Siemens SIPROTEC 4 7SJ61 User Manual

Buffered messages are signaled to the fault log, CFC and to the system interface with the original time flag
only when a TRIP command is initiated by a protection function other than the intermittent ground fault
protection. This ascertains that a pickup, although delayed, is always signaled in association with each TRIP
command.
All pickup messages which usually do not occur during an intermittent ground fault are not affected by this
mechanism. Among others this includes the pickup and TRIP commands of the following protective functions:
•
Breaker failure protection,
•
Overload protection,
The pickup signals of these functions will still be logged immediately. A TRIP command of one of these protec-
tive functions will cause the buffered messages to be cleared since no connection exists between tripping
function and buffered message.
A fault event is cleared when the time T-reset has expired or the TRIP command
IEF Trip has been termi-
nated.
Terminating a fault event for the intermittent ground fault protection thus is a special case. It is the time T-
reset that keeps the fault event opened and not the pickup.
Setting Notes
General
The protection function for intermittent ground faults can only take effect and is only accessible if the current
to be evaluated was configured in address 133, INTERM.EF (with Ignd or with with 3I0 or with
Ignd,sens.). If not required, this function is set to Disabled.
The function can be turned ON or OFF under address 3301 INTERM.EF.
The pickup threshold (r.m.s. value) is set in address 3302 Iie>. A rather sensitive setting is possible to
respond also to short ground faults since the pickup time shortens as the current in excess of the setting
increases. The setting range depends on the selection of the current to be evaluated at address 133
INTERM.EF.
The pickup time can be prolonged at address 3303 T-det.ext.. This pickup stabilization is especially impor-
tant for the coordination with existing analog or electromechanical overcurrent relays. The time T-det.ext.
can also be disabled (T-det.ext. = 0).
The stabilized pickup starts the counter T-sum det.. This counter is stopped but not reset when the picked
up function drops out. Based on the last counter content the counter resumes counting when the stabilized
function picks up next. This sum of individual pickup times, which are to initiate tripping, is set at address
3304 T-sum det.. It represents one of the four selectivity criteria (pickup value Iie>, detection extension
time T-det.ext., counter T-sum det. and reset time T-reset) for coordinating the relays on adjacent
feeders and is comparable to the time grading of the time overcurrent protection. The relay in the radial
network which is closest to the intermittent fault and picks up, will have the shortest summation time T-sum
det..
The reset time, after which the summation is reset in healthy operation and the protection resumes normal
status, is configured to T-reset at address 3305.
2.10.2
Functions
2.10 Intermittent Ground Fault Protection
144 SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016

Siemens SIPROTEC 4 7SJ61 Specifications

General

Brand	Siemens
Model	SIPROTEC 4 7SJ61
Category	Relays
Language	English