في عالم الهندسة الكهربائية، وخاصة في مجال أنظمة الطاقة، يحمل مصطلح "الكتاب البني" مكانة هامة. لا يشير هذا المصطلح إلى كتاب مادي بل هو لقب لمجموعة من المعايير والارشادات الفنية المعروفة باسم كتب IEEE الملونة. توفر هذه الوثائق معلومات شاملة حول مجموعة واسعة من مواضيع أنظمة الطاقة، وتقدم إرشادات للمهندسين والمهنيين العاملين في تصميم وتشغيل وصيانة أنظمة الطاقة الكهربائية.
يشير الكتاب البني تحديداً إلى معيار IEEE 242، والذي يُطلق عليه غالباً اسم "ممارسة IEEE الموصى بها لحماية وتنسيق أنظمة الطاقة الصناعية والتجارية". ركزت هذه الوثيقة، التي نُشرت في عام 1986 وتم تحديثها عدة مرات منذ ذلك الحين، على حماية أنظمة الطاقة. تغطي جوانب مختلفة، بما في ذلك:
بالإضافة إلى الكتاب البني، تشمل كتب IEEE الملونة مجموعة أوسع من المعايير التي تغطي مجالات مختلفة داخل أنظمة الطاقة، مثل:
تشكل هذه المنشورات الملونة موردًا هامًا للمهندسين الكهربائيين والمهنيين، وتوفر إطارًا شاملاً لتصميم وتشغيل وصيانة أنظمة الطاقة الكهربائية الآمنة والموثوقة. يبرز الكتاب البني، على وجه الخصوص، كدليل أساسي لفهم وتطبيق مبادئ الحماية، لضمان سلامة ومقاومة أنظمة الطاقة ضد التحديات المختلفة.
Instructions: Choose the best answer for each question.
1. What is the full name of the "Brown Book"?
a) IEEE Std 141 - Recommended Practice for Electric Power Distribution for Industrial Plants.
Incorrect. This is the Blue Book.
Incorrect. This is the Red Book.
Correct! This is the full name of the Brown Book.
Incorrect. This is the Yellow Book.
2. Which of the following is NOT a topic covered in the Brown Book?
a) Protective Relaying
Incorrect. This is a key topic in the Brown Book.
Incorrect. This is another major focus of the Brown Book.
Correct! While the Brown Book deals with fault protection, it doesn't delve into detailed fault analysis.
Incorrect. This is a key aspect of the Brown Book.
3. The Brown Book provides guidance for selecting relay settings. What is the primary reason for this?
a) To ensure all relays trip simultaneously in case of a fault.
Incorrect. While simultaneous tripping can be desirable in some cases, it's not the primary reason for relay setting coordination.
Correct! Proper relay settings ensure that only the necessary equipment is isolated, minimizing damage and service interruption.
Incorrect. Different relay settings are necessary to achieve coordinated tripping across the system.
Incorrect. While relay coverage is important, the primary focus is on achieving coordinated protection.
4. Which of the following IEEE Color Books focuses on grounding of power systems?
a) Blue Book
Incorrect. This book focuses on power distribution for industrial plants.
Correct! The Red Book is specifically about grounding of industrial and commercial power systems.
Incorrect. This book deals with harmonic control in power systems.
Incorrect. This book focuses on the design of reliable industrial and commercial power systems.
5. What is the primary purpose of the IEEE Color Books?
a) To provide a comprehensive guide for designing electrical power systems.
Correct! The Color Books offer a broad framework for various aspects of power systems design, operation, and maintenance.
Incorrect. While safety is a key concern, the Color Books mainly provide guidance and best practices.
Incorrect. The Color Books are primarily focused on system-level design and operation, not component specifications.
Incorrect. While the Brown Book includes fault protection, it doesn't delve into detailed diagnosis and repair procedures.
Scenario:
A 10 MVA transformer is protected by an overcurrent relay (OC Relay) with a setting of 500A and a time delay of 0.5 seconds. The downstream feeder is protected by a fuse with a melting time-current characteristic shown in the following table:
| Current (A) | Melting Time (s) | |---|---| | 1000 | 10 | | 1500 | 2 | | 2000 | 0.8 | | 2500 | 0.4 |
Task:
Determine if the OC Relay and the fuse are properly coordinated. Explain your reasoning.
The relay and the fuse are **not properly coordinated**. Here's why:
1. **Fault Current:** Consider a fault current of 1500A on the feeder. The fuse will melt in 2 seconds. However, the OC relay will only trip after 0.5 seconds (its time delay) plus the time it takes to reach its pick-up current (500A). This time delay is likely significantly less than 2 seconds.
2. **Coordination Failure:** In this scenario, the relay would trip before the fuse blows, meaning the relay is not protecting the transformer from the fault. The fault current will flow through the transformer, potentially causing damage.
To achieve proper coordination, the relay time delay needs to be adjusted to ensure the fuse blows first, clearing the fault before the relay trips. This would typically involve increasing the relay's time delay or reducing the fuse's melting time.
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