ABB RET670 - Setting Parameters

Power system protection, by load shedding
The setting has to be well below the lowest occurring "normal" frequency and well
above the lowest 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) depends very much on the characteristics of the power system under
consideration. The size of the "largest loss of production" compared to "the size of the
power system" is a critical parameter. In large systems, the load shedding can be set at
a fairly high frequency level, and the time delay is normally not critical. In smaller
systems the frequency pickup level has to be set at a lower value, and the time delay
must be rather short.
The voltage related time delay is used for load shedding. The settings of the
underfrequency function could be the same all over the power system. The load
shedding is then performed firstly in areas with low voltage magnitude, which
normally are the most problematic areas, where the load shedding also is most efficient.
3.9.1.3 Setting parameters
Table 139: SAPTUF (81) Group settings (basic)
Name Values (Range) Unit Step Default Description
Operation Disabled
Enabled
- - Disabled Disable/Enable Operation
Vbase 0.05 - 2000.00 kV 0.05 400.00 Base voltage
PUFrequency 35.00 - 75.00 Hz 0.01 48.80 Frequency setting pickup value.
IntBlockLevel 0 - 100 %VB 1 50 Internal blocking level in % of VBase.
TimeDlyOperate 0.000 - 60.000 s 0.001 0.200 Operate time delay in over/under-frequency
mode.
TimeDlyReset 0.000 - 60.000 s 0.001 0.000 Time delay for reset.
TimeDlyRestore 0.000 - 60.000 s 0.001 0.000 Restore time delay.
RestoreFreq 45.00 - 65.00 Hz 0.01 50.10 Restore frequency if frequency is above
frequency value.
TimerOperation Definite timer
Volt based timer
- - Definite timer Setting for choosing timer mode.
VNom 50 - 150 %VB 1 100 Nominal voltage in % of VBase for voltage
based timer.
VMin 50 - 150 %VB 1 90 Lower operation limit in % of VBase for
voltage based timer.
Exponent 0.0 - 5.0 - 0.1 1.0 For calculation of the curve form for voltage
based timer.
t_MaxTripDelay 0.010 - 60.000 s 0.001 1.000 Maximum time operation limit for voltage
based timer.
t_MinTripDelay 0.010 - 60.000 s 0.001 1.000 Minimum time operation limit for voltage
based timer.
Section 3 1MRK504116-UUS C
IED application
544
Application manual