Arcteq AQ F3 0 Series, Инструкция по эксплуатации

Страница: 80 / 162

Instruction manual – AQ F3x0 Feeder protection IED 80 (162
)
Calculation method Calc(B):
If the CURRENT_OK status signal is true and the VOLT_OK_HIGH status signal is true as
well, then the current is suitable for calculation and the voltage is sufficient for the
directionality decision. In this case, normal impedance calculation is performed based on
the sampled currents and voltages. (The calculation method - the function
” f ” - is explained
later.)
R, X=f(u, i)
Calculation method Calc(C):
If the CURRENT_OK status signal is true but the VOLT_OK_HIGH status signal is false or
there are voltage swings, the directionality decision cannot be performed based on the
available voltage signals temporarily. In this case, if the voltage is above a minimal level (in
the range of possible capacitive voltage transformer swings), then the VOLT_OK_LOW
status is
“ true ” , the magnitude of R and X is calculated based on the actual currents and
voltages but the direction of the fault (the +/- sign of R and X) must be decided based on
the voltage value stored in the memory 80 ms earlier. (The high voltage level setting assures
that during the secondary swings of the voltage transformers, no distorted signals are
applied for the decision). This procedure is possible only if there are stored values in the
memory for 80 ms and these values were sampled during a healthy period.
R, X=f(u, i) direction = f(Umem, i) /in the first 35 ms/
After 35 ms (when the secondary swings of the voltage transformers decayed), the
directional decision returns to the measured voltage signal again:
R, X=f(u, i) direction = f(u, i) /after 35 ms/
Calculation method Calc(D):
If the voltage is below the minimal level, then the VOLT_OK_LOW status is “ false ” but if
there are voltage samples stored in the memory for 80 ms, then the direction is decided
based on the sign either of the real part of the impedance or that of the imaginary part of
the impedance, whichever is higher.
R, X=f(u, i) direction = f(max{R(Umem, i), X(Umem,i)})