ABB RELION REX640, Техническое руководство, Страница: 596 / 1960

(Equation 116)
where
G
oTot
= Conductance representing the total system shunt losses, i.e. losses of the
coil(s), the parallel resistor and the total network shunt losses.
|
B
oFdTot
| = The sum of absolute values of capacitive and inductive susceptances
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
cap
and the inductive susceptance of the distributed coils at the feeder
equal 20A
ind
, then the sum of absolute values of susceptances of the feeder
equal 40A.
|
B
oTot
| = The sum of absolute values of capacitive and inductive susceptances
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
cap
and the inductive susceptance of the central and distributed coils equal
100A
ind
, then the sum of absolute values of susceptances of the network equal
200A.
G
oFdTot
= Conductance representing the total shunt losses of protected feeder i.e.
losses of the coil(s) located at the feeder and natural shunt losses of the feeder.
• In unearthed networks
EF validity Min Curr should be selected based on
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
EF validity Min Curr should be selected based on
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
Ena cyclic reset =
“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
Intr EF reset time
and a cyclic accumulation of admittance (real- or imaginary part converted into
equivalent current value) exceeds
EF validity Min Curr, the validity evaluation of
earth-fault current estimate is reset and restarted. As default, setting
Ena cyclic
reset = “Enable”.
Information about the validity of earth-fault current estimate is also
available in
Recorded data: Valid EF detection.
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
Protection functions 1MRS759142 F
596 REX640
Technical Manual