Primary relay or primary protection relay is the first line of power system protection whereas backup relay is operated only when primary relay fails to be operated during a fault. Hence backup relay is slower in action than primary relay.
Which relays are used for the protection of EHV lines?
There are several types of circular impedance relay: full impedance circle, directional impedance circle, and offset impedance circle. It is the most widely used impedance relay in traditional relay protection.
What are the types of protection relays?
Basic classification of protective relays includes:
- Electromagnetic Relays: Armature. Induction cup / induction disc.
- Static Relays: Analog input signals are processed by solid state devices.
- Digital / Numerical Relays: Uses programmable solid state devices based on digital signal processing.
Which is most suitable relay for protection of long lines?
Distance relays: Power swings are more common in long transmission lines because of load variations. The relay which is less affected due to power swings is selected for the protection of long transmission lines. Mho relay is less affected due to power swings and also less affected due to load encroachment.
Which relay is used for long EHV lines Mcq?
Mho relay comes in the category of the distance relay protection scheme. The mho type relay is most suited for long lines because there are more chances of severe synchronizing power surges on the system.
Which is an example of relay?
A relay allows circuits to be switched by electrical equipment: for example, a timer circuit with a relay could switch power at a preset time. For many years relays were the standard method of controlling industrial electronic systems.
What are the requirements of protection of lines?
The protection scheme must satisfy the following requirements: a) Under normal conditions the breakers are not tripped. b) Under fault conditions only the breakers closest to the fault on the source side are tripped. c) If the closest breaker fails to operate, the next breaker closer to the source should trip.