Schweitzer Engineering Laboratories SEL-749M - The Basic Thermal Element; Figure F.1 Motor Thermal Limit Characteristic Plotted with Motor Starting Current; Figure F.2 Electrical Analog of a Thermal System

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F.3

Date Code 20080918 Instruction Manual SEL-749M Relay

Motor Thermal Element

The Basic Thermal Element

Figure F.1

Motor Thermal Limit Characteristic Plotted With Motor Starting Current

The Basic Thermal Element

Figure F.2 shows a simple electrical analog for a thermal system. The thermal

element includes:

➤ A heat source, modeled as a current source.

➤ A thermal capacitance, modeled as a capacitor.

➤ A thermal impedance to ambient, modeled as a resistor.

➤ A comparator to compare the present heat estimate, U, to the

thermal trip value.

Figure F.2 Electrical Analog of a Thermal System

0246810

100

Current in Multi

les of Full Load Am

Time in Seconds

1000

Overload

Running

Current

Locked Rotor

Starting

Current

Thermal Trip

Thermal Trip Value

—

Heat

Source

Courtesy of NationalSwitchgear.com

Main Page

Table of Contents3
List of Tables7
Preface15
Manual Overview15
Conventions16
Safety and General Information17
Overview21
Features21
Models, Options, and Accessories23
Applications24
Getting Started25
Table 1.1 SEL-749M Serial Port Settings26
Figure 1.1 Response Header26
Figure 1.2 STA Command Response-No Communications Card or Communications Card/Modbus RTU Protocol26
Figure 1.3 STA Command Response-Communications Card/Devicenet Protocol26
Section 2: Installation33
Overview33
Relay Placement33
I/O Configuration34
Table 2.1 Slot Allocations for Different Cards34
Figure 2.1 Relay Panel-Mount Dimensions34
Table 2.2 Communications Ports35
Table 2.3 Communications Card Interfaces and Connectors36
Table 2.4 Voltage Card Terminal Designation36
Table 2.5 Current Card Terminal Designation37
Table 2.6 I/O Card (3 DI/4 DO/1 AO) Terminal Allocation37
Table 2.7 I/O Card (8 DI) Terminal Allocation37
Rear-Panel Connections39
Figure 2.2 Rear-Panel Connections of Card Options39
Figure 2.3 PTC Input, EIA-232/EIA-485 Communications Card, 3 DI/4 DO/1 AO Card, and Voltage Card Options40
Figure 2.4 IRIG-B Input, Devicenet Card, 3 DI / 4 DO/1 AO Card, and Voltage Card Options41
Figure 2.5 IRIG-B Input, 8 DI Card, 3 DI /4 DO / 1 AO Card, and Voltage Card Options42
Table 2.8 PTC Cable Requirements44
Figure 2.6 Control I/O Connections44
AC/DC Control Connection Diagrams45
Table 2.9 Wire-Size Guide45
Figure 2.7 Output OUT103 Relay Output Contact Configuration45
Figure 2.8 OUT103 Contact Fail-Safe and Nonfail-Safe Options46
Figure 2.9 Contactor Application Using Factory Default Settings46
Figure 2.10 Voltage Connections47
Figure 2.11 AC Connections with Core-Balance CT48
Figure 2.12 Control Connections for Failsafe Tripping48
Figure 2.13 AC Connections for Star-Delta Starting49
Figure 2.14 Control Connections for Star-Delta Starting49
Figure 2.15 AC Connections for a Two-Speed Motor-Paralleled Cts50
Field Serviceability51
Section 3: PC Software53
Overview53
Table 3.1 SEL Software Solutions53
Table 3.2 AC SEL ERATOR Quickset SEL-5030 Software53
Setup54
Figure 3.1 Serial Port Communication Dialog Box54
Figure 3.2 Serial Port Communication Parameters Dialog Box54
Terminal55
Figure 3.3 Tools Menu55
Figure 3.4 Device Response to the ID Command55
Settings Database Management and Drivers56
Settings57
Table 3.3 File/Tools Menus58
Figure 3.5 Selection of Drivers58
Figure 3.6 Update Part Number59
Figure 3.7 New Setting Screen59
Figure 3.8 Expressions Created with Expression Builder61
