What are the basic overcurrent protection devices for generators?
As with other motors, NEC 445.11 requires a generator to have a nameplate giving the manufacturer’s name, the rated frequency, power factor, number of AC phases, the subtransient and transient impedances, the rating in kilowatts or kilovolt amperes, a rating for the normal volts and amps, rated revolutions per minute, insulation system class, any rated ambient temperature or temperature rise, and a time rating.
The size and type of OCPD will be based on this critical data. NEC 445.12 defines the basic overcurrent protection standards for various types of generators. A constant-voltage generator must be protected from overloads by either the generator’s inherent design or circuit breakers, fuses, or other forms of overcurrent protection that are considered suitable for the conditions of use.
This is true except for AC generator exciters.
Two-wire, DC generators are allowed to have overcurrent protection in only one conductor if the overcurrent device is triggered by the entire current that is generated other than the current in the shunt field. For this reason, the overcurrent device cannot open the shunt field.
If the two-wire generator operates at 65 V or less and is driven by an individual motor then the overcurrent device protection device needs to kick-in if the generator is delivering up to 150% of its full-load rated current.
When a two-wire DC generator is used in conjunction with balancer sets it accomplishes the neutral points for the three-wire system. This means it requires an overcurrent device that is sized to disconnect the three-wire system if an extreme unbalance occurs in the voltage or current.
For three-wire DC generators, regardless of whether they are compound or shunt wound, one overcurrent device must be installed in each armature lead, and must be connected so that it is activated by the entire current from the armature.
These overcurrent devices need to have either a double-pole, double-coil circuit breaker or a four-pole circuit breaker connected in both the main and equalizer leads, plus two more overcurrent devices, one in each armature lead.
The OCPD must be interlocked so that no single pole can be opened without simultaneously disconnecting both leads of the armature from the system.
The ampacity of the conductors that run from the generator terminals to the first distribution device that contains overcurrent protection cannot be less than 115% of the nameplate current rating for the generator per NEC 445.13.
All generators must be equipped with at least one disconnect that is lockable in the open position that will allow the generator and all of its associated protective devices and controls to be disconnected entirely from the circuits that are supplied by the generator.
ARC FLASH BOUNDARY SAFE DISTANCE BASIC INFORMATION AND TUTORIALS
Arc-flash boundaries need to be established around electrical equipment such as switchboards, panelboards, industrial control panels, motor control centers, and similar equipment if you plan to work on or in the proximity of exposed energized components.
Parts are considered exposed if they are energized and not enclosed, shielded, covered, or otherwise protected from contact. Work on these parts includes activities such as examinations, adjustment, servicing, maintenance, or troubleshooting.
Equipment energized below 240 V does not require arc-flash boundary calculation unless it is powered by a 112.5 KVA transformer or larger.
The arc-flash boundary is the limit at which a person working on energized parts can be standing at the time of an arc-flash without risking permanent injury unless they are wearing flame-resistant clothing. Permanent injury results from an arc-flash that causes an incident energy of 1.2 calories/centimeter2 (cal/cm2) or greater and causes a minimum of second-degree burns.
This distance can only be effectively determined by calculating the destructive potential of an arc.
First you must determine the magnitude of the arc based on the available short circuit current, then estimate how long the arc will last based on the interrupting time of the fuse or circuit breaker.
Finally, you will need to calculate how far away an individual must be to avoid being exposed to an incident energy of 1.2 cal/cm2. It may sound like a lot of math and factoring in of potentials, but believe me the extra time you take to determine the arc flash boundary is well worth your safety and well-being.
Calculating flash protection boundaries for systems over 600 V requires performing a flash hazard analysis coupled with either the NFPA 70E Hazard Risk Category/PPE tables or the Incident Energy Formula.
Additionally, Section 4 of IEEE 1584 Guide for Arc Flash Hazard Calculations states that the results of the arc flash hazard analysis are used to identify the flash-protection boundary and the incident energy at assigned working distances throughout any position or level in the overall electrical system.
