Siemens 7SJ82 Manual page 602

Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
[lo_start condition and dir. determ, 1, en_US]
Figure 6-141
Measured Values, Methods of Measurement
The device can measure the residual voltage at the broken-delta winding. The measured voltage is converted
to a value with reference to the zero-sequence voltage V0. If the residual voltage is not available to the device
as a measurand, the zero-sequence voltage V0 is calculated from the measured phase-to-ground voltages V
V , and V using the defining equation.
B C
For the measured value 3I0 and the method of measurement, you can find more information in section
ured Value 3I0, Method of Measurement , Page
The function uses the fundamental-component value of V0 and the 3rd, 5th, or 7th harmonic phasor of V0
and 3I0 for direction determination. The specific harmonic phasor to be used is determined by the Harmonic
selection setting.
Ground-Fault Detection, Pickup
If the fundamental-component value of the zero-sequence voltage V0 exceeds the threshold V0>
threshold value, the stage detects the ground fault and the timer Dir. determination delay starts.
If the following 2 conditions are met, the ground-fault signaling and direction determination start:
•
The fundamental-component value of the zero-sequence voltage V0 keeps exceeding the threshold V0>
threshold value during the period of the timer Dir. determination delay.
•
The absolute value of the zero-sequence harmonic current 3I0harm. exceeds the threshold Min. 3I0>
harmonic when the timer Dir. determination delay expires.
602
Logic Diagram of the Start Conditions and of the Direction Determination
569.
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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