Introduction to Power System Protection

Power system protection systems have three basic components: Instrument transformers, Relays, Circuit breakers

The function of the CT is to reproduce in its secondary winding a current I' that is proportional to the primary current I. The CT converts primary currents in the kiloamp range to secondary currents in the 0-5 ampere range for convenience of measurement.

The function of the relay is to discriminate between normal operation and fault conditions. The OC relay in Figure 2 has an operating coil, which is connected to the CT secondary winding, and a set of contacts. When |I'| exceeds a specified ''pickup'' value, the operating coil causes the normally open contacts to close. When the relay contacts close, the trip coil of the circuit breaker is energized, which then causes the circuit breaker to open.

System-protection components have the following design criteria:
• Reliability: Operate dependably when fault conditions occur, even after remaining idle for months or years. Failure to do so may result in costly damages.
• Selectivity: Avoid unnecessary, false trips.
• Speed: Operate rapidly to minimize fault duration and equipment damage. Any intentional time delays should be precise.
• Economy: Provide maximum protection at minimum cost.
• Simplicity: Minimize protection equipment and circuitry.

Since it is impossible to satisfy all these criteria simultaneously, compromises must be made in system protection.

The book consists from the following sections:

1. Chapter 1: Power System Faults:
2. Chapter 2: Instrument Transformers.
3. Chapter 3: Overcurrent and Earth Fault Protection Relays.
4. Chapter 4: Radial System Protection.
5. Chapter 5: Zones of Protection.
6. Chapter 6: Differential Relays.
7. Chapter 7: Distance Relays.
8. Chapter 8: Transformer Protection.
9. Chapter 9: Generator Protection.
10. Chapter 10: Busbar Protection.
11. Chapter 11: Circuit Breakers.
12. Chapter 12: Fuses.

13. Chapter 13: References.

    I am Dr. Hidaia Mahmoud Mohamed Alassouli. I completed my PhD degree in Electrical Engineering from Czech Technical University by February 2003, and my M. Sc. degree in Electrical Engineering from Bahrain University by June 1995. I completed also one study year of most important courses in telecommunication and computer engineering courses in Islamic university in Gaza. So, I covered most important subjects in Electrical Engineering, Computer Engineering and Telecommunications Engineering during my study. My nationality is Palestinian from gaza strip.

    I obtained a lot of certified courses in MCSE, SPSS, Cisco (CCNA), A+, Linux.
    I worked as Electrical, Telecommunicating and Computer Engineer in a lot of institutions. I worked also as a computer networking administrator.

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