The purpose is to establish safe work distances and the PPE required to protect workers from injury. A flash-hazard analysis is comprised of the following three different electrical system studies:
1. A short circuit study
2. A protective device time-current coordination study
3. The flash-hazard analysis and application of the data
Parts are considered exposed if they are energized and not enclosed, shielded, covered, or otherwise protected from contact. Work on these parts includes activities such as examinations, adjustment, servicing, maintenance, or troubleshooting.
Equipment energized below 240 V does not require arc-flash boundary calculation unless it is powered by a 112.5 KVA transformer or larger.
The arc-flash boundary is the limit at which a person working on energized parts can be standing at the time of an arc-flash without risking permanent injury unless they are wearing flame-resistant clothing. Permanent injury results from an arc-flash that causes an incident energy of 1.2 calories/centimeter2 (cal/cm2) or greater and causes a minimum of second-degree burns.
This distance can only be effectively determined by calculating the destructive potential of an arc.
First you must determine the magnitude of the arc based on the available short circuit current, then estimate how long the arc will last based on the interrupting time of the fuse or circuit breaker.
Finally, you will need to calculate how far away an individual must be to avoid being exposed to an incident energy of 1.2 cal/cm2. It may sound like a lot of math and factoring in of potentials, but believe me the extra time you take to determine the arc flash boundary is well worth your safety and well-being.
Calculating flash protection boundaries for systems over 600 V requires performing a flash hazard analysis coupled with either the NFPA 70E Hazard Risk Category/PPE tables or the Incident Energy Formula.
Additionally, Section 4 of IEEE 1584 Guide for Arc Flash Hazard Calculations states that the results of the arc flash hazard analysis are used to identify the flash-protection boundary and the incident energy at assigned working distances throughout any position or level in the overall electrical system.
The purpose is to establish safe work distances and the PPE required to protect workers from injury. A flash-hazard analysis is comprised of the following three different electrical system studies:
1. A short circuit study
2. A protective device time-current coordination study
3. The flash-hazard analysis and application of the data
ELECTRICAL PROTECTIVE HIGH TENSION GLOVES BASIC INFORMATION AND TUTORIALS
What are high tension gloves?
High voltage gloves are a form of PPE that is required for employees who work in close proximity to live electrical current. OSHAs Electrical Protective Equipment Standard (29 CFR 1910.137) provides the design guidelines and in-service care and use requirements for electrical insulating gloves and sleeves as well as insulating blankets, matting, covers, and line hoses.
Electrical protective gloves are categorized by the level of voltage protection they provide. Voltage protection is broken down into the following classes:
n Class 0—Maximum use voltage of 1000 V AC/proof tested to 5000 V AC.
n Class 1—Maximum use voltage of 7500 V AC/proof tested to 10,000 V AC.
n Class 2—Maximum use voltage of 17,000 V AC/proof tested to 20,000 V AC.
n Class 3—Maximum use voltage of 26,500 V AC/proof tested to 30,000 V AC.
n Class 4—Maximum use voltage of 36,000 V AC/proof tested to 40,000 V AC.
Once the gloves are issued, OSHA requires that they be maintained in a safe, reliable condition. This means that high voltage gloves must be inspected for any damage before each day’s use, and immediately following any incident that may have caused them to be damaged.
This test method is described in the ASTM section F 496, Specification for In-Service Care of Insulating Gloves and Sleeves. Basically, the glove is filled with air, manually or by an inflator, and then checked for leakage.
The easiest way to detect leakage is by listening for air escaping or holding the glove against your cheek to feel air releasing.
OSHA recognizes that gloves meeting ASTM D 120-87, Specification for Rubber Insulating Gloves, and ASTM F 496, Specification for In- Service Care of Insulating Gloves and Sleeves, meet its requirements.
In addition to daily testing, OSHA requires periodic electrical tests for electrical protective equipment and ASTM F 496 specifies that gloves must be electrically retested every 6 months. Many power utility companies will test gloves and hot sticks for a reasonable fee.
High voltage gloves are a form of PPE that is required for employees who work in close proximity to live electrical current. OSHAs Electrical Protective Equipment Standard (29 CFR 1910.137) provides the design guidelines and in-service care and use requirements for electrical insulating gloves and sleeves as well as insulating blankets, matting, covers, and line hoses.
