Aspects and directions of internal arc protectio

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Understanding and Quantifying Arc Flash Hazards in the Mining Industry

Arc flash generally refers to the dangerous exposure to thermal energy released by an arcing fault on an electrical power system, and in recent years, arc flash hazards have become a prominent safety issue in many industries. This problem however, has not been effectively addressed in the mining industry. MSHA data for the period 1990 through 2001 attributes 836 injuries to non-contact electric arc burns , making it the most common cause of electrical injury in mining. This paper presents results from several elements of a recent NIOSH study of arc flash hazards in mining, and provides information and recommendations that can help reduce these injuries. Characteristics of past arc flash injuries in mining are first outlined, such as the electrical components and work activities involved (based on MSHA data). This is followed by a review of important concepts and terminology needed to understand this hazard. Next, methods for identifying, measuring, and managing arc flash hazards on a power system are covered, with emphasis on recommendations found in NFPA 70E, Standard for Electrical Safety in the Workplace. Finally, results are presented from a detailed arc flash hazard analysis performed on a sample mine electrical power system using IEEE 1584-2004a, focusing on components and locations presenting severe hazards as well as engineering solutions for reducing the risk to personnel. Index terms - electrical arcing, electrical burns, mining, arc flash hazard analysis2007835

The initiation of electric arcs and the possible impact in industrial environments

Advancing knowledge and understanding of electrical arc flash and arc blast hazards through experimentation, modelling and analysis is the main goal of the present thesis. To achieve this, initially, significant work has been carried out to analyse existing data on arc flash hazards and mitigation engineering practices in industrial premises. Then, experimental investigations on the electrical arc characteristics have been conducted which together with the development of an analytical model for quantification of arc's energy components have formed the core of the research project.;Electrical characteristics of the initial stage of the arc have been obtained experimentally using different test systems developed in the course of this study. Two different arc initiation mechanisms have been examined: self-breakdown spark gap (SBSG) and wire-guided spark gap (WGSG) discharge initiation. Data post-processing techniques have been developed to obtain arc voltage and current waveforms for calculating the electrical arc energy available in the discharge.;An analytical model has been developed based on the hydrodynamic approach, to further analyse the energy dissipated and to obtain the energy components associated with thermal, acoustic-kinetic and light emission processes. This analysis of the energy components provides data for safety considerations which are currently not taken into account by the existing standards. Furthermore, analysis and evaluation of the suitability of black-box models for predicting the arc characteristics during its initiation taking into account electric circuit parameters have been performed.;Initial conditions for analysis of the ratio of the arc current over voltage have been obtained from experimental waveforms to investigate the arc-electrical circuit interaction. This can be considered as a first step towards establishment of a complete accurate link between the microscale and macroscale manifestation of the arc flash and arc blast phenomena. It is envisaged that further understanding of the complex energy conversion processes taking place in the post-arc-initiation process can provide additional tools for quantifying arc energy components and improving arc flash and arc blast safety.Advancing knowledge and understanding of electrical arc flash and arc blast hazards through experimentation, modelling and analysis is the main goal of the present thesis. To achieve this, initially, significant work has been carried out to analyse existing data on arc flash hazards and mitigation engineering practices in industrial premises. Then, experimental investigations on the electrical arc characteristics have been conducted which together with the development of an analytical model for quantification of arc's energy components have formed the core of the research project.;Electrical characteristics of the initial stage of the arc have been obtained experimentally using different test systems developed in the course of this study. Two different arc initiation mechanisms have been examined: self-breakdown spark gap (SBSG) and wire-guided spark gap (WGSG) discharge initiation. Data post-processing techniques have been developed to obtain arc voltage and current waveforms for calculating the electrical arc energy available in the discharge.;An analytical model has been developed based on the hydrodynamic approach, to further analyse the energy dissipated and to obtain the energy components associated with thermal, acoustic-kinetic and light emission processes. This analysis of the energy components provides data for safety considerations which are currently not taken into account by the existing standards. Furthermore, analysis and evaluation of the suitability of black-box models for predicting the arc characteristics during its initiation taking into account electric circuit parameters have been performed.;Initial conditions for analysis of the ratio of the arc current over voltage have been obtained from experimental waveforms to investigate the arc-electrical circuit interaction. This can be considered as a first step towards establishment of a complete accurate link between the microscale and macroscale manifestation of the arc flash and arc blast phenomena. It is envisaged that further understanding of the complex energy conversion processes taking place in the post-arc-initiation process can provide additional tools for quantifying arc energy components and improving arc flash and arc blast safety

Shaping frontline practices: a scoping review of human factors implicated in electrical safety incidents

Injuries sustained while performing electrical work are a significant threat to the health and safety of workers and occur frequently. In some jurisdictions, non-fatal serious incidents have increased in recent years. Although significant work has been carried out on electrical safety from a human factor perspective, reviews of this literature are sparse. Thus, the purpose of this review is to collate and summarize human factors implicated in electrical safety events. Articles were collected from three databases (Scopus, Web of Science, and Google Scholar), using the search terms: safety, electri*, human factors, and arc flash. Titles and abstracts were screened, full-text reviews were conducted, and 18 articles were included in the final review. Quality checks were undertaken using the Mixed Methods Appraisal Tool and the Critical Appraisal Skills Program. Environmental, individual, team, organizational, and macro factors were identified in the literature as factors which shape frontline electrical worker behavior, highlighting the complexity of injury prevention. The key contributions of this paper include: (1) a holistic and integrated summary of human factors implicated in electrical safety events, (2) the application of an established theoretical model to explain dynamic forces implicated in electrical safety incidents, and (3) several practical implications and recommendations to improve electrical safety. It is recommended that this framework is used to develop and test future interventions at the individual, team, organizational, and regulator level to mitigate risk and create meaningful and sustainable change in the electrical safety spac

