The IFPTOC has inbuild directional transient detector module for detecting earth-
fault transients. Transient detector module is used to count the number of
transients during an earth fault to discriminate intermittent earth fault from
continuous earth fault.
Transient detector module counts the number of transients during an
earth fault both in faulty and healthy feeders. Detection of transients is
indicated with
PEAK_IND
output.
Internal start of intermittent earth-fault module is obtained when the presence of
earth fault is indicated (
EF_IND
), it’s validity is confirmed (
VALID_EF
) and at least
one transient is detected in the protected feeder. Whenever a fault transient is
detected, this is indicated with the
PEAK_IND
output.
When the number of detected transients reaches the
Intr EF counter Lim setting,
INTR_EF
output is activated. Activation of
INTR_EF
output indicates detection of a
restriking or intermittent earth fault in the protected feeder.
Figure 358: Illustration of operation of intermittent earth-fault module. Setting Intr
EF counter Lim = 3
When a required number of intermittent earth-fault transients set with the
Intr
EF counter Lim setting are detected without the function being reset (depends
on the drop-off time set with the setting
Intr EF reset time) and the presence of
single-phase earth fault in the protected feeder is confirmed (activation of
EF_IND
and
VALID_EF
outputs), the
START
and
ST_INTR_EF
outputs are activated. The
OPERATE
and
OP_INTR_EF
outputs are activated when operate delay time
Intr EF
operate time has elapsed (from fault beginning), required number of transients
exceeds setting
Intr EF counter Lim (so actually for operation there must be Intr
1MRS759142 F
Protection functions
REX640
Technical Manual
631