Fundamentals of Electrical Switchgear
Learn the functions of switchgear and the protection of induction motors, busbars and more in this free online course.Publisher: NPTEL
CertificationView course modules
This free online course will provide you with the knowledge and understanding of the protection systems used to safeguard motors and busbars against faults in a power system network. Large high voltage (HV) induction motors are used to drive water pumps, fans, and other auxiliary items in industries and power generating systems. Therefore, the crucial roles they play cannot be overemphasized. The damage of a motor due to any type of fault results in a decrease in production, which results in a loss of revenue. Hence, the protection of induction motors is very essential for their reliable performance. In this course, you will first discover the different types of faults or abnormal conditions experienced in motors. Then, you will study the types of protection commonly used for each type of fault. Thereafter, you will be introduced to busbars and learn how to protect them against faults. A busbar is the junction of an electrical network where many lines are connected together. Whenever a fault occurs, the busbar protection scheme operates and trips all the transmission lines connected to the bus. You will learn why it is crucial to safeguard the busbar from damage and to prevent potentially prolonged power outages. You will therefore learn the various protection schemes for busbars as well as the different types of arrangement of busbars.
Next, protection against transients and surges will be discussed. You will learn about the sources of transients and surges, as well as the various protection schemes used for these faults. Furthermore, the arc interruption theory will be introduced, whereby Slepian’s theory, Cassie’s theory, and the theory of arc quenching will then be discussed. Quenching of an arc in an AC circuit requires a mechanism that converts the conduction path across the contacts of a circuit breaker into a non-conducting path, and this will be expounded in detail. The concept of current-chopping, which is the interruption of small inductive currents, will also be highlighted.
Finally, the different types of circuit breakers that fall under two broad categories of low voltage and high voltage circuit breakers will be described. Switches, fuses, miniature circuit breakers and earth leakage circuit breaker are part of the low voltage circuit breakers that will be broken down in this module. Then, you will learn about the air brake circuit breakers, oil circuit breakers, vacuum circuit breakers and the sulphur hexafluoride circuit breakers, which are collectively known as the high voltage circuit breakers. Too, you will learn the types of tests usually performed on relays, as well as the commissioning and maintenance of relays in the concluding part of the course. Protection of motors, busbars, and other critical components of a power system network is essential. Thus, this course will be of benefit to professionals in power system networks seeking to refresh or expand their knowledge base, as well as anyone considering a career in the field of power systems protection. So why wait? Start this course today!Start Course Now
Protection of Induction Motors and Busbars
Learning Outcomes - Protection of Induction Motors and Busbars
Protection of Induction Motors
Protection of Busbars
Protection against Transients and Surges
Lightning Arresters and Islanding
Lesson Summary - Protection of Induction Motors and Busbars
Circuit Breakers and Maintenance of Relays
Learning Outcomes - Circuit Breakers and Maintenance of Relays
Arc Interruption Theory in Circuit Breakers
Slepian’s and Cassie’s Theories
Factors Affecting RRRV, Recovery Voltage and TRV
Capacitive Current and Ratings of Circuit Breakers
Types of Circuit Breakers
Types of Relay Tests
Commissioning and Acceptance Tests
Lesson Summary - Circuit Breakers and Maintenance of Relays
By the end of this course, you will be able to:
- Explain the different types of protection used in induction motors.
- Discuss the various kinds of protection schemes for busbars.
- Summarize the protection schemes used for transients and surges.
- Explain the theory of arc quenching in an alternating current circuit.
- Evaluate the properties of the different types of circuit breakers.
- Outline the various tests carried out on relays.
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