Event Analysis62
Figure 3.9 Composite Screens for Retrieving Events62
Meter and Control63
Figure 3.10 Saving the Retrieved Event63
Figure 3.11 Device Overview Screen64
Figure 3.12 Control Screen65
Figure 3.13 Remote Operation Selection65
Available Help66
Section 4: Protection and Logic Functions67
Overview67
Application Data68
Main Settings (SET Command)69
Table 4.1 Identifier Settings69
Table 4.2 CT Configuration and Full Load Current Settings69
Table 4.3 Voltage Settings69
Basic Motor Protection70
Table 4.4 Overload (Thermal Model) Settings71
Figure 4.1 Thermal Overload Limits (Rating Method)72
Table 4.5 Thermal Limit Tripping Times in Seconds Vs. Multiples of Full-Load Amps (Service Factor = 1.01)74
Figure 4.2 Thermal Overload Limits (Curve Method)74
Table 4.6 Overload Settings (Alarm, Start Inhibit, Cooling, and RTD Bias)75
Table 4.7 Phase Overcurrent Settings76
Table 4.8 Neutral Overcurrent Settings77
Figure 4.3 Overcurrent Element Logic78
Table 4.9 Residual Overcurrent Settings79
Table 4.10 Load Jam Settings79
Figure 4.4 Ground Fault Protection Using Core-Balance CT79
Table 4.11 Undercurrent Settings80
Figure 4.5 Load-Jam Element Logic80
Figure 4.6 Undercurrent (Load-Loss) Logic80
Table 4.12 Current Imbalance Settings81
Table 4.13 Protection Disable Settings82
Table 4.14 Start Monitor Settings82
Figure 4.7 Current Imbalance Element Logic82
Table 4.15 Star-Delta Settings83
Table 4.16 Start Inhibit Settings83
Figure 4.8 Monitoring Starting Time83
Table 4.17 Phase Reversal Setting84
Figure 4.9 Phase Reversal Element Logic85
PTC/RTD-Based Protection86
Table 4.18 Speed Switch Settings86
Figure 4.10 Stalling During Starting86
Figure 4.11 Speed Switch Logic86
Voltage-Based Protection90
Table 4.21 Undervoltage Settings90
Table 4.22 Overvoltage Settings90
Figure 4.13 Undervoltage Element Logic91
Figure 4.14 Overvoltage Element Logic91
Table 4.24 Underpower Settings92
Figure 4.15 Reactive Power (VAR) Element Logic92
Table 4.25 Power Factor Settings93
Figure 4.16 Underpower Element Logic93
Figure 4.17 Power Factor Elements Logic94
Figure 4.18 Loss-Of-Potential (LOP) Logic95
Frequency and Load Control Settings96
Table 4.26 Frequency Settings96
Figure 4.19 Over- and Underfrequency Element Logic96
I/O Configuration97
Table 4.27 Load Control Settings97
Table 4.28 Analog Output Setting97
Table 4.29 Scaling of Analog Output98
Table 4.30 Trip Inhibit Settings98
Table 4.31 Trip and Close Logic Settings99
Figure 4.20 Stop/Trip Logic100
Figure 4.21 Thermal Element Lockout Logic101
Table 4.32 Motor Control Settings102
Figure 4.22 Motor State Logic102
Figure 4.23 Start Logic103
Logic Settings (SET L Command)104
Table 4.33 Settings Selected by SPEED2 Input104
Table 4.34 SEL OGIC Enable Settings104
Table 4.35 Latch Bits Equations Settings104
Table 4.37 Control Output Equations and Contact Behavior Settings105
Global Settings (SET G Command)106
Table 4.38 General Global Settings106
Table 4.39 Target Reset Setting106
Table 4.40 Setting Change Disable Setting106
Figure 4.24 Phase Rotation Setting106
Port Settings (SET P Command)107
Table 4.41 Front-Panel Serial Port F Settings107
Table 4.42 Rear-Panel Serial Port 3 Settings107
Table 4.43 Rear-Panel Serial Port 4 Settings107
Front-Panel Set (SET F Command)108
Table 4.44 Rear-Panel Devicenet Port Settings108
Table 4.45 General LCD Display Settings108
Table 4.46 Display Enable Settings109
Table 4.47 Target LED Settings109
Report Settings (SET R Command)110
Table 4.48 SER Trigger Settings110
Table 4.49 Event Report Settings110
Logic Functions111
Table 4.50 Motor Start Report Setting111
