This document discusses arc flash mitigation using active high-speed switch (HSS) systems. It provides background on arc flashes, their hazards, and conventional mitigation methods. It then introduces HSS systems as an innovative method to detect and quench internal arcs in less than 1/3 of an electrical cycle. By rapidly redirecting fault current, HSS systems can collapse voltage to extinguish arcs and reduce incident energy and equipment damage compared to circuit breaker tripping. The document explores application considerations and performance benefits of HSS systems for improving safety and reliability.
1) Arc flashes occur when there is a loss of insulation between energized electrical conductors, causing a flashover. They produce extremely high temperatures, loud sounds, and pressure waves that can cause serious injury.
2) The document discusses standards for analyzing and mitigating arc flash hazards, including defining flash protection boundaries and determining appropriate personal protective equipment based on potential incident energy levels.
3) ABB offers solutions for minimizing arc flash effects through selective coordination of circuit breakers and other protective devices to rapidly clear faults, reducing exposure to arc flash hazards for electrical workers.
The document summarizes major changes in the 2015 edition of NFPA 70E: Standard for Electrical Safety in the Workplace. Key changes include replacing terms like "harm" and "probablility" with more accurate terms, expanding definitions of terms like "qualified person" and "risk assessment", strengthening electrical safety program requirements, expanding training requirements, and modifying shock and arc flash risk assessment procedures and PPE categories. Changes aim to improve safety for electrical work by providing clearer guidance and better alignment with other safety standards.
An electrical contractor was removing an old circuit breaker from a 480 volt main distribution panel and installing a new one without de-energizing the panel first. As the journeyman electrician was loosening a live contact, it shifted towards another live contact. The master electrician grabbed the contact with pliers and his bare hand to hold it in place. His grip failed, causing an arc blast that severely burned both electricians. Proper safety precautions such as de-energizing the panel, using appropriate PPE, and ensuring solid grips on live parts could have prevented this incident.
Arc flash and electrical safety hazards can cause severe injury or death. Proper safety procedures and personal protective equipment are necessary when working with energized equipment. An arc flash incident captured on video shows three workers engulfed in flames after an arc flash from a 13,200V switchgear, resulting in severe burns over 60% of their bodies. Employers, employees, and owners all share responsibility for electrical safety programs, policies, training, and coordinating hazards.
This document provides an overview of arc flash hazards and safety. It discusses what an arc flash is, common injuries caused, and important temperature thresholds. The document reviews revisions to NFPA 70E standards regarding arc flash safety. It explains key terms like flash protection boundaries and limits of approach. The document outlines procedures for performing arc flash calculations and determining appropriate personal protective equipment.
Practical Arc Flash Protection for Electrical Safety ProfessionalsLiving Online
Electrical safety is an important issue for those working on electrical facilities in utility networks and large industrial installations. A number of serious accidents including fatalities occur every year due to accidents involving electricity resulting in huge financial losses and wasted man-hours. Arc flashes in electrical equipment are now considered one of the major causes of electrical accidents even surpassing the well known hazards of electric shock. Avoiding arc flash incidents and the resulting injuries is one of major challenges today facing electrical workers and requires adequate attention in the stages of system planning, design, installation, operation and maintenance.
Injuries due to arc flash can depend on many factors, one of which is the incident thermal energy on a worker exposed to a flash. Today, a considerable body of knowledge exists as a result of research efforts and is available to designers and maintenance engineers in the form of standards such as IEEE 1584 and NFPA 70E. This workshop will detail the basis of this approach and also about the major advances that have been made in the area of PPE made of FR fabrics and rated for different levels of thermal exposure.
Prevention however still remains the best form of protection and switchgear manufacturers have made considerable design advances to ensure that the effect of arc flash incidents is contained within the enclosure of switchgear (often called arc flash resistant switchgear) and methods of testing such switchgear have also evolved simultaneously. Another important factor is the approach to avoid arc incidents within the switchgear by proper design and maintenance and techniques to reduce the severity of the flash should such incidents occur.
These would form the key focus areas of this workshop.
MORE INFORMATION: http://www.idc-online.com/content/practical-arc-flash-protection-electrical-safety-professionals-22
This document discusses fire and electrical hazards in industrial plants. It defines fire and explains the three factors required for combustion. Electrical hazards are also defined, including how shocks occur through direct or indirect contact with energized circuits. The document outlines different types of electrical circuits and provides tips to prevent hazards, such as grounding equipment, inspecting for defects, and using insulated tools. Fire hazards are controlled through plant layout, isolation of operations, fire-resistant construction, and installation of alarms and extinguishing equipment.
This document discusses arc flash hazards and NFPA 70E standards for electrical safety. It provides the following key points:
1. Arc flashes produce extremely high temperatures that can cause severe burns and pressure waves. Following NFPA 70E standards helps protect workers from arc flash injuries.
2. NFPA 70E requires hazard analyses to determine shock, flash boundaries and personal protective equipment requirements. Employers must implement electrical safety programs, train workers, and ensure only qualified personnel work on live equipment.
3. Analyses consider incident energy levels, fault currents and clearing times to determine appropriate protective boundaries and PPE. Proper work procedures and well-maintained equipment help prevent arc flash incidents.
1) Arc flashes occur when there is a loss of insulation between energized electrical conductors, causing a flashover. They produce extremely high temperatures, loud sounds, and pressure waves that can cause serious injury.
2) The document discusses standards for analyzing and mitigating arc flash hazards, including defining flash protection boundaries and determining appropriate personal protective equipment based on potential incident energy levels.
3) ABB offers solutions for minimizing arc flash effects through selective coordination of circuit breakers and other protective devices to rapidly clear faults, reducing exposure to arc flash hazards for electrical workers.
The document summarizes major changes in the 2015 edition of NFPA 70E: Standard for Electrical Safety in the Workplace. Key changes include replacing terms like "harm" and "probablility" with more accurate terms, expanding definitions of terms like "qualified person" and "risk assessment", strengthening electrical safety program requirements, expanding training requirements, and modifying shock and arc flash risk assessment procedures and PPE categories. Changes aim to improve safety for electrical work by providing clearer guidance and better alignment with other safety standards.
An electrical contractor was removing an old circuit breaker from a 480 volt main distribution panel and installing a new one without de-energizing the panel first. As the journeyman electrician was loosening a live contact, it shifted towards another live contact. The master electrician grabbed the contact with pliers and his bare hand to hold it in place. His grip failed, causing an arc blast that severely burned both electricians. Proper safety precautions such as de-energizing the panel, using appropriate PPE, and ensuring solid grips on live parts could have prevented this incident.
Arc flash and electrical safety hazards can cause severe injury or death. Proper safety procedures and personal protective equipment are necessary when working with energized equipment. An arc flash incident captured on video shows three workers engulfed in flames after an arc flash from a 13,200V switchgear, resulting in severe burns over 60% of their bodies. Employers, employees, and owners all share responsibility for electrical safety programs, policies, training, and coordinating hazards.
This document provides an overview of arc flash hazards and safety. It discusses what an arc flash is, common injuries caused, and important temperature thresholds. The document reviews revisions to NFPA 70E standards regarding arc flash safety. It explains key terms like flash protection boundaries and limits of approach. The document outlines procedures for performing arc flash calculations and determining appropriate personal protective equipment.
Practical Arc Flash Protection for Electrical Safety ProfessionalsLiving Online
Electrical safety is an important issue for those working on electrical facilities in utility networks and large industrial installations. A number of serious accidents including fatalities occur every year due to accidents involving electricity resulting in huge financial losses and wasted man-hours. Arc flashes in electrical equipment are now considered one of the major causes of electrical accidents even surpassing the well known hazards of electric shock. Avoiding arc flash incidents and the resulting injuries is one of major challenges today facing electrical workers and requires adequate attention in the stages of system planning, design, installation, operation and maintenance.
Injuries due to arc flash can depend on many factors, one of which is the incident thermal energy on a worker exposed to a flash. Today, a considerable body of knowledge exists as a result of research efforts and is available to designers and maintenance engineers in the form of standards such as IEEE 1584 and NFPA 70E. This workshop will detail the basis of this approach and also about the major advances that have been made in the area of PPE made of FR fabrics and rated for different levels of thermal exposure.