Electrical protective gloves are categorized by the level of voltage protection they provide. Voltage protection is broken down into the following classes:
n Class 0—Maximum use voltage of 1000 V AC/proof tested to 5000 V AC.
n Class 1—Maximum use voltage of 7500 V AC/proof tested to 10,000 V AC.
n Class 2—Maximum use voltage of 17,000 V AC/proof tested to 20,000 V AC.
n Class 3—Maximum use voltage of 26,500 V AC/proof tested to 30,000 V AC.
n Class 4—Maximum use voltage of 36,000 V AC/proof tested to 40,000 V AC.
Once the gloves are issued, OSHA requires that they be maintained in a safe, reliable condition. This means that high voltage gloves must be inspected for any damage before each day’s use, and immediately following any incident that may have caused them to be damaged.
This test method is described in the ASTM section F 496, Specification for In-Service Care of Insulating Gloves and Sleeves. Basically, the glove is filled with air, manually or by an inflator, and then checked for leakage.
The easiest way to detect leakage is by listening for air escaping or holding the glove against your cheek to feel air releasing.
OSHA recognizes that gloves meeting ASTM D 120-87, Specification for Rubber Insulating Gloves, and ASTM F 496, Specification for In- Service Care of Insulating Gloves and Sleeves, meet its requirements.
In addition to daily testing, OSHA requires periodic electrical tests for electrical protective equipment and ASTM F 496 specifies that gloves must be electrically retested every 6 months. Many power utility companies will test gloves and hot sticks for a reasonable fee.
RECOGNIZING HAZARDS IN ELECTRICAL WORKS BASIC INFORMATION AND TUTORIALS
The first step is to recognize and identify the existing and potential hazards associated with the work you need to perform. A task and hazard analysis and pre-job briefing are two of the tools you can utilize to ascertain the risks involved in your work for the day.
It’s a good idea to include everyone who will be involved in the task or associated work to discuss and plan for the hazards. Sometimes a coworker will think of hazards that you have overlooked, and it will ensure that everyone involved will be on the same page.
Careful planning of safety procedures reduces the risk of injury. Determine whether everyone has been trained for the job they need to do that day. Do you need to present a safety training focused on specific risks that are present today?
Decisions to lockout and tagout circuits and equipment and any other action plans should be made part of recognizing hazards. Here are some other topics to address:
n Is the existing wiring inadequate?
n Is there any potential for overloading circuits?
n Are there any exposed electrical parts?
n Will you be working around overhead power lines?
n Does any of the wiring have damaged insulation that will produce a shock?
n Are there any electrical systems or tools on the site that are not grounded or double insulated?
n Have you checked the condition of any power tools that will be used to confirm that they are not damaged and that all guards are in place?
n What PPE is required for the tasks to be performed?
n Have you reviewed the MSDS for any chemicals present on the site or that will be used that could be harmful?
n Will any work need to be performed from ladders or scaffolding and are these in good condition and set-up properly? Is there any chance of ladders coming in contact with energized circuits?
n Are the working conditions or equipment likely to be damp or wet or affected by humidity?
It’s a good idea to include everyone who will be involved in the task or associated work to discuss and plan for the hazards. Sometimes a coworker will think of hazards that you have overlooked, and it will ensure that everyone involved will be on the same page.
Careful planning of safety procedures reduces the risk of injury. Determine whether everyone has been trained for the job they need to do that day. Do you need to present a safety training focused on specific risks that are present today?
Decisions to lockout and tagout circuits and equipment and any other action plans should be made part of recognizing hazards. Here are some other topics to address:
n Is the existing wiring inadequate?
n Is there any potential for overloading circuits?
n Are there any exposed electrical parts?
n Will you be working around overhead power lines?
n Does any of the wiring have damaged insulation that will produce a shock?
n Are there any electrical systems or tools on the site that are not grounded or double insulated?
n Have you checked the condition of any power tools that will be used to confirm that they are not damaged and that all guards are in place?
n What PPE is required for the tasks to be performed?
n Have you reviewed the MSDS for any chemicals present on the site or that will be used that could be harmful?
n Will any work need to be performed from ladders or scaffolding and are these in good condition and set-up properly? Is there any chance of ladders coming in contact with energized circuits?
n Are the working conditions or equipment likely to be damp or wet or affected by humidity?
