Siemens 7SR105 Rho User Manual page 175

Motor protection relay

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Contents

Section 1: Introduction ....................................................................................................................................... 4

1.1 Plant Design - Motors ........................................................................................................................ 4

Section 2: Protection Functions .......................................................................................................................... 5

2.1 Thermal Protection ............................................................................................................................ 5

2.1.2

Stall Protection (14) ............................................................................................................ 10

2.1.3

Start Protection (66) ........................................................................................................... 12

2.1.4

Phase Unbalance Protection (46)........................................................................................ 12

2.2 Setting Example - Thermal Protection............................................................................................... 13

2.3 Current Protection: Loss of load - Undercurrent (37)......................................................................... 17

2.4 Overcurrent (50-n, 51-n) .................................................................................................................. 18

2.4.2

Time Delayed Overcurrent (51-n) ........................................................................................ 18

2.5 Earth-fault Protection (50G/50N) ...................................................................................................... 18

2.6 High Impedance Restricted Earth Fault Protection(87REF) ............................................................... 19

2.7 Voltage Protection (27/59)................................................................................................................ 19

2.7.1

Under Voltage .................................................................................................................... 19

2.7.2

Over Voltage ...................................................................................................................... 20

2.8 Negative Phase Sequence (NPS) Overvoltage (47) .......................................................................... 20

2.9 Frequency (81) ................................................................................................................................ 20

2.10 Power Protection ............................................................................................................................. 20

2.10.1

Power (32) ......................................................................................................................... 20

2.10.2

Sensitive Power (32S) ........................................................................................................ 20

2.10.3

Power Factor (55) .............................................................................................................. 20

Section 3: Current Transformer (CT) Requirements .......................................................................................... 21

3.1 CT ratio ........................................................................................................................................... 21

3.2 Thermal and Overcurrent Protection CTs .......................................................................................... 21

3.3 Earth Fault Protection CTs ............................................................................................................... 21

3.4 Sensitive Power (32S) ..................................................................................................................... 21

Section 4: Supervision and Monitoring Functions .............................................................................................. 22

4.1 Breaking Capacity Limit (50BCL) ...................................................................................................... 22

4.2 Backspin Protection (81B) ................................................................................................................ 22

4.3 Current Transformer Supervision (60CTS) ........................................................................................ 22

4.4 Voltage Transformer Supervision (60VTS) ........................................................................................ 23

4.5 Trip-Circuit Supervision (74TCS) ...................................................................................................... 23

4.6 Trip/Close Circuit Supervision (74T/CCS) ......................................................................................... 24

4.6.1

Trip Circuit Supervision Connections ................................................................................... 24

4.6.2

Close Circuit Supervision Connections ................................................................................ 26

4.7 Circuit-Breaker Fail (50BF) ............................................................................................................... 27

4.8 Temperature Inputs (TEMP) ............................................................................................................. 28

Section 5: Control & Logic Functions ................................................................................................................ 30

5.1 User Defined Logic .......................................................................................................................... 30

5.1.1

Undervoltage Auto Restart (Restoration of Supply) .............................................................. 30

5.2 Motor Start/Stop .............................................................................................................................. 30

Section 6: Application Examples....................................................................................................................... 31

6.1 Function and Connection Diagrams .................................................................................................. 31

7SR105 Rho and 7SR17 Rho Applications Guide

Chapter 7 Page 2 of 31

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