Prevention however still remains the best form of protection and switchgear manufacturers have made considerable design advances to ensure that the effect of arc flash incidents is contained within the enclosure of switchgear (often called arc flash resistant switchgear) and methods of testing such switchgear have also evolved simultaneously. Another important factor is the approach to avoid arc incidents within the switchgear by proper design and maintenance and techniques to reduce the severity of the flash should such incidents occur.
These would form the key focus areas of this workshop.
MORE INFORMATION: http://www.idc-online.com/content/practical-arc-flash-protection-electrical-safety-professionals-22
This document discusses fire and electrical hazards in industrial plants. It defines fire and explains the three factors required for combustion. Electrical hazards are also defined, including how shocks occur through direct or indirect contact with energized circuits. The document outlines different types of electrical circuits and provides tips to prevent hazards, such as grounding equipment, inspecting for defects, and using insulated tools. Fire hazards are controlled through plant layout, isolation of operations, fire-resistant construction, and installation of alarms and extinguishing equipment.
This document discusses arc flash hazards and NFPA 70E standards for electrical safety. It provides the following key points:
1. Arc flashes produce extremely high temperatures that can cause severe burns and pressure waves. Following NFPA 70E standards helps protect workers from arc flash injuries.
2. NFPA 70E requires hazard analyses to determine shock, flash boundaries and personal protective equipment requirements. Employers must implement electrical safety programs, train workers, and ensure only qualified personnel work on live equipment.
3. Analyses consider incident energy levels, fault currents and clearing times to determine appropriate protective boundaries and PPE. Proper work procedures and well-maintained equipment help prevent arc flash incidents.
This document provides an overview of electrical safety. It discusses common causes of electrical fires such as defective devices and circuit overloading. It then covers important electrical safety topics like grounding, overcurrent protection devices like fuses and circuit breakers, GFCIs, proper and improper use of power strips and extension cords, damaged/unapproved devices, container bonding/grounding, and responsibilities of facilities and users. An example incident of electrocution from improper equipment use is also described to illustrate the importance of electrical safety.
The document discusses arc flash hazards, defining an arc flash as a dangerous condition caused by an electric arc. It provides information on what causes arc flashes, the governing agencies that regulate arc flash safety, and how to determine arc flash boundaries and label equipment. The company discussed provides arc flash safety services like analyses, training, and labeling to help clients comply with safety standards.
SASCO provides training on NFPA 70E, which establishes guidelines for electrical safety in the workplace. It addresses electrical hazards like shock, arc flash, and fire ignition. Arc flashes produce extremely high temperatures that can cause serious burns. Following the guidelines in NFPA 70E helps ensure electrical work is performed safely, such as through establishing limited approach boundaries and determining the proper personal protective equipment based on the potential hazards. Proper safety protocols, hazard analyses, and emergency response procedures can help minimize risks to workers from electrical incidents and injuries.
Regards, Mr. SYED HAIDER ABBAS
MOB. +92-300-2893683 MBA in progress,NEBOSH IGC, IOSH, HSRLI, NBCS,GI,FST,FOHSW,ISO 9001, 14001,
'BS OHSAS 18001, SAI 8000, Qualified .
An arc flash is caused by an arcing fault where electricity flows somewhere unintended, creating an electric arc that releases dangerous amounts of energy. Arc flashes cause severe burn injuries and cost millions in medical treatment. Proper personal protective equipment (PPE) and following safety regulations and standards can prevent arc flash injuries. Regulations require calculating arc flash hazards, using appropriate PPE based on hazard levels, training workers, and implementing safety programs with responsibilities and warning labels defined. Different levels of protective clothing are required depending on the estimated arc exposure intensity level. Selecting the proper flame-resistant clothing and other PPE can minimize worker injuries from electric arc accidents.
This document discusses arc flash safety and the dangers of electrical arc flashes. It notes that arc flashes can cause severe third-degree burns, blindness, cardiac arrest, and other serious injuries. The document outlines best practices for preventing arc flash incidents, including following NFPA 70E guidelines, assessing hazards to determine proper protective equipment, working on de-energized systems whenever possible using lock-out/tag-out procedures, and always wearing appropriate PPE suited for the potential energy level of the work being performed. Failure to follow safety procedures can expose workers to live parts and result in arc flash burns or death.
Arc Flash Safety Training by Pennsylvania Department of Labor and IndusryAtlantic Training, LLC.
This document discusses arc flash safety and electrical hazards. It notes that arc flashes are a serious risk and can cause burns, fires, and even death. An arc flash occurs when an electrical discharge travels through the air, releasing intense heat up to 5,000°F. The document recommends conducting an arc flash hazard analysis to determine appropriate personal protective equipment and safe working distances according to the voltage level. It also identifies some common causes of arc flashes such as overloading circuits, damaged equipment, and improper wiring. Following lockout/tagout procedures and wearing proper PPE rated for the voltage and distance is key to avoiding arc flash injuries when working on energized electrical equipment.
This document discusses arc flash energy and protection. It summarizes that an arc flash is a sudden release of heat and energy caused by an electric arc. OSHA and NFPA 70E now require arc flash hazard analyses to determine proper personal protective equipment. The analyses calculate incident arc energy levels and arc flash boundaries to determine the required PPE category, with higher incident energy requiring more protective flame-resistant clothing. Proper PPE is important as electricians can be severely injured by arc flash events every day.
The document discusses electrical safety precautions. It provides guidance on safely handling electrical appliances and working with electrical installations. Key safety measures include ensuring equipment is properly earthed, using insulated tools, disconnecting power before repairs, and not touching multiple terminals at once. Proper earthing helps limit voltages, provide fault protection, and reduce shock hazards. Critical components of an earthing system include earth electrodes, mats, and bonds to safely dissipate currents to earth.
The document discusses electrical hazards and safety. It defines electrical hazards, describes the types of injuries that can result from electric shock like burns and muscle paralysis. It explains how factors like current path through the body, shock duration, and skin resistance impact injury severity. The document provides guidance on helping someone receiving a shock, and safety measures like insulation, grounding, using qualified personnel, and regular inspections to prevent electrical accidents. The key messages are that electricity can be deadly if not used properly, but following safety precautions and procedures can minimize risk.
Electrical Safety. Electrical hazards can cause burns, shocks and electrocution (death). Assume that all overhead wires are energized at lethal voltages. Never assume that a wire is safe to touch even if it is down or appears to be insulated.
Many workers working on energised equipment are injured and/or killed each year. Several of these casualties are a result of arc flash.
Arc Flash is considered as one of the most destructive and dangerous instances when dealing with electrical wirings. A single occurrence can destroy metals and it has the ability to kill a person if not protected by Arc Flash Clothing. An arc flash can create an arc blast that can shatter anything because it is as hot as the as surface of the sun. This kind of heat can destroy metals instantly and completely burn a body beyond recognition.
Arc Flash ProtectionSerious injuries are caused by the arc flash:
Burns
Respiratory system damage
Hearing damage
Skin penetration from flying debris
Eye and face injuries
An arc flash may happen instantly and if the worker does not have the correct protection, they will already be dead when the arc flash hits them.
The use of Arc Flash Protective Equipment will lessen the damages caused by an arc flash because all of these equipments are solely made to withstand the heat.
Typical Arc Flash Clothing Applications
Working on electrical systems and switchrooms at 500 volts, live testing and proving dead on electrical systems, fitting and removal of LV-HV earths on electrical systems, working on panels/control circuits with exposed energised conductors, removal of bolted covers from energised electrical equipment, racking in/out of switchgear, racking in/out of starters and control gear, live testing and proving dead on electrical systems 11-33kV - T&D UK stock a broad range of Arc Flash Clothing and PPE.
This document provides information on electrical safety for workers. It discusses common electrician tasks like reading blueprints and connecting wires. It then describes the dangers of electricity, including causes of workplace deaths. An accident description details how an electrician was injured installing a breaker without proper permits or protective equipment. Key safety deficiencies are identified. Finally, the document outlines measures to prevent electrical shock, such as personal protective equipment, lockout/tagout procedures, and ground fault circuit interrupters.
