DALCM Initiates 11 New Projects as Part of 2012 Program

An arc flash on a transmission or distribution system results in high energy emission, mostly in the form of heat energy. This may present a concern to the safety of employees in the vicinity of the arc flash in open areas such as overhead lines, electrical distribution equipment, panels or substation equipment. A thorough understanding of arc flashes is necessary to accurately model them for identifying potential electrically hazardous areas, developing safe approach distances, and selecting the appropriate personal protective equipment and operating practices.

In the first phase of this study, the most common type of faults, switching practices, and operating procedures which can lead to severe arc flashes are identified. Information about arc flashes, including the definition of arc resistance, heat flux calculations, and the effects of distance from the flash, is provided to help educate personnel within a utility about the concerns and hazards of an arc flash.
The second phase looks at arc fault hazard in enclosed underground utility systems, such as manholes, pull pits and vaults. This danger stems mainly from convective heat transfer, which is not accounted for in existing models used to evaluate the burn hazard from an arc fault. This phase led to the creation of user-friendly software that can be employed to conduct more accurate arc fault hazard calculations.
The third phase of the project is an Arc Flash Scoping Study which assesses the cost and effort involved in acquiring experimental data to overcome the shortcomings identified in existing arc flash models, including questionable results from Personal Protective Equipment testing and a lack of models that predict incident energies and that quantify pressure hazards.

For more information, please contact Peter Gelineau:
peter.gelineau@ceati.com
514-866-5377 ext 228

This Guide provides engineering knowledge on overcurrent protection designs and practices and the application of devices for the protection of distribution power systems. It is intended for the use of distribution power utility staff. The Guide describes overcurrent protective devices and their functionality, operation, application, and coordination. It includes information on devices such as reclosers, sectionalizers, vacuum and SF6 circuit breakers, and microprocessor-based relays. Particular emphasis is given to modern devices and their application, such as the use of programmable logic. Since the introduction of electronic and microprocessor-controlled protective devices, the possibilities for distribution system protection have widened enormously and are changing ever more quickly. The added flexibility, however, has created a steep learning curve for the distribution utility engineers who are entrusted with designing and operating protection systems. This Guide provides a summary and reference tool for distribution engineering staff, covering North American distribution system practices. It deals primarily with overhead and underground radial distribution rated for 34.5 kV and lower.

The CEATI Utility Guide to Root Cause Analysis of Distribution Failures provides comprehensive information and systematic procedures for the analysis of distribution power system failures by utility engineers and technologists. The Guide focuses on North American overhead and underground power distribution system equipment failures, but for the most part, the methodologies generally apply to utilization and distribution systems. The Guide provides background information on distribution equipment, such as transformers, fuses, arresters, cables, splices, elbows, and network transformers. For each type of equipment, the degradation mechanisms and possible failure modes are discussed, and then tools and methodologies are presented to aid in determining the most likely root cause of a failure event.

This document is a comprehensive guide for the selection and application of high-voltage fuses on electric power distribution systems. The target users are engineers and technologists involved in the design of distribution overcurrent protection systems and standards. The intent in producing the guide was to bring together the fundamental information required in high voltage fuse application. The guide also builds upon the base of available material by updating older methodologies and by covering devices such as electronic fuses, SF6 fuses, and vacuum fuses. Furthermore, the guide attempts to bring into the application arena a number of novel techniques for protection design. The guide provides descriptions, operating theory and characteristics for fuses and related protection equipment. It describes selection criteria, application considerations, and coordination principles, and provides illustrative examples. The guide is written from a utility perspective providing information on utility problems and equipment failure modes. The guide attempts to answer common questions and clarify common misconceptions regarding fuse application. It is intended that this document be a valuable technical reference for utility staff as they develop fusing practices for their distribution systems.

The application of surge arresters to protect and improve the lightning performance of unshielded transmission lines is analyzed by means of a statistical simulation tool developed in the MATLAB environment, in conjunction with EMTP‐RV. The lightning performance of three unshielded lines with different configurations and different voltage levels is evaluated. The use of line surge arresters to improve the line performance was examined for gapped as well as gapless arresters. In every case, the possibility of reducing the insulation level in the presence of surge arresters is investigated. The failure rates of the surge arresters are also computed. The effect of eliminating shield wires on the values of step potential, under fault conditions, was investigated using CYMGRD.

This research study provides utilities with guidelines for the formulation of safety grounding policies on overhead, radial distribution lines at phase-to-phase voltages up to 86.6 kV. The guidelines are based on about 10,000 computer simulation of representative distribution systems. While the relative advantages and disadvantages of certain forms of safety grounding have been known for some time, the actual voltage levels to be expected on a given type of distribution system when these safety grounding methods are implemented has not been so clear; nor have the allowable work site voltage levels been easy to establish, due to the highly variable electrical properties of wood poles. This has resulted in proposed safety limits for pole-top voltages as a function of pole characteristics. In addition, this report provides an overview of safety grounding concepts and detailed discussions of the particularities of the different systems studied. This report provides decision-makers implementing safety grounding policies with an understanding of the concepts which underlie safety grounding and practical guidelines and reference data that they can consult in the review or formulation of their procedures.

Wording of the present version of the Canadian Electrical Code Part I, Section 36 makes it difficult to verify compliance of the great variety of outdoor and indoor customer-owned substation grounds with the Code. This verification is virtually impossible without the use of sophisticated and complex analyses requiring specialized data not available in readily usable form. This project provides several useful tools in the form of reference documentation, tables, charts, figures and engineering software, which will help design and verify the adequacy of customer-owned substation grounds. The research work consisted essentially of a literature search, a comprehensive survey of utility distribution engineers and chief electrical inspectors, and a parametric and sensitivity analysis, using state of the art software, of customer-owned distribution substation grounding systems. Results of the analysis yielded the suggested new Canadian Electrical Code Guidelines, as well as an array of practical analysis tools, the most notable of which is a dedicated user-friendly software package. The software packages, as well as the alternative hand-calculation and graphical tools which were developed, require a minimal background in grounding theory to use.