DC task team report

Voltage sags are momentary dips in voltage that may cause misoperations to the electric utility customers' sensitive loads. These misoperations may only be an annoyance to the residential sector, but, on the industrial and commercial front, they can cost millions of dollars each year. It is impossible to eliminate all of these faults and associated voltage sags, but an improvement can be achieved through power system modifications on both the utility system and the industrial or commercial power system. The evaluation of these system modifications was difficult in the past, but the authors describe a voltage sag analysis program, developed by Power Technologies, Inc., which has simplified the task. The program uses methodologies developed for the update of the IEEE Gold Book (IEEE Standard 493, Recommended Practice for the Design of Reliable industrial and Commercial Power Systems). The results of this sag analysis program form the basis of possible future cost-benefit analysis enabling electric utilities and utility customers to make the most economic system modification.

For short-circuit analysis in industrial and commercial power systems, a new approach of the ohmic method in such a form as to facilitate, as far as possible, its use and the realization of its evaluation is suggested. The 'characteristic' current method, by replacing the impedance of each equipment with the corresponding value of the 'characteristic' current, permits the application of the impedance properties to the inverse of the current values, either in meshed or nonmeshed networks. In order to achieve the correct design, rating and protection coordination of the whole power system, it is necessary to know and calculate step by step the values of short circuit current for each system component, from the utility or local generating connection point until the branch-circuits and the utilization equipments. The proposed approach assumes the above mentioned short-circuit current directly as calculation and comparison parameters. With the 'characteristic' currents as parameters the short-circuit analysis of substantial radial systems is made easier and a better matching of power system design requirements is permitted. >

IEEE Std. 902-1998, Guide for Maintenance, Operation, and Safety of Industrial and Commercial Power Systems, also known as the IEEE Yellow Book, has been an excellent resource for management, safety professionals, and maintenance personnel since it was published in 1998.

This paper discusses bus and breaker fail protection in modern industrial and commercial power systems. Fault current levels are increasing due to increases in power transmission system capacities and in-plant power generation. Such high fault currents as well as in-plant generator dynamics and system arc flash incident energy limiting requirements necessitate fast bus fault clearing. Meanwhile advancements of numerical relays proved more appealing economically and technically for MV and LV bus protection applications. On the other hand, when bus and breaker fail protection operate, the interrupted segment of the system is larger than a single feeder protection's operation. Consequently, mal-operations of either bus or breaker fail protection are less tolerable than mal-operations of single feeder schemes. This paper is intended to aid protection engineers in making decisions; first if dedicated fast bus and breaker fail protection schemes are required and second what concerns need to be addressed during the selection and the design of such systems. The topics are presented in two separate parts. Part 1 covers scope, introduction and bus protection topics. Part 2 covers breaker fail protection concepts, conclusions and bibliography of additional reference material.

Chapter 10 - Harmonic load flow applications for industrial power systems design

Amicrogrid is a combination of clusters of distributed generators connected to fulfill the requirement of dedicated load. A microgrid can be operated with standalone or grid connected mode. A microgrid when operated in standalone mode with a limited voltage and power rating is more likely prone to a serious damage due to its unpredictable faults. Load flow, voltage stability & short circuit analysis of a micro-grid is essential for both design and performance monitoring and to ensure reliable microgrid operations. The faults with a continuously varying in nature affects the normal operation of buses and so to the peripherals associated to the micro-grid. The cause and severity of such faults plays a vital role while designing protection scheme in standalone micro-grid as standalone mode has confined generation. In this paper, electrical model of a 52.3 kW Photo-voltaic based micro-grid is developed on Electrical Transient Analysis Program (ETAP) and various transient conditions such as load flow, loss of DG & short circuit analyses are performed. A detailed short circuit analysis puts light on various short circuit conditions and provides useful analysis. ETAP is the most comprehensive analysis platform for the design, simulation, operation, and automation of generation, distribution, and industrial power systems. ETAP also provides the industry leading transient analysis of power system and micro-grid so chosen for this transient analysis study. A short circuit analysis is calculated based onIEC Std. 60909 using ETAP. This paper presents a simulated model of micro-grid with actual system oriented results and analyzes responses of system during fault conditions and various contingencies.