This document discusses electrical hazards, their sources, and how to detect and reduce them. It defines electrical hazards and lists typical circuit wiring components. Major causes of electrical shocks are identified as short circuits, water contact, electrostatic hazards, arcs and sparks. Detection methods include using a circuit tester, receptacle tester, and continuity tester. The effects of electric current on humans at different levels are provided. Techniques to reduce hazards include proper grounding, bonding, ground fault interrupters, fuses, circuit breakers, double insulation, and interlocks.
1. Electrical safety is the 4th largest contributor to fatalities in the construction industry, with 5% of deaths due to electric shock or discharge.
2. Conductors readily allow the flow of electricity while insulators have high resistance and prevent electricity from flowing. Water and human skin are normally insulators but become conductors when wet.
3. Electric shock occurs when a person becomes part of an electrical circuit, with current entering and leaving the body. The severity of shock depends on current amount, path through the body, and time in the circuit. Effects range from tingling to cardiac arrest.
Electricity can cause serious injuries and death if not properly respected and safety protocols followed. There are three main electrical hazards: fires caused by overheating conductors, electrical shocks from contact with a power source, and electrical burns when enough current passes through the body. Many accidents occur due to failure to properly lockout electrical systems during maintenance, use of defective or wet equipment, and not following safe work practices such as grounding equipment and circuits. Proper safety includes never overloading circuits, staying away from unguarded conductors, inspecting cords, and using protective equipment.
Arc flash typically occurs when the electrical insulation or isolation between live conductors is severed or can no longer withstand the applied voltage. Near the high power electrical equipment, the short-circuit power available is high and consequently so is the energy associated with the electrical arc in case of a fault.
In Europe, regulation and standardization are mainly aimed at protecting workers against the risks of direct contact during work and interventions on and near electrical installations. The risks in the case of electric arc and the means to prevent them are mentioned but not developed.The effects of the electric arc:
The electric arc produces intense light and heat, high noise, high overpressure
Heat and splashes of molten metal can cause lethal burns
Noise can lead to permanent or temporary hearing loss, a flash of vision disorders
The overpressure can open and project the doors of electrical cabinets or cause falls during work at height
In addition to personal injury, an arc flash can result in serious damage to electrical equipment. which can cause disruption to electrical systems in manufacturing and process industry environments or tertiary buildings. The cost of downtime can be considerable. elec calc™ Arc Flash module provides the professionals of the electrical industry with a fundamental tool in the sector, as the user will be able to develop its safety analysis in the vicinity of switchboards and panels. By design, elec calc™ has almost all the data allowing the calculation of the figures of the arc flash, from which the user will be able to elaborate his security analysis near the tables and boxes.
The document discusses electrical hazards. It defines electrical hazards as any potential or actual threat due to electricity to the well-being of people, machinery, or the environment. It lists types of electrical hazards such as electric shock, burns, and arc blasts. It provides examples of workplace electrical hazards like damaged power lines, exposed conductors, and improper grounding. It also discusses sources of electrical hazards such as working with unearthed or improperly grounded electrical equipment.
This document discusses electrical hazards associated with welding and cutting equipment. It provides instructions on how to avoid electric shock, including properly grounding equipment, wearing protective clothing, inspecting cables, and not working alone in hazardous conditions. It recommends using certain equipment like DC constant voltage welders in damp or cramped areas, and provides procedures for responding to electric shock incidents.
This document discusses arc flash hazards in the workplace. It defines what an arc flash is, noting that it is a dangerous condition caused by the rapid release of energy from an electric arc. Arc flashes present serious risks of injury from burns, flying debris, and blasts of hot air and vapor. The document recommends performing arc flash studies to calculate potential hazards at electrical equipment and establish safety procedures and personal protective equipment requirements to protect workers. The goal of an arc flash study is to identify hazards and help employees avoid exposure through training and adherence to safety practices.
This document discusses methods for calculating arc flash hazards to help select proper personal protective equipment (PPE). It describes three primary calculation methods: 1) Ralph Lee's theoretical model from 1982, 2) equations and tables in NFPA 70E-2004, and 3) the comprehensive equations presented in IEEE Std 1584-2002. The document provides guidelines for determining which calculation method is correct for a given situation, such as verifying the method applies to the system voltages and fault currents and using device-specific equations over general equations. It also summarizes types of PPE defined in NFPA 70E-2004 based on the degree of arc flash protection required.
An arc flash is an electrical explosion caused by a fault or short circuit when a live conductor makes contact with another object, allowing current to flow through the air. Temperatures in an arc flash reach over 35,000 degrees Fahrenheit, vaporizing copper and producing an explosive blast. Arc flashes can destroy equipment and severely injure or kill nearby people without warning. Proper safety measures like arc flash studies, personal protective equipment (PPE), and electrical safety training are required to limit arc flash hazards. OSHA regulations mandate that employers identify electrical hazards and provide appropriate training and PPE to employees. NFPA 70E, IEEE 1584, and the NEC provide guidance on conducting arc flash studies to determine required PPE and
This document provides an overview of electrical safety. It discusses common causes of electrical fires such as defective devices and circuit overloading. It then covers important electrical safety topics like grounding, overcurrent protection devices like fuses and circuit breakers, GFCIs, proper and improper use of power strips and extension cords, damaged/unapproved devices, container bonding/grounding, and responsibilities of facilities and users. An example incident of electrocution from improper equipment use is also described to illustrate the importance of electrical safety.
The document discusses arc flash hazards, defining an arc flash as a dangerous condition caused by an electric arc. It provides information on what causes arc flashes, the governing agencies that regulate arc flash safety, and how to determine arc flash boundaries and label equipment. The company discussed provides arc flash safety services like analyses, training, and labeling to help clients comply with safety standards.
SASCO provides training on NFPA 70E, which establishes guidelines for electrical safety in the workplace. It addresses electrical hazards like shock, arc flash, and fire ignition. Arc flashes produce extremely high temperatures that can cause serious burns. Following the guidelines in NFPA 70E helps ensure electrical work is performed safely, such as through establishing limited approach boundaries and determining the proper personal protective equipment based on the potential hazards. Proper safety protocols, hazard analyses, and emergency response procedures can help minimize risks to workers from electrical incidents and injuries.
Regards, Mr. SYED HAIDER ABBAS
MOB. +92-300-2893683 MBA in progress,NEBOSH IGC, IOSH, HSRLI, NBCS,GI,FST,FOHSW,ISO 9001, 14001,
'BS OHSAS 18001, SAI 8000, Qualified .
An arc flash is caused by an arcing fault where electricity flows somewhere unintended, creating an electric arc that releases dangerous amounts of energy. Arc flashes cause severe burn injuries and cost millions in medical treatment. Proper personal protective equipment (PPE) and following safety regulations and standards can prevent arc flash injuries. Regulations require calculating arc flash hazards, using appropriate PPE based on hazard levels, training workers, and implementing safety programs with responsibilities and warning labels defined. Different levels of protective clothing are required depending on the estimated arc exposure intensity level. Selecting the proper flame-resistant clothing and other PPE can minimize worker injuries from electric arc accidents.
This document discusses arc flash safety and the dangers of electrical arc flashes. It notes that arc flashes can cause severe third-degree burns, blindness, cardiac arrest, and other serious injuries. The document outlines best practices for preventing arc flash incidents, including following NFPA 70E guidelines, assessing hazards to determine proper protective equipment, working on de-energized systems whenever possible using lock-out/tag-out procedures, and always wearing appropriate PPE suited for the potential energy level of the work being performed. Failure to follow safety procedures can expose workers to live parts and result in arc flash burns or death.
Arc Flash Safety Training by Pennsylvania Department of Labor and IndusryAtlantic Training, LLC.
