ABB RELION REX640, Техническое руководство, Страница: 1400 / 1960

detection in monitored data is set to TRUE. Monitored data is set to FALSE once
fault current has dropped below start value.
The module calculates the duration for currents continuously staying above the set
Phase start value (or Residual start value). If the calculated duration is between
¼ cycles and cycles set by
Maximum fault cycle, then it is regarded as the SCF
and corresponding SCF indication in monitored data is set to TRUE. Simultaneously
corresponding SCF counter in monitored data is increased.
The parameter settings
Residual start value, Residual current limit are
dimmed when
Ena selfclear Det EF setting is set to “FALSE”. And also
Monitoring for residual current (Io), can be disabled by setting
Ena
selfclear Det EF to “FALSE”.
If the setting
Adaptive Str Val Ena is set to TRUE. the adaptive phase and residual
start value are defined based on the one-minute phase and residual averages, the
Minimum load current (for phase) and Residual current limit (for earth) setting.
At end of the every healthy state one-minute period, new one-minute phase and
residual current averages are calculated. If it is greater than the
Minimum load
current (for phase) and Residual current limit (for earth) setting, then the adaptive
start value will be updated as twice the calculated value.
If one-minute phase and ground averages are less than the
Minimum load current
and
Residual current limit, then the adaptive start value are set to twice the
Minimum load current and Residual current limit.
In case fault is detected, the adaptive start value will hold the last updated one-
minute average of phase and residual current.
The adaptive start values of corresponding phases (or residual) are displayed in
monitored data ADP_ST_VAL_A, ADP_ST_VAL_B, ADP_ST_VAL_C and ADP_ST_VAL_N.
If the SCF is detected in at least one phase or residual current channel, the
ALARM
output is set to TRUE. When one phase detects a fault, the algorithm waits for 1
cycle time and if during this period two other phases also detect fault, then the fault
is considered as three phase SCF and the SLFCLR_3PH in monitored data is set to
TRUE.
The counter type monitored data can be reset to their initial value along with the
all the outputs in the monitored data via a control parameter RCFD1 reset that is
located under the clear menu.
When
BLOCK
input is activated, the
ALARM
output is set to FALSE, and also the
Boolean type monitored data are set to FALSE and ADP_ST_VAL_x (phase A,B and C)
are defaulted to
Phase start value setting (ADP_ST_VAL_N is defaulted to Residual
start value setting), Counter type monitored data are not affected and will retain
last SCF fault count.
7.4.6 Application
The self-clearing fault will not the damage the cable initially, but if the frequency of
the self-clearing fault slowly increases and causes the cable insulation breakdown.
7.4.7 Signals
Condition monitoring functions 1MRS759142 F
1400 REX640
Technical Manual