Table 4.51 SEL-749M Logic Inputs and Outputs111
Figure 4.25 Example Operation of Optoisolated Inputs IN101-IN102112
Figure 4.26 Example Operation of Optoisolated Inputs IN401-IN403112
Figure 4.27 Remote Control Switches Drive Remote Bits RB1-RB8113
Figure 4.28 Traditional Latching Relay114
Figure 4.29 Latch Control Switches Drive Latch Bits LT01-LT08114
Table 4.52 Operator Precedence116
Figure 4.32 Factory Default Contact Output OUT101 Operation117
Section 5: Metering and Monitoring119
Overview119
Metering119
Table 5.1 Measured Values120
Table 5.2 Thermal Meter Values120
Table 5.3 RTD Input Status Messages121
Figure 5.1 METER Command Report with Voltage Option121
Figure 5.2 METER T Command Report with Rtds121
Power Measurement Conventions122
Figure 5.3 Complex Power Measurement Conventions-Motor Action122
Motor Operating Statistics123
Figure 5.4 MOTOR Command Example123
Motor Start Report124
Motor Start Trending125
Figure 5.5 Motor Start Report Example125
Figure 5.6 Motor Start Trending Report Example126
Section 6: Settings127
Overview127
Table 6.1 Methods of Accessing Settings127
View/Change Settings Using the Front Panel128
Figure 6.1 Front-Panel Setting Entry Example129
View/Change Settings with Serial Port130
Table 6.2 SHOW Command Options130
Table 6.3 SET Command Options130
Setting Entry Error Messages131
Table 6.4 SET Command Editing Keystrokes131
Table 6.5 SET Command Format131
Table 6.6 Setting Interdependency Error Messages132
SEL-749M Settings Sheets133
Section 7: Communications149
Overview149
Communications Interfaces149
Table 7.1 SEL-749M Port Interfaces149
Table 7.2 EIA-232/EIA-485 Serial Port Pin Functions151
Figure 7.1 EIA-232 DB-9 Connector Pin Numbers151
Figure 7.2 SEL Cable C234A-SEL-749M to DTE Device151
Figure 7.3 SEL Cable C227A-SEL-749M to DTE Device152
Figure 7.4 SEL Cable C222-SEL-749M to Modem152
Figure 7.5 SEL Cable C272A. SEL-749M to SEL Communications Processor (Without IRIG-B Signal)152
Figure 7.6 SEL Cable C273A. SEL-749M to SEL Communications Processor (with IRIG-B Signal)152
Communications Protocol153
Table 7.3 PROTO Setting and Command Sets153
Figure 7.7 Port 4A EIA-485 Serial Port Connections153
SEL ASCII Protocol Details154
Table 7.4 Serial Port Automatic Messages155
Table 7.5 Command Response Header157
Table 7.6 Access Commands158
Table 7.8 ANALOG Command Format159
Table 7.9 BNAMES Command160
Table 7.11 CEVENT Command (Compressed Event Report)161
Table 7.12 CEVENT Command Format161
Table 7.13 CHISTORY Command (Compressed History)161
Table 7.14 CHISTORY Command Format161
Table 7.15 CONTROL Command162
Table 7.16 CONTROL Subcommands162
Table 7.17 CSTATUS Command (Compressed Status)162
Table 7.18 CSUMMARY Command162
Table 7.21 EVENT Command (Event Reports)163
Table 7.22 EVENT Command Format163
Table 7.24 HISTORY Command164
Table 7.25 IDENTIFICATION Command164
Table 7.26 IRI Command164
Table 7.27 L_D Command (Load Firmware)165
Table 7.28 METER K (Instantaneous Metering)165
Table 7.29 METER T (Thermal and RTD Metering)166
Table 7.30 MOTOR Command166
Table 7.31 MSR (Motor Start Report) Command167
Table 7.32 MST (Motor Start Trend) Command167
Table 7.33 PASSWORD Command167
Table 7.34 PAS Command Format167
Table 7.35 Factory Default Passwords for Access Levels 1 and 2168
Table 7.36 Valid Password Characters168
Table 7.37 QUIT Command168
Table 7.38 R_S Command (Restore Factory Defaults)169
Table 7.39 SER Command (Sequential Events Recorder Report)169
Table 7.40 SER Command Format169
Table 7.41 SET Command (Change Settings)170
Table 7.42 SET Command Format170
Table 7.43 SET Command Editing Keystrokes170
