Comparison of Different Type Relay:

Characteristic Electro Mechanical Relay Static Relay Digital Relay Numerical Relay
Technology Standard 1st generation Relays. 2nd generation Relays. Present generation Relays. Present generation Relays.
Operating Principle They use principle of electromagnetic principle. In this relays transistors and IC’s r been used They use Microprocessor. Within built software with predefined values They use Microprocessor. Within built software with predefined values
Measuring elements/ Hardware Induction disc,Electromagnets, Induction cup, Balance Beam R, L, C, Transistors, Analogue ICs comparators Microprocessors, Digital ICs, Digital Signal Processors Microprocessor s,Digital ICs, DigitalSignal processors
Measuring method Electrical Qtysconverted intomechanical force, torque Level detects,comparison withreference value in analogue Comparator A/D conversion,Numericalalgorithmtechniques A/D conversion,Numericalalgorithmtechniques
Surrounding Environment Depend upon gravitation and the value changes to the surrounding magnetic fields also. There value may vary with respect to temperature also.
Relay Size Bulky Small Small Compact
Speed of Response Slow Fast Fast Very Fast
Timing function Mechanical clock works, dashpot Static timers Counter Counter
Time of Accuracy Temp .Dependant Temp. Dependant Stable Stable
Reliability High Low High High
Vibration Proof No Yes Yes Yes
Characteristics Limited Wide Wide Wide
Requirement of Draw Out Required Required Not Required Not Required
CT Burden High Low Low Low
CT Burden 8 to 10 VA 1 VA <0.5 VA <0.5 VA
Reset Time Very High Less Less Less
Auxiliary supply Required Required Required Required
Range of settings Limited Wide Wide Wide
Isolation Voltage Low High High High
Function Single Function Single Function Multi Function Single Function
Maintenance Frequent Frequent Low Very Low
Resistance 100 mille ohms 10 Ohms 10 Ohms 10 Ohms
Output Capacitance < 1 Pico Farad > 20 Pico Farads > 20 Pico Farads > 20 Pico Farads
Deterioration due to Operation Yes No No No
Relay Programming No Partially Programmable Programmable
SCADA Compatibility No No Possible Yes
Operational value indication Not Possible Possible Possible Possible
Visual indication Flags, targets LEDs LEDs, LCD LEDs, LCD
Self monitoring No Yes Yes Yes
Parameter setting Plug setting, dial setting Thumb wheel,dual in line switches Keypad for numeric values,through computer Keypad for numeric values,through computer
Fault Disturbance Recording Not possible Not possible possible possible

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