Commercial Power Distribution Systems Research Articles

Practical Challenges of Inverse and Definite-Time Overcurrent Protection Coordination in Modern Industrial and Commercial Power Distribution System

The characteristics of an overcurrent relay (OCR) in protection coordination are determined by adjusting the current and time delay function. This characteristic is adjusted once, fixed, and expected to overcome any disturbances in the system, which raises the risk of incorrect operation of the protection system, such as an overlapping trip or the incapability to limit the current exposure in the protected equipment. This article summarizes different efforts to overcome the modern challenges of overcurrent protection coordination (OCPC) in low or medium voltage industrial and commercial distribution systems. A brief background is introduced from a general perspective and then specifically describes in detail the problem of equipment coordination with a thorough link among mathematical concepts and fundamentals in practice. The operation challenges and ideas to avoid incorrect performance, under normal operation, are discussed. Finally, the article proposes a new optimization method based on the combination of the firefly algorithm and target remedy to overcome such challenges. The optimization considers the combination of inverse-time (ANSI 51) and definite-time (ANSI 50) function in OCR. The method is described and validated in the IEEE 242.2001 to meet the existing regulation of protection coordination. By assessing the critical cases, this article is expected to enhance the OCPC under different fault scenarios with complex coordination of time-current curves.

The Hartley series and its application to power quality assessment

An analog to the Fourier series (FS) that is based on the cosine-and-sine function is presented. The new series is related to the Hartley transform and is termed the Hartley series (HS). Properties and applications of the Hartley series are discussed in general. The technique is valuable for the assessment of power quality in industrial and commercial power distribution systems. In particular, the impact of switched and pulse modulated loads and AC/DC converters can be analyzed. An example is given in which an industrial distribution system impacted by a six-pulse rectifier load is analyzed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Reliability Insurance---When It Is Practical

The components of industrial and commercial power distribution systems are subject to electrical breakdown. There are many factors which affect the exposure and the severity of the accident. The potential can be minimized by utilizing quality appratus well-suited for the application, adequately maintained, properly protected, and a well-organized safety practice. Never-theless, serious electrical breakdowns do occur to cause major financial losses. Most corporations have found it practical to insure, at least to some degree, to guarantee financial reliability. The various forms of casualty insurance applicable to power distribution systems are discussed. The all-inclusive broad coverage form of casualty insurance incorporating a reasonably large deductible feature is the most common type of contract. A progressive corporation relies on effective maintenance to minimize the preventable types of electrical breakdowns.