Protection Components

Protection systems typically consist of the following components:

[A] Current and voltage transformers, which reduce the high voltages and currents of the electrical power system to levels manageable by the relays.

[B] Protective relays that detect faults and initiate a trip or disconnection order.

[C] Circuit breakers that open and close the system according to relay and autorecloser commands.

[D] Batteries that provide power in the event of a system power disconnection, including DC supply systems (110VDC & 50VDC), chargers, and battery banks.

[E] Communication channels that enable the analysis of current and voltage at remote terminals and facilitate remote tripping of equipment.

[F] Control cables (2.5 mm², 4.0 mm², etc.) to ensure proper connections and operations.

Protection Types

Protection systems are classified into apparatus protection and system protection.

[A] Apparatus Protection
Apparatus protection focuses on identifying faults within the apparatus and providing the necessary protection. This type of protection can be further categorized into the following:

1. Transmission Line Protection and feeder protection




Transmission Line Protection




2. Transformer Protection




Transformer Protection




3. Generator Protection




Generator Protection






Generator Differential Protection




4. Motor Protection




Motor Protection




5. Busbar Protection




Busbar Protection




6. Capacitor Bank Protection




Capacitor Bank




7. Reactor Protection




Reactor Protection

[B] System Protection

System protection involves detecting when the system is nearing an unstable operating region and taking control actions to restore stability and/or prevent equipment damage. Instability in the system can result in partial or complete blackouts. Various devices, such as under-frequency relays, out-of-step protection, islanding systems, rate-of-change-of-frequency relays, reverse power flow relays, and voltage surge relays, are utilized for system protection. Control actions for system protection can be categorized into preventive or emergency actions.

NOTE

Protection types based on functions include Main protection and Backup protection. Main protection is designed to act first, swiftly and selectively clearing faults within the boundaries of the circuit section or element it protects.

Backup protection steps in if the main protection fails. It is configured with a time delay to allow the primary protection adequate time to respond. Backup protection also takes over when the main protection is faulty or undergoing maintenance.

Classes of Protective Relays
There are five basic classes of protective relays as shown in the following diagram: