3.9.3 Rate-of-change frequency protection SAPFRC (81)
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Rate-of-change frequency protection SAPFRC
SYMBOL-N V1 EN
81
3.9.3.1 Application
Rate-of-change frequency protection (SAPFRC, 81), is applicable in all situations,
where reliable detection of change of the fundamental power system voltage frequency
is needed. SAPFRC (81) can be used both for increasing frequency and for decreasing
frequency. SAPFRC (81) provides an output signal, suitable for load shedding or
generator shedding, generator boosting, HVDC-set-point change, gas turbine start up
and so on. Very often SAPFRC (81) is used in combination with a low frequency
signal, especially in smaller power systems, where loss of a fairly large generator will
require quick remedial actions to secure the power system integrity. In such situations
load shedding actions are required at a rather high frequency level, but in combination
with a large negative rate-of-change of frequency the underfrequency protection can be
used at a rather high setting.
3.9.3.2 Setting guidelines
The parameters for Rate-of-change frequency protection SAPFRC (81) are set via the
local HMI or PCM600.
All the frequency and voltage magnitude conditions in the system where SAPFRC (81)
performs its functions should be considered. The same also applies to the associated
equipment, its frequency and time characteristic.
There are especially two application areas for SAPFRC (81):
1. to protect equipment against damage due to high or too low frequency, such as
generators, transformers, and motors
2. to protect a power system, or a part of a power system, against breakdown by
shedding load or generation, in situations where load and generation are not in
balance.
SAPFRC (81) is normally used together with an overfrequency or underfrequency
function, in small power systems, where a single event can cause a large imbalance
between load and generation. In such situations load or generation shedding has to take
1MRK504116-UUS C Section 3
IED application
547
Application manual
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