This document discusses arc flash safety and electrical hazards. It notes that arc flashes are a serious risk and can cause burns, fires, and even death. An arc flash occurs when an electrical discharge travels through the air, releasing intense heat up to 5,000°F. The document recommends conducting an arc flash hazard analysis to determine appropriate personal protective equipment and safe working distances according to the voltage level. It also identifies some common causes of arc flashes such as overloading circuits, damaged equipment, and improper wiring. Following lockout/tagout procedures and wearing proper PPE rated for the voltage and distance is key to avoiding arc flash injuries when working on energized electrical equipment.
This document discusses arc flash energy and protection. It summarizes that an arc flash is a sudden release of heat and energy caused by an electric arc. OSHA and NFPA 70E now require arc flash hazard analyses to determine proper personal protective equipment. The analyses calculate incident arc energy levels and arc flash boundaries to determine the required PPE category, with higher incident energy requiring more protective flame-resistant clothing. Proper PPE is important as electricians can be severely injured by arc flash events every day.
The document discusses electrical safety precautions. It provides guidance on safely handling electrical appliances and working with electrical installations. Key safety measures include ensuring equipment is properly earthed, using insulated tools, disconnecting power before repairs, and not touching multiple terminals at once. Proper earthing helps limit voltages, provide fault protection, and reduce shock hazards. Critical components of an earthing system include earth electrodes, mats, and bonds to safely dissipate currents to earth.
The document discusses electrical hazards and safety. It defines electrical hazards, describes the types of injuries that can result from electric shock like burns and muscle paralysis. It explains how factors like current path through the body, shock duration, and skin resistance impact injury severity. The document provides guidance on helping someone receiving a shock, and safety measures like insulation, grounding, using qualified personnel, and regular inspections to prevent electrical accidents. The key messages are that electricity can be deadly if not used properly, but following safety precautions and procedures can minimize risk.
Electrical Safety. Electrical hazards can cause burns, shocks and electrocution (death). Assume that all overhead wires are energized at lethal voltages. Never assume that a wire is safe to touch even if it is down or appears to be insulated.
Many workers working on energised equipment are injured and/or killed each year. Several of these casualties are a result of arc flash.
Arc Flash is considered as one of the most destructive and dangerous instances when dealing with electrical wirings. A single occurrence can destroy metals and it has the ability to kill a person if not protected by Arc Flash Clothing. An arc flash can create an arc blast that can shatter anything because it is as hot as the as surface of the sun. This kind of heat can destroy metals instantly and completely burn a body beyond recognition.
Arc Flash ProtectionSerious injuries are caused by the arc flash:
Burns
Respiratory system damage
Hearing damage
Skin penetration from flying debris
Eye and face injuries
An arc flash may happen instantly and if the worker does not have the correct protection, they will already be dead when the arc flash hits them.
The use of Arc Flash Protective Equipment will lessen the damages caused by an arc flash because all of these equipments are solely made to withstand the heat.
Typical Arc Flash Clothing Applications
Working on electrical systems and switchrooms at 500 volts, live testing and proving dead on electrical systems, fitting and removal of LV-HV earths on electrical systems, working on panels/control circuits with exposed energised conductors, removal of bolted covers from energised electrical equipment, racking in/out of switchgear, racking in/out of starters and control gear, live testing and proving dead on electrical systems 11-33kV - T&D UK stock a broad range of Arc Flash Clothing and PPE.
This document provides information on electrical safety for workers. It discusses common electrician tasks like reading blueprints and connecting wires. It then describes the dangers of electricity, including causes of workplace deaths. An accident description details how an electrician was injured installing a breaker without proper permits or protective equipment. Key safety deficiencies are identified. Finally, the document outlines measures to prevent electrical shock, such as personal protective equipment, lockout/tagout procedures, and ground fault circuit interrupters.
This document discusses electrical hazards, their sources, and how to detect and reduce them. It defines electrical hazards and lists typical circuit wiring components. Major causes of electrical shocks are identified as short circuits, water contact, electrostatic hazards, arcs and sparks. Detection methods include using a circuit tester, receptacle tester, and continuity tester. The effects of electric current on humans at different levels are provided. Techniques to reduce hazards include proper grounding, bonding, ground fault interrupters, fuses, circuit breakers, double insulation, and interlocks.
1. Electrical safety is the 4th largest contributor to fatalities in the construction industry, with 5% of deaths due to electric shock or discharge.
2. Conductors readily allow the flow of electricity while insulators have high resistance and prevent electricity from flowing. Water and human skin are normally insulators but become conductors when wet.
3. Electric shock occurs when a person becomes part of an electrical circuit, with current entering and leaving the body. The severity of shock depends on current amount, path through the body, and time in the circuit. Effects range from tingling to cardiac arrest.
Electricity can cause serious injuries and death if not properly respected and safety protocols followed. There are three main electrical hazards: fires caused by overheating conductors, electrical shocks from contact with a power source, and electrical burns when enough current passes through the body. Many accidents occur due to failure to properly lockout electrical systems during maintenance, use of defective or wet equipment, and not following safe work practices such as grounding equipment and circuits. Proper safety includes never overloading circuits, staying away from unguarded conductors, inspecting cords, and using protective equipment.
Arc flash typically occurs when the electrical insulation or isolation between live conductors is severed or can no longer withstand the applied voltage. Near the high power electrical equipment, the short-circuit power available is high and consequently so is the energy associated with the electrical arc in case of a fault.
In Europe, regulation and standardization are mainly aimed at protecting workers against the risks of direct contact during work and interventions on and near electrical installations. The risks in the case of electric arc and the means to prevent them are mentioned but not developed.The effects of the electric arc:
The electric arc produces intense light and heat, high noise, high overpressure
Heat and splashes of molten metal can cause lethal burns
Noise can lead to permanent or temporary hearing loss, a flash of vision disorders
The overpressure can open and project the doors of electrical cabinets or cause falls during work at height
In addition to personal injury, an arc flash can result in serious damage to electrical equipment. which can cause disruption to electrical systems in manufacturing and process industry environments or tertiary buildings. The cost of downtime can be considerable. elec calc™ Arc Flash module provides the professionals of the electrical industry with a fundamental tool in the sector, as the user will be able to develop its safety analysis in the vicinity of switchboards and panels. By design, elec calc™ has almost all the data allowing the calculation of the figures of the arc flash, from which the user will be able to elaborate his security analysis near the tables and boxes.
The document discusses electrical hazards. It defines electrical hazards as any potential or actual threat due to electricity to the well-being of people, machinery, or the environment. It lists types of electrical hazards such as electric shock, burns, and arc blasts. It provides examples of workplace electrical hazards like damaged power lines, exposed conductors, and improper grounding. It also discusses sources of electrical hazards such as working with unearthed or improperly grounded electrical equipment.
This document discusses electrical hazards associated with welding and cutting equipment. It provides instructions on how to avoid electric shock, including properly grounding equipment, wearing protective clothing, inspecting cables, and not working alone in hazardous conditions. It recommends using certain equipment like DC constant voltage welders in damp or cramped areas, and provides procedures for responding to electric shock incidents.
This document discusses arc flash hazards in the workplace. It defines what an arc flash is, noting that it is a dangerous condition caused by the rapid release of energy from an electric arc. Arc flashes present serious risks of injury from burns, flying debris, and blasts of hot air and vapor. The document recommends performing arc flash studies to calculate potential hazards at electrical equipment and establish safety procedures and personal protective equipment requirements to protect workers. The goal of an arc flash study is to identify hazards and help employees avoid exposure through training and adherence to safety practices.
This document discusses methods for calculating arc flash hazards to help select proper personal protective equipment (PPE). It describes three primary calculation methods: 1) Ralph Lee's theoretical model from 1982, 2) equations and tables in NFPA 70E-2004, and 3) the comprehensive equations presented in IEEE Std 1584-2002. The document provides guidelines for determining which calculation method is correct for a given situation, such as verifying the method applies to the system voltages and fault currents and using device-specific equations over general equations. It also summarizes types of PPE defined in NFPA 70E-2004 based on the degree of arc flash protection required.
