ABB Relion 670 Series Applications Manual page 283

1MRK 511 401-UEN Rev. K
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 start value is set in Hz. All voltage magnitude related settings are made as a
percentage of a settable global base voltage parameter
as a primary phase-to-phase value.
Some applications and related setting guidelines for the frequency level are given below:
Equipment protection, such as for motors and generators
The setting has to be well above the highest occurring "normal" frequency and well below the
highest acceptable frequency for the equipment.
Power system protection, by generator shedding
The setting must be above the highest occurring "normal" frequency and below the highest
acceptable frequency for power stations, or sensitive loads. The setting level, the number of
levels and the distance between two levels (in time and/or in frequency) depend very much on
the characteristics of the power system under consideration. The size of the "largest loss of
load" compared to "the size of the power system" is a critical parameter. In large systems, the
generator shedding can be set at a fairly low frequency level, and the time delay is normally not
critical. In smaller systems the frequency START level has to be set at a higher value, and the
time delay must be rather short.
11.3 Rate-of-change of frequency protection SAPFRC
11.3.1 Identification
Function description
Rate-of-change of frequency
protection
11.3.2 Application
Rate-of-change of frequency protection (SAPFRC) is applicable in all situations, where reliable
detection of change of the fundamental power system voltage frequency is needed. SAPFRC
can be used both for increasing frequency and for decreasing frequency. SAPFRC 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 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.
Bay control REC670
Application manual
IEC 61850
identification
SAPFRC
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UBase . The UBase value should be set
IEC 60617 ANSI/IEEE C37.2
identification device number
81
df/dt > <
SYMBOL-N V1 EN-US
Section 11
Frequency protection
IP15748-1 v4
M14868-1 v4
M14966-3 v5
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