Rate-Of-Change Of Frequency Protection Sapfrc (81); Identification; Application - Hitachi Relion 670 Series Applications Manual
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1MRK511407-UUS Rev. N
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:
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 PICKUP
level has to be set at a higher value, and the time delay must be rather short.
10.3
Rate-of-change of frequency protection SAPFRC (81)
10.3.1
Identification
Function description
Rate-of-change of frequency protection
10.3.2
Application
Rate-of-change of 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.
Phasor measurement unit RES670
Application manual
IEC 61850
identification
SAPFRC
© 2017 - 2023 Hitachi Energy. All rights reserved
IEC 60617
ANSI/IEEE C37.2
identification
device number
81
df/dt > <
SYMBOL-N V1 EN-US
Section 10
Frequency protection
IP15748-1 v4
M14868-1 v4
M14966-3 v5
163
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