ABB RELION REX640 Technical Manual page 968

Protection functions
~
Figure 540: The fault loop impedance model for phase-to-phase impedance
measuring elements
R
1
X
1
R
F
The resistive reach setting is common for phase-to-phase and three-phase
impedance measuring elements.
The operation time delay is defined with the setting
1... 5). The timer can be disabled with the setting
This blocks the OPERATE_Zx (x = 1... 5) output of the phase-to-phase measuring
elements.
Three-phase impedance measuring element
DSTPDIS has a dedicated measuring element for a three-phase short circuit fault
for each zone. The three-phase measuring element uses the positive-sequence
quantities for a fault loop impedance estimation which increases the accuracy by
reducing the influence of line parameter asymmetry. This is advantageous especially
in case of non-transposed, asymmetrical lines. The three-phase impedance
measuring element is enabled together with the phase-to-phase impedance
elements by the setting
The reach of the three-phase measuring element is based on the loop impedance
Three-phase measuring element reach = Z + R =
968
R X
1 1
R
Positive-sequence resistance from measuring point to fault location.
Positive-sequence reactance from measuring point to fault location.
Physical fault resistance between phases, for example, arc resistance.
The phase-to-phase impedance measuring elements measure only half
of the physical fault resistance between phases. This must be taken into
account when the resistive reach of the phase-to-phase elements is set
(that is, setting the value of 5 Ω corresponds 5+5=10 Ω of physical arc
resistance between phases).
Op Mod PP loops Znx (x = 1... 5) = "True".
X
X
1
/2
F
PP Op delay Mod Znx = "False".
R + j
1 F
1MRS759142 F
R /2
F
R
R
1
PP operate delay Znx (x =
X X + R
1 1 F
(Equation 269)
Technical Manual
REX640