Preface to the Second Edition
Some twenty years have passed since the original publication of this book, normally sufficient to warrant an updating dictated by events and heralding the arrival of a new century. The explosion of electronically operated devices (computers, robots, automatic controls, etc. ) have required micro refinements in the quality of electric supply that could not tolerate those associated with the macro commercial supply of this commodity; necessary corrective actions peculiar to each such application were (and are) undertaken by the individual consumer.
But the continually increasing dependence on electricity in practically every one of life’s endeavors also called for improvements in the quality standards of its supply to which this updating is addressed. Notable events during this twenty-year period that helped in calling for better quality standards for those elements associated with reliability include the deregulation of electric (and other) utilities, the events of September 11, 2001, and the blackouts on northeast North America on August 14, 2004, in the London area and Italian peninsula within two weeks of each other. And on the positive side, the proliferation of automation brought about by the blooming electronic technology.
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Transmission systems have been the subject of the greater changes. Under deregulation, their role in the supply chain has been essentially reversed, from being the back up and peak supplier in generation-based systems, they become the main source of supply with generation reduced to a minimum if not entirely eliminated (to reduce capitalization and its effect on rate structures in a competitive market) Figure P-1. For economic and environmental reasons, transmission lines are situated in areas of sparse population making them subject to the vagaries of man and nature, tailor made for assaults by vandals and saboteurs. Finally, with transmission lines connected together in a grid, supposedly for better reliability and economy, failures causing the outage of a line may cause another of the lines to trip open from overload, causing another and another line to “cascade” open until total area blackout occurs.
It appears, quite unexpectedly, that the application of loop circuits substantially improves the reliability of such transmission lines. Loop circuits essentially provide a two way feed to the consumers, insuring them continuity of service should a fault develop on the circuit (except for those situated on the section on which the fault occurs) and especially if both halves of the loop circuit are not mounted on the same supporting structures. The reliability of the deregulated line is enhanced, and similarly, the damage inflicted by a saboteur or vandal may be limited to a section of the line.
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In the case of the transmission grid, supplanting it with a number of loop circuits not only removes the possibility of lines cascading open from overloads or instability, but permits the circuits to be loaded nearer their full capacity. Distribution systems have also been affected by these events, although not in the same manner of vulnerability as transmission systems. Where additional generation, and/or transmission was not available, or too great an expenditure to supply some additional distribution loads, distributed generation made its entry on the scene. Here small generating units, usually powered by small gas turbines, are connected directly to the distribution system, in the same manner as larger cogeneration units.
These units may be both consumer- or utility-owned and operated, and may constitute safety hazards. The chapter on street lighting is relegated to the appendices not only as essentially obsolete, but as an example of constant current circuitry. In its stead is a description of direct-current transmission line with its positive and negative features, but an excellent future feature in the electric supply scenario.