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This paper provides a discussion on the theory behind reducing the risk and severity of an arc flash incident. In particular, the variables associated with the calculations of energies from an arcing fault are presented in an effort to show the futility of present methods for the determination of incident energy levels in the electrical industry. A number of commonly ignored design concepts that significantly reduces the risk of electrical hazards will be discussed two of which include 1) the system grounding and, 2) solid insulation. This paper will discuss risk and the management of risk as a means of reducing the probability of an incident. It will then show how risk-reduction should be used in the design, construction, operation and maintenance of electrical equipment as means for the safeguarding of employees in the workplace.
Models for the calculation of a bolted fault and associated fault studies are essentially a proven technology. Fault simulations on power systems have been performed in order to adequately verify the validity and accuracy of the models. However, the modeling of an arcing fault has proved to be very difficult, if not totally elusive. The reason for this elusiveness is that each arcing fault is unique and cannot be repeated. Even tests on arcing faults in the laboratory are difficult to repeat.
There are many variables that make the repeatability of any particular test difficult. In fact, the probability of two identical arcing faults in the real world is a physical impossibility because of the random nature of the arcing in a plasma cloud. Acknowledgement of this fact will allow a more reasonable approach to understanding the arcing fault which involves the consideration of numerous variables. Some of these variables are controllable, but many are not. Once there is a good understanding of the controllable versus non-controllable variables, it is of importance to develop a simple yet effective way of understanding the electrical hazards. Then, and only Bolted fault is a fault with no fault arc impedance then, can reasonable progress be made in an effort to develop reasonable solutions to improve electrical arc flash safety in the workplace.
|The Effects of System Grounding, Bus Insulation and Probability on Arc Flash Hazard Reduction-The Missing Links|