Modeling and analysis of electrical system for offshore oil and gas platform

The main objective of power system analysis is to ensure that the electrical power system is modeled in a safe, reliable, and efficient manner. Short-circuit analysis is a power system analysis investigating the maximum and minimum currents during a fault or short-circuit. The power system analysis software PowerFactory by DIgSILENT was used for modeling and analyzing an 11kV offshore oil and gas platform that is powered from shore through an HVDC cable. Short-circuit analysis according to IEC 60909 was conducted for variouscombinations of open and closed bus-ties between the 690V switchboards or the 11kV switchboards under normal operation mode. Maximum and minimum short circuit currents were considered to ensure compliance with switchgear ratings and protective devise coordination. The results display short-circuit currents within defined limits, indicating the electrical network is modeled safely and reliably. For further work, it is recommended to develop the electrical model further by doing analysis for other operation types, like essential and emergency operations, and conducting other power system analyses, for instance, arc flash analysis and load flow

EXPANDED PREDICTIVE EQUATION FOR DC ARC-FLASH INCIDENT ENERGY IN 125V BATTERY SYSTEMS

Arc-flash is a dangerous phenomenon that can occur during an arcing fault in an electrical system. People nearby may be subjected to extreme heat, light, pressure, and sound. Research regarding arc-flash has focused primarily on AC arc-flash due to the prevalence of AC electricity in the grid. However, the grid has begun to integrate more DC electrical sources as a result of decentralization efforts and environmental concerns. The increased proliferation of DC electrical sources demands research into DC arc-flash to assess the hazard as low-voltage DC sources have already become commonplace. Some DC arc-flash models have been produced to estimate incident energy. These models are either theoretical or semi-empirical in nature, as empirical research pertaining to DC arc-flash is scarce. The lack of empirical DC arc-flash data inspired a series of tests at American Electric Power’s (AEP’s) Dolan Technology Center (DTC) that were conducted in August 2018. These tests allowed the development of a limited empirical equation for incident energy. The research presented in this thesis is a continuation of the August 2018 DC arc-flash testing with the objective of generating an expanded incident energy equation. Furthermore, this research seeks to address the effects of some atmospheric conditions on the behavior of low-voltage DC arcs

ARC FLASH DETECTION THROUGH VOLTAGE/CURRENT SIGNATURES

Arc Flash events occur due to faults in electrical equipment combined with a significant release of energy across an electrical arc. Due to the large energy release, plasma is generated, pressures increase, and the plasma expands. Under these conditions the plasma becomes excited enough to liquefy metal causing physical damage to equipment and any humans in the vicinity. This thesis investigates the state of art for detection of arc flash events and investigates a method of improving detection reliability, and speed by monitoring the high frequency voltage / current patterns utilizing methods similar to arc flash circuit interrupters (AFCI). A second alternative detection approach is determined through analysis of the physics of plasma development. The current state of art is based upon light detection. However this thesis experimentally investigates what happens before the arc event emits visible light. The results show that current flows to ground during an arc event slightly prior to the production of light. Further it shows through analysis of the physics of plasma that a high speed plasma detector has the potential to identify an arc event before the presence of visible light. Through the design and construction of experimental test setups, and physics analysis, this thesis provides new paths for detecting arc events that present opportunities to improve detection time

Early warning: a people-centred approach to early warning systems and the 'last mile'

The people-centred approach to early warning focuses on how communities can understand threats and avoid them. Disasters are partly caused by external hazards, but they also stem simply from vulnerability: people being in the wrong place without adequate protection. Perhaps the most well-known risk assessment method of recent years is the “vulnerability and capacity assessment”, developed by the Red Cross Red Crescent. There is a consensus that information must extend to communities so as to facilitate their adoption of protective actions. The linking of early warning and early action with development aspirations is what motivates people to engage. Factors as diverse as knowledge, power, culture, environment, lifestyle and personality often determine whether people heed warnings. Engaging people outside any warning system is called the “last mile” – a term that expresses the sentiment that warnings often do not reach those who need them most. Addressing vulnerability in disaster reduction is often similar to promoting development, but in the developed world “top-down” approaches to risk assessment and early warning dominate

The dilemmas of risk-sensitive development on a small volcanic island

In the Small Islands Developing State (SIDS) of St Vincent and the Grenadines in the Caribbean, the most destructive disasters in terms of human casualties have been the multiple eruptions of La Soufrière volcano situated in the north of St Vincent. Despite this major threat, people continue to live close to the volcano and national development plans do not include risk reduction measures for volcanic hazards. This paper examines the development options in volcanic SIDS and presents a number of conundrums for disaster risk management on the island of St Vincent. Improvements in monitoring of volcanic hazards and ongoing programmes to enhance communications systems and encourage community preparedness planning have increased awareness of the risks associated with volcanic hazards, yet this has not translated into more risk-informed development planning decisions. The current physical development plan in fact promotes investment in infrastructure in settlements located within the zone designated very high-hazard. However, this is not an anomaly or an irrational decision: severe space constraints in SIDS, as well as other historical social and economic factors, limit growth and options for low-risk development. Greater attention needs to be placed on developing measures to reduce risk, particularly from low-intensity hazards like ash, limiting where possible exposure to volcanic hazards and building the resilience of communities living in high-risk areas. This requires planning for both short- and longer-term impacts from renewed activity. Volcanic SIDS face multiple hazards because of their geography and topography, so development plans should identify these interconnected risks and options for their reduction, alongside measures aimed at improving personal preparedness plans so communities can learn to live with risk

Light environment - A. Visible light. B. Ultraviolet light

Visible and ultraviolet light environment as related to human performance and safety during space mission