ANSI CODES for protection devices
| List of Device Numbers and Acronyms | |
| 1 - Master Element | 51 - AC Inverse Time Overcurrent Relay | 
| 2 - Time Delay Starting or Closing Relay | 52- AC Circuit Breaker | 
| 3 - Checking or Interlocking Relay | 53 - Exciter or DC Generator Relay | 
| 4 - Master Contactor | 54 - Turning Gear Engaging Device | 
| 5 - Stopping Device | 55 - Power Factor Relay | 
| 6 - Starting Circuit Breaker | 56 - Field Application Relay | 
| 7 - Rate of Change Relay | 57 - Short-Circuiting or Grounding Device | 
| 8 - Control Power Disconnecting Device | 58 - Rectification Failure Relay | 
| 9 - Reversing Device | 59 - Overvoltage Relay | 
| 10 - Unit Sequence Switch | 60 - Voltage or Current Balance Relay | 
| 11 - Multi-function Device | 61 - Density Switch or Sensor | 
| 12 - Overspeed Device | 62 - Time-Delay Stopping or Opening Relay | 
| 13 - Synchronous-speed Device | 63 - Pressure Switch | 
| 14 - Underspeed Device | 64 - Ground Detector Relay | 
| 15 - Speed - or Frequency, Matching Device | 65 - Governor | 
| 16 - Data Communications Device | 66 - Notching or Jogging Device | 
| 17 - Shunting or Discharge Switch | 67 - AC Directional Overcurrent Relay | 
| 18 - Accelerating or Decelerating Device | 68 - Blocking or "Out-of-Step" Relay | 
| 19 - Starting to Running Transition Contactor | 69 - Permissive Control Device | 
| 20 - Electrically Operated   Valve | 70 - Rheostat | 
| 21 - Distance Relay | 71 - Liquid Level Switch | 
| 22 - Equalizer Circuit Breaker | 72 - DC Circuit Breaker | 
| 23 - Temperature Control Device | 73 - Load-Resistor Contactor | 
| 24 - Over Fluxing Relay | 74 - Alarm Relay | 
| 25 - Synchronizing or   Synchronism-Check Device 25A - Automatic Synchronizing relay | 75 - Position Changing Mechanism | 
| 26 - Apparatus Thermal Device | 76 - DC Overcurrent Relay | 
| 27 - Under-voltage Relay 27P- Phase UV relay 27N/27G - Neutral/Ground UV relay 27A- Aux. UV relay | 77 - Telemetering Device | 
| 28- Flame Detector | 78 - Phase-Angle Measuring Relay | 
| 29 - Isolating Contactor or Switch | 79 - AC Reclosing Relay | 
| 30- Annunciator Relay | 80 - Flow Switch | 
| 31 - Separate Excitation Device | 81 - Frequency Relay | 
| 32R- Reverse Power Relay 32F- Low Forward Power Relay | 82 - DC Reclosing Relay | 
| 33 - Position Switch | 83 - Automatic Selective Control or Transfer Relay | 
| 34 - Master Sequence Device | 84 - Operating Mechanism | 
| 35 - Brush-Operating or Slip-Ring Short-Circuiting Device | 85 - Communications,Carrier or Pilot-Wire Relay | 
| 36 - Polarity or Polarizing Voltage Devices | 86 - Lockout Relay | 
| 37 - Undercurrent or Under-power Relay | 87 - Differential Protective Relay | 
| 38 - Bearing Protective Device | 88 - Auxiliary Motor or Motor Generator | 
| 39 - Mechanical Condition Monitor | 89 - Line Switch | 
| 40 - Loss of field (Field Failure or Loss of Excitation. | 90 - Regulating Device | 
| 41 - Field Circuit Breaker | 91 - Voltage Directional Relay | 
| 42 - Running Circuit Breaker | 92 - Voltage and Power Directional Relay | 
| 43 - Manual Transfer or Selector Device | 93 - Field Changing Contactor | 
| 44 - Unit Sequence Starting Relay | 94 - Tripping or Trip-Free Relay | 
| 45 - Abnormal Atmospheric Condition Monitor | 95 - For specific applications where other numbers are not suitable | 
| 46 - Reverse-phase or Phase-Balance Current Relay | 96 - For specific applications where other numbers are not suitable | 
| 47 - Phase-Sequence or Phase-Balance Voltage Relay | 97 - For specific applications where other numbers are not suitable | 
| 48 - Incomplete Sequence Relay | 98 - For specific applications where other numbers are not suitable | 
| 49 - Machine or Transformer, Thermal Relay | 99 - For specific applications where other numbers are not suitable | 
| 50 - Instantaneous Overcurrent Relay | AFD - Arc Flash Detector | 
| DFR - Digital Fault Recorder | CLK - Clock or Timing Source | 
| ENV - Environmental Data | DDR - Dynamic Disturbance Recorder | 
| HIZ - High Impedance Fault Detector | PDC - Phasor Data Concentrator | 
| HMI - Human Machine Interface | PMU - Phasor Measurement Unit | 
| HST - Historian | PQM - Power Quality Monitor | 
| LGC - Scheme Logic | RIO - Remote Input/Output Device | 
| MET - Substation Metering | RTU - Remote Terminal Unit/Data Concentrator | 
| SER - Sequence of Events Recorder | |
| TCM - Trip Circuit Monitor | |
| SOTF - Switch On To Fault For Description of all codes visit perticular pages...not full completed....as soon as I will finish I will post remaining also. | 
 
