| 摘要 |
The invention relates to two evaluation principles for detecting both a continuous d.c. fault current and a changing fault current/pulsating d.c. fault current independently of one another, using only one summation current transformer (4). The induction principle is used to detect the changing fault current and the principle known as controlled induction is used to detect the d.c. fault current. The residual current device (2) is characterised by the bipolar control of a control winding (6) together with a generator (16). The selection of a specific core material for the summation current transformer (2) and the special circuit arrangement ensure the effectiveness and reliability of the residual current device.
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