17 June 2024

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Generator protection functions

The generator protection functions with their English and Dutch description, including ASCI/IEEE device codes and IEC symbols, are implemented in a table.

The first colomn contains the ANSI/IEEE Device Numbers that are worldwide most commonly used. The second column is derived from IEC 60617 (part 7). In older drawings this standard is used widely. IEC 61850 is a modern, globally accepted standard for communication in electrical substations via Ethernet. In the table below we present the ‘Logical Node Class’. For further specification, a pre-code is used.


IEEE C37-2 IEC 60617 IEC 61850 Protective Function Beveiligingsfunctie
21 Z < PDIS Distance Distantie
24 V/Hz > PVPH V/Hz (Overexcitation) V/Hz (Overbekrachtiging)
26 T > PTTR Overtemperature Temperatuurbewaking
27 U < PTUV Undervoltage Onderspanning
27TN   PHIZ 3rd Harmonic Neutral Undervoltage Onderspanning in sterpunt, 3e harmonische
32R -P > PDOP Reverse Power (Motoring) Terugwatt
37, 32LF P < PDUP Underpower (Low Forward Power) Laag wattvermogen
38   PTTR Bearing Overtemperature Temperatuurbewaking lager
39     Bearing High Vibration Lagertrillingsbewaking
40 X < PDIS Loss of Field Veldverlies
46 I2 > PTOC Negative Sequence Overcurrent Stroomonbalans (asymmetrie)
49 T > PTTR Stator Thermal (RTD or replica) Temperatuurbewaking stator (RTD of model)
50/27   PIOC Inadvertent Energizing Onbedoelde inschakeling
50 I >> PIOC Instantaneous Overcurrent Overstroom, onvertraagd
50DT I > PIOC Definite Time Overcurrent Onafhankelijk maximaal stroomtijd
51 I > PTOC (Inverse) Time Overcurrent Afhankelijk maximaal stroomtijd
51N Io > PTOC Neutral Overcurrent (Ground Fault) Overstroom in nulleider (aardfout)
51V U↗I> PVOC Voltage Dependent Overcurrent Spanningsafhankelijk afhankelijk maxIt
58     Diode Failure Diodefout
59 U > PTOV Overvoltage Overspanning
59N Uo > PTOV Neutral Overvoltage (Ground Fault) Overspanning in sterpunt (aardfout)
64F   PRTR Field (Rotor) Ground Fault Rotoraardfout
64S     100% stator ground fault with subharmonic voltage injection 100% stator aardfout met subharm. spanningsinjectie
67N   PSDE Directional Ground Overcurrent Richtingsgevoelig aardfoutstroom
76 Ife >   Excitation Field Overcurrent Maximaal bekrachtigingsstroom
78   PPAM Out of Step – Pole Slip Poolslip
81U f < PTUF Underfrequency Onderfrequentie
81O f > PTOF Overfrequency Overfrequentie
81R df/dt> PFRC Rate of Frequency Change Frequentieverloop
87G Id > PDIF Generator Differential Generatordifferentiaal
87T Id > PDIF Transformer Differential Transformatordifferentiaal
87U Id > PDIF Unit Differential Blokdifferentiaal
87GN, 64REF Idn > PDIF Generator Ground Differential Nulstroomdifferentiaal


Some other functions that are not directly protective functions, but functions that can be integrated in the generator protection system are given in the table below.

IEEE C37-2 Afk. IEC 61850 Function Functie
11G MGPS   Multifunction generator protection system Multifunctioneel generator beveiligingsrelais
25 SYNC RSYN Synchronism-check Synchrocheck
41 FCB   Field Circuit Breaker Veldschakelaar
50BF BF RBRF Breaker Failure Fout in schakelaar
52G GCB XCBR Generator Circuit Breaker Generatorschakelaar
52L LCB XCBR Line Circuit Breaker Koppelschakelaar
  CTS LLN0 Current Transformer Supervision Verlies van meetstroom
60-FL VTS LLN0 Voltage Transformer Supervision (Fuse Loss) Verlies van meetspanning
74TC TCS SCBR Trip circuit supervision Tripcircuitbewaking
86 LR   Hand-reset Lockout Relay Houdrelais met handmatige reset


See also



  • IEEE C37.2-2008 – IEEE Standard Electrical Power System Device Function Numbers, Acronyms, and Contact Designations
  • IEEE C37.102-2006 – IEEE Guide for AC Generator Protection
  • IEC 60617-7 – Graphical symbols for diagrams. Part 7: Switchgear, controlgear and protective devices (withdrawn)
  • IEC 61850 – Communication Networks and Systems in Substations