Ravel F. Ammerman

Dc arc models and incident energy calculations

There are many industrial applications of large-scale dc power systems, but only a limited amount of scientific literature addresses the modeling of dc arcs. Since the early dc-arc research focused on the arc as an illuminant, most of the early data was obtained from low-current dc systems. More recent publications provide a better understanding of the high-current dc arc. The dc-arc models reviewed in this paper cover a wide range of arcing situations and test conditions. Even with the test variations, a comparison of dc-arc resistance equations shows a fair degree of consistency in the formulations. A method for estimating incident energy for a dc arcing fault is developed based on a nonlinear arc resistance. Additional dc-arc testing is needed so that more accurate incident-energy models can be developed for dc arcs.

Electrical arcing phenomena: a historical perspective and comparative study of the standards: IEEE 1584 and NFPA 70 E

The exposure to hazards associated with electrical arcing phenomena when working on energized equipment is a topic of significant interest to industrial plant personnel. This article provides an overview of the current arc-flash standards, focusing on the methods used to calculate incident energy levels in a system. A thorough sensitivity analysis of the arc-flash hazard incident energy calculations currently adopted by the IEEE 1584 standard leads to some possible conservative simplification of the equations. These simple equations could be used for a quick first-cut assessment of the incident energy levels present in a system. A case study using data from a typical petrochemical application provides a comparison of the National Fire Protection Association (NFPA) 70E and IEEE 1584 arc-flash incident energy equations and the results obtained using the proposed simplified calculations.

Comparative study of arc modeling and arc flash incident energy exposures

Despite the growing awareness and increased understanding of the hazards associated with arcing faults, incidents of this type continue to occur and individuals exposed to the hazards may be severely injured or killed as a result. Accurately estimating the available thermal energy is a critical aspect of assessing the severity of the arc flash. Over the past few years, a number of researchers have worked to quantify the thermal energy present during an arc flash exposure. This paper will address the three categories of incident energy models that have been developed: theory based, statistically developed, and semi-empirically derived. Because of the limitations and discrepancies observed using the different techniques, no standard approach has been agreed upon by the engineering community. This work includes an analysis of published arc energy and incident energy data from the past to the present and serves as a critique of available incident energy equations. The insight gained from this evaluation may shape the direction of future arc testing and model development. The authors hope that this paper will help to close the gap between the experimental results, scientific based theory and industrial applications.

Modeling and tracking Transmission Line Dynamic Behavior in Smart Grids using structured sparsity

In this work a new and fast network-wide framework is addressed for modeling and tracking the dynamic behavior of transmission lines in Power Networks (PN). A sparse-based mathematical formulation for Transmission Line Dynamic Behavior Tracking (TLDBT) is formed by incorporating a PN Port-Hamiltonian model. Among the TLDBT a new set of intermediate parameters called the line dynamic index coefficients (LDIC) are defined based on the wave propagation analysis of current waves in transmission lines. It is shown how these coefficients can reflect the dynamic behavior of the transmission lines. The online monitoring of variations in these index coefficients is interpreted as an alternative approach for TLDBT in power grids. Finally, exploiting the inherent sparsity in the PN structure this TLDBT problem is reformulated as a Structured Sparse Recovery Problem (SSRP) and the TLDBT-SSRP is solved for LDICs. The simulation results indicate that the proposed framework can be considered as an alternative approach to address the new challenges in the future generation of smart power grids modeling, monitoring and congestion-management strategies.

Arc flash evaluation and hazard mitigation for the Colorado School of Mines electrical power distribution system

An arc flash is the release of electrical energy during an arcing fault, which dissipates in the form of heat energy, intense light, blast pressure, severe sound waves, electromagnetic radiation, and toxic gases. The thermal energy, concussive forces, and flying debris can pose serious threats to the safety of personnel working in close proximity to electrical equipment. In order to identify the severity of an arc flash hazard at the Colorado School of Mines (CSM), an arc flash hazard evaluation of the electrical power distribution system has been conducted. The arc flash analysis has been performed in accordance with NFPA 70E: Standard for Electrical Safety in the Workplace, and IEEE 1584: Guide for Performing Arc Flash Hazard Calculations. The analysis of the existing system configuration has revealed that many locations on the CSM campus are in the “dangerous” arc flash hazard category, and consequently work cannot be performed on energized equipment at these locations. With an understanding of the thermal energy available, design recommendations, including the selection and coordination of fuses and circuit breakers, were investigated to reduce the severity of arc flash events. Implementation of the selected protective devices can decrease the incident energy levels of CSM locations and eliminate any instances of “dangerous” hazard risk categories. Other hazard mitigation considerations include increasing the working distance, and utilizing arc suppression blankets while performing maintenance. In addition, electrician training to promote safe work practices is strongly encouraged.

Modeling High-Current Electrical Arcs: A Volt-Ampere Characteristic Perspective for AC and DC Systems

The development of models used to represent electrical arcs has been the focus of numerous research studies through the years. A variety of models, ranging from the simplistic to the elaborate, have been proposed by the international scientific community for DC, single-phase AC, and three-phase AC system calculations. This paper features volt-ampere characteristics of high-current electrical arcs, compiling information and providing an appraisal of some of the different models that utilize this approach. Given the highly chaotic and non-linear behavior of arcing phenomena, as well as the number of variables involved, the models summarized in this paper provide consistent results.

Electrical Safety Education in an Undergraduate Engineering Program: Curriculum Development and Assessment

In an effort to develop increased safety awareness related to the electric power industry, Colorado School of Mines (CSM), electrical specialty students are required to take a one- week intensive electrical safety training course. Though safety training should start with young people, it is also an important part of the education for experienced electrical technical personnel too. Engineers, designers, and operators continue to develop insights about electrical safety throughout their careers. This paper discusses the electrical safety training course curriculum developed at CSM and provides an assessment of the effectiveness of the program. Based on the success of the program this has become a permanent part of the Field Session curriculum.

Work in Progress – The Kolb Learning Model Applied to an Advanced Energy Systems Laboratory

An Advanced Electric Power and Energy Systems Laboratory was offered for the first time at Colorado School of Mines (CSM) during the spring 2005 semester. The pilot course represents an innovative approach to lab instruction. This paper describes the course materials developed to introduce the power flow problem to a group of senior level undergraduate students using the Kolb learning model. The Kolb model is helpful for conceptualizing how people learn and for developing course curriculum that will accommodate the various learning styles. A special feature of this laboratory experience was the utilization of industrial contacts to provide the students with added motivation to learn. Initial feedback from students and industry representatives has been very positive. Based on the success of the pilot program, the course will now become a permanent part of the undergraduate power engineering curriculum at CSM