An arc flash is an electrical explosion caused by a fault or short circuit when a live conductor makes contact with another object, allowing current to flow through the air. Temperatures in an arc flash reach over 35,000 degrees Fahrenheit, vaporizing copper and producing an explosive blast. Arc flashes can destroy equipment and severely injure or kill nearby people without warning. Proper safety measures like arc flash studies, personal protective equipment (PPE), and electrical safety training are required to limit arc flash hazards. OSHA regulations mandate that employers identify electrical hazards and provide appropriate training and PPE to employees. NFPA 70E, IEEE 1584, and the NEC provide guidance on conducting arc flash studies to determine required PPE and
An arc flash is an electrical explosion caused by a fault or short circuit when a live conductor contacts another object, allowing current to flow through air. Temperatures in an arc flash reach over 35,000 degrees F, vaporizing copper and producing an explosive blast. Arc flashes can destroy equipment and severely injure or kill nearby people without warning. Proper safety measures like arc flash studies and training per NFPA 70E are required to limit arc flash hazards. OSHA regulations mandate that employers identify electrical hazards and provide appropriate protection and training to employees. NFPA 70E, IEEE 1584, and the NEC provide guidance on conducting arc flash studies to determine protection requirements and properly label equipment with arc flash warnings.
An arc flash is a dangerous event that occurs due to an arcing fault in an electrical system, which can release tremendous heat energy and cause severe burns, injuries or death. Proper personal protective equipment is required depending on the calculated incident energy level at different locations. Regular maintenance, worker training and safety programs are important to reduce arc flash hazards by preventing faults and minimizing exposure times.
Practical Arc Flash Protection for Electrical Safety Engineers and TechniciansLiving Online
The document discusses electrical hazards and safety measures. It outlines various types of hazards in industry including electrical, mechanical, fire, and hazardous materials. Electrical hazards include electric shock, arc flash burns, falls, and thermal injuries. Arc flash hazards pose serious risks of burns and are impacted by fault energy and clearing time. The document also lists common safety hazards of electrical equipment and recommends general safety measures like safe equipment design, maintenance, training, inspections, and use of personal protective equipment. Failure to isolate equipment and lack of safety procedures are identified as primary causes of electrical accidents.
Five to 10 arc flash explosions occur daily in the US, often severely injuring workers. The document discusses arc flash hazards, describing the intense heat, pressure, and dangers of arc flashes. It outlines standards from OSHA, NFPA, and IEEE to protect workers through analyzing hazards, establishing personal protective equipment requirements, and enforcing safety practices. The analysis process calculates incident energy levels and flash protection boundaries to determine the appropriate PPE category and safely work near energized equipment.
The document discusses arc flash hazards, describing that arc flashes occur frequently in the US and can cause severe burns. It explains the differences between bolted and arcing faults, lists various standards to protect workers from arc flash like OSHA, NFPA 70E, and IEEE 1584, and describes how to perform an arc flash analysis to determine appropriate personal protective equipment.
CATU Arc Flash 10 cal Clothing & PPE Protection Kit includes:
Arc Flash Face Shield
Helmet
Safety Glasses
Protective Hood
Arc Flash Jacket or Coverall Made From Indura Ultra Soft Fabric
The CATU 10 cal Arc Flash clothing and protection kit weighs approximately 4.03kg.
CATU arc flash protective clothing kits are in compliance with NFPA 70E and ASTM standards.
CATU Electrical manufacture a broad range of Arc Flash Clothing, PPE and Protection Kits - this includes arc flash suits, arc flash hoods, arc flash helments (face shields) and arc flash overall suits in both Indura and Nomex arc flash and flame retardant fabrics.
Arc flash can occur during live cable jointing, phasing in operations, racking in and out of switchgear, reclosing of electrical switchgear onto a fault, switchgear failure, excavating near live cables or accidental contact with live conductors during maintenance.
The document discusses electrical safety hazards and precautions in construction. It notes that electrocutions are a leading cause of death in construction, accounting for 12% of fatalities annually. Over 30,000 non-fatal shocks also occur each year. It then defines various electrical terms and describes the types of burns, shocks, and electrocutions that can result from electrical accidents. The document outlines safety practices like lockout/tagout procedures, proper use of ground fault circuit interrupters and personal protective equipment, and safe operation of electrical tools to prevent injuries and fatalities from electricity on work sites.
Five to 10 arc flash explosions occur daily in the US, often requiring specialized burn treatment. There are two types of faults that can cause arcs: bolted faults where current flows through a solid connection, and arcing faults where current arcs through ionized air. Arcing faults are more dangerous as the energy is released into the environment. Standards like NFPA 70E and OSHA requirements aim to protect workers by enforcing safety practices like arc flash analyses and requiring personal protective equipment suitable for the estimated incident energy levels. Proper maintenance and use of protective equipment can reduce arc flash exposure hazards.
The document discusses the theory of circuit interruption in power systems. It begins by introducing circuit breakers, which can manually or automatically open a circuit under normal or fault conditions. When contacts within a circuit breaker open under a fault, an arc is produced that must be extinguished to interrupt current flow. There are two main methods for extinguishing arcs: the high resistance method, which lengthens and cools the arc to increase its resistance over time; and the low resistance or current zero method, used for AC circuits, which maintains a low resistance arc until current reaches zero to naturally extinguish the arc.
This document provides information on OPR lightning protection systems, including:
- An overview of lightning mechanisms and how different lightning protection systems work.
- Descriptions of early streamer emission air terminals, single rod air terminals, meshed cages, and stretched wires.
- Details on how to perform risk analysis and technical studies to design a lightning protection system.
- The procedure for measuring the early streamer emission of air terminals according to industry standards.
- Information on surge protection devices to protect against indirect lightning effects.
- The importance of equipotential bonding and maintaining separation distances between the lightning protection system and building components.
Why Test Series - Arc Flash Evaluations CS-00158Carolyn Dakis
Burns account for about 80% of all injuries from electrical accidents, usually resulting from exposure to intense heat generated by an arcing fault. Arc flash studies are important to determine the minimum protective equipment workers must wear near energized equipment, as mandated by OSHA regulations, and help quantify hazard levels. An arc flash study evaluates available arc fault exposure at electrical panels to determine the proper protective equipment to limit incident energy to a treatable level.
The document is a catalog describing ABB hélita® lightning protection systems. It provides information on lightning mechanisms, protection technologies like early streamer emission air terminals and meshed cages, standards, and installation procedures. Lightning protection systems aim to provide a preferred path for lightning to be conducted safely to ground to prevent damage to structures. Early streamer emission technology enhances the formation of upward streamers to better intercept downward lightning leaders. Meshed cages divide the lightning current over multiple conductors.
The document discusses electrical hazards and safety. It describes the risks of electrical shock and how the effects on the body depend on factors like current pathway and amount. Electrical shock can occur when a worker comes into contact with both an energized conductor and a grounded object. The document also discusses types of electrical burns, arc flash hazards, battery hazards, safe distances from power lines, and the use of ground fault circuit interrupters to prevent electric shock.
Electrical arc flash poses severe burn risks and can be fatal. Arc flash temperature reaches 35,000°F, which is four times hotter than the sun's surface. Even low levels of exposure energy from 1-2 cal/cm2 can cause second degree burns. OSHA and NFPA have established regulations and standards including requirements for personal protective equipment, flash hazard analyses, and labeling of electrical equipment to warn of potential arc flash hazards. Performing arc flash analyses allows employers to determine appropriate PPE for different voltage levels and proximity to live parts.
This document discusses methods for protecting water and wastewater treatment plants from lightning strikes and electrical surges. It identifies areas at high risk for lightning strikes, such as pump lift stations and radio antennas. Traditional surge protection methods using MOVs and SADs can be overwhelmed by lightning strikes. Newer triggered arc gap technology provides better protection against high-energy lightning strikes by diverting surge currents to ground. The document describes how triggered arc gaps and additional surge protectors were installed to protect a water treatment plant in Florida that experienced frequent lightning damage.
