Arc Flash Studies
In order to identify the specific arc flash hazard at a given piece of equipment within a facility, an arc flash study must be performed. There are several software packages available, similarly to short circuit study and coordination study software packages, to facilitate this analysis by a “Those involved with the design, implantation and evaluation of electrical distribution systems mush have an understanding of arc flash hazards and how to evaluate the hazards as well as minimize or mitigate the hazard to the electrical worker.”
Qualified professional electrical engineer. In order to perform the arc flash study a short circuit and coordination study must first be performed or the results of these studies must be available to the engineer performing the arc flash study.
Arc Flash is caused by high impedance at an electrical source which results in a burst of energy and extreme heat. This might happen during energized works when two conductors are shorted. It can be caused by un-insulated tools, metal worn by workers, loose cable connections, faulty circuit breakers or other protective devices.
Consequences might include burns, loss of life severe property damage and related financial and reputational loss. Electric shock is formed by a low impedance path to ground. It can be caused by exposed metal parts like panels, bus bars and cables carrying fault currents which come in contact with personnel. Consequences might include injuries from light to severe, even loss of life.
To determine if and how work at energized installations or equipment can be carried out in a safe way, an arc flash and electrical shock hazard study needs to be performed in compliance with the following standards *:
IEEE Standard 1584 Guide for Performing Arc Flash Hazard Calculations
OSHA 29 Code of Federal Regulations (CFR) Part 1910 Subpart S
NFPA 70 National Electric Code
NFPA 70E Standard for Electrical Safety in the Workplace (2012 edition)
* and/or relevant local and national standards and regulations
The Arc Flash and Electric Shock Hazard Study will be carried out based on the following schedule:
1.Collecting preliminary data on all electrical equipment and installations.
2.Scoping Visit and Service Quote: Carried out on-site to obtain preliminary information to allow detailed quoting of services(time and costs).More conservative service quotes can be provided without on-site visit if adequate information is provided.
3.Data Collection & Verification: Site Visit. Analyzing each and every power distribution system, verifying the existing documentation, adding missing information and/or equipment with the aim to be able to prepare as-built line diagrams which are the prerequisite for the analysis to follow.
•Preparation of as-built line diagrams
•List of details of all relevant existing electrical equipment
•Fault current calculation
•Protection device coordination study
•Arc Flash Analysis
•Electrical Shock Hazard Analysis
•Respective modelling (preparing best / worst case) with advice on reducing arc flash exposure
5.Labelling: To carry out labelling of all electrical panels analyzed for Arc Flash and Electric Shock to ensure that technical staff at any time has all relevant information at hand
6.Training: Based on the site requirements, designated technical staff will be trained in understanding Arc Flash hazards and safe working practices to prevent arc flash and electric shock exposure.
Updated single line diagrams of the electrical systems: Fully updated line diagrams are required to allow modelling and development of various scenarios, leading to reduction of arc flash exposure and lower PPE levels.
Fault Current Study: Calculating the fault current at each panel, busbars, and/or switchboard
Protection Device Coordination Study :Indication of in-coordination of cascaded protective devices.
Arc Flash Analysis :Leading to detailed information on incident energy and duration, arc flash boundaries, and the resulting PPE requirement
Electric Shock Hazard Analysis : The calculation of the fault currents of every circuits leads to the definition of boundaries to prevent electric shock. These boundaries (Limited / Restricted / Prohibited Approach Boundary) are printed on each warning label.
Compliant Labelling :All affected equipment will be labelled in accordance with the respective standard. Warning and Danger labels are provided depending on the severity of exposure.
Final Report : All details documented, including updated line diagrams, list of protective equipment, fault current calculations (analysis), protective device data, time coordination graphs, resulting PPE levels, approach boundaries, warning/danger labels etc.. Furthermore, advice on improving the electrical installation to reduce arc flash intensity and to reduce PPE levels will be prepared.
Training : Based on requirement of the site, designated technical staff will be trained in understanding Arc Flash hazards, safe working to prevent arc flash and electric shock exposures.
Follow-up Services: Depending on the results, it might be necessary to verify implemented improvements to adjust single line diagrams, calculations, and labels
Benefits to Organisation:
One aim of the study is to ensure the analysed site is in compliance with the most demanding requirement of international standards (NFPA / IEEE / OSHA) and respective local standards as well. Compliance with the latest international
standards guarantees state-of-the-art installations regarding Arc Flash and Electric Shock exposures, a prerequisite to prevent accidents, financial losses, negative reputation issues and legal actions - to name some.
•Occupational Health & Safety Improvement
The nature of Arc Flash Studies is to eliminate as far as possible any arc flash incident. This demanding goal might not always be achievable. However, the frequency (probability) of arc flash events will be significantly reduced and - equally important - the severity of any remaining incident will be lowered to a level where severe injuries and property losses are not expected anymore. By providing relevant information regarding electrical safety throughout the plant on all panels and other parts of the power distribution system, staff members have required electric safety information right in front of their eyes where they need it and can respond accordingly. Of course, relevant training is part of the study.
•Higher Level of Asset / Business Interruption Protection
Arc flash is a severe ignition source for fires in industrial and commercial environments. Statistics show arc flash being a significant cause of fires and explosions (arc blast) with their devastating effect on physical property. Reducing the probability and severity of arc flash incidents not only decreases the direct physical losses, the impact on consequential financial losses is usually even higher, thus financial losses overall can be expected to be significantly reduced as well.
•Higher Reliability of the Electrical Distribution System
The Arc Flash Study is an exercise that covers the complete electric power distribution system of a plant. It is one of the few opportunities in a plant to look at the whole of the distribution system in one go. Deviations from good design and installation will be observed. Equipment or circuits with a high incident and loss potential will be identified and the respective severity quantified.
Results of Study:
Updated Single Line Diagrams
Changes in electric power distribution systems are reality and do happen on an on-going basis. Unfortunately, these changes are not always documented. As-built line diagrams are what every Maintenance Manager wants to work with, but reality is that only few plants keep their documents on an as-built level.
Protection Device Coordination Study
Optimized coordination of all protection devices in an electric power distribution system will significantly reduce down-time of the system or parts of it. A system that is not coordinated in an optimal way will cause unnecessary shut-down of parts that should not be affected by the tripping of a protection device.
Best Case / Worst Case Simulation
All locations with incident energy requiring PPE higher than Level 2 will run through a worst case and best case simulation to develop technical solutions that will reduce the PPE level to level 2 or below.
Additional Indirect Benefits:
By analyzing the complete power distribution system deviations from best practices will be observed and loss potentials identified. Examples in this respect are:
Poor cable management, faulty or neglected installations or connections, contamination and other housekeeping issues, misuse of protected/prohibited areas, etc.
Equipment not in compliance to special hazard exposures (explosion / dust / water / natural hazards), overloading, wrong cable diameters, lack of physical impact protection, etc.
Non-compliance to existing SOPs, deviations from preventive maintenance practices, lack of documentation, insufficient training and qualification of staff, etc.