ABB REL650 series, Applications Manual, Page: 277 / 516

9.2.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Overfrequency protection SAPTOF
f >
SYMBOL-O V1 EN
81
9.2.2 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.
9.2.3 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 two specific 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 global base voltage parameter
VBase . The UBase value
should be set as a primary phase-to-phase value.
Some applications and related setting guidelines for the frequency level are given below:
1MRK 506 334-UUS A
Section 9
Frequency protection
271
Application manual