ABB Relion 670 Series Applications Manual page 239

1MRK 511 401-UUS F
10.2.3 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 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
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)
Bay control REC670
Application manual
IEC 61850
identification
SAPFRC
© Copyright 2017 ABB. All rights reserved
VBase . The UBase value should be set as a
IEC 60617 ANSI/IEEE C37.2
identification device number
81
df/dt > <
SYMBOL-N V1 EN-US
Section 10
Frequency protection
M14959-3 v7
IP15748-1 v4
M14868-1 v4
M14966-3 v5
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