scholarly journals Risk Assessment of Polluted Glass Insulator Using Leakage Current Index Under Different Operating Conditions

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 175827-175839
Author(s):  
Ali Ahmed Salem ◽  
Rahisham Abd-Rahman ◽  
Samir Ahmed Al-Gailani ◽  
Zainal Salam ◽  
Muhammad Saufi Kamarudin ◽  
...  
Author(s):  
Franco Stellari ◽  
Peilin Song ◽  
James C. Tsang ◽  
Moyra K. McManus ◽  
Mark B. Ketchen

Abstract Hot-carrier luminescence emission is used to diagnose the cause of excess quiescence current, IDDQ, in a low power circuit implemented in CMOS 7SF technology. We found by optical inspection of the chip that the high IDDQ is related to the low threshold, Vt, device process and in particular to transistors with minimum channel length (0.18 μm). In this paper we will also show that it is possible to gain knowledge regarding the operating conditions of the IC from the analysis of optical emission due to leakage current, aside from simply locating defects and failures. In particular, we will show how it is possible to calculate the voltage drop across the circuit power grid from time-integrated acquisitions of leakage luminescence.


Author(s):  
Antonio Velazquez ◽  
R. Andrew Swartz

The study of efficiency and safety for wind turbine structures under variable operating conditions is increasingly important for wind turbine design. Optimum aerodynamic performance of a wind turbine demands that serviceability effects and ultimate strength loads remain under safety design limits. From the perspective of wind turbine efficiency, variations in wind speed causes bluffing effects and vortex shedding that lead to vibration intensities in the longitudinal and transversal direction that can negatively impact aerodynamic performance of the turbine. From the perspective of wind turbine safety, variations in loading may lead to transient internal loads that threaten the safety of the structure. Inertial effects and asynchronous delays on rotational-force transmission may generate similar hazards. Monitoring and controlling displacement limits and load demands at critical tower locations can improve the efficiency of wind power generation, not to mention the structural performance of the turbine from both a strength and serviceability point of view. In this study, a probabilistic monitoring approach is developed to measure the response of the combined tower/nacelle/blade system to stochastic loading, estimate peak demand, and compare that demand to building code-derived estimates of structural resistance. Risk assessment is performed for the effects of along and across-wind forces in a framework of quantitative risk analysis with the goal of developing a near real-time estimate of structural risk that may be used to monitor safety and serviceability of the structure as well as regulate the aggressiveness of the controller that commands the blade angle of attack. To accomplish this goal, a numerical simulation of the aerodynamic performance of a wind turbine (including blades, the nacelle and the tower) is analyzed to study the interaction between the structural system and incoming flow. A model based on distributed-stationary random wind load profile for the combined along-wind and across-wind responses is implemented in Matlab to simulate full aero-elastic dynamic analysis to simulate tower with nacelle, hub, rotor and tower substructures. Self-weight, rotational, and axial effects of the blades, as well as lateral resistance of substructure elements are incorporated in the finite element model, including vortex-shedding effects on the wake zone. Reliability on the numerical solution is inspected on the tower structure by comparing the numerical solution with established experimental-analytical procedures.


Author(s):  
N. A. Othman ◽  
M. A. M. Piah ◽  
Z. Adzis ◽  
Nasir A. Al-geelani

This paper deals with the analysis of partial discharge (PD) occurrences based on leakage current (LC) pulses distribution under different level of contamination. In this work, laboratory based contamination performance tests are conducted on four units of glass insulator string stacked in I-position. Results show that PD can be characterized (according to their occurrence with respect to the AC supply) as follows: corona discharge occurring dominantly in lightly contaminated insulators, surface discharge occurring dominantly in medium contaminated insulators and finally internal discharge occurring dominantly in heavily contaminated insulators. The ability to distinguish the type of PDs from the LC waveform could be used to monitor and predict the condition of the insulator. The outcome can be incorporated in a conditioning monitoring system.


Author(s):  
G. Wang ◽  
P. Sapienza ◽  
R. J. Fetterman ◽  
M. Y. Young ◽  
J. R. Secker ◽  
...  

Similar to many existing Pressurized Water Reactors (PWR), the AP1000® cores will undergo sub-cooled nucleate boiling in the upper grid spans of some fuel assemblies at normal operating conditions. Sub-cooled nucleate boiling may increase crud deposits on the fuel cladding surface which may increase the risk of Crud Induced Power Shift (CIPS) and/or Crud Induced Localized Corrosion (CILC). A CIPS/CILC risk assessment has been performed to support the AP1000 fuel assembly design finalization. In this paper, the advanced thermal-hydraulic (TH) methodology used in the AP1000 plant CIPS/CILC risk assessments are summarized and discussed, and the relationship between the CIPS/CILC mechanisms, fuel reliability, and plant operating conditions is also presented. Finally, acceptable AP1000 core CIPS/CILC risk assessment results are summarized and suggestions that specifically target reducing CIPS/CILC risks for AP1000 plants are described.


