Impedance calculation
This module receives positive sequence voltage (U
1
) and negative sequence voltage
(U
2
) which are calculated from fundamental frequency three phase voltages.
Also positive sequence current (I
1
) and negative sequence current (I
2
) which are
respectively calculated from fundamental frequency three phase currents.
Once activated the negative sequence impedance (Z
2
) is calculated from the
negative sequence current, the negative sequence voltage and Relay characteristic
angle (RCA) using the below equation.
(Equation 278)
The RCA in the above equation can be obtained from
Characteristic angle
setting.
The Z
2
value in primary ohms is available as Z2_VALUE in monitored data.
Table 972: Direction value for monitored data view
Criterion for direction information The value for DIRECTION
Default (low level blocking active) 0 = unknown
Z
2
> 0 1 = forward
Z
2
< 0 2 = backward
Fault direction detector
This module checks if the value of Z
2
meets the operation criteria. Detection to only
forward direction can be achieved by setting the
Direction mode
to “Forward”. Thus,
forward fault is detected if the value of Z
2
is higher than the
Ng Seq impedance Fw
setting. Respectively operation to only reverse direction can be activated by setting
Direction mode
is set to “Reverse”. Reverse fault is detected if the value of Z
2
is
below the setting
Ng Seq impedance Rv
setting. In case
Direction mode
is set to
“Non-directional”, operation is allowed if condition for forward or reverse direction
is fulfilled.
The
Ng Seq impedance Fw
setting and
Ng Seq impedance Rv
settings are
set in primary ohms.
FAULT_DIR gives the direction information during fault, if operation criteria is
satisfied. that is, when the START output is active. The fault direction (FAULT_DIR) is
available in monitored data and as function block output. FAULT_DIR values are the
same as for DIRECTION output given in the
Table 972
. The FAULT_DIR is set to value
0 = unknown after the START output is deactivated.
Figure 579
illustrates the directional operating characteristics on negative sequence
impedance level as shown in the vertical line.
Protection functions
1MRS759142 F
1040 REX640
Technical Manual
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