وبلاگ فنی مهندسي برق و کامپیوتر

One can only appreciate the magnitude of effort required to develop a dictionary by actually experiencing it. Although I had written nine other books, I certainly did not know what I was getting into when in January of 1996 I agreed to serve as Editor-in- Chief for this project. Now, after 2 1/2 years I understand. Unlike other books that I have written, creating this dictionary was more a test of will and stamina and an exercise in project management than mere writing. And although I have managed organizations of up to 80 academics, nothing is more like herding cats” than motivating an international collection of almost 200 distinguished engineers, scientists, and educators scattered around the globe almost entirely via email. Yet, I think there is no other way to undertake a project like this. I still marvel at how Noah Webster must have managed to construct his English Dictionary without the benefits of modern communication. But this project, as much as it is a monument to individual will, is really the collaborative work of many brilliant and dedicated men and women. This is their ictionary and your dictionary

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The Art & Science Of Protective Relaying

WHAT IS PROTECTIVE RELAYING

We usually think of an electric power system in terms of its more impressive partsÐthe big generating stations, transformers, high-voltage lines, etc. While these are some of the basic elements, there are many other necessary and fascinating components Protective relaying is one of these

The role of protective relaying in electric-power-system design and operation is explained by a brief examination of the over-all background. There are three aspects of a power system that will serve the purposes of this examination. These aspects are as follows:

A. Normal operation

B. Prevention of electrical failure.

C. Mitigation of the effects of electrical failur

Relay

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ELECTRICAL EQUIPMENT HANDBOOK

ELECTRICAL EQUIPMENT HANDBOOK

INTRODUCTION

Electric power is generated most economically at 14 to 25 kV. System loads such as motors, lights, etc., require a voltage source of 440, 220, and 110 V. Transformers are needed to change the voltage level. They are also used for these reason

To reduce transmission losses between power plants and the load by stepping up the voltage. (When the voltage is stepped up, the current will be stepped down. This results reduction of transmission losses which are proportional to the square of the current.) Reduction in the diameter of the transmission line (amount of copper or aluminum) due to a reduction in the current flowing in the line. Typical transmission voltages are 13.2, 22, 66, 230, 345, and 500 kV. In general, the longer the distance, the higher the voltage used

machine