Table 7.44 SHOW Command (Show/View Settings)171
Table 7.45 SHOW Command Format171
Figure 7.8 SHOW Command Example171
Table 7.46 SNS Command172
Table 7.47 STATUS Command (Relay Self-Test Status)172
Table 7.48 STATUS Command Report and Definitions172
Figure 7.9 STATUS Command Example173
Table 7.49 STOP Command174
Table 7.50 STR Command174
Figure 7.10 Typical Relay Output for STATUS Command174
Table 7.52 TARGET Command (Display Relay Word Bit Status)175
Table 7.53 TARGET Command Format175
Table 7.54 Front-Panel Leds and the TAR 0 Command175
Figure 7.11 SUMMARY Command Example175
Table 7.55 TIME Command (View/Change Time)176
Table 7.56 TRIGGER Command (Trigger Event Report)176
Section 8: Front-Panel Operations177
Overview177
Front-Panel Layout177
Figure 8.1 Front-Panel Pushbuttons-Overview177
Human-Machine Interface178
Table 8.1 Front-Panel Automatic Messages178
Figure 8.2 Access Level Security Padlock Symbol179
Figure 8.3 Password Entry Screen179
Table 8.2 Front-Panel Pushbutton Functions180
Figure 8.4 Front-Panel Pushbuttons180
Figure 8.5 SEL-749M Front-Panel Menu Structure (Continued)181
Figure 8.6 RELAY Heading Example184
Operation and Target Leds185
Figure 8.7 Factory Default Front-Panel Leds185
Table 8.3 Possible Warning Conditions (Flashing TRIP LED)186
Section 9: Analyzing Events189
Overview189
Event Reporting190
Table 9.1 Event Types192
Figure 9.1 Example Event Summary192
Figure 9.2 Sample Event History194
Table 9.2 Event Report Current and Voltage Columns195
Table 9.3 Output, Input, and Protection, and Control Element Event Report Columns196
Figure 9.3 Example Standard 15-Cycle Event Report 1/4-Cycle Resolution199
Figure 9.4 Derivation of Event Report Current Values and RMS Current Values from Sampled Current Waveform200
Figure 9.5 Derivation of Phasor RMS Current Values from Event Report Current Values201
Sequential Events Recorder (SER) Report202
Table 9.4 Example SER Event Report Explanation202
Figure 9.6 Example Sequential Events Recorder (SER) Event Report202
Section 10: Testing and Troubleshooting203
Overview203
Testing Tools203
Table 10.1 Resultant Scale Factors for Inputs204
Figure 10.1 Low-Level Test Interface (J2 and J4)204
Commissioning Tests205
Figure 10.2 Three-Phase Wye AC Connections207
Figure 10.3 Three-Phase Open-Delta AC Connections207
Table 10.2 Serial Port Commands that Clear Relay Data Buffers208
Table 10.3 Phase Current Measuring Accuracy209
Figure 10.4 Current Source Connections209
Table 10.4 Current Unbalance Measuring Accuracy210
Figure 10.5 Wye Voltage Source Connections210
Table 10.5 Power Quantity Accuracy-Wye Voltages211
Figure 10.6 Delta Voltage Source Connections211
Periodic Tests (Routine Maintenance)212
Table 10.6 Power Quantity Accuracy-Delta Voltages212
Table 10.7 Periodic Relay Checks212
Self-Test213
Table 10.8 Relay Self-Tests213
Troubleshooting215
Factory Assistance215
Table 10.9 Troubleshooting215
Table A.1 Firmware Revision History217
Appendix A: Firmware and Manual Versions Firmware218
Instruction Manual219
Table A.2 Instruction Manual Revision History219
Appendix B: Firmware Upgrade Instructions221
Overview221
Upgrade Instructions221
Figure B.1 Firmware File Transfer Process222
Table C.1 Supported Serial Command Sets225
Appendix C: SEL Communications Processors SEL Communications Protocols226
Table C.2 Compressed ASCII Commands226
SEL Communications Processor227
Figure C.1 SEL Communications Processor Star Integration Network227
Table C.3 SEL Communications Processors Protocol Interfaces228
Figure C.2 Multitiered SEL Communications Processor Architecture228
