- Title
- A systematic earthing system design procedure employing probabilistic analysis of discrete decisions
- Creator
- Carman, William Donald
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2002
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This thesis develops an earthing system design procedure that is flexible in applicability, and that leads the designer to make conscious articulated decisions to identify hazards, meet appropriate risk targets and maintain compliance with performance requirements over the life of the installation. A critique of the most popular standards and methodologies in use today identifies many deficiencies and inconsistencies in meeting such a goal. A close examination of the basis behind the physiological safety criteria identifies inconsistencies introduced in transferring laboratory date to published acceptable body current criteria. Based upon a derivation of statistical probability distribution characteristics for key shock circuit parameters an appraisal of the actual safety levels afforded by commonly accepted safety criteria is made. The resultant safety levels are clearly shown not to comply with underlying probabilistic safety risk targets without specification of additional factors such as series impedance (e.g. footwear crushed rock and asphalt) and fault/contact coincidence probability conditions. A rigorous definition of series impedance parameters is based upon probabilistic characteristic derived from extensive field and laboratory testing. Such factors are clearly articulated and incorporated in a technique for deriving defensible safety guidelines which link site and system specific conditions with a family of 'safety characteristics'. The development of a decision theory basis for underlying safety risk targets is presented based on a synthesis of a range of heuristic requirements including: acceptability, reasonableness, practicality and defensibility. Recommendations are made regarding reshaping of regulations in the light of this analysis and inadequacies identified in many existing safety regulations. Unfortunately, safety characteristics and regulations alone are incapable of delivering safe power systems under earth fault conditions. To meet this need a design methodology is developed which optimises the design configuration to produce robust, practical, cost justified designs which comply with applicable performance criteria. Inadequacy in initial phases of design, installation and commissioning, or changes in the electrical and physical configurations can give rise to such risks. A key component of the coordinated design and management philosophy is the ability to identify and eliminate, reduce or manage vulnerability to these risks. Flexible, stages probabilistic models are developed for the active parameters and systems in order to facilitate analysis of the time and spatial dependencies inherent in the occurrence of, and response to, an earth fault condition. The resultant risk analysis based design process identifies the significant parameters, the required level of accuracy, and how best to integrate the individual risk profiles to achieve an overall robust design based upon techniques developed throughout the thesis.
- Subject
- earthing design; earthing system design procedure; hazards; work health and safety requirements
- Identifier
- http://hdl.handle.net/1959.13/1312586
- Identifier
- uon:22435
- Rights
- Copyright 2002 William Donald Carman
- Language
- eng
- Hits: 1117
- Visitors: 1061
- Downloads: 0