3.9.2 Overfrequency protection SAPTOF (81)Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberOverfrequency protection SAPTOFf >SYMBOL-O V1 EN813.9.2.1 ApplicationOverfrequency protection function SAPTOF (81) is applicable in all situations, wherereliable detection of high fundamental power system frequency is needed. The powersystem frequency, and rate of change of frequency, is a measure of the unbalancebetween the actual generation and the load demand. High fundamental frequency in apower system indicates that the available generation is too large compared to the powerdemanded by the load connected to the power grid. SAPTOF (81) detects suchsituations and provides an output signal, suitable for generator shedding, HVDC-set-point change and so on. SAPTOF (81) is very sensitive and accurate and can also beused to alert operators that frequency has slightly deviated from the set-point, and thatmanual actions might be enough.3.9.2.2 Setting guidelinesAll the frequency and voltage magnitude conditions in the system where SAPTOF (81)performs its functions must be considered. The same also applies to the associatedequipment, its frequency and time characteristic.There are especially two application areas for SAPTOF (81):1. to protect equipment against damage due to high frequency, such as generators,and motors2. to protect a power system, or a part of a power system, against breakdown, byshedding generation, in over production situations.The overfrequency PICKUP value is set in Hz. All voltage magnitude related settingsare made as a percentage of a settable base voltage, which normally is set to thenominal voltage level (phase-to-phase) of the power system or the high voltageequipment under consideration.Some applications and related setting guidelines for the frequency level are given below:1MRK504116-UUS C Section 3IED application545Application manual
