29-12-2012, 05:28 PM
STATIC RELAYS
[attachment=45846]
Introduction
It has no armature/other moving element.
Response can be obtained without mechanical motion.
Electronic Circuits Commonly Used in Static Relays
1.Auxiliary DC voltage supply: Usually a dc-dc converter is used.
2.Full wave bridge rectifier: Used to filter the input from ac to dc.
3.Smoothing circuits: Comprises of RC/RL networks to smoothen the rectifier output.
4.Voltage stabilization Circuitry
5.Time delay Circuit: Used for introducing a very short delay using RC circuits.
Advantages of Static Relays
High degree of accuracy & High speed.
Low power consumption-No moving parts.
Testing methods are simple.
No moving contacts – No problems of arcing, contact bounce & replacement.
Self-supervision.
Static relays can ‘THINK’.
Applications
Dept. of Electrical & Electronics Engg., BVBCET, Hubli
Used in ultra-high speed protection schemes of EHV – AC lines utilizing distance protection.
Used in over current & earth fault protection schemes.