Huazheng HZ-5000, Руководство пользователя

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57

As shown in the figure above, the ground at both ends of the zero line and ground
line of the low-voltage cable are all unwound, and the output of the transmitter is
connected directly between the fault phase and the ground.

The signal flows from the transmitter to the fault phase, flows to the ground at the
fault point, and returns to the transmitter.

2) Fixed-point method

Similar to the cable break fault point, the receiver is kept perpendicular to the cable,
using the peak method, starting near the transmitter and gradually moving the detection
to the far end.

The signal is strong before the fault point and weak after the fault point.

The point at which the signal begins to weaken is the point of failure.

The signal has no pitch change before and after the fault point.

3) Matters needing attention:

Whether induction method can be used to butt the fault point on the ground mainly
depends on the size of the fault resistance. The larger the fault resistance is, the weaker
the signal changes before and after the fault point are, so that it is impossible to
distinguish.

The lower the low frequency is, the more obvious the strength change before and
after the fault point is, so it is recommended to use low frequency detection (such as
512Hz or 1KHz).

For phase fault, step voltage method is the dominant method, and this method is the
auxiliary method.

Before stepping over the voltage barrier, path detection is usually carried out first.

During the path tracking process, observe whether there is an obvious change in the
amplitude of the signal. If there is, it will be taken as a suspect, and focus on the stepping
voltage fixed point in this region.

If no sudden change of signal is observed, then this method is not applicable and
step voltage method should be used instead.