AMERICAN NATIONAL STANDARD INSTITUTE (ANSI) AND ITS RELATION TO SAFETY
American national standards institute
The ANSI is a nonprofit organization that oversees the development of voluntary standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international standards so that American products can be used worldwide.
For example, standards make sure that people who own cameras can find the film they need for them anywhere around the globe.
The ANSI mission is to enhance the global competitiveness of U.S. business and the U.S. quality of life by promoting and facilitating conformity and voluntary consensus standards and maintaining their integrity.
ANSI accredits standards that ensure consistency among the characteristics and performance of products, that people use the same definitions and terms regarding materials, and that products are tested the same way.
ANSI also accredits organizations that certify products or personnel in accordance with requirements that are defined in international standards. The institute is like the umbrella that covers thousands of guidelines that directly impact businesses in almost every sector.
Everything from construction equipment, to dairy standards, to energy distribution, and electrical materials is affected. ANSI is also actively engaged in accrediting programs that assess conformance to standards, including globally recognized programs such as the ISO 9000 Quality Management and ISO 14,000 Environmental Systems.
The ANSI has served as administrator and coordinator of the United States private sector voluntary standardization system since 1918. It was founded by five engineering societies and three government agencies.
Today, the Institute represents the interests of its nearly 1000 company, organization, government agency, institutional, and international members through its headquarters in Washington, D.C. Accreditation by ANSI signifies that a procedure meets the Institute’s essential requirements for openness, balance, consensus, and due process safeguards.
For this reason, American National Standards are referred to as “open” standards. In this context, open refers to a process that is used by a recognized organization for developing and approving a standard. The Institute’s definition of “open” basically refers to a collaborative, balanced, and consensus-based approval process.
The criteria used to develop these open standards balance the interests of those who will implement the standard with the interests and voluntary cooperation of those who own property or use rights that are essential to or affected by the standard.
For this reason, ANSI standards are required to undergo public reviews. In addition to facilitating the creation of standards in our country, ANSI promotes the use of U.S. standards internationally and advocates U.S. policy and technical positions in international and regional standards organizations.
The ANSI is a nonprofit organization that oversees the development of voluntary standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international standards so that American products can be used worldwide.
For example, standards make sure that people who own cameras can find the film they need for them anywhere around the globe.
The ANSI mission is to enhance the global competitiveness of U.S. business and the U.S. quality of life by promoting and facilitating conformity and voluntary consensus standards and maintaining their integrity.
ANSI accredits standards that ensure consistency among the characteristics and performance of products, that people use the same definitions and terms regarding materials, and that products are tested the same way.
ANSI also accredits organizations that certify products or personnel in accordance with requirements that are defined in international standards. The institute is like the umbrella that covers thousands of guidelines that directly impact businesses in almost every sector.
Everything from construction equipment, to dairy standards, to energy distribution, and electrical materials is affected. ANSI is also actively engaged in accrediting programs that assess conformance to standards, including globally recognized programs such as the ISO 9000 Quality Management and ISO 14,000 Environmental Systems.
The ANSI has served as administrator and coordinator of the United States private sector voluntary standardization system since 1918. It was founded by five engineering societies and three government agencies.
Today, the Institute represents the interests of its nearly 1000 company, organization, government agency, institutional, and international members through its headquarters in Washington, D.C. Accreditation by ANSI signifies that a procedure meets the Institute’s essential requirements for openness, balance, consensus, and due process safeguards.
For this reason, American National Standards are referred to as “open” standards. In this context, open refers to a process that is used by a recognized organization for developing and approving a standard. The Institute’s definition of “open” basically refers to a collaborative, balanced, and consensus-based approval process.
The criteria used to develop these open standards balance the interests of those who will implement the standard with the interests and voluntary cooperation of those who own property or use rights that are essential to or affected by the standard.
For this reason, ANSI standards are required to undergo public reviews. In addition to facilitating the creation of standards in our country, ANSI promotes the use of U.S. standards internationally and advocates U.S. policy and technical positions in international and regional standards organizations.
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