Correct Answer - Option 3 : Reactance relay
Reactance Relay:
- The reactance relay is a high-speed relay.
- It consists of two elements an overcurrent element and a current-voltage directional element.
- The current element developed positive torque and a current-voltage developed directional element which opposes the current element depending on the phase angle between current and voltage.
- Reactance type relay is very suitable as a ground relay for ground fault because its reach is not affected by fault impedance.
- Also, used for the protection of short transmission lines.
Overcurrent Relay:
- Which operates only when the value of the current is greater than the relay setting time.
- Depending on the time of operation the overcurrent relay is categorized as
- Instantaneous Overcurrent relay
- Inverse time Overcurrent Relay
- Definite Time Overcurrent Relay
- Inverse Definite Time Overcurrent Relay
- Very Inverse Definite Time Overcurrent Relay
- Extremely Inverse Definite Time Overcurrent Relay
- Instantaneous Overcurrent relay
Directional Relay:
Operates when the fault is driving power to flow in a particular direction. It senses the direction of the current flowing.
Non Directional Relay:
When there is a fault in the power system, power flows through fault. Non directional relays operate irrespective of direction of flow of current.
Impedance Relay:
- An impedance relay is a voltage-restrained overcurrent relay.
- The relay measures impedance up to the point of fault and gives tripping command if this impedance is less than the relay setting Z.
- Relay setting Z is known as replica impedance and it is proportional to the set impedance.
