, the hygro-chemo-mechanical model has been taken for different years consideration. Through the failure risk assessment of serviceability and safety level, the target reliability index has been determined here for an existing CGD in Korea. Despite several types of research on the CGD safety assessment, the main novelty of this proposed approach will help the dam operator to check the safety barrier for the aged-CGD. A safety index is investigated by comparing the target reliability-index of the age-CGD with the reliability-index for two potential earthquake levels. However, the proposed approach can implement to check the safety range of any seismic site for any set of earthquakes.

Determination of reliability index of cantilever retaining wall by RVM, MPMR and MARS

Overturning criterion is an important parameter for designing cantilever retaining wall. This study adopts relevance vector machine (RVM) based first order second method (FOSM), minimax probability machine regression (MPMR) based FOSM and multivariate adaptive regression spline (MARS) based FOSM for determination of reliability index of cantilever retaining wall based on overturning criterion. RVM, MPMR and MARS have been used to overcome the limitations of the FOSM method. An example is illustrated how the proposed RVM based FOSM, MPMR based FOSM and MARS based FOSM analysis can be carried out. A comparative study has been carried out between the developed techniques. The results demonstrate that the developed techniques have ability to overcome the limitations of FOSM. This article describes new methods based on RVM, MPMR and MARS for determination of reliability index of retaining wall. The adopted methods eliminate the limitation of FOSM.

Structure orderliness assessment of grid development to improve the reliability of coal mine external electrical power supply

State-of-the-art reliability assessment methods require a large amount of initial statistical data, which does not always have the necessary degree of accuracy for accurate assessment. Moreover, this data is often difficult to obtain, which can ultimately delay the execution of calculations and increase error within results. This paper explores an alternative assessment method using the “structural orderliness indicator” and minimal initial data to calculate the change in reliability indicators in connection with reinforcement decisions. This paper includes the cost of reconstruction associated with the introduction of a new unit cost indicator for increasing the structure orderliness index. As a real-world application, the following discussion proposes improvements to external electrical power supply reliability for coal-mining enterprises within the Russian Federation, such as in the Kemerovo region (the biggest coal-producing region of Russia). In recent years, the number of production process suspensions and emergency shutdowns of life support facilities has increased due to external power supply disruptions. The performed calculations made possible qualitatively comparison the proposed method and state-of-the-art method based on the determination of reliability indices (SAIDI, SAIFI, etc.).

System-reliability analysis of steel truss towers

Steel truss towers are important structures in civil engineering, used as, for example, antenna towers, architectural towers, transmission towers, chimney towers, light towers, viewing towers, or water towers. In the paper, the latter structural type is analysed. Three types of truss towers with different topology are discussed. The towers are designed according to the standards. Next, reliability analysis is performed and the influence of type of truss topology on reliability is analysed. Reliability analysis concerns formulation of the limit state, calculation of failure probability and determination of reliability index. In the paper, the system approach is proposed, definitely more complete than that obtained using approximation-simulation methods. In the case of structures analysed in the paper, the types of reliability models are determined. Identification of reliability models relies on studies on the transformation of the safe structural system into the geometrically variable system (mechanism). The investigations made it possible to determine the kinematically admissible failure mechanisms which contain minimal critical sets of elements. In order to identify the mechanism, spectral analysis of the linear stiffness matrix is used. In the case of the towers of concern, the formulas specifying the number of mechanisms for any number of repeating sections are determined.

Determination of Reliability Indices for Distribution System using a State Transition Sampling Technique Accounting Random Down Time Omission

In this paper, a state transition sampling technique has been developed for evaluating reliability indices accounting random down time omission at load points for distribution system. Reliability indices, i.e. mean up time, mean down time and average interruption duration hours per year have been obtained accounting random down time omission. The algorithm has been implemented on sample radial and meshed distribution system.

A statistical probability approach to estimating the effects of input data accuracy on the determination of reliability indices

Methods and results are given for research on the accuracy of determining reliability parameters for monitoring during metrological expert evaluation when there are errors in the input data used in the estimation.