3.9.2 Overfrequency protection SAPTOF (81)
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Overfrequency protection SAPTOF
SYMBOL-O V1 EN
81
3.9.2.1 Application
Overfrequency protection function SAPTOF (81) is applicable in all situations, where
reliable detection of high fundamental power system frequency is needed. The power
system frequency, and rate of change of frequency, is a measure of the unbalance
between the actual generation and the load demand. High fundamental frequency in a
power system indicates that the available generation is too large compared to the power
demanded by the load connected to the power grid. SAPTOF (81) detects such
situations 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 be
used to alert operators that frequency has slightly deviated from the set-point, and that
manual actions might be enough.
3.9.2.2 Setting guidelines
All the frequency and voltage magnitude conditions in the system where SAPTOF (81)
performs its functions must be considered. The same also applies to the associated
equipment, 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 motors
2. to protect a power system, or a part of a power system, against breakdown, by
shedding generation, in over production situations.
The overfrequency PICKUP value is set in Hz. All voltage magnitude related settings
are made as a percentage of a settable base voltage, which normally is set to the
nominal voltage level (phase-to-phase) of the power system or the high voltage
equipment under consideration.
Some applications and related setting guidelines for the frequency level are given below:
1MRK504116-UUS C Section 3
IED application
545
Application manual
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