Author(s):  
Jerzy Mikulik ◽  
Mirosław Zajdel

Automatic Risk Control Based on FSA Methodology Adaptation for Safety Assessment in Intelligent BuildingsThe main area which Formal Safety Assessment (FSA) methodology was created for is maritime safety. Its model presents quantitative risk estimation and takes detailed information about accident characteristics into account. Nowadays, it is broadly used in shipping navigation around the world. It has already been shown that FSA can be widely used for the assessment of pilotage safety. On the basis of analysis and conclusion on the FSA approach, this paper attempts to show that the adaptation of this method to another area—risk evaluating in operating conditions of buildings—is possible and effective. It aims at building a mathematical model based on fuzzy logic risk assessment with different habitat factors included. The adopted approach lets us describe various situations and conditions that occur in creating and exploiting of buildings, allowing for automatic control of the risk connected to them.


Author(s):  
N. A. Othman ◽  
M. A. M. Piah ◽  
Z. Adzis ◽  
Nasir A. Al-geelani

This paper deals with the analysis of partial discharge (PD) occurrences based on leakage current (LC) pulses distribution under different level of contamination. In this work, laboratory based contamination performance tests are conducted on four units of glass insulator string stacked in I-position. Results show that PD can be characterized (according to their occurrence with respect to the AC supply) as follows: corona discharge occurring dominantly in lightly contaminated insulators, surface discharge occurring dominantly in medium contaminated insulators and finally internal discharge occurring dominantly in heavily contaminated insulators. The ability to distinguish the type of PDs from the LC waveform could be used to monitor and predict the condition of the insulator. The outcome can be incorporated in a conditioning monitoring system.


Author(s):  
Oliver J. Hodgson ◽  
Dennis W. J. Keen ◽  
Malcolm Toft

A Pipeline Integrity Management System (PIMS) is a comprehensive, systematic, and integrated set of arrangements implemented by an operator to assess, mitigate, and manage pipeline risk. Over the past 16 years, Penspen have performed over 30 PIMS audits of pipeline operators internationally. This paper presents the collated findings from these audits, and examines the common areas in which operators have fallen short of best practice. The paper concludes with a series of recommendations based on the findings, which can be adopted by operators to improve their PIMS arrangements and practices. Penspen’s standardized 17 -element PIMS Model takes a holistic view of pipeline integrity. The audits, which are based on the Model, assess the adequacy and effectiveness of operators’ management systems and arrangements in keeping risks to people, the environment, and to the business to acceptable levels, given the anticipated pipeline operating conditions and taking into account the pipeline’s history and current status. Starting at the ‘top level’ of a PIMS, the audits consider the adequacy of operators’ pipeline policies, objectives, and performance metrics, and how these are subject to monitoring, review, and audit. The audits look at the organization responsible for managing the integrity of pipelines, and examine how all those with a role to play in the wider PIMS work together to this end. The numerous activities that take place during a pipeline’s lifecycle are investigated, to assess how the risk assessment results are used to determine the control and mitigation measures to be implemented during the pipeline’s design, construction, handover, commissioning, operation, inspection and maintenance, and how the operator ensures the effectiveness of these measures. The audits also study those ‘supporting’ processes and systems which play an important part in pipeline integrity management, including procurement, emergency response and recovery, incident investigation, change control, document and data management, and legal and code compliance. The collated results from the 30+ audits reveal that while operators typically have good control systems in place for the project stages of the pipeline lifecycle, controls for the operational stages have been found to be less robust. In terms of management and organization, operators can fail to recognize how many different individuals and teams have a role to play in the management of pipeline integrity. Furthermore, while operators often have good corporate systems in place for change control, emergency response, and risk assessment, such systems may not take into account pipeline-specific risks or requirements. Operators can tend to focus on pipeline safety and/or environmental-related risks, when through holistic assessment it can be shown that risks associated with production interruptions will tend to drive actions in practice.


2020 ◽  
Vol 23 (6) ◽  
pp. 643-666 ◽  
Author(s):  
A.V. Glushchenko ◽  
E.N. Samedova ◽  
V.A. Temnikov

Subject. This article deals with the issues of financial risk assessment and management of economic entities. It also considers the application and implementation of risk assessment techniques by small and medium-sized enterprises. Objectives. The article aims to develop applied aspects of the original methodology of stepwise assessment of a company's total financial risk using mild conditions of software maintenance. Methods. For the study, we used the methods of SWOT and scenario analyses, scoring, expert assessment, index numbers and ratio analysis methods, and the tabular, graphical, financial risk map, and event tree techniques. Results. Using the SME subject as a case study, the article reveals the applied aspects of the implementation of the total financial risk assessment methodology steps. By analyzing the performance and operating conditions of the company, it identifies the main risk components of financial risk, assesses the probability and cost of losses from their implementation, and determines risk indices and total financial risk. The article presents certain proposals for the financial recovery of the organization on the basis of internal changes and standards of indicators that ensure financial stability. A subsequent assessment of the effectiveness of the proposed measures shows the positive dynamics of the forecast financial indicators. Conclusions. Providing insight into the original methodology use at SMEs helps assess the potential for its practical application using relatively moderate data volumes and no specialized software.


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