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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 1 OVERCURRENT PROTECTION

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 1

OVERCURRENT PROTECTION

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 2

TIME-CURRENT CHARACTERISTICS

Definite-time Overcurrent Relay

Instantaneous Overcurrent Relay

Inverse-time Overcurrent Relay

Inverse Definite-time Overcurrent Relay

Very Inverse-time Overcurrent Relay

Extremely Inverse-time Overcurrent Relay

Special characteristics

Method of Defining shape of Time-current Characteristics

Technique to Realise Various Time-current Characteristics

using Electromechanical Relays

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 3

Definite-time and Inverse-time characteristic of Overcurrent relays

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 4

Very Inverse-time Overcurrent Relay

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 5

Extremely Inverse-time Overcurrent Relay

5 I.D.M.T., very inverse-time and extremely inverse-time characteristics

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 6

Method of defining shape of Time-current characteristics

The general expression for time-current characteristics is given

by

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 7

Current settings

Standard I.D.M.T ccharacteristic

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 8

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 9

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 10

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 11

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 12

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 13

Over current protection schemes

Time-graded system

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 14

Current-graded system

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 15

A combination of time and current grading

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 16

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 17

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 18

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 19

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 20

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 21

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 22

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 23

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 24

Reverse power or Directional Relay

24 Induction disc type directional relay

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 25

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 26

26 Induction cup type directional relay

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 27

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 28

Directional relay connections

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 29

Directional over current relay

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 30

Protection of parallel feeders

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 31

Protection of ring mains

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 32

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 33

EARTH FAULT AND PHASE FAULT PROTECTION

Earth fault relay and over current relay

Earth fault Protective schemes

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 34

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 35

Combined Earth Fault and Phase fault protective

scheme

35 Two over current and one earth fault relay

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 36

36 Two over current and one earth fault relay

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 37

Directional earth fault relay

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 38

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Five limb VT

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 39

Static over current relay

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 40

Instantaneous over current relay

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 41

Definite Time over current relay

41 Block diagram of Definite Time over current relay

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 42

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 43

Inverse-time over current relay

43 Block diagram of Inverse-time over current relay

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 44

Directional over current relay

44 Block diagram of Directional over current relay

S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 45

Numerical over current relay

Microprocessor-based over current relay

Microcontroller-based over current relay

Digital Signal Processor (DSP)-based relays

Field Programming Gate Arrays (FPGA)-based over current

relays.

Artificial Neural Network (ANN) based numerical relays

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 46

REVIEW QUESTIONS

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S.Padmini A.P (Sr.G)/EEE Dept. of EEE SRM University Page 47

Contd....

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