ABB Relion 670 Series RES670, Technical Manual

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10.2.7.1 Measurement principle
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
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).
10.2.7.3 Blocking
It is possible to block overfrequency protection SAPTOF (81) partially or completely, by
binary input signals or by parameter settings, where:
BLOCK: blocks all outputs
BLKTRIP: blocks the TRIP output
If the measured voltage level decreases below the setting of MinValFreqMeas in the
preprocessing function both the PICKUP and the TRIP outputs are blocked.
Section 10
1MRK 511 365-UUS A
Frequency protection
306 Phasor measurement unit RES670 2.1 ANSI
Technical manual