ABB Relion 670 series, Technical Manual

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10.2.6 Monitored data
PID-3897-MONITOREDDATA v6
Table 390: SAPTOF (81H) Monitored data
Name Type Values (Range) Unit Description
VLevel REAL - kV Level of measured voltage
FREQ REAL - Hz Measured frequency
10.2.7 Operation principle
M14958-3 v6
Overfrequency protection SAPTOF (81) is used to detect high power system frequency. SAPTOF
(81) has a settable definite time delay. If the frequency remains above the set value for a time
period corresponding to the chosen time delay, the corresponding TRIP signal is issued. To avoid
an unwanted TRIP due to uncertain frequency measurement at low voltage magnitude, a voltage
controlled blocking of the function is available from the preprocessing function, that is, if the
voltage is lower than the set blocking voltage in the preprocessing function, the function is
blocked and no PICKUP or TRIP signal is issued.
10.2.7.1 Measurement principle
M14958-6 v8
The fundamental frequency of the positive sequence voltage is measured continuously, and
compared with the set value, PUFrequency. Overfrequency protection SAPTOF (81) is dependent
on the voltage magnitude. If the voltage magnitude decreases below the setting MinValFreqMeas
in the SMAI preprocessing function, which is discussed in the Basic IED Functions chapter and is
set as a percentage of a global base voltage parameter
VBase, SAPTOF (81) is blocked and the
output BLKDMAGN is issued. All voltage settings are made in percent of the
VBase, which should
be set as a phase-phase voltage in kV. To avoid oscillations of the output PICKUP signal, a
hysteresis has been included.
10.2.7.2 Time delay
M14958-9 v7
The time delay for Overfrequency protection SAPTOF (81) is a settable definite time delay,
specified by the setting
tDelay.
TRIP signal issuing requires that the overfrequency condition continues for at least the user set
time delay, tReset. If the PICKUP condition, with respect to the measured frequency ceases during
this user set delay time, and is not fulfilled again within a user defined reset time,
tReset, the
PICKUP output is reset, after that the defined reset time has elapsed. It is to be noted that after
leaving the hysteresis area, the PICKUP condition must be fulfilled again and it is not sufficient for
the signal to only return back to the hysteresis area.
The total time delay consists of the set value for time delay plus minimum trip time
of the pickup function (80 - 90 ms).
1MRK 502 066-UUS B Section 10
Frequency protection
673
Technical manual