04-06-2013, 04:05 PM
EVALUATION OF PROTECTIVE RELAYS
EVALUATION OF PROTECTIVE.pdf (Size: 43.54 KB / Downloads: 25)
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
REQUIRES PERIODICAL MAINTANENCE AND ADJUSTMENT.
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
ADJUSTMENT.
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.
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:
DISADVANTAGES ARE SAME AS ABOVE.