The following figure shows a simplified network that applies the pulse-pattern detection method.
The pulse pattern in the ground current 3I0 is generated by switching on and off a capacitor in parallel to the
arc-suppression coil:
•
When the capacitor is switched on, an additional capacitive ground current is generated and the 3I0
compensation changes.
•
When the capacitor is switched off, the additional capacitive ground current is vanished and the 3I0
compensation returns to the normal state.
[dw_pulse detection network, 1, en_US]
Figure 6-146
Network that Uses the Pulse-Pattern Detection
Cs Capacitance of the switched capacitor
L Inductance of the arc-suppression coil
Pulse Pattern during a Ground Fault
The following figure shows the 3I0 pulse pattern in an overcompensated system for a low-impedance ground
fault and a high-impedance ground fault.
•
For low-impedance ground faults, the 3I0 pulse pattern exists only in the faulty feeder.
•
For high-impedance ground faults, the pulse pattern is also present in the healthy feeders with lower
amplitude but in phase opposition to the faulty feeder.
Applying a different switch-on/switch-off duration allows distinguishing between faulty and healthy
feeders in case of high-impedance ground faults.
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
620 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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