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Instruction manual
–
AQ F3x0 Feeder protection IED
63 (162
)
3.2.12
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The deviation of the frequency from the rated system frequency indicates unbalance
between the generated power and the load demand. If the available generation is large
compared to the consumption by the load connected to the power system, then the system
frequency is above the rated value.
The over-frequency protection function is usually applied to decrease generation to control
the system frequency. Another possible application is the detection of unintended island
operation of distributed generation and some consumers. In the island, there is low
probability that the power generated is the same as consumption; accordingly, the detection
of high frequency can be an indication of island operation. Accurate frequency measurement
is also the criterion for the synchro-check and synchro-switch functions.
The frequency measurement is based on channel No. 1 (line voltage) or channel No. 4
(busbar voltage) of the voltage input module. In some applications, the frequency is
measured based on the weighted sum of the phase voltages. The accurate frequency
measurement is performed by measuring the time period between two rising edges at zero
crossing of a voltage signal.
For the confirmation of the measured frequency, at least four subsequent identical
measurements are needed. Similarly, four invalid measurements are needed to reset the
measured frequency to zero. The basic criterion is that the evaluated voltage should be
above 30% of the rated voltage value. The over-frequency protection function generates a
start signal if at least five measured frequency values are above the preset level.
Содержание AQ F3 0 Series
Страница 1: ...INSTRUCTION MANUAL AQ F3x0 Feeder protection IED ...
Страница 44: ...Instruction manual AQ F3x0 Feeder protection IED 44 162 ...
Страница 84: ...Instruction manual AQ F3x0 Feeder protection IED 84 162 Figure 3 45 Polygon characteristics logic ...
Страница 148: ...Instruction manual AQ F3x0 Feeder protection IED 148 162 Figure 6 3 Panel cut out and spacing of AQ 35x IED ...
Страница 149: ...Instruction manual AQ F3x0 Feeder protection IED 149 162 Figure 6 4 Dimensions of the AQ 39x IED ...
Страница 150: ...Instruction manual AQ F3x0 Feeder protection IED 150 162 Figure 6 5 Panel cut out and spacing of the AQ 39x IED ...