Setting Guidelines; Frequency Time Accumulation Protection Function Ftaqfvr (81A); Identification - Hitachi Relion 670 Series Applications Manual

Section 10
Frequency protection
10.3.3

Setting guidelines

The parameters for Rate-of-change frequency protection SAPFRC (81) are set via the local HMI or or
through the Protection and Control Manager (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 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 place very quickly, and there might not be enough time
to wait until the frequency signal has reached an abnormal value. Actions are therefore taken at a
frequency level closer to the primary nominal level, if the rate-of-change frequency is large (with respect
to sign).
The pickup value for SAPFRC (81) is set in Hz/s. All voltage magnitude related settings are made as a
percentage of a settable base voltage, which normally is set to the primary nominal voltage level (phase-
phase) of the power system or the high voltage equipment under consideration.
SAPFRC (81) is not instantaneous, since the function needs some time to supply a stable value. It is
recommended to have a time delay long enough to take care of signal noise. However, the time, rate-of-
change frequency and frequency steps between different actions might be critical, and sometimes a
rather short operation time is required, for example, down to 70 ms.
Smaller industrial systems might experience rate-of-change frequency as large as 5 Hz/s, due to a single
event. Even large power systems may form small islands with a large imbalance between load and
generation, when severe faults (or combinations of faults) are cleared - up to 3 Hz/s has been
experienced when a small island was isolated from a large system. For more "normal" severe
disturbances in large power systems, rate-of-change of frequency is much less, most often just a fraction
of 1.0 Hz/s.
10.4 Frequency time accumulation protection function
FTAQFVR (81A)
10.4.1

Identification

Function description
Frequency time accumulation protection
164
IEC 61850
identification
FTAQFVR
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IEC 60617 ANSI/
identification IEEEidentificatio
n
f<> 81A
Phasor measurement unit RES670
1MRK511407-UUS Rev. N
M14971-3 v7
GUID-124A1F91-44C0-4DB6-8603-CC8CA19AE2A6 v3
GUID-87605DA0-EAA6-4A6C-BF03-7FDB187E1B29 v2
Application manual