High power wiring of power generators is an expensive affair that needs more attention. The cost of replacement after all paths are pulled and covered is high, and the defect is not always visible such as squeezing or bending but hidden. Therefore, due to the need for electrical testing, almost 80% of all tests performed in power systems are related to insulation quality testing. This is much more cost-effective than changing the wiring later. Most electrical equipment in industrial and commercial power systems uses 50 or 60 Hz AC voltage, depending on the range. So, using an AC power source to test insulation seems a logical choice. At the same time, however, isolation systems are extremely capacitive, which is one of the reasons that DC testing has found a large niche in this technology. In this paper, we present the implementation of a DC power supply adjustable between 0 and 500 V DC used for underground cable insulation testing.

Finding the reliability expression of different substation configurations can help design a distribution system with the best overall reliability. This paper presents a computerized a nd implemented algorithm, based on Disjoint Sum of Product (DSOP) algorithm. The algorithm was synthesized and applied for the first time to the determination of reliability expression of a substation to determine reliability indices and costs of different substation arrangements. It deals with the implementation and synthesis of a new designed algorithm for DSOP implemented using C/C++, incorporating parallel problem solving capability and overcoming the disadvantage of Monte Carlo simulation which is the lengthy computational time to achieve satisfactory statistical convergence of reliability index values. The major highlight of this research being that the time consuming procedures of the DSOP solution generated for different substation arrangements using the proposed method is found to be significantly lower in comparison with the time consuming procedures of Monte Carlo-simulation solution or any other method used for the reliability evaluation of substations in the existing literature such as meta-heuristic and soft computing algorithms. This implementation gives the possibility of RBD simulation for different substation configurations in C/C++ using their path-set Boolean expressions mapped to probabilistic domain and result in simplest Sum of Disjoint Product which is on a one-to-one correspondence with reliability expression. This software tool is capable of handling and modeling a large, repairable system. Additionally, through its intuitive interface it can be easily used for industrial and commercial power systems. With simple Boolean expression for a configuration’s RBD inputted, users can define a power system utilizing a RBD and, through a fast and efficient built-in simulation engine, the required reliability expressions and indices can be obtained. Two case studies will be analyzed in this paper. The effects of different substation configurations on the reliability are analyzed and compared. Then, the reliability of a radial distribution system will be evaluated using DSOP solution. The failure results will be combined with a load flow scenario, and indices such as SAIDI, SAIFI will be determined.

The P1015 Working Group of the IEEE Low Voltage Protection Subcommittee is preparing an application guide for low voltage circuit breakers used in industrial and commercial power systems, to be published as the IEEE Blue Book. The purpose of this guide is to provide information for selecting the proper circuit breaker for a particular application. This guide helps the application engineer specify the type of breaker, rating, trip functions, accessories, acceptance tests, and maintenance requirements. This guide also discusses circuit breakers for special-purpose applications; for example, thermal only, instantaneous only, and switches. >

Many system reliability prediction methods are based solely on equipment failures, neglecting the human component of man-machine systems (MMS). These methods do not consider the identification of the root causes of human errors. The reliability and safety of industrial and commercial power systems and processes (i.e., MMS) are dependent upon human characteristics and many dependent and dynamic interactive factors. The consequences of human errors are very diverse and can range from damage to equipment and property, injury to personnel or fatalities, to disruption of scheduled system operation, all of which represent a significant cost to society. This paper focuses on accidents-injuries and the disruption of scheduled system operation caused by human element factors and shows that the human element is a very significant factor affecting the reliability and safety of electrical systems. The paper initially presents several case studies to reveal the frequency of human errors which disrupted scheduled computer and utility system operation. This paper also presents statistics on the injury accident rate in electric utilities and the number of days lost to injury accidents. It presents some of the factors that direct human behavior and discusses how these factors help identify the possible root causes of electrical accidents, using an accident-injury sequence model to determine the cause of human errors. Knowledge of human factors can be used to mitigate their impact on power system interruptions and injury accidents (e.g., increased productivity, increased reliability, decreased errors, increased safety, etc.).