Arc flash incidents can be costly in terms of personnel injury and equipment repair/replacement. This presentation provides an overview of the NFPA 70E 2012 Standard for Electrical Safety in the Workplace and the requirements of the standards, which are intended to better protect electrical workers from injury when they work on energized electrical equipment. This includes all aspects of facility and employer responsibilities for compliance to the NFPA 70E standards, as well as the current status of OSHA enforcement of these standards. Copyright AIST Reprinted with Permission.
An arc flash is a dangerous event caused by an electric arc releasing energy through the air between conductors or conductors and ground. Common causes include work incidents involving tools or panels, insulation failures, loose connections, and improper installation. Statistics show that arc flash explosions send over 2,000 workers to burn centers each year with severe injuries, as the temperature can reach up to 19,000 degrees Celsius. Safety protocols establish boundaries like prohibited, restricted, and limited approaches to prevent injuries from arc flash burns.
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ARC FLASH MITIGATION USING ACTIVE HIGH-SPEED SWITCHING
1. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 1 GCE Kannur
CHAPTER 1
INTRODUCTION
The mitigation of arcing fault hazards in medium voltage switchgear is an urgent
concern that is being addressed in many ways by safe work practices, operator training, and
innovative products and installations. One method of mitigating arc flash hazards associated with
medium-voltage switchgear is the installation of active high-speed switch (HSS) systems[1].
These systems are designed to detect and quench a burning internal arc in less than one-third of
one electrical cycle. The internal arc is extinguished by the HSS’s action of redirecting the fault
current path from arcing through open air back to the intended current path of the switchgear
bus. The new low-impedance current path provided by the HSS operation collapses the voltage
at the point of the fault to near zero so that the arc is no longer sustainable. The system’s high
speed of operation compared to arc quenching via circuit breaker tripping translates directly to
lower arc flash incident energy and minimal equipment damage[1]. This paper explores
application considerations of HSS systems relative to other available means of controlling and
reducing the hazards of internal arcing faults in medium-voltage switchgear.
HSS designs have not been in existence for very many years. As time passes, more
success stories that confirm the robustness that manufacturers claim for the switch, light sensors,
and electronics are expected.
HSS systems may be a viable solution to arc flash hazard mitigation in particular
situations such as the following:
1) where equipment is expected to be opened while energized;
2) where other means of AFIE reduction do not reach the target PPE category;
3) where selective coordination is most critical;
4) where extended switchgear downtime cannot be tolerated;
5) where the switchgear location cannot accommodate venting mechanisms for arc by-
products.
2. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 2 GCE Kannur
CHAPTER 2
ARC FLASH AND HAZARDS
2.1 ARC HISTORY
In 1802, an English scientist Humphrey Davis demonstrated that electric current can flow
between two copper rods separated in air by short distance. Electric current will be in the form
of a band of ionised air that looks like an upward bow as in the figure. In fact electrical science
started with the study of electric arc. Soon, a number of inventions came forth such as arc lamps,
arc furnaces, spark plugs, arc welders and etc.
Fig 2.1 Electric arc
The electric arc is again a subject of great interest and study because of the hazards it
creates in electrical distribution systems due to its intense heat. It can destroy equipment and
cause severe or fatal injuries to unprotected personnel who are unfortunate to be in close
proximity to it.
An electric arc is an ongoing plasma discharge resulting from current flowing through
air, which is a normally nonconductive media. The effects of an electric arc depend on the
individual circumstances, but all are dangerous: extreme temperatures that can reach up to
30,000 °F, explosive pressure forces caused by the rapid expansion of gases and elements such
as vaporized copper, intense light, high noise levels and toxic fumes, as shown in Figure below.
3. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 3 GCE Kannur
Fig 2.2 Electrical arc.
2.2 DEFINITION OF ARC FLASH AND RELATED TERMS
Arc-flash hazard: a dangerous condition associated with the release of energy caused by an
electric arc.
Electric hazard: a dangerous condition in which inadvertent or unintentional contact or
equipment failure can result in shock, arc-flash burn, thermal burn, or blast.
Flash protection boundary: an approach limit at a distance from exposed live parts within
which a person could receive a second-degree burn if an electrical arc flash were to occur. The
incident heat energy from an arcing fault falling on the surface of the skin is 1.2 calories/cm2.
Incident energy: the amount of energy impressed on a surface, a certain distance from the
source, generated during an electrical arc event. One of the units used to measure incident energy
is calories per centimeter squared (cal/cm2).
Limited approach boundary: an approach limit at a distance from an exposed live part within
which a shock hazard exists.
4. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 4 GCE Kannur
Fig. 2.3 Flash Protection Boundary
Qualified person: one who has skills and knowledge related to the construction and operation
of the electrical equipment and installations and has received safety training on the hazards
involved.
Restrictedapproach boundary: an approach limit at a distance from an exposed live part within
which there is an increased risk of shock, due to electrical arc over combined with inadvertent
movement, for personnel working in close proximity to the live part.
Prohibited approach boundary: an approach limit at a distance from an exposed live part
within which work is considered the same as making contact with the live part.
Working distance: the dimension between the possible arc point and the head and body of the
worker positioned in place to perform the assigned task. Thus, the Flash Protection Boundary
becomes an important approach distance from live equipment within which qualified personnel
must wear protective clothing and equipment and within which unqualified personnel are
prohibited. An exposure to 1.2 calories/cm2 would normally result in a curable second-degree
burn. Within this boundary, workers are required to wear protective clothing like fire resistant
(FR) shirts and pants and other equipment to cover various parts of the body. The flash protection
boundary distance varies with the type of equipment used. It is primarily a function of the
available voltage and fault current of the system at that point, and the tripping characteristics of
the upstream protective device.
5. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 5 GCE Kannur
CATEGORIES OF PPE (PERSONAL PROTECTIVE EQUIPMENT) AS DESCRIBED IN
NFPA 70E
Category Cal/cm2 Clothing
0 1.2 Untreated Cotton
1 5 Flame retardant (FR) shirt and FR pants
2 8 Cotton underwear FR shirt and FR pants
3 25 Cotton underwear FR shirt, FR pants and FR coveralls
4 40 Cotton underwear FR shirt, FR pants and double layer switching coat
and pants
Table 2.1 Categories of PPE
2.3 ARC FLASH IN SWITCHGEAR
Internal free burning arcs in LV switchgear such as a motor control centre (MCC) arise
when a short circuit occurs and causes a current to flow through air inside the assembly. This
current can flow between phases, or between phases and the neutral or ground, or through a
combination of all these paths. The amount of energy released depends on the strength of the
current and the length of time that it flows. The results can be catastrophic—the internal
explosion, consisting of expansion of copper to 67,000 times its original volume, temperatures
at 19,000 °C, along with pressure and sound waves can threaten human life. Such arcs can result
from unfavourable environmental conditions leading to conductive deposits on isolating support
elements. Other causes can include vermin ingress or the growth of silver or tin whiskers on
exposed conductors. However, a far more likely cause is human error; from tools or excess
material left inside the system after inspection, maintenance, or testing. In fact, an estimated
70% of arcs arise from human error. If an arc does occur, the most obvious threat is to any
maintenance or operating personnel in close proximity to the arc event site. In addition to the
human impact, there are business impacts. In an arc event, all affected switchgear is likely to be
permanently damaged. This takes any connected production equipment out of service even if it
is fully operational. Beyond loss of production, impacts can be felt in the form of lawsuits,
increased insurance costs and lowered common stock values.
6. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 6 GCE Kannur
Fig 2. 4 Arc flash switchgear explosion
2.4 ARC FLASH HAZARDS
An electric arc, or arcing fault, is a flashover of electric current through the air from
one live conductor to another or to ground. An Arc Flash hazard is the danger that comes from
the heat energy generated in an Arc. Electric Arcs produce intense heat, sound blast and
pressure waves, and can ignite clothing, causing severe burns that are often fatal.
The demand for uninterrupted power has created the need for electrical workers to
operate and perform maintenance work on exposed live parts of electrical equipment. This
creates a hazard from potential electric shock. The electric shock hazard has been addressed in
electrical safety programs since electricity use began. However, only recently has the hazard
brought about by Arc Flash been prominently addressed.
