ABB RELION REX640 Technical Manual page 596

Protection functions
where
G
coil(s), the parallel resistor and the total network shunt losses.
|
of the protected feeder. This term represents the energy stored in the LC-
branches of the feeder. For example, if the capacitive susceptance of the feeder
equals 20A
equal 20A
equal 40A.
|
of the network. This term represents the energy stored in the LC-branches of
the total network. For example if capacitive susceptance of the network equal
100A
100A
200A.
G
losses of the coil(s) located at the feeder and natural shunt losses of the feeder.
• In unearthed networks
the earth-fault current of connected feeders. Value must be smaller than
the capacitive earth-fault current due to parallel feeders. Based on practical
experience, value of 3A is found to be suitable for most applications.
• In resistance earthed networks
the value of earthing resistor. Value must be smaller than the ampere value of
earthing resistor.
To adapt the earth-fault current validity determination to a possible fault direction
change during the fault, for example during manual fault location process, a cyclic
accumulation of admittance phasor can be enabled with setting
"Enable". The duration of this evaluation cycle is only few fundamental cycles so
that function can rapidly adapt to changes in fault direction. Evaluation is based
on monitoring the sign of the accumulation of admittance phasor compared with
sign of transient admittance stored at fault ignation. In case change of polarity
is detected, and duration of polarity change exceeds setting
and a cyclic accumulation of admittance (real- or imaginary part converted into
equivalent current value) exceeds
earth-fault current estimate is reset and restarted. As default, setting
reset = "Enable".
596
= Conductance representing the total system shunt losses, i.e. losses of the
oTot
B
| = The sum of absolute values of capacitive and inductive susceptances
oFdTot
cap
and the inductive susceptance of the distributed coils at the feeder
ind
, then the sum of absolute values of susceptances of the feeder
B
| = The sum of absolute values of capacitive and inductive susceptances
oTot
cap
and the inductive susceptance of the central and distributed coils equal
ind
, then the sum of absolute values of susceptances of the network equal
= Conductance representing the total shunt losses of protected feeder i.e.
oFdTot
Information about the validity of earth-fault current estimate is also
Recorded data: Valid EF detection .
available in
Magnitude of transient resistive or reactive current component used in
evaluation of earth-fault current validity is given in recorded data as
Transient Ris Comp and Transient React Comp (fundamental frequency
magnitude) and in Monitored data as TR_RIS_COMP and TR_REACT_COMP
EF validity Min Curr should be selected based on
EF validity Min Curr should be selected based on
EF validity Min Curr , the validity evaluation of
1MRS759142 F
(Equation 116)
Ena cyclic reset =
Intr EF reset time
Ena cyclic
REX640
Technical Manual