SEL Communications Processor and Relay Architecture229
Figure C.3 Enhancing Multidrop Networks with SEL Communications Processors230
SEL Communications Processor Example231
Table C.4 SEL Communications Processor Port 1 Settings231
Table C.5 SEL Communications Processor Data Collection Automessages231
Figure C.4 Example of SEL Relay and SEL Communications Processor Configuration231
Table C.6 SEL Communications Processor Port 1 Automatic Messaging Settings232
Table C.7 SEL Communications Processor Port 1 Region Map232
Table C.8 Communications Processor METER Region Map232
Table C.9 Communications Processor TARGET Region233
Appendix D: Modbus RTU Communications Protocol235
Overview235
Communications Protocol235
Table D.1 Modbus Query Fields235
Table D.2 SEL-749M Modbus Function Codes236
Table D.3 SEL-749M Modbus Exception Codes236
Table D.4 03H Read Holding Register Command237
Table D.5 Responses to 03H Read Holding Register Query Errors237
Table D.6 04H Read Input Register Command238
Table D.7 Responses to 04H Read Input Register Query Errors238
Table D.8 06H Preset Single Register Command238
Table D.9 Responses to 06H Preset Single Register Query Errors238
Table D.10 10H Preset Multiple Registers Command239
Table D.11 10H Preset Multiple Registers Query Error Messages239
Table D.12 60H Read Parameter Information Command239
Table D.13 60H Read Parameter Descriptor Field Definition240
Table D.14 60H Read Parameter Conversion Field Definition240
Table D.15 Responses to 60H Read Parameter Information Query Errors241
Table D.16 61H Read Parameter Text Command241
Table D.17 61H Read Parameter Text Query Error Messages241
Table D.18 62H Read Enumeration Text Command242
Table D.19 61H Read Parameter Enumeration Text Query Error Messages242
Table D.20 7Dh Encapsulated Packet with Control Command242
Table D.21 7Dh Encapsulated Packet Query Errors243
Table D.22 7Eh NOP Command243
Modbus Register Map245
Table D.23 Modbus Register Map245
Table 4.19 PTC Settings267
Table 4.20 RTD Settings267
Table 4.23 VAR Settings268
Appendix E Devicenet271
Overview271
Devicenet Card271
Figure E.1 SEL-749M Motor Relay Back Panel View with Devicenet271
Features272
Figure E.2 Devicenet Card Component Overview272
Electronic Data Sheet273
Appendix F Motor Thermal Element275
Overview275
Purpose of Motor Thermal Protection276
The Basic Thermal Element277
Figure F.1 Motor Thermal Limit Characteristic Plotted with Motor Starting Current277
Figure F.2 Electrical Analog of a Thermal System277
Figure F.3 Typical Induction Motor Current, Torque, and Rotor Resistance Versus Slip278
Motor Starting Protection280
Figure F.4 Motor Starting Thermal Element280
Motor Running Protection281
Figure F.5 Motor Running Thermal Element with Resistance and Trip Level Undefined281
Figure F.6 Calculating the Normal Operating Energy by Using Locked Rotor Trip Times281
Interpreting Percent Thermal Capacity Values283
Thermal Element Trip-Time Equations283
Appendix G Relay Word Bits287
Overview287
Table G.1 SEL-749M Relay Word Bits287
Definitions288
Table G.2 Relay Word Bit Definitions for the SEL-749M288
Glossary295
Index301
Table 7.7 ANALOG Command301
Table 7.10 CASCII Command301
Table 7.19 Date Command302
Table 7.20 DNAMES Command302
Table 7.23 FILE Command302
Table 7.51 SUMMARY Command302
SEL-749M Relay Command Summary307

Schweitzer Engineering Laboratories SEL-749M - The Basic Thermal Element; Figure F.1 Motor Thermal Limit Characteristic Plotted with Motor Starting Current; Figure F.2 Electrical Analog of a Thermal System

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