Siemens 7SJ82 Manual page 557

Intermittent Ground-Fault Indication
The stage counts the 3I0 pulses. If the sum of forward pulse counts, reverse counts, and directional undefined
counts is equal to or greater than No.of pulses for interm.GF, the signal
is issued.
If the signal Intermittent gnd.flt. is issued, the pickup indications of some protection functions will be
restraint to avoid an indication burst during an intermittent ground fault.
Operate
The conditions for issuing the signal
Operating Mode
Counter
Integrator and counter
When an opposite current pulse against the setting Directional mode is detected, the Integrator T-sum
and the Counter are reset.
Reset Time for the Definition of the Interval between Independent Ground Faults
If there is a large interval between independent ground faults or if the ground fault extinguishes and does not
restrike again within a larger time, the stressed equipment can cool down. In this case, no operate is neces-
sary. The interval between ground faults is monitored with the reset time. If a ground fault occurs, the Timer
T-reset with the setting Reset time and the Integrator T-sum are launched simultaneously. Unlike the inte-
grator, each new ground-current pulse restarts the reset time with its initial value. If the Timer T-reset
expires, that is, no new ground fault was detected during that period, all memories and the stage logics are
reset. The Timer T-reset thus determines the time during which the next ground fault must occur to be
processed yet as intermittent ground fault in connection with the previous fault. A ground fault that occurs
later is considered as a new ground-fault event.
Reset Conditions
Under one of the following 2 conditions, Timer T-reset is reset:
•
The intermittent ground-fault protection stage operates.
•
The general operate indication is going.
Under one of the following conditions, Integrator T-sum and Counter are reset and the whole stage is reset
and returns to its idle state:
•
The Timer T-reset expires without an operate signal of this stage or another function was issued.
•
The operate signal of the intermittent ground-fault protection stage is going.
•
The general operate indication is going without the operate signal of the intermittent ground-fault
protection stage issued.
Maximum Value 3I0 of the Ground Fault
The stage records the maximum RMS value of 3I0 during the intermittent ground fault.The statistic value
max. is a percentage value calculated through dividing the primary maximum RMS value by the rated current
value of the protected object. If the function resets or operates, this value is logged via the signal
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
Operate depend on the operating mode.
Conditions for Issuing the Operate Signal
•
The current-pulse counter reached the No. of pulses for
operate, which is signaled via the
•
The pickup is active, which is signaled via the
•
The 3I0 current integration value reaches the predefined Sum of
extended PU times, which is signaled via the
reached indication.
•
The current-pulse counter reached the No. of pulses for
operate, which is signaled via the
•
The pickup is active, which is signaled via the
Protection and Automation Functions
6.14 Directional Intermittent Ground-Fault Protection
Intermittent gnd.flt.
Pulse no. reached indication.
Pickup indication.
Sum limit
Pulse no. reached indication.
Pickup indication.
3I0
3I0 max. .
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