Areva MiCOM P441, Техническое руководство

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Relay Description P44x/EN HW/E33
MiCOM P441/P442 & P444 Page 31/44
Following are the different phase selections:
•
SAN = T x RAN x
BN
R
x
CN
R
single-phase A to ground fault
•
SBN = T x RBN x
AN
R
x
CN
R
single-phase B to ground fault
•
SCN = T x RCN x
BN
R
x
CN
R
single-phase C to ground fault
•
SABN = T x RAB x ZAN x ZBN double-phase A to B to ground fault
•
SBCN = T x RBC x ZBN x ZCN double-phase B to C to ground fault
•
SCAN = T x RCA x ZAN x ZCN double-phase C to A to ground fault
•
SAB =
T
x RAB x
BC
R
x
CA
R
double-phase A to B fault
•
BC =
T
x RBC x
AB
R
x
CA
R
double-phase B to C fault
•
CA =
T
x RCA x
AB
R
x
BC
R
double-phase B to C fault
•
SABC = ZAN x ZBN x ZCN x ZAB x ZBC x ZCA three-phase fault
For a three-phase fault, the fault resistance of one of the two-phase loops is less than half of
the fault resistances of the other two-phase loops, it will be used for the directional and
distance measuring function. If not, the loop AB will be used.
NOTE: Impedance phase selection is used only if current phase selection is
unable to make a decision.
4.3.4 Directional Decision
The fault direction is defined on the basis of the calculation of the phase shift between the
stored voltage and the derivative of a current. The current and the voltage used are those of
the measuring loop(s) defined by the phase selection.
For the two-phase loops, the calculation of the phase shift between the stored voltage and
the derivative of the current on the faulty two-phases.
For the single-phase loops, the calculation of the phase shift between the stored voltage and
the current (I'x + k0 . 3 x I'0), where:
I'x = derivative of current on the faulted single-phase where x = A, B, or C
3 x I’0 = derivative of residual current
k0 = ground compensation factor, where for example k01 = (Z0–Z1)/3Z1
The directional angle is fixed between-30° and +150° (RCA =60°).
4.3.5 Directional Decision during SOTF/TOR (Switch On To Fault/Trip On Reclose)
The directional information is calculated from the stored voltage values if the network is
detected as healthy. The calculations vary depending on the type of fault, i.e., single-phase
or multiphase.
If the network frequency cannot be measured and tracked, the directional element cannot be
calculated from the stored voltage. A zero sequence directional will be calculated if there are
enough zero-sequence voltage and current. If the zero-sequence directional is not valid, a
negative-sequence directional will be calculated if there are enough negative sequence
voltage and current. If both directional cannot be calculated, the directional element will be
forced forward.