Sz-efi-1 in order to solve this problem, we have developed hh-3710 type earth fault fixed-point system, which is mainly used in 380v-10kv distribution network when single-phase earth occurs. At the same time, it can also measure single-phase load current by using hand-held detection and hand-held device. The product has the characteristics of light structure, simple operation, accurate positioning, convenient load current measurement, etc.
■ based on the principle of injecting 20 Hz characteristic signal into fault phase, the position of single-phase ground fault can be accurately determined;
■ it is less affected by the distributed capacitance of the line, and can detect the ground impedance of 0-10k Ω;
■ the signal source adopts built-in 12v10ah high-energy lithium-ion battery, which can work continuously for up to 10 hours;
■ the signal source can adopt AC220V AC charging and 12V DC charging of on-board cigarette lighter;
■ the load current of power supply line can be easily measured by hand-held detection and hand-held device;
■ the volume of the signal source is exquisite and light, which is easy to carry;
■ inverted U-shaped structure is adopted for hand-held detection, which is convenient for hanging rod measurement;
■ it can quickly locate the ground fault point, shorten the fault detection time, and greatly save human and material resources.
When there is a ground fault in the line, after the fault phase fault section is determined, 10ma220hz characteristic AC signal is injected into the fault phase line by 20Hz signal source. According to Kirchhoff's law, the characteristic AC signal must also form a loop through the fault point, and the signal source characteristic signal injection point is the starting point. Then the injection signal can be measured on the path from the beginning of the line to the fault point The approximate equivalent characteristic AC signal can only be measured in the non fault area (including the non fault branch and after the fault point) because of the influence of transformer and Pt on the line. Therefore, the characteristic AC signal flowing through each branch is detected by hand-held detector and hand-held device at the key branch along the line. If a branch can be detected Characteristic AC signal indicates that the fault point is downstream of the branch. If the characteristic AC signal cannot be detected, the fault point is upstream of the branch. According to this principle, the ground fault point can be accurately determined.