In industrial and commercial sectors, loads are becoming increasingly sensitive to brief supply voltage disturbances. As a consequence, today voltage dips have more impact than just a few years ago. Fast voltage conditioners, improving the load immunity characteristics and accordingly reducing the expected number of load interruptions or malfunctions due to supply voltage dips, can allow large cost savings. Different categories of voltage conditioners are existing today, ranging from energy‐stored devices (like uninterruptible power supply) to no energy‐stored devices (like static voltage booster). To reduce the effects of supply voltage dips on a given plant, usually several different possible arrangements must be investigated, depending on the conditioners type, size and bus location. To determine the optimal arrangement is not always immediate. A methodology based on the minimum revenue requirement (MRR) is proposed in the paper, and a numerical example is given as well.

ABSTRACTThis paper focuses on the engineering design of modular systems in the manufacturing industry, in which companies can benefit from modular and configurable products that fulfil a variety of customer needs. The purpose of this paper is to study the types of challenges faced in the engineering design of modular systems and the types of support needed to address these challenges. The topic is studied via a literature review and seven industrial case studies. The analysis method for the case studies combines engineering and business perspectives. The engineering perspective highlights engineering concepts related to designing modular systems, while the business perspective focuses on related managerial issues. We find that the studied companies emphasised different aspects of modular system development, despite having similar high-level goals related to the benefits of modularity and design reuse. We also identify several challenges, along with the need for support related to the engineering design of modular systems in the manufacturing industry. Current engineering design practices related to modular systems are not sufficient to generate the typical benefits related to modularity and design reuse; organisations must also focus on other aspects of the design process, such as knowledge retrieval.

Total reliance on sensitive electronic systems for such important functions as data processing, communications, and process control is now a way of life in our commercial, industrial, and governmental activities. This development has necessitated a new concern toward the quality of the electric power supply. Intermittent power disturbances, capable of disrupting electronic equipment are inherent to both commercial and industrial power systems. Any disruption causing downtime and financial loss, power-related or otherwise, is likely to precipitate a study to determine appropriate corrective actions. Unfortunately, analyzing the cause and effect of power disturbances can be difficult, particularly when sophisticated computer systems are involved. The ultimate purpose is to assist the electronic equipment users in reducing power-related downtime.

The technical standard IEEE P3003.2 “Recommended Practice for Equipment Grounding and Bonding in Industrial and Commercial Power Systems” published the month of October 2014, is an evolution of Chapter 2 of IEEE Std 142-2007 (also referred to as Green Book). P3003.2 has been developed by industry experts, based on their knowledge and experience in this field, and drafted after wide consultation and consensus. P3003.2 provides the fundamental concepts related to the grounding and bonding of equipment in industrial and commercial power systems. The main objective of the standard is to offer recommended practice for the minimization of the risk of electric shock by properly sizing conductors and allowing the prompt disconnection of supply. To better achieve this purpose, new terminology, not present in the Green Book, has been included in the standard. The objective was to facilitate the safety-by-design approach, as well as align P3003.2 with other technical standards used worldwide. In this paper, the author, chair of the working group, seeks to clarify the new terminology, providing the proper interpretation and reasons behind it.

Maximizing the reliability of a medium-voltage energy-delivery system requires an extensive amount of distribution engineering knowledge. When that system is to have the added flexibility of having its standby generators operate while tied into the utility grid, the depth of the knowledge needed increases significantly. In many cases, it would require more knowledge than many experienced consulting firms might possess. The standby generator project case history discussed in this paper involved a lesser known but very important code compliance issue. That issue became important when less-flammable oil-filled pad-mounted transformers were selected to provide an isolating link between those generators and the utility distribution system serving a commercial facility. The isolating link was intended to protect those generators from damage should they suffer ground faults. This paper is intended to point out two important facts. First, to provide an explanation and background of what is a lesser known, yet critically important, issue-specifically, the requirement that maximum i/sup 2/t let-through limits for less-flammable transformers comply with NEC Listing requirements. Secondly, the paper points out how the broad network of talented engineers within the Industrial and Commercial Power Systems (I&CPS) Department of the IEEE Industry Applications Society was able to help the project's design engineer to both understand this issue and to assist in obtaining the equipment needed to successfully complete the project.