Instruction manual
–
AQ G3x7 Generator protection IED
152 (211
)
Figure 3-91: IEEE standard dependent time characteristics (enlarged)
This inverse type characteristic is also combined with a minimum time delay, the value of
which is set by user parameter VPH24_MinDel_TPar_ (Min. Time Delay). This time delay
is valid if the flux is above the setting value VPH24_Emax_IPar_ (Start U/f HighSet).
Reset time
If the calculated flux is below the drop-off flux value (when
S
G
0.95*
G
), then the
calculated flux value decreases linearly to zero. The time to reach zero is defined by the
parameter VPH24_CoolDel_TPar_ (Cooling Time).
3.2.24.2
Analogue input of the function
Overexcitation is a typically symmetrical phenomenon. There are other dedicated protection
functions against asymmetry. Accordingly, the processing of a single voltage is sufficient.
In a network with isolated neutral, the phase voltage is not exactly defined due to the
uncertain zero sequence voltage component. Therefore, line-to-line voltages are calculated
based on the measured phase voltages, and one of them is assigned to overfluxing
protection.