The results of arc flash can be catastrophic—the internal explosion, consisting of
expansion of copper to 67,000 times its original volume, temperatures at 19,000 °C, along with
pressure and sound waves can threaten human life.
7. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 7 GCE Kannur
The physical effects of an arc flash are:
• Pressure wave in the environment where the arc is generated;
• Heating of the materials coming into touch with the arc flash;
• Potentially harmful light and sound.
Personnel hazards due to the release of energy generated by an arc event may include:
• Burns;
• Injuries due to ejection of materials;
• Damage to hearing and to eye-sight
; • Inhalation of toxic gases
BURNS
The high temperature levels of the gases produced by the electrical arc and the expulsion
of incandescent metal particles may result in severe burns. Flames can cause all types of burns,
up to carbonization: the red-hot solid metal fragments can cause third degree burns, superheated
steam causes burns similar to hot liquids and the radiant heat generally causes less severe burns.
INJURIES DUE TO EJECTED MATERIALS
The ejection of metal particles or other loose items caused by the electric arc can result
in severe injuries to the most sensitive parts of the human body, like the eyes. The materials
expelled due to the explosion produced by the arc may penetrate the cornea. The extent of the
lesions depends on the characteristics and kinetic energy of these objects. Also, the eye area can
sustain injuries to the mucosa, such as the cornea or retina, because of the gases released by the
arc and the emission of ultraviolet and infrared rays.
HEARING
As already mentioned, the electric arc is a true explosion, whose sound may cause
permanent hearing loss.
INHALATION OF TOXIC GASES
The fumes produced by burnt insulating materials and molten or vaporized metals can
be toxic. These fumes are caused by incomplete burning and are formed by carbon particles
and by other solid substances suspended in the air.
8. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 8 GCE Kannur
2.5 MITIGATION
The mitigation of arcing fault hazards in medium voltage switch gear is an urgent
concern. It is being addressed in many ways by safe work practices, operator training and
innovative products and installations. Mitigation is defined as to make milder, less severe or less
violent. Arc flash mitigation involves taking steps to minimize the level of hazard or the risk
associated with an arc flash event.
The two ways of avoiding arc flash effects are
i) Reduce arc flash energy to a level where permitted tasks can be performed.
ii) Locate the workers so that he is not subject to harm.
2.6 CONVENTIONAL EQUIPMENT TO LIMIT THE EFFECT OF AN ARC
FLASH
Conventional electrical protection equipment does not sufficiently limit the effect
of an arc-flash:-
The duration of an Arc-Flash is mainly determined by the time it takes for overcurrent
or earth-fault protective devices to detect the fault, send a trip signal to the circuit breaker and
for the circuit breaker to subsequently disconnect the energy source. Fast acting fuses may
disconnect the circuit from the energy source in 8 ms or less when subjected to the high short-
circuit currents usually appearing in three-phase symmetrical bolted cases, while other devices
may take much longer to operate and remove the source of energy. But unbalanced, single-phase
and high-impedance fault currents are lower than three-phase bolted-fault currents, so protection
devices may not necessarily detect and limit arc-fault current and will require more time to clear
the fault.
9. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 9 GCE Kannur
CHAPTER 3
HIGH SPEED SWITCHING (HSS) SYSTEM
3.1 FEATURES
• Method of mitigating arc flash hazards in which reduction of arc flash energy is
employed.
• It is conceptually very simple and effective.
• Used to detect and quench internal arc in less than one-third of one electrical cycle
Fig. 3.1 HSS typical schematic
3.2 HIGH SPEED SWITCHING
The high-speed switch (HSS) system is one method of mitigating arc flash hazards
associated with medium-voltage switchgear. It is conceptually very simple and effective but
often viewed skeptically as a radical approach that places too much stress on the power system
when it operates. In fact, it does transfer an internal arcing fault to the switchgear bus which does
create a bolted fault on the system. When the HSS control system detects illumination with
characteristics similar to that of an internal arc, confirmed by a corresponding rate of change of
current, an arc flash event is declared, and the normally open HSS very rapidly closes to create
a three-phase bolted fault, which thereby extinguishes the higher impedance internal arc, such as
that shown in Fig 3.1.
Arc fault:-
Short circuit current resulting from conductors at different voltages making less than solid
contact. Results in a relatively high resistance connection compared to a bolted fault.
10. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 10 GCE Kannur
Bolted fault:-
Short circuit current resulting from conductors at different voltages becoming solidly connected
together.
Some HSS designs may operate based on other characteristics from internal arcing other than
light and current, such as temperature, pressure, sound, harmonics, etc.
The bolted fault remains on the system until cleared by the source overcurrent device.
The stress of a bolted fault is certainly a valid concern, but the HSS should not be dismissed
without carefully considering the benefits provided. The intrinsic benefits are as follows:
1) speed of operation:
a) effective incident energy (arc flash) reduction;
b) reduction of equipment damage and corresponding downtime due to an internal arcing
event;
c) Reduction of motor contribution to an internal arcing event.
2) effective protection even with exposed live parts;
3) independence from overcurrent coordination and arcing fault current variations;
4) No impact on switchgear room (no additional ventilation or ducting requirements).
These benefits translate to improved worker safety, procedural simplicity, power system
reliability, improved system availability, and, in some cases, reduced installed cost.
11. SEMINAR REPORT 2016 ARCFLASH MITIGATION USING ACTIVEHSS
Dept.EEE 11 GCE Kannur
CHAPTER 4
PERFORMANCE
This chapter mainly includes the main benefits of the high speed switching system
4.1 SPEED OF OPERATION
Commercially available HSS systems detect an arc and close in approximately 4–6ms
(0.2–0.3 cycle at 50 Hz). In contrast, modern vacuum circuit breakers can typically detect and
clear an arcing fault in not less than 50ms considering overcurrent or flash detection relay trip
contact closure time plus circuit breaker clearing time. In many cases, the operating time is
greater than 50ms, depending on the use of lockout relays, relay and circuit breaker vintage and
vendor type, and other variables. Lockout relays add one cycle. In retrofit scenarios, older
circuit breakers may be 5 or 8 cycle rated.
HSS is therefore about ten times faster than the fastest circuit breaker-based arc
detection and quenching schemes, which leads to the following benefits.
4.1.1 AFIE REDUCTION:
Arc flash incident energy (AFIE) is directly proportional to the time required to
extinguish the arc. Accumulated AFIE versus time is shown in Fig.4.1 for an arbitrary example
system: 13.8-kV system with 50-kA available fault current, solidly grounded using standard
36-in (914 mm) working distance and 153-mm bus gap per IEEE 1584.
Fig. 4.1 AFIE accumulation versus time example.
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For the Fig 4.1 example system, AFIE calculations for switchgear with HSS result in less
than 1.2 cal/cm2 (the industry referenced second degree burn threshold). At this calculated AFIE,
non-melting or untreated natural fibre clothing may be worn along with hearing protection, eye
protection, and leather gloves as needed. For the best case circuit breaker tripping times shown
in Fig 4.1, heavier personal protective equipment (PPE) with flame resistant clothing is required
for higher energy exposures. PPE for higher energy exposures is progressively more bulky, hot,
and difficult to work in due to loss of visibility and dexterity. Workers are relieved to get out of
PPE in hot locations (although there are cooling systems available to lessen the discomfort).
Personal protective equipment (PPE):- Safety devices worn by personnel to protect against
hazards. PPE includes helmets, hearing protection, face shields, gloves, safety boots, respirators
etc.
4.1.2 EQUIPMENT DAMAGE REDUCTION:
Arc blast effects can destroy equipment with the same phenomena that kill and injure
people. The IEEE Std. C37.20.7 guide for testing arc-resistant metal-enclosed switchgear does
not include internal equipment destruction as a failure criterion. Rework or replacement is
expected.
HSS manufacturer tests and actual field events, however, illustrate that the fast arc
quenching limits the damage to the point of the arc occurrence, with minimal additional damage.
As a result, troubleshooting, repair, testing, and return to service are simplified and relatively
quick. “As a general rule, removing the fault quickly will minimize the damage; however, the
overpressure event typically occurs in a time frame of less than 1 electrical cycle”.
For medium-voltage switchgear, HSS systems are the only available devices to date that
can compete with the speed of overpressure and equipment destruction, as illustrated in Fig 4.1.
4.1.3 REDUCTION OF MOTOR CONTRIBUTION TO AFIE:
Large induction and synchronous motors can contribute significantly to AFIE in some
industrial settings. The medium-voltage feeder breakers supplying motor loads will not trip for
motor contribution levels in many cases, so the full motor contribution can persist for several
cycles regardless of the main circuit breaker tripping time. In the case of bus differential relay
application, the motor contribution will persist until it decays to zero or the associated bus
lockout relay and feeder breaker trips, whichever comes first.
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HSS addresses this issue in large measure due to the fast arc quenching time. Again, the
margin of improvement is approximately a factor of 10, based on the speed of quenching the arc
via HSS versus circuit breaker.
4.2 EFFECTIVE PROTECTIONWITH EXPOSED LIVE PARTS
The IEEE Guide C37.20.7 guide for testing arc-resistant metal-enclosed switchgear
states that “The use of equipment qualified to this guide is intended to provide an additional
degree of protection to the personnel performing normal operating duties in close proximity to
the equipment while the equipment is operating under normal conditions.” The standard excludes
alteration of the equipment from normal operating condition and from activities above or below
the equipment, such as catwalks, installations on open grating, cable vaults, and so forth. Any
opening in the equipment invalidates the arc resistant category and can expose personnel to the
full effects of the arcing event. Arc-resistant switchgear is arc resistant only when all covers are
secured in place.
HSS systems, however, operate effectively regardless of exposed live parts or the
personnel performing work above or below the equipment. Working around exposed live parts
should normally be prohibited, but situations can and do arise where the risks associated with
equipment shutdown exceed the risks of working with the equipment opened.
4.3 INDEPENDENCE FROM OVERCURRENT COORDINATION
HSS systems rely on light sensors, current transformers, and possibly sensors for
other parameters to detect an arc and initiate HSS closing. The bolted fault current resulting from
HSS actuation has to be cleared by the source overcurrent device within the withstand ratings of
the switchgear and HSS system, but the protection of the worker is effective even if the relays in
the system are improperly coordinated or if the arcing fault magnitude is not as anticipated.
The selective coordination of overcurrent devices is often in direct conflict with the
need to trip the source circuit breaker(s) as fast as possible for arc flash hazard mitigat ion
purposes. For example, if the instantaneous trip level is above the lowest arcing fault current
magnitude, the relay may not trip instantaneously, resulting in high AFIE. On the other hand, if
the instantaneous trip level is set low enough to trip quickly for all possible values of arcing
current, selective coordination with downstream devices is frequently compromised. Therefore,
all values of arcing fault current magnitude must be considered from highest to lowest. This
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requires careful judgment and frequent trade-offs between selective coordination and AFIE
mitigation. There are many reasons that arcing fault current levels can change, including utility
system upgrades or system switching, plant switching between main, tie, and in-plant generator
circuit breakers, varying quantities of running motors, and so forth. Additionally, many times,
the utility system changes without the customer being made aware.
Various means of addressing these issues have been implemented with success.
Bus differential relays are fast (approximately 80ms from overcurrent detection to
arcing fault elimination) yet inherently selective but cannot detect arcing faults outside the
protected zone current transformers, which, in most metal clad switchgear, do not encompass the
cable compartments. For example, the bus differential relays installed at the health care facility
cited in this paper did not detect the arcing fault condition because the bus differential current
transformers are inside the breaker cell while the fault occurred in the cable compartment.
Another example is that, while a worker may have an additional degree of protection when
racking a breaker from the front of the equipment, he may not be protected if the cable
compartment is opened.
Zone selective interlocking schemes (approximately 80 ms from overcurrent
detection to arcing fault elimination), also called fast trip schemes, achieve selective
coordination via restraint signals from the feeder circuit breakers going back to the main. If the
main detects a fault but receives a restraint signal from the feeder, the main breaker relay times
out normally per its time–current curve, allowing the feeder to selectively clear the downstream
fault. If the main detects a fault without a restraint signal, the main trips instantaneously since
the fault logically must be on the switchgear bus. The main circuit breaker relay must, however,
detect the fault at arcing current level, and it must still coordinate with the feeder. Feeder
breakers cannot be permitted to trip on motor contribution; otherwise, they will restrain the
source breaker(s) and defeat the scheme entirely. Multisource line-ups such as main–tie–main
add still more complexity.
Alternative maintenance setting switches (approximately 80 ms from overcurrent
detection to arcing fault elimination) are used to lower relay pickup levels and sacrifice
coordination only when personnel are present or maintenance is being performed. Again, the
main circuit breaker relay must detect the fault at arcing current level, and careful procedural
rules must be implemented to ensure that personnel do not forget to turn on the maintenance trip
settings when beginning the work or forget to turn it off when done. Occupancy sensors have
been used to turn on inputs to electronic relays that automatically lower the relay instantaneous
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settings and then restore them when personnel leave. While the reduced settings are in effect,
there is a possibility of nuisance nonselective tripping.
Arc flash detection relays (52–57 ms from arc detection to arcing fault elimination)
that combine light sensors, current sensing, and high speed relay outputs are immune to
overcurrent coordination and arcing fault current magnitude but rely on the relatively slow
circuit breaker tripping to quench the arc.
HSS systems (4–6 ms from arc detection to arcing fault elimination) are likewise
immune to the downstream coordination and arcing fault current magnitude considerations but
have the advantage of speed. The short-circuit withstand rating of the HSS itself is all that needs
to be considered in setting the source circuit breaker relays with regard to arc flash protection.
For circuit breaker-based arc quenching (other than arc flash detection relays), relay settings are
critical and must consider all possible arcing fault current magnitudes.
Power system short circuit, coordination, and arc flash studies must be kept up-to-date
and relay changes implemented as necessary. This statement is always true, but for HSS
installations, it is less critical because the arc flash hazard protection is unaffected. A related
benefit is that selective coordination for critical systems is made much simpler.
4.4 NO IMPACT ON SWITCHGEAR ROOM
Arc-resistant switchgear that relies on circuit breaker tripping must have a safe path to
vent the arc by-products. Ceiling and wall clearances, overhead equipment, doors, windows,
building capability to absorb pressure wave, fireproofing, weather, and vermin ingress are among
the considerations. Additionally, the arc-resistant switchgear may be larger and heavier than the
standard switchgear. These factors can grow the size, cost, and complexity of the switchgear
room. Some HSS systems have been tested and comply with IEEE C37.20.7, and they negate
the need to purchase passive arc containment (heavily reinforced cubicles).
HSS system installations may require an additional section to accommodate the HSS;
otherwise, the installation is identical to that of the standard non-arc-resistant switchgear, as no
arc by products need to be accommodated.
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4.5 DRAWBACKS OF HSS SYSTEM
• It places too much stress on the power system when it operates.
• Bolted fault remains on the system until cleared by the source overcurrent device.
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CHAPTER 5
CONCLUSION
The HSS system may be likened to an automobile airbag. Hopefully, it will never
have reason to operate for the entire life of the equipment, but if needed at any time, it must
operate instantly. Nuisance operation is unforgivable. The device cannot be tested in normal
operation. It has to be trusted.
HSS systems should be seriously considered for installation in medium-voltage
switchgear. Other means of enhanced equipment protection from arc flash hazards are available.
Switchgear size, importance, cost, complexity, growth needs, and architectural considerations
should be considered along with plant safe work practices, procedures, and other available arc
flash mitigating features.
A risk versus benefit analysis is recommended when installing HSS on the secondary
of older or less robust power transformers that, due to operating history or test results, are
considered near end of life.
Large medium-voltage motors should be evaluated for use on HSS-equipped systems
using actual machine and supply conductor impedances as well as manufacturer input. In many
cases, the additional stresses placed on the motor due to HSS closing will be minimal.
HSS systems can provide substantial rewards without exposing the power system to
undue risks beyond the unavoidable.