Relay and Types
Relay
A relay is a device that detects the fault or abnormal condition in the power system and sends the signal to the circuit breaker for circuit interruption. Relay acts as the brain in the protection system.
Types
Relays are classified according to the following;
- Function
- Construction
- Time Characteristics
Let's discuss one by one in detail.
1. Types of Relay According to Their Functions
- Overcurrent
- Overvoltage
- Undervoltage
- Directional Power
- Differential Relay
- Distance Relay
- Under frequency
- Over frequency
- Earth Fault Relay
2. Types of Realy According to Their Construction
- Electromechanical or Electromagnetic Relay
- Static or Solid State Relay
- Digital or microprocessor-based Relay
3. Types of Relay According to Their Time Characteristics
- Instantaneous Relay
- Inverse Time Relay
- Definite Minimum Time Lag Relay
- Inverse Definite Minimum Time (IDMT) Relay