ABB RELION REX640, Техническое руководство, Страница: 949 / 1960

• The “Vol Dep Overcur” method combines overcurrent and undervoltage
conditions. An undervoltage condition allows lower current threshold settings
and increases the sensitivity of the fault detection.
• The “Under impedance” method uses fault loop impedance for identifying the
faulted phases. The underimpedance characteristic can be either quadrilateral
or circular in shape. The sensitivity of the fault detection is defined by an
independent setting in resistive and reactive reaches. The underimpedance
method is supervised by a load encroachment logic which ensures that the load
impedance does not interfere with the faulted phase selection.
The ”OC AND Und impedance” method combines “Overcurrent” and “Under
impedance” methods so that both criteria have to be fulfilled.
All phase selection methods require that all three phase currents are measured
and all three phase-to-earth voltages are available. If only phase-to-phase voltages
are available (
Phase voltage Meas = “Ph-to-ph without Uo”), only phase-to-phase
measuring loops can be released for measurement. The release of phase-to-earth
fault measuring elements is then blocked,
RELEASE_PE
= “No fault”.
The operation of the faulted phase selection function is highly dependent on the
earth-fault detection function. The phase preference or faulted loop selection logic
can be set to filter the faulted phases to be released for measurement in the
protection zones.
The general indication of a fault is given in the binary output
START_GFC
. The
faulted phase information can be found from the integer monitored data signal
STARTS_GFC
.
Table 909: Enumeration values for integer monitored data signal STARTS_GFC
Enumeration name Value
No fault -5
AG Fault 1
BG Fault 2
CG Fault 3
AB Fault 4
BC Fault 5
CA Fault 6
ABC Fault 7
The fault loops released for measurement are indicated with the integer monitored
data signals
RELEASE_PE
and
RELEASE_PP
. These signals may be filtered by the
phase preference of the faulted loop selection logic.
Table 910: Enumeration values for integer monitored data signal RELEASE_PE
Enumeration name Value
No fault -5
AG Fault 1
BG Fault 2
CG Fault 3
AB Fault 4
Table continues on the next page
1MRS759142 F Protection functions
REX640
Technical Manual
949