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Logic
The following figure illustrates the activation criteria of the sensitive ground fault protection. The operational
mode of the ground fault detection can be set under address 3101.
If set to ON, tripping is possible and a fault log is generated.
If set to Alarm Only, tripping is not possible and only a ground fault log is generated.
The pickup of the displacement voltage element V
Element drops out, fault recording is terminated (see logic diagrams 2-64 and 2-65).
The entire function can be blocked under the following conditions:
• A binary input is set,
• the Fuse Failure Monitor or the voltage transformer protection breaker pick up and parameter 3130 PU
CRITERIA is set to Vgnd AND INs,
• the Fuse Failure Monitor or the voltage transformer protection breaker pick up and parameter 3130 PU
CRITERIA is set to Vgnd OR
Switching off or blocking means that measurement is deactivated. Therefore, time delays and pickup messages
are reset.
All elements can be blocked individually via binary inputs. In this case pickup and, if possible, direction and
grounded phase will still be reported, however, tripping does not take place since the time elements are
blocked.
Figure 2-63
Generation of a pickup message, for both current elements, is dependent on the direction selection for each
Element and the setting of parameters 3130 PU CRITERIA. If the Element is set to Non-Directional and
parameter PU CRITERIA = Vgnd OR
is exceeded, irrespective of the status of the V
is Vgnd AND INs, the V
However, if a direction is programmed, the current element must be picked up and the direction determination
results must be present to generate a message. Once again, a condition for valid direction determination is that
the voltage Element V
Parameter PU CRITERIA specifies, whether a fault is generated by means of the AND-function or the OR-
combination of displacement voltage and pickup of the ground current. The former may be advantageous if the
pickup setting of displacement voltage element V
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
INs, and both current elements are in directional operation mode.
Activation of the sensitive ground-fault detection for cos-ϕ -/sin-ϕ measurement
INs, a pickup message is generated as soon as the current threshold
–Element must have picked up also for non-directional mode.
0
be picked up.
0
2.11 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
starts the ground fault recording. As the pickup of the V
0
Element. If, however, the setting of parameter PU CRITERIA
0
was chosen to be very low.
0
Functions
0
189
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