Instruction manual
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AQ G3x7 Generator protection IED
37 (211
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Figure 14: Structure of the instantaneous residual overcurrent algorithm.
The algorithm generates a trip command without additional time delay based on the Fourier
components of the phase currents or peak values of the phase currents in case if the user
set pick-up value is exceeded. The operation of the function is phase wise and it allows
each phase to be tripped separately. Standard operation is three poles.
The function includes a blocking signal input which can be configured by user from either
IED internal binary signals or IED binary inputs through the programmable logic.
Table 3-15 Setting parameters of the residual instantaneous overcurrent function
Parameter
Setting value, range
and step
Description
Operation
Off
Peak value
Fundamental value
Operating mode selection of the function. Can be disabled,
operating based into measured current peak values or
operating based into calculated current fundamental
frequency RMS values. Default setting is “Peak value”
.
Start current
10…400 %, by step
of 1%
Pick-up setting of the function. Setting range is from 10 % to
400 % of the configured nominal secondary current. Setting
step is 1 %. Default setting is 200 %.
3.2.4
T
HREE PHASE TIME OVERCURRENT
I>,I>>
(50/51)
Three phase time overcurrent function includes the definite time and IDMT characteristics
according to the IEC and IEEE standards. The function measures the fundamental Fourier
components of the measured three phase currents.
The structure of the algorithm consists of following modules. Fourier calculation module
calculates the RMS values of the Fourier components of the 3-phase currents.
Characteristics module compares the Fourier basic harmonic components of the phase