Logic - Siemens siprotec SJ62 User Manual

2 Functions

2.12.4 Logic

Figure 2-70 Activation of the sensitive ground current protection
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The following figure illustrates a state logic of the sensitive ground fault protection.
Ground fault detection can be switched ON or OFF or set to Alarm Only (address
3101). When ground fault protection is ON, tripping is possible. The pickup of the dis-
placement voltage V starts the ground fault recording. As the pickup of the V
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drops out, fault recording is terminated. In mode Alarm Only, ground faults are re-
corded in a separate log file for ground faults. In this operating mode, the annunciation
303 „sens Gnd flt" opens and closes the log file for ground faults and the present
fault number is included (see logic diagrams from Figures 2-71 and 2-72).
The entire function may be blocked via binary input. Switching off or blocking means
the measurement logic is deactivated. Therefore, time delays and pickup messages
are reset.
All stages can be blocked individually via binary inputs. In this case pickup and, if pos-
sible, direction and grounded phase will still be reported, however, tripping does not
take place since the time elements are blocked.
Generation of a pickup message, for both current elements, is dependent on the di-
rection 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
INs, a pickup message is generated as soon as the current threshold is exceeded,
irrespective of the status of the V
CRITERIA is Vgnd AND INs, the V
rectional mode.
But, if a direction is programmed, the current element must be picked up and the di-
rection determination results must be present to generate a message. Once again, a
condition for valid direction determination is that the voltage element V
Setting at address 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 voltage
element V was chosen to be very low.
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element. If, however, the setting of parameter PU
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–element must have picked up also for non-di-
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SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
element
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be picked up.
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