EVALUATION
OF
PROTECTIVE
RELAYS
PREPARED BY
GOPALA KRISHNA PALEPU ADE/MRT(PROTECTION)
1 ST GENERATION
FIRST GENERATION RELAYS :
THESE ARE ELECTRO MAGNETIC RELAYS
IN THIS NO OF ELECTROMAGNETIC RELAYS PROVIDED FOR ARRIVING A SPECIFIC FUNCTION i.e EACH FUNCTION OF THE SCHEME HAVING A SEPARATE RELAY. COMBINING ALL IS CALLED ONE PROTECTION FUNCTION. NO OF RELAYS ARE MORE AND SPACE OCUPATION IS MORE AND INTER CONNECTION WIRING DIAGRAM IS MORE.
DISADVANTAGES: ELECTROMECHANICAL RELAYS HAVE A LOT OF MECHANICAL PARTS, WHICH MAY BECOME CLOGGED WITH DIRT OR CORRODED DUE TO ENVIRONMENTAL CONDITIONS, AFFECTING BOTH OPERATION, CALIBRATION AND MOVEMENT OF THE DISKS. IT
1 ST GENERATION
NEXT MODIFICATION :
ELECTRO MAGNETIC RELAYS WITH STATIC COMPONENTS
IN THIS SOME OF THE FUNCTIONS ARE DERIVED FROM STATIC COMPONENTS PROVIDED ON THE PCB. IN THIS QUANTITY OF ELECTROMAGNETIC RELAYS ARE REDUCED. COMBINING ALL IS CALLED ONE PROTECTION FUNCTION. QUANTITY OF RELAYS ARE REDUCED AND SPACE OCUPATION IS REDUCED SOME WHAT.
DISADVANTAGES: THE PCBs ARE MADE WITH TRANSISTORS AND ARE BROUGHTOUT ITEMS WITH DIFFERENT MAKE. AFTER SOME TIME THESE ARE TO BE REPLACED FOR CORRECT OPERATION WITHOUT DRIFT. THE PCBs & COMPONENTS PERFORMANCE MAY BE AFFECTED DUE TO DIST & DIRT. IT REQUIRES PERIODICAL MAINTANENCE AND
2 ND GENERATION
SECOND GENERATION RELAYS :
STATIC RELAYS WITH TRANSISTORS
IN THIS ALL OF THE FUNCTIONS ARE DERIVED FROM STATIC COMPONENTS PROVIDED ON THE PCB. IN THIS INITIALLY EACH FUNCTION IS DERIVED WITH SEPATATE STATIC RELAY. QUANTITY OF STATIC RELAYS ARE MORE BUT SPACE OCCUPATION IS LESS. COMBINING ALL IS CALLED ONE PROTECTION FUNCTION. INTER CONNECTION WIRING DIAGRAM IS STILL NOT REDUCED.
DISADVANTAGES: Static relays generally employ a lot of electronic components made by other manufacturers. If these electronic components are not tested with rigorous quality control, the chances of failure of components during the relay life time may exist. A reliable DC power source within the relay, to electronically measure circuits has to be generated from available external power sources. Most of the static relays employ series, shunt, or switched mode power supply designs. For a variety of reasons, if these power supplies fail, the measuring circuits are inoperative and the relay is dead for any measurements. No protection is available to the network. Most of the static relays in use do not have the means to detect the failure of power supply and initiate an alarm. It requires periodical Maintanence.
2 ND GENERATION
NEXT MODIFICATION :
STATIC RELAYS ON SINGLE PCB
IN THIS ALL OF THE FUNCTIONS ARE DERIVED FROM STATIC COMPONENTS PROVIDED ON THE PCB. IN THIS ALL STATIC RELAYS ARE TAKEN TO ONE MASTER PCB AND EACH FUNCTION PCB WILL BE ADD ON CARD TYPE. SO TOTAL RELAY IS ONE BUT FOR EVERY FUNCTION IS PCB IS AVAILABLE AND CONNECTED TO MAIN PCB. SPACE OCCUPATION IS LESS. COMBINING ALL IS CALLED ONE PROTECTION FUNCTION. NO INTER CONECTION WIRING. THIS IS PART OF MAIN PCB.
DISADVANTAGES:
3 ND GENERATION
THIRD GENERATION RELAYS :
STATIC RELAYS WITH ICs
IN THIS NO OF COMPONENTS ARE REDUCED AND BROUGHT OR BUILT IN ONE INTEGRATED CHIP. DUE TO THIS THE RELAY SIZE IS REDUCED AND SOME OF THE FUNCTIONS ALSO TAKEN IN TO ONE INTEGRATED CHIP. THIS ALSO BUILT IN ONE PCB. ALL OF THE FUNCTIONS ARE DERIVED FROM STATIC COMPONENTS PROVIDED ON THE PCB. IN THIS ONLY MASTER PCB IS AVAILABLE, NO SEPARATE PCB FOR EACH FUNCTION , ALL ARE INTEGRATED IN ONE PCB. PROBLEMS ARE SOME WHAT REDUCED. SPACE OCCUPATION IS LESS. ONE PROTECTION FUNCTION ONLY ONE RELAY AND ALL FUNCTIONS ARE INTEGRATED. NO INTER CONNECTION WIRING DIAGRAM.
3 ND GENERATION
NEXT MODIFICATION :
SEMI NUMERIC RELAYS
IN THIS SOME FUNCTIONS ARE CAN BE PROGRAMMABLE AND INTERFACE THROUGH PC. SOME ICs ARE HAVING THE FACILITY TO INTERACT THROUGH COMMUNICATION PORT. IT IS SOME WHAT MODIFICATION TO IC BASED RELAYS. IN THIS SOME FUNCTION CAN BE ENABLED AND DISABLED, BASED